BATTERY CONTROL DEVICE

A battery control device which obtains a state of charge of a secondary battery from characteristics representing a relationship of a state of charge and a voltage of the secondary battery comprises a calling unit which calls a first characteristic among a plurality of the characteristics stored in advance based on use history information of the secondary battery, a correction limit width designation unit which designates a correction limit width for prescribing a tolerance level of correcting the first characteristic, and a direct detection correction unit which creates a second characteristic in which the first characteristic has been corrected according to the correction limit width based on a current value and a voltage value of the secondary battery, wherein the state of charge of the secondary battery is obtained using the second characteristic.

TECHNICAL FIELD

The present invention relates to a battery control device.

BACKGROUND ART

Conventionally, chargeable/dischargeable secondary batteries have been used in a variety of fields including mobile phones and other mobile terminals, and in the stabilization of power system interconnections. Furthermore, in recent years, electric vehicles, hybrid vehicles and other vehicles that use the power of secondary batteries as its power source are attracting attention in light of global warming countermeasures, emission controls, and measures for preventing the depletion of fossil fuels. A system equipped with these secondary batteries generally comprises a battery control device for using the batteries safely and for maximizing the performance of the batteries. A battery control device detects the voltage, temperature and current of the batteries, and operates battery parameters such as the state of charge (SOC) and the state of health (SOH) of the batteries based on the results of such detection.

The state of charge (SOC) of a battery can generally be acquired using an SOC-OCV characteristic, which is the relationship between the SOC and the open circuit voltage (OCV) of the battery. Nevertheless, the SOC-OCV characteristic is known to change depending on the degradation or individual variation of the battery. In recent years, inclination of the SOC-OCV characteristic is decreasing due to the improvement of electrode materials, and the degradation or individual variation of the SOC-OCV characteristic is becoming a problem as the cause of an SOC error. Thus, in order to calculate the SOC accurately, a logic for detecting and correcting the changes in the SOC-OCV characteristic is required.

As methods of operating the SOC according to the changes in the SOC-OCV characteristic, for example, known are the technologies described in PTL 1 and PTL 2 below. PTL 1 discloses a controller of an electricity storage system which calculates, by using an average SOC and an average battery temperature of a period in which a full charge capacity has not been estimated (unestimated period) from the time that the full charge capacity was previously calculated to date and a decrease rate map in which a decrease rate that changes according to the average SOC and the average battery temperature is prescribed in advance, the decrease rate during the unestimated period, and calculates a first elapsed time of an electrical storage device when the full charge capacity was previously calculated based on the decrease rate during the unestimated period and an initial full charge capacity. PTL 1 further discloses that the controller of the electricity storage system calculates a present full charge capacity based on a present second elapsed period of the electrical storage device calculated from the first elapsed period and the unestimated period, the decrease rate during the unestimated period, and the initial full charge capacity. PTL 2 discloses a method of estimating a state of charge of a secondary battery based on an open voltage value and a current integrated value including the steps of updating an instantaneous state of charge map which prescribes a relationship of an instantaneous open voltage value when estimating a state of charge and a state of charge estimated value based on charge/discharge characteristic data after start of use of the secondary battery, calculating an instantaneous state of charge estimated value when estimating a state of charge based on the updated instantaneous state of charge map, calculating the state of charge estimated value based on an integrated value of a current flowed through the secondary battery, and calculating a control state of charge estimated value for use in controlling the secondary battery based on the instantaneous state of charge estimated value and the state of charge estimated value based on the current integrated value.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

With the method of PTL 1, it is not possible to deal with differences in the SOC-OCV characteristics based on individual variations that occur during the manufacture of the batteries. Moreover, when the actual conditions of use of the battery and the degradation condition prescribed in the decrease rate map stored in the controller are different, an error will occur between the prediction result of the SOC-OCV characteristic and the actual SOC-OCV characteristic. Thus, there is a problem in that the operational precision of the SOC will be low. Meanwhile, with the method of PTL 2, when there is a measurement error in the OCV or the current integrated value, there is a problem in that it is not possible to accurately update the instantaneous state of charge map corresponding to the SOC-OCV characteristic, and that a gross error will consequently occur in the operation result of the SOC. In particular, with hybrid vehicles that do not perform charge/discharge externally, since the operational range of the SOC is generally narrow, it is difficult to update the instantaneous state of charge map with a high degree of accuracy.

Means to Solve the Problems

The battery control device according to the present invention obtains a state of charge of a secondary battery from characteristics representing a relationship of a state of charge and a voltage of the secondary battery, and comprises a calling unit which calls a first characteristic among a plurality of the characteristics stored in advance based on use history information of the secondary battery, a correction limit width designation unit which designates a correction limit width for prescribing a tolerance level of correcting the first characteristic, and a direct detection correction unit which creates a second characteristic in which the first characteristic has been corrected according to the correction limit width based on a current value and a voltage value of the secondary battery, wherein the state of charge of the secondary battery is obtained using the second characteristic.

Advantageous Effects of the Invention

According to the present invention, the SOC can be operated with a high degree of accuracy even when the SOC-OCV characteristic changes due to the degradation or individual variation of a battery.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention is now explained with reference to the appended drawings. In the following embodiment, explained is a case of applying the present invention to a battery system configuring a power source of a plug-in hybrid electric vehicle (PHEV). However, the present invention is not limited to the configuration of the embodiment explained below, and the present invention can also be applied to a capacitor control circuit of an electrical storage device configuring the power source of passenger vehicles such as hybrid electric vehicles (HEV) and electric vehicles (EV), and industrial vehicles such as hybrid railway vehicles.

Moreover, while the following embodiment explains a case of adopting a lithium ion battery, other batteries such as a nickel hydride battery, a lead battery, an electric double-layer capacitor, and a hybrid capacitor may also be used so long as it is a chargeable/dischargeable secondary battery. Furthermore, in the following embodiment, while an assembled battery is configured by connecting a plurality of single batteries in series, the assembled battery may also be configured by additionally connecting in series a plurality of assembled batteries configured by connecting a plurality of single batteries in parallel, or the assembled battery may also be configured by connecting in parallel a plurality of assembled batteries configured by connecting a plurality of single batteries in series.

FIG.1is a diagram showing the battery system100according to an embodiment of the present invention and the peripheral configuration thereof. The battery system100is connected to an inverter400via relays300,310, and connected to a charger420via relays320,330. The battery system100comprises an assembled battery110, a single battery management unit120, a current detection unit130, a voltage detection unit140, an assembled battery control unit150, and a storage unit180.

The assembled battery110is configured from a plurality of single batteries111. The single battery management unit120monitors the state of the single battery111. The current detection unit130detects the current flowing through the battery system100. The voltage detection unit140detects the total voltage of the assembled battery110. The assembled battery control unit150detects and manages the state of the assembled battery110.

The assembled battery control unit150receives the battery voltage and the temperature of the single batteries111sent from the single battery management unit120, the current value flowing through the battery system100sent from the current detection unit130, and the total voltage value of the assembled battery110sent from the voltage detection unit140. The assembled battery control unit150detects the state of the assembled battery110based on the received information. The results of the state detected by the assembled battery control unit150are sent to the single battery management unit120and the vehicle control unit200.

The assembled battery110is configured by electrically connecting in series a plurality of single batteries111capable of storing and releasing electrical energy (charging/discharging DC power). The single batteries111configuring the assembled battery110are grouped into a predetermined number of units upon managing and controlling the state. The grouped single batteries111are electrically connected in series and configure single battery groups112a,112b. The number of single batteries111configuring the single battery group112may be the same in all single battery groups112, or the number of single batteries111may differ for each single battery group112.

The single battery management unit120monitors the state of the single batteries111configuring the assembled battery110. The single battery management unit120comprises a single battery control unit121provided for each single battery group112. InFIG.1, single battery control units121aand121bare provided in correspondence to the single battery groups112aand112b. The single battery control unit121monitors and controls the state of the single batteries111configuring the single battery group112.

In this embodiment, in order to simplify the explanation, the single battery groups112aand112bare configured by electrically connecting four single batteries111in series, and the single battery groups112aand112bare further electrically connected in series to configure the assembled battery110comprising a total of eight single batteries111.

The assembled battery control unit150and the single battery management unit120send and receive signals via an insulation element170as represented by a photocoupler and a signal communication means160. The reason why the insulation element170is provided is because the assembled battery control unit150and the single battery management unit120use different operating power sources. In other words, while the single battery management unit120operates by using the power from the assembled battery110, the assembled battery control unit150uses an in-vehicle auxiliary battery (such as a 14V-system battery) as its power source. The insulation element170may be mounted on a circuit board configuring the single battery management unit120, or may be mounted on a circuit board configuring the assembled battery control unit150. Note that the insulation element170may be omitted depending on the system configuration.

The communication means between the assembled battery control unit150and the single battery control units121aand121bconfiguring the single battery management unit120is now explained. The single battery control units121aand121bare connected in series in descending order of the potential of the single battery groups112aand112bthat are respectively monitored by the single battery control units121aand121b. The signals sent by the assembled battery control unit150to the single battery management unit120are input to the single battery control unit121avia the insulation element170and the signal communication means160. The output of the single battery control unit121ais input to the single battery control unit121bvia the signal communication means160, and the output of the single battery control unit121bof the lowest numerical position is transmitted to the assembled battery control unit150via the insulation element170and the signal communication means160. In this embodiment, while the insulation element170is not provided between the single battery control unit121aand the single battery control unit121b, the signals may also be sent and received via the insulation element170.

The storage unit180stores information such as the internal resistance characteristics, full charge capacity, polarization characteristics, degradation characteristics, individual difference information, and characteristics of the SOC and the OCV of the assembled battery110, the single battery111, and the single battery group112. Note that, in this embodiment, while the storage unit180is configured to be disposed outside the assembled battery control unit150or the single battery management unit120, the configuration may also be such that the assembled battery control unit150or the single battery management unit120comprises a storage unit, and the foregoing information may be stored therein.

The vehicle control unit200controls the inverter400connected to the battery system100via the relay300by using the information sent by the assembled battery control unit150. Moreover, the vehicle control unit200controls the charger420connected to the battery system100via the relays320and330. While the vehicle is running, the battery system100is connected to the inverter400, and drives the motor generator410using the energy stored in the assembled battery110. When charging the batteries, the battery system100is connected to the charger420, and charged with the power supplied from a household power source or a charging station.

The charger420is used for charging the assembled battery110using an external power source as represented by a household power source or a charging station. In this embodiment, while the charger420is configured to control the charging voltage and the charging current based on commands from the vehicle control unit200, the charging voltage and the charging current may also be controlled based on commands from the assembled battery control unit150. Moreover, the charger420may be installed within the vehicle according to the vehicle configuration, performance or purpose of use of the charger420, or installation condition of the external power source, or may be installed outside the vehicle.

When a vehicle system equipped with the battery system100is to be activated and driven, based on the management of the vehicle control unit200, the battery system100is connected to the inverter400, the motor generator410is driven using the energy stored in the assembled battery110, and the assembled battery110is charged based on the generated power of the motor generator410during regeneration. When a vehicle comprising the battery system100is connected to an external power source as represented by a household power source or a charging station, the battery system100and the charger420are connected based on the information transmitted by the vehicle control unit200, and the assembled battery110is charged until reaching a predetermined condition. The energy stored in the assembled battery110based on charging is used when the vehicle is subsequently driven, or used for operating the electrical components inside and outside the vehicle. Furthermore, in certain cases such energy is released to an external power source as represented by a household power source as needed.

FIG.2is a diagram showing the circuit configuration of the single battery control unit121. The single battery control unit121comprises a voltage detection circuit122, a control circuit123, a signal input/output circuit124, and a temperature detection unit125. The voltage detection circuit122measures the inter-terminal voltage of each single battery111. The control circuit123receives the measurement results from the voltage detection circuit122and the temperature detection unit125, and sends the received measurement results to the assembled battery control unit150via the signal input/output circuit124. Note that the circuit configuration that is generally equipped in the single battery control unit121for equalizing the voltage variation and the SOC variation between the single batteries111that occur pursuant to a self-discharge or consumption current variation is well known, and the explanation thereof has been omitted.

The temperature detection unit125equipped in the single battery control unit121shown inFIG.2includes a function of measuring the temperature of the single battery group112. The temperature detection unit125measures one temperature of the single battery group112as a whole, and treats the representative temperature value of the single batteries111configuring the single battery group112as the temperature of the single battery group112. The temperature measured by the temperature detection unit125is used for various types of operations for detecting the state of the single batteries111, the single battery group112, or the assembled battery110. InFIG.2, based on the foregoing premise, one temperature detection unit125is provided to the single battery control unit121. While it is also possible to provide the temperature detection unit125to each single battery111and measure the temperature for each single battery111and execute various types of operations based on the temperature of each single battery111, in the foregoing case, since the number of temperature detection units125will increase, the configuration of the single battery control unit121will become complicated.

FIG.2shows the temperature detection unit125in a simplified manner. In effect, a temperature sensor is installed on the temperature measuring object, the installed temperature sensor outputs the temperature information as a voltage, the measurement result is sent to the signal input/output circuit124via the control circuit123, and the signal input/output circuit124outputs the measurement result outside the single battery control unit121. The function for realizing the series of processes is mounted on the single battery control unit121as the temperature detection unit125, and the voltage detection circuit122may also be used for measuring the temperature information (voltage).

FIG.3is a diagram showing the functional configuration of the SOC operation system155in the assembled battery control unit150. The assembled battery control unit150is the part that determines the state of each single battery111in the assembled battery110and the power that can be input to and output from each single battery111based on the current value and the voltage value of each single battery111detected while the vehicle is moving, and includes the SOC operation system155shown inFIG.3as one functional constituent element thereof. The SOC operation system155is the part that assumes the function corresponding to the battery control device according to an embodiment of the present invention, and has the function of operating the state of charge (SOC) of each single battery111. Note that, while the assembled battery control unit150is also equipped with various functions required for controlling the assembled battery10in addition to the SOC operation system155, such as the function of operating the state of health (SOH) of each single battery111and the function of the determining the input/output power of each single battery111, since these functions are well known and not directly related to the present invention, the detailed explanation thereof is omitted.

The SOC operation system155includes, as its functions, the respective functional blocks of an OCV operation unit153, a capacity calculation unit154, an SOC-OCV correction unit151, and an SOC operation unit152. The SOC operation system155operates, based on these functional blocks, the SOC of each single battery111based on the current of the assembled battery110, or the current of each single battery111, detected by the current detection unit130, and the voltage and the temperature of each single battery111detected by the single battery management unit120. Specifically, the SOC operation system155foremost obtains, based on the OCV operation unit153, the open circuit voltage (OCV) of each single battery111based on the current, the close circuit voltage (CCV), the temperature and the state of health (SOH) of each single battery111. Note that the SOH of each single battery111can be obtained, for example, with the SOH operation unit (not shown) in the assembled battery control unit150. Next, the SOC-OCV correction unit151corrects the predetermined characteristic representing the relationship of the SOC and the OCV (SOC-OCV characteristic) of each single battery111based on the OCV of each single battery111obtained by the OCV operation unit153. Finally, the SOC operation unit152calculates the SOC of each single battery111using the SOC-OCV characteristic corrected by the SOC-OCV correction unit151. The value of the thus calculated SOC of each single battery111is output as the SOCcontrolfrom the SOC operation system155and used in the various types of control of the assembled battery110.

Note that, while a case of the SOC operation system155calculating the SOC of each single battery111was explained above, the SOC of a plurality of single batteries111may also be calculated collectively. For example, the SOC may be calculated for each of the single battery groups112a,112bor the SOC may be calculated for the assembled battery110as a whole. Even in the foregoing cases, the SOC can be calculated based on the same processing as the single batteries111. Moreover, the SOC of each single battery111can be calculated based on the same processing. Accordingly, in the following explanation, the operation of the SOC operation system155will be explained by referring to the calculation target of the SOC simply as a “battery”.

The OCV operation unit153uses the CCV, the current I, the temperature T, and the SOH of the battery as the inputs, and outputs the OCV and the polarization voltage (overvoltage) Vpof the battery based on these inputs. Specifically, the OCV operation unit153operates the OCV using Formula (1) below according to an equivalent circuit model of the battery. Note that the polarization voltage Vpis operated as the voltage value of each equivalent circuit component when multiplying the equivalent circuit model of the battery by the current I, and is generally configured from a plurality of elements such as a direct current resistance component and a polarization component. Here, the value of each element of the equivalent circuit model of the battery is generally dependent on the temperature T and the SOH of the battery. Moreover, as the SOH of the battery, generally used is the SOHR which indicates the increase rate of the direct current resistance of the battery, or the SOHQ which indicates the decrease rate of the battery capacity. In this embodiment, while the explanation is provided by using the SOHR as the SOH, the same applies to cases where the SOHQ is used as the SOH.

The capacity calculation unit154uses the SOH as the input, and outputs the battery capacity Qmax. In this embodiment, for example, based on the known empirical rule that the battery capacity takes on an inverse relationship of the SOH, the battery capacity Qmaxcorresponding to the input SOH is acquired by the capacity calculation unit154.

The SOC-OCV correction unit151corrects the pre-stored SOC-OCV characteristic based on the current I and the SOH input to the SOC operation system155, the OCV and the polarization voltage Vpcalculated by the OCV operation unit153, and the battery capacity Qmaxcalculated by the capacity calculation unit154. The SOC-OCV correction unit151subsequently outputs the corrected SOC-OCV characteristic as the SOC-OCVtemp, which is the SOC-OCV characteristic to be temporarily used in the SOC operation unit152.

The SOC operation unit152calculates the SOC corresponding to the OCV calculated by the OCV operation unit153using the SOC-OCVtempcalculated by the SOC-OCV correction unit151. The SOC operation unit152subsequently outputs the SOCcontrolto be used for controlling the battery based on the value of the calculated SOC.

The SOC-OCV correction unit151is now explained in detail. The SOC-OCV correction unit151can be realized based on various embodiments as explained below.

First Embodiment

FIG.4is a diagram showing the functional configuration of the SOC-OCV correction unit151according to the first embodiment of the present invention. The SOC-OCV correction unit151in this embodiment includes a pattern calling unit510, a correction limit width designation unit520, and a direct detection correction unit530.

The pattern calling unit510determines the degradation pattern of the battery based on the use history information of the battery, and calls the SOC-OCV characteristic corresponding to that degradation pattern among a plurality of SOC-OCV characteristics stored in advance. The pattern calling unit510subsequently outputs the information of the called SOC-OCV characteristic as the SOC-OCVpattern. The use history information of a battery is information representing the previous use history (operating history) of the battery in the battery system100, and is used as the index for indicating the state of health (SOH) of the battery. In this embodiment, the SOH is used as the use history information of the battery.

The correction limit width designation unit520designates the correction limit width for prescribing the tolerance level of the correction to be performed by the direct detection correction unit530to the SOC-OCVpattern.FIG.5is a diagram showing an example of the correction limit width designated by the correction limit width designation unit520according to the first embodiment of the present invention. In this embodiment, for example, as shown in the left diagram ofFIG.5, the correction limit width designation unit520designates a certain OCV width for each SOC of the SOC-OCVpatternas the correction limit width. This OCV width is set, for example, according to the tolerance of the OCV based on the production tolerance of the battery. In other words, when a change in the OCV that is greater than the production tolerance occurs in the battery, the correction limit width designation unit520designates the correction limit width so that the direct detection correction unit530can exclude such change as an operational error. Otherwise, for example, as shown in the right diagram ofFIG.5, the correction limit width designation unit520may also designate a certain SOC width for each OCV of the SOC-OCVpatternas the correction limit width. In the foregoing case, the range of correction to be performed by the direct detection correction unit530to the SOC-OCVpatternis limited to be within the range of the SOC width designated based on the correction limit width.

The direct detection correction unit530corrects the SOC-OCVpatternoutput from the pattern calling unit510based on the current I and the OCV according to the correction limit width designated by the correction limit width designation unit520. The direct detection correction unit530subsequently outputs the correction result as the SOC-OCVtempexplained above.

FIG.6is a diagram showing the functional configuration of the pattern calling unit510according to the first embodiment of the present invention. The pattern calling unit510includes a pattern determination unit511, and an SOC-OCV library512.

The SOC-OCV library512has a database of the SOC-OCV characteristics corresponding to various types of SOH.FIG.7is a diagram showing an example of the SOC-OCV characteristics of the SOC-OCV library512according to the first embodiment of the present invention.FIG.7shows that, in each case where the value of the SOH is 100%, 120%, 140%, . . . , respectively different SOC-OCV characteristics are stored in the SOC-OCV library512. Here, the SOC-OCV library512can be realized, for example, by conducting a degradation test of each single battery111and acquiring in advance the relationship of the SOC and the OCV when the degradation of each single battery111advances and the value of the SOH changes, and compiling a database of the relationship.

The pattern determination unit511performs pattern determination to the input SOH, and calls the SOC-OCV characteristic corresponding to that pattern determination result by searching the SOC-OCV library512. The pattern determination unit511subsequently generates the SOC-OCVpatternfrom the called SOC-OCV characteristic and outputs the generated SOC-OCVpattern. Here, it is also possible to call the SOC-OCV characteristic of the SOH condition that is closest to the input SOH, and directly output the called SOC-OCV characteristic as the SOC-OCVpattern. Otherwise, it is also possible to identify two mutually adjacent SOH values (SOH1, SOH2) that become SOH1<SOH<SOH2in relation to the input SOH, call the SOC-OCV characteristics respectively corresponding to such SOH values from the SOC-OCV library512and operate the SOC-OCV characteristic based on interpolation, and output the obtained SOC-OCV characteristic as the SOC-OCVpattern. The SOC-OCVpatternoutput from the pattern determination unit511is stored, for example, in a memory not shown, and read by the direct detection correction unit530.

FIG.8is a diagram showing the functional configuration of the direct detection correction unit530according to the first embodiment of the present invention. The direct detection correction unit530includes a corrected OCV pair/integrated current acquisition unit531, an SOC-OCV direct detection correction unit532, and an SOC-OCV overwrite determination unit533.

The corrected OCV pair/integrated current acquisition unit531uses the current I, the OCV, the battery capacity Qmaxand the polarization voltage Vpthat respectively change with time according to the battery state as the inputs, and outputs a difference ΔSOC of the SOC based on direct detection and a pair (OCV1, OCV2) of the OCV based on these inputs. Specifically, the corrected OCV pair/integrated current acquisition unit531acquires the OCV pair (OCV1, OCV2) by acquiring two points of an OCV value which is stable within a range of a predetermined duration. The corrected OCV pair/integrated current acquisition unit531subsequently uses Formula (2) below to calculate a difference ΔSOC of the SOC based on direct detection by obtaining a current integrated value in a period from the acquisition of the OCV1to the acquisition of the OCV2and dividing the obtained current integrated value by the battery capacity Qmax. Note that, in Formula (1), t(OCV1) and t(OCV2) represent the time that the OCV1was acquired and the time that the OCV2was acquired, respectively.

FIG.9is a diagram explaining the acquisition method of a stable OCV pair (OCV1, OCV2). The corrected OCV pair/integrated current acquisition unit531determines that the OCV value is stable, for example, as shown inFIG.9, when the absolute value of the current I is smaller than a predetermined current threshold, and the absolute value of the polarization voltage Vpis smaller than a predetermined polarization voltage threshold. When the period between two points of time t(OCV1) and t(OCV2) which satisfy these stable conditions is equal to or greater than a predetermined time threshold t1 and equal to or less than a predetermined time threshold t2 (t1<t2), the two OCV values at time t(OCV1) and time t(OCV2) are acquired as the OCV1and the OCV2. Note that three or more OCV values that satisfy these conditions may also be acquired as a combination of stable OCVs.

The SOC-OCV direct detection correction unit532corrects the SOC-OCVpatternbased on the OCV pair (OCV1, OCV2) detected by the corrected OCV pair/integrated current acquisition unit531and the ΔSOC calculated based thereon, and outputs the correction result as the SOC-OCVpattern, fixed. Specifically, in this embodiment, the SOC-OCV direct detection correction unit532uses at least one point on the SOC-OCV characteristic indicated by the input SOC-OCVpatternas the origin (reference point), and, each time that it acquires the ΔSOC and the OCV1, OCV2from the corrected OCV pair/integrated current acquisition unit531, the SOC-OCV direct detection correction unit532corrects the SOC-OCVpatternbased thereon and creates the SOC-OCVpattern, fixed.

For example, when the point (OCV1, SOC1) corresponding to the OCV1in the SOC-OCV characteristic indicated by the SOC-OCVpatternis used as the reference point, the value of the SOC in the directly detected OCV2can be obtained based on Formula (3) below.

Similarly, the SOC-OCVpattern, fixed can also be created by correcting the SOC-OCV characteristic indicated by the SOC-OCVpatternone point at a time using a plurality of combinations of the OCV and the SOC respectively obtained based on direct detection. Specifically, when the SOC-OCV characteristic indicated by the SOC-OCVpatternis divided into k-number of SOC-OCV characteristics on the SOC axis and the n-th acquisition point is located at the k-th point, the SOC-OCVpattern, fixed can be obtained by correcting the SOC-OCV characteristic using the recurrence formula shown in Formula (4) below. In Formula (4), k represents the fineness of the interval for expressing the SOC-OCV characteristic as a sequence, and the SOC-OCV characteristic will be smoother as the k is greater. Moreover, the OCVk, 0and the SOCk, 0respectively represent the OCV value and the SOC value at the reference point set on the SOC-OCV characteristic indicated by the SOC-OCVpattern. Moreover, no represents the weight when the SOC-OCVpatterntakes on an initial value, and is a value that is equal to or greater than 0. When n0=0, the SOC-OCVpattern, fixed is created by using the SOC-OCVpatternonly at the origin. In this embodiment, as a result of creating the SOC-OCVpattern, fixed by using this kind of recurrence formula, it is possible to reduce the memory for storing the point (OCV, SOC) obtained based on direct detection.

Note that the SOC-OCV direct detection correction unit532may also create the SOC-OCVpattern, fixedbased on the SOC-OCV characteristic expressed as the sum average of a plurality of points obtained based on direct detection rather than using the recurrence formula of Formula (4) above. Specifically, for example, the SOC-OCVpattern, fixed can be obtained by correcting the SOC-OCV characteristic indicated by the SOC-OCVpatternusing Formula (5) below. In the foregoing case, while the number of calculations performed is less in comparison to the case of using Formula (4), the data volume of the point (OCV, SOC) to be stored in the memory will increase. It would be preferable to use this calculation method when it is desirable to concentrate the calculation load in a single time step.

The SOC-OCV direct detection correction unit532outputs the SOC-OCVpattern, fixed obtained by correcting the SOC-OCVpatternin the manner described above, and additionally outputs a sequence Ncountrepresenting the correction count at each point k on the SOC-OCV characteristic.

The SOC-OCV overwrite determination unit533determines the timing of overwriting the SOC-OCVtemp(overwrite timing of the SOC-OCV characteristic) based on the SOC-OCVpattern, fixed by using the correction limit width input from the correction limit width designation unit520. The SOC-OCV overwrite determination unit533determines the overwrite timing of the SOC-OCV characteristic, for example, in the following manner based on the sequence Ncountoutput from the SOC-OCV direct detection correction unit532.

FIG.10is a diagram explaining the overwrite timing of the SOC-OCV characteristic. Foremost, as shown inFIG.10, the SOC-OCV overwrite determination unit533determines whether the sequence Ncountis equal to or greater than a predetermined threshold sequence Nthat all points k. Note that, inFIG.10, Ncount(k) represents the value of the sequence Ncountat each point k, and Nth(k) represents the value of the threshold sequence Nthat each point k. Consequently, the SOC-OCV overwrite determination unit533continues to correct the SOC-OCVpatternwithout overwriting the SOC-OCVtempwhen the sequence Ncountis less than the threshold sequence Nthin at least one point k, and determines whether the SOC-OCVpattern, fixedis within the correction limit width when the sequence Ncountbecomes equal to or greater than the threshold sequence Nthat all points k. Here, the value of the threshold sequence Nthcan be set according to the frequency that the SOC and the OCV are acquired while the vehicle is actually moving, or the likelihood of the individual variation of the battery. Consequently, when the SOC-OCVpattern, fixedis within the correction limit width, the SOC-OCV overwrite determination unit533determines that it is the overwrite timing of the SOC-OCV characteristic, overwrites the SOC-OCVtempwith the SOC-OCVpattern, fixed, and outputs the result. Meanwhile, when the SOC-OCVpattern, fixedis exceeding the correction limit width, the SOC-OCV overwrite determination unit533resets the previously stored SOC-OCVpattern, fixed, and re-performs the operation.

FIG.11is a diagram explaining the method of determining whether the SOC-OCVpattern, fixed, which is the corrected SOC-OCV characteristic, is within the correction limit width based on the SOC-OCV overwrite determination unit533. When obtaining the SOC-OCVpattern, fixedby correcting the SOC-OCVpattern, each point may move in both the SOC axis direction and the OCV axis direction. Thus, as shown inFIG.11, when a point701on the SOC-OCVpattern, fixedis located between two points702,703on the SOC-OCVpattern, a perpendicular line is drawn downward from the point701relative to the line segment that connects these two points, and an intersection point704of the perpendicular line and the line segment is obtained. In other words, when the values of the SOC and the OCV at the point701are expressed as (SOCfixed, i, OCVfixed, i), the values of the SOC and the OCV at the point702are expressed as (SOCpattern, i, OCVpattern, i), and the values of the SOC and the OCV at the point703are expressed as (SOCpattern, i+1, OCVpattern, i+1), the values of the SOC and the OCV on the intersection point704can be expressed as (SOCfixed, i, OCV′pattern, i). Here, the value of the OCV′pattern, iexists between the OCVpattern, iand the OCVpattern, i+1, and can be decided according to the ratio of the difference between the SOCfixed, iand the SOCpattern, iand the difference between the SOCfixed, iand the SOCpattern, i+1.

Once the values of the SOC and the OCV on the intersection point704have been acquired in the manner described above, the squared difference of the OCV at the point701and the intersection point704is evaluated by being compared with the correction limit width based on Evaluation Formula (6) below. Consequently, it is determined that the point701is within the correction limit width when Evaluation Formula (6) is satisfied, and it is determined that the point701is exceeding the correction limit width when Evaluation Formula (6) is not satisfied. As a result of performing the foregoing evaluation to all points k on the SOC-OCVpattern, fixed, it is possible to determine whether the SOC-OCVpattern, fixedis within the correction limit width.

: correction limit width

Note that the determination method explained above is an example of a determination method in a case where, as shown in the left diagram ofFIG.5explained above, a certain OCV width for each SOC of the SOC-OCVpatternhas been designated as the correction limit width. When a certain SOC width for each OCV of the SOC-OCVpatternhas been designated as the correction limit width as shown in the right diagram ofFIG.5, it is possible to determine whether the SOC-OCVpattern, fixedis within the correction limit width based on a similar method by switching the SOC and the OCV in the foregoing determination method.

The overall operation of the SOC-OCV correction unit151is now explained with reference to the flowchart ofFIG.12.FIG.12is a flowchart showing the processing flow of the SOC-OCV correction unit151according to the first embodiment of the present invention. As the previous step of the processing flow ofFIG.12, let it be assumed that the SOC-OCV correction unit151has acquired the SOC-OCV characteristic for each state of health corresponding to the operating history of the battery (SOH in this embodiment) from the results of the degradation test of the battery conducted in advance, and such acquired SOC-OCV characteristics are stored in the SOC-OCV library512.

In initial START step601ofFIG.12, the processing of step602onward is performed by causing the SOC-OCV correction unit151to start a predetermined SOC-OCV characteristic correction logic.

In battery system ON determination step602, whether the key of the vehicle has been turned ON and the battery system100has been consequently turned ON is determined. Step602is repeated when the battery system100is OFF, and the processing is advanced to subsequent step603when it is confirmed that the battery system100has been turned ON.

In battery history reading step603, the use history information of the battery is read. Here, the values of the SOCcontrol, the SOC-OCVtemp, the SOH and the like at the time that the previous processing was ended are read from the storage unit180as the use history information of the battery, and read into the memory.

In degradation pattern determination step604, the degradation pattern is determined from the battery history read in step603. Here, the pattern determination unit511of the pattern calling unit510determines the degradation pattern according to the SOH read in step603based on the method described above.

In pattern SOC-OCV reading step605, the SOC-OCV characteristic corresponding to the degradation pattern obtained in step604is read. Here, the SOC-OCV characteristic corresponding to the degradation pattern determined in step604is called among the various SOC-OCV characteristics stored in the SOC-OCV library512of the pattern calling unit510, and stored in the memory as the SOC-OCVpattern.

In direct detection correction limit width decision step606, the correction limit width designation unit520decides the correction limit width for the SOC-OCVpatternread from the SOC-OCV library512in step605.

In direct detection correction step607, the direct detection correction unit530corrects the SOC-OCVpatternbased on direct detection by using the respective state measurement values of the battery capacity Qmax, the current I, the OCV, and the polarization voltage Vpobtained from the battery system100, and the SOC-OCVpatternread from the SOC-OCV library512in step605. Here, foremost, the corrected OCV pair/integrated current acquisition unit531of the direct detection correction unit530acquires a stable OCV pair (OCV1, OCV2) as described above based on the respective state measurement values of the battery, and obtains the difference ΔSOC of the SOC therebetween. Subsequently, based on these values, the SOC-OCV direct detection correction unit532calculates the SOC-OCVpattern, fixed, which is the SOC-OCV characteristic obtained by correcting the SOC-OCVpattern, and the sequence Ncountrepresenting the correction count at each point based on the method described above.

In direct detection correction count determination step608, the acquisition count of the SOC and the OCV based on direct detection; that is, whether the correction count of the SOC-OCV characteristic based thereon is equal to or greater than a predetermined threshold is determined. Here, the SOC-OCV overwrite determination unit533of the direct detection correction unit530determines whether the sequence Ncountof the correction count calculated in step607is equal to or greater than a predetermined threshold sequence Nthat all points. If the Ncountis consequently less than the Nthin at least one point, the processing is returned to step607and the correction of the SOC-OCVpatternbased on direct detection is continued. Meanwhile, the processing is advanced to step609when the Ncountis equal to or greater than the Nthat all points.

In correction limit width determination step609, whether the SOC-OCVpattern, fixedobtained as the corrected SOC-OCV characteristic in step607is within the range of the correction limit width decided in step606is determined. Here, the SOC-OCV overwrite determination unit533determines whether the SOC-OCVpattern, fixedis within the correction limit width based on the method described above. The processing is advanced to calculation reset step610when the SOC-OCVpattern, fixedis outside the correction limit width, the previously obtained values of the SOC-OCVpattern, fixedand the Ncountare reset in step610, and the operation is thereafter re-performed from step607. Meanwhile, the processing is advanced to step611when the SOC-OCVpattern, fixedis within the correction limit width.

In SOC-OCV characteristic overwrite step611, the SOC-OCV overwrite determination unit533overwrites the SOC-OCVtempto be used for the operation of the SOCcontrolwith the SOC-OCVpattern, fixedobtained in step607, and outputs the result.

In SOC-OCV characteristic storage step612, the SOC-OCVtempoverwritten in step611is stored in the storage unit180.

In key OFF determination step613, whether the key OFF operation of the vehicle has been performed is determined. When the key OFF operation has not been performed and the key of the vehicle is still ON, this step is repeated. When the key OFF operation is detected, the processing is advanced to subsequent step614.

In battery history storage step614, the values of the SOCcontrol, the SOC-OCVtemp, the SOH and the like when the key OFF operation was performed are stored in the storage unit180as the use history information of the battery.

In battery system OFF step615, the power source of the battery system100is turned OFF.

In final END step616, the operation ofFIG.12is ended, and the operation of the SOC-OCV correction unit151is stopped.

Note that, in this embodiment, the correction of the SOC-OCV characteristic performed by the SOC-OCV correction unit151may be performed to one SOC-OCV characteristic representing the overall assembled battery110as described above, or may be performed individually to all single batteries111in the assembled battery110. With the assembled battery110, generally speaking, since the internal temperature distribution is not uniform and the temperature of the center part becomes highest, differences in the progress of degradation will occur for each single battery111. Accordingly, by correcting the SOC-OCV characteristic for each single battery111, it is possible to obtain an accurate SOC-OCV characteristic according to the temperature distribution.

The effect of the present invention is now explained with reference toFIG.13andFIG.14.

FIG.13is a diagram explaining the divergence inhibiting effect of the SOC-OCV characteristics according to the present invention. InFIG.13, a conceptual diagram801on the left side shows a case where the SOC-OCVpattern, fixedis within the range of the correction limit width. In this conceptual diagram801, the SOC-OCVpatternbefore correction is shown with a curved line803, and the correction limit width designated for this SOC-OCVpatternis shown with two broken lines804. Moreover, each point on the SOC-OCVpattern, fixedis shown with each point as represented by a point805. In the foregoing case, since all points on the SOC-OCVpattern, fixedexist within the range of the correction limit width shown with the broken lines804, in correction limit width determination step609of the processing flow ofFIG.12, it is determined that the SOC-OCVpattern, fixedis within the correction limit width. Consequently, the processing is advanced to SOC-OCV characteristic overwrite step611, and the SOC-OCVtempis overwritten with the SOC-OCVpattern, fixedin this step. It is thereby possible to perform battery control based on a SOC-OCV characteristic that is close to the true value which reflects the individual variation and the degradation variation of the battery.

Meanwhile, when a measurement data error is included in the values of the OCV and the SOC obtained based on direct detection, a part or all of the SOC-OCVpattern, fixedmay fall outside the range of the correction limit width. InFIG.13, a conceptual diagram802on the right side shows a case where the SOC-OCVpattern, fixedis outside the correction limit width. In this conceptual diagram802, similar to the conceptual diagram801on the left side, the SOC-OCVpatternbefore correction is shown with a curved line803, and the correction limit width designated for this SOC-OCVpatternis shown with two broken lines804. Moreover, each point on the SOC-OCVpattern, fixedis shown with each point as represented by a point806. In the foregoing case, since certain points on the SOC-OCVpattern, fixedexist outside the range of the correction limit width shown with the broken lines804, in correction limit width determination step609of the processing flow ofFIG.12, it is determined that the SOC-OCVpattern, fixedis outside the correction limit width. Consequently, the processing is not advanced to SOC-OCV characteristic overwrite step611, and the value of the SOC-OCVpattern, fixedis reset in calculation reset step610.

In cases where the SOC-OCV characteristic is corrected by overwriting the SOC-OCVtempwith the SOC-OCVpattern, fixedcontaining an error, when the error of the SOC obtained based on direct detection relative to the actual SOC of the battery is great, there is a possibility that such error may contrarily expand. Nevertheless, as shown in the conceptual diagram802, the present invention compares the corrected SOC-OCV characteristic with the correction limit width, and does not reflect the correction result in the calculation of the SOC when the corrected SOC-OCV characteristic is outside the range of the correction limit width. Accordingly, it is possible to suppress the divergence of the SOC-OCV characteristic.

FIG.14is a diagram explaining the improvement of the SOC operational precision according to the present invention. The assembled battery control unit150calculates the OCV of the battery in a predetermined operation period from the respective state values of the current, the voltage, the temperature, the SOH and the like according to the state of the battery, and the SOCcontrolis output using the SOC-OCVtemp. Here, as shown inFIG.14, let it be assumed that the true value of the SOC-OCV characteristic has changed from the initial SOC-OCV characteristic shown with the dashed-dotted line to that of the solid line in the diagram due to the degradation or individual variation of the battery. When the value of the OCV acquired here is expressed as OCV(t), the SOC operational error in cases where the SOC-OCV characteristic is not corrected and the initial SOC-OCV characteristic is directly used as the SOC-OCVtempwill be the value of the range shown with reference numeral1401in the diagram. In other words, in the foregoing case, the degradation and variation of the SOC-OCV characteristic are not dealt with, and a gross error will occur in the operation result of the SOC.

Moreover, the SOC operational error in cases where the SOC-OCVpatternread according to the SOH among the SOC-OCV characteristics stored in advance in the SOC-OCV library512is used as the SOC-OCVtempwill be the value of the range shown with reference numeral1402in the diagram. In other words, in the foregoing case, while the operational error of the SOC will be smaller in comparison to the case of directly using the initial SOC-OCV characteristic as a result of using the SOC-OCV characteristic which gives consideration to the degradation of the battery, the error resulting from the prediction error of the individual variation and degradation pattern of the battery will remain.

Meanwhile, as explained in this embodiment, the SOC operational error in cases where the SOC-OCVpattern, fixed, which was obtained by correcting the SOC-OCVpatternbased on the values of the SOC and the OCV obtained based on direct detection, is used as the SOC-OCVtempwill be the value of the range shown with reference numeral1403in the diagram. In other words, in the foregoing case, since the error resulting from the prediction error of the individual variation and degradation pattern of the battery is corrected, the value of the SOC operational error can be further reduced in comparison to the case of directly using the read SOC-OCVpatternas the SOC-OCVtemp.

Note that, when correcting the SOC-OCVpatternbased on direct detection, a point to become the origin (reference point) of the ΔSOC is required as described above, and in this embodiment a point on the SOC-OCVpatternis used as the origin. Thus, it is possible to reduce the offset error in the corrected SOC-OCV characteristic in comparison to the case of obtaining the origin from the initial SOC-OCV characteristic.

According to the first embodiment of the present invention explained above, the pattern of the SOC-OCV characteristic according to the state of health of the battery is called, the corresponding correction limit width is prescribed, and the SOC-OCV characteristic is corrected from the actual measurement data of the battery. It is thereby possible to resolve the conventional problem of not being able to deal with the pattern calling of the SOC-OCV characteristic according to the state of health in the following manner.

First, the present invention can deal with errors caused by the individual variation and degradation prediction of the battery. The degradation prediction of a secondary battery is generally obtained by subjecting a certain charge/discharge pattern to cycle testing in a thermostatic bath. Nevertheless, it is known that the SOC-OCV characteristics of secondary batteries differ due to variations during the manufacture thereof, and it is not possible to deal with this problem based on conventional pattern calling. Moreover, since the actual use history (temperature, SOC, current and the like) of the battery will never coincide with the conditions of the cycle testing, an error will invariably occur in the degradation prediction of the battery. Meanwhile, the present invention can obtain a SOC-OCV characteristic that coincides with the actual characteristic of the secondary battery by combining direct detection with pattern calling.

Second, the present invention can determine the divergence of the SOC-OCV characteristic by using the pattern calling and correction limit width based on the operating history that is not influenced by direct detection or indirect detection. Thus, it is possible to correct the SOC-OCV characteristic only based on the signals of the battery system while the vehicle is being driven without having to use a power source or sensors outside the vehicle.

According to the first embodiment of the present invention explained above, the following operation and effect are yielded.

(1) An SOC operation system155functions as a battery control device which obtains a state of charge (SOC) of a single battery111, which is a secondary battery, and an assembled battery110based on a SOC-OCV characteristic representing a relationship of the SOC and a voltage of these batteries. An SOC-OCV correction unit151in the SOC operation system155comprises a pattern calling unit510which calls a first characteristic (SOC-OCVpattern) among a plurality of SOC-OCV characteristics stored in advance based on use history information of the battery, a correction limit width designation unit520which designates a correction limit width for prescribing a tolerance level of correcting the SOC-OCVpattern, and a direct detection correction unit530which creates a second characteristic (SOC-OCVtemp) in which the SOC-OCVpatternhas been corrected according to the correction limit width based on a current value I and a voltage value OCV of the battery. An operation unit152in the SOC operation system155obtains the SOC of the battery using the SOC-OCVtemp. As a result of adopting the foregoing configuration, the SOC can be operated with a high degree of accuracy even when the SOC-OCV characteristic changes due to the degradation or individual variation of a battery.

(2) The pattern calling unit510calls the SOC-OCVpatternby using the state of health (SOH) of the battery as the use history information of the battery. As a result of adopting the foregoing configuration, an appropriate SOC-OCVpatterncan be easily called according to the state of health of the battery.

(3) As shown inFIG.5, the correction limit width designation unit520designates, as the correction limit width, a certain OCV width for each SOC or a certain SOC width for each OCV. As a result of adopting the foregoing configuration, the correction limit width can be easily designated according to the production tolerance of the battery or the variation in the state of health.

(4) The SOC operation system155additionally comprises an OCV operation unit153which calculates an open voltage value OCV and a polarization voltage value Vpof the battery based on the current value I and the voltage value CCV of the battery. As explained inFIG.9, the direct detection correction unit530acquires, a plurality of times within a predetermined time range, an open voltage value OCV (OCV1, OCV2) of the battery when the current value I and the polarization voltage value Vpare respectively smaller than a predetermined threshold, obtains the SOC based on Formula (2) and Formula (3) described above by using each of the acquired open voltage values OCV1, OCV2, a current integrated value in an acquisition period of each of the open voltage values, and the SOC-OCVpattern, creates the SOC-OCVpattern, fixedbased thereon, and thereby creates the SOC-OCVtemp. As a result of adopting the foregoing configuration, it is possible to correct the SOC-OCVpatternfrom the values of the OCV and the SOC acquired based on direct detection, and create an appropriate SOC-OCVtempaccording to the state of the battery.

(5) Based on the configuration shown inFIG.8, the direct detection correction unit530corrects the SOC-OCVpatternbased on the current value I and the voltage value OCV of the battery, and creates the SOC-OCVtempby limiting the SOC-OCVpattern, fixed, which represents the corrected SOC-OCVpattern, to be within a range of the correction limit width. As a result of adopting the foregoing configuration, it is possible to suppress the divergence of the correction result while appropriately correcting the SOC-OCVpatternaccording to the state of the battery.

Second Embodiment

The second embodiment of the present invention is now explained. The foregoing first embodiment explained an example where the correction limit width designation unit520designates a certain OCV width for all SOCs or designates a certain SOC width for all OCVs as the correction limit width. Meanwhile, the following second embodiment explains an example where an OCV width which is different for each SOC or an SOC width which is different for each OCV is designated as the correction limit width.

FIG.15is a diagram showing the functional configuration of the SOC-OCV correction unit151according to the second embodiment of the present invention. The SOC-OCV correction unit151in this embodiment is configured in the same manner as the first embodiment other than the point of comprising a correction limit width designation unit520ain substitute for the correction limit width designation unit520.

The correction limit width designation unit520adesignates the correction limit width for prescribing the tolerance level of the correction to be performed by the direct detection correction unit530to the SOC-OCVpattern.FIG.16is a diagram showing an example of the correction limit width designated by the correction limit width designation unit520aaccording to the second embodiment of the present invention. In this embodiment, the correction limit width designation unit520adesignates as the correction limit width, for example, as shown inFIG.16, an OCV width that differs for each value of the SOC for each SOC of the SOC-OCVpattern. This OCV width is set, for example, by acquiring in advance the SOC-OCV characteristics of a plurality of batteries in their brand new state and based on their state of health, and setting the OCV width in correspondence with the individual difference thereof. It is thereby possible to set a relatively large correction limit width in an SOC region where variation is likely to occur and appropriately correct the SOC-OCVpatternin correspondence with the actual variation, and set a relatively small correction limit width in an SOC region where the variation is small and more finely prevent the divergence of the correction result of the SOC-OCVpatterncaused by the various errors.

Note that, whileFIG.16shows an example of designating an OCV width that differs for each value of the SOC as the correction limit width, as shown in the right diagram ofFIG.5in the first embodiment, it is also possible to designate an SOC width that differs for each value of the OCV as the correction limit width upon designating the range of the SOC relative to each OCV of the SOC-OCVpatternas the correction limit width. Even in the foregoing case, it is also possible to appropriately correct the SOC-OCVpatternin correspondence with the actual variation, and more finely prevent the divergence of the correction result of the SOC-OCVpatterncaused by the various errors.

FIG.17is a diagram explaining the effect based on the second embodiment of the present invention in comparison to the effect of the first embodiment. Here, as shown in the left diagram ofFIG.17, considered is a case where the SOC-OCVpatternas shown with a solid line in the first embodiment and this embodiment is each called relative to the SOC-OCV true value shown with a double line, and the same SOC-OCVpattern, fixedis operated.

In the first embodiment, as shown in the center diagram ofFIG.17, the correction limit width is assigned based on a certain OCV width. Here, let it be assumed that the region having a high SOC shown with reference numeral1701is a region where the variation in the SOC-OCV characteristic caused by degradation or manufacturing errors is great. In this region1701, considered is a case where the points on the SOC-OCVpattern, fixedin the diagram have fallen outside the SOC-OCVpattern. In the foregoing case, since the correction limit width is assigned based on a fixed OCV width in the first embodiment, when the correction limit width is small, the points on the SOC-OCVpattern, fixedin the region1701will fall outside the range of the correction limit width, and the correction of the SOC-OCVpatternis not performed. Accordingly, it is not possible to overwrite the SOC-OCVtemp.

Meanwhile, in this embodiment, as shown in the right diagram ofFIG.17, the correction limit width is assigned based on an OCV width corresponding to the variation in the SOC-OCV characteristics of each SOC. Thus, as a result of the points on the SOC-OCVpattern, fixedin the region1701falling within the range of the correction limit width, it is possible to correct the SOC-OCVpatternand obtain the SOC-OCVtemp. Consequently, it is possible to obtain the SOC-OCV characteristic, which more accurately reflects the state of battery, as the overwritten SOC-OCVtemp, and the SOC can be operated accurately.

Moreover, let it be assumed that the region where the SOC is midrange as shown with reference numeral1702is a region where the variation in the SOC-OCV characteristics is small. Since the correction limit width is assigned based on a fixed OCV width in the first embodiment, in order for the correction of the SOC-OCVpatternto be performed in the region1701described above, the correction limit width also needs to be set broadly in this region1702. Accordingly, there is a possibility that the SOC-OCVpatternmay be corrected excessively.

Meanwhile, in this embodiment, as shown in the right diagram ofFIG.17, the correction limit width is assigned based on an OCV width corresponding to the variation in the SOC-OCV characteristics of each SOC. Thus, it is possible to set the correction limit width broadly in the region1701and set the correction limit width narrowly in the region1702, and the possibility of the SOC-OCVpatternbeing corrected excessively can be eliminated. In other words, when the relationship of the OCV and the SOC that deviates from the true value is acquired based on direct detection due to measurement errors or other reasons, it is possible to eliminate the possibility of the SOC-OCV characteristic being corrected based thereon. Consequently, it is possible to prevent an SOC-OCV characteristic containing a gross error from being used as the SOC-OCVtemp, and the SOC can be operated accurately.

In this embodiment, the two effects explained above are obtained and, consequently, the SOC-OCVtempcan be overwritten using the SOC-OCVpattern, fixedwhich is closer to the true value of the SOC-OCV in comparison to the first embodiment.

According to the second embodiment of the present invention explained above, the following operation and effect are yielded in addition to those explained in the first embodiment.

(6) As shown inFIG.16andFIG.17, the correction limit width designation unit520adesignates, as the correction limit width, an OCV width which differs for each predetermined SOC or an SOC width which differs for each predetermined OCV. As a result of adopting the foregoing configuration, since it is possible to designate the correction limit width in detail according to the actual production tolerance of the battery or the variation in the actual state of health of the battery, the SOC can be operated with a higher degree of accuracy.

Third Embodiment

The third embodiment of the present invention is now explained. The foregoing first and second embodiments explained an example where the correction limit width designation units520,520arespectively designate a certain correction limit width without depending on the state of health of the battery. Meanwhile, the following third embodiment explains an example where the correction limit width is changed according to the operating history of the battery.

FIG.18is a diagram showing the functional configuration of the SOC-OCV correction unit151according to the third embodiment of the present invention. The SOC-OCV correction unit151in this embodiment is configured in the same manner as the first embodiment other than the point of comprising a pattern calling unit510band a correction limit width designation unit520bin substitute for the pattern calling unit510and the correction limit width designation unit520, respectively, and the point of additionally comprising a correction limit width library521.

The pattern calling unit510boutputs the SOC-OCVpatternin the same manner as the pattern calling unit510in the first embodiment. In addition, the pattern calling unit510boutputs, as the pattern determination result, the determination result of the degradation pattern of the battery when the SOC-OCVpatternwas called from the SOC-OCV library512.

The correction limit width designation unit520binputs the foregoing pattern determination result, and calls and acquires the correction limit width corresponding to that degradation pattern among a plurality of correction limit widths stored in advance in the correction limit width library521based thereon. The correction limit width designation unit520bsubsequently designates the acquired correction limit width in the direct detection correction unit530.

The correction limit width library521has a database of the correction limit widths corresponding to various degradation patterns of the battery. For example, the correction limit width library521can be built by acquiring in advance the correction limit width according to the degradation pattern as a result of conducting a degradation test of different conditions to a plurality of batteries and obtaining the difference between the SOC-OCV characteristics of the batteries having the same SOH, and compiling a database of the relationship. In other words, the contents of the correction limit width library521can be decided by acquiring in advance the variation of the SOC, which can be acquired relative to the same OCV based on the actual degradation and individual variation of the battery, according to the state of health of the battery.

The correction limit width is decided as the error that is anticipated between the SOC-OCVpatternand the true SOC-OCV characteristic. This error occurs due to the determination error of the manufacturing variation and degradation pattern of the battery. Since the determination error of the degradation pattern will expand as the operating history of the battery becomes longer, in the first and second embodiments, the estimation error margin of the degradation pattern needs to be included in the correction limit width so that the correction limit width will properly function under both conditions where the operating history is short and where the operating history is long.

Meanwhile, the correction limit width decided by the correction limit width designation unit520bin this embodiment changes according to the operating history of the battery.FIG.19is a diagram showing an example of the correction limit width designated by the correction limit width designation unit520baccording to the third embodiment of the present invention. In this embodiment, as shown inFIG.19, in order to deal with the estimation error margin of the degradation pattern that expands according to the progress of the degradation of the battery, the correction limit width designated by the correction limit width designation unit520bis gradually expanded according to the operating history of the battery. Consequently, it is possible to reduce the correction limit width and suppress the divergence of the SOC-OCV characteristics in a state where the battery is basically brand new where the difference in the SOC-OCV characteristics among the batteries is small, and increase the correction limit width and perform control corresponding to the variation of each battery in a state of health where the difference in the SOC-OCV characteristics among the batteries is great.

FIG.20is a diagram explaining the effect based on the third embodiment of the present invention in comparison to the effect of the second embodiment. Here, as shown respectively in the upper left diagram and the lower left diagram ofFIG.20, considered is a case where the SOC-OCVpatternas shown with a solid line in the second embodiment and this embodiment is each called relative to the SOC-OCV true value shown with a double line, and the same SOC-OCVpattern, fixedis operated. Here, let it be assumed that the SOC-OCVpattern, fixed, due to some kind of error factor, has an OCV that is higher than the SOC-OCV true value in a region having a high SOC respectively shown with reference numeral2001in the upper and lower center diagram and right diagram ofFIG.20. Thus, in the region2001, it is necessary to set the correction limit width by increasing the estimation error margin of the degradation pattern.

In the second embodiment, the correction limit width is set by fixing the estimation error margin of the degradation pattern irrespective of the operating history of the battery. Thus, when the operating history of the battery is short, as shown in the upper center diagram ofFIG.20, the correction limit width is set relatively broadly in the region2001, and the points on the SOC-OCVpattern, fixedshown in the diagram fall within the range of the correction limit width. Consequently, the correction of the SOC-OCVpatternis performed and the SOC-OCVtempis overwritten.

Meanwhile, in this embodiment, when the operating history of the battery is short, the correction limit width is set by reducing the estimation error margin of the degradation pattern. Thus, in the foregoing case, as shown in the upper right diagram ofFIG.20, the correction limit width is set in the region2001to be narrower than the second embodiment, and the points on the SOC-OCVpattern, fixedshown in the diagram will fall outside the range of the correction limit width. Consequently, the correction of the SOC-OCVpatternis not performed, and the SOC-OCVtempis not overwritten. Accordingly, this embodiment is able to obtain a more accurate SOC.

Moreover, in the second embodiment, when the operating history of the battery is sufficiently long, as shown in the lower center diagram ofFIG.20, the correction limit width is set to be relatively narrow in the region2001, and the points on the SOC-OCVpattern, fixedshown in the diagram will fall outside the correction limit width. Consequently, the correction of the SOC-OCVpatternis not performed, and the SOC-OCV temp is not overwritten.

Meanwhile, in this embodiment, when the operating history of the battery is sufficiently long, the correction limit width is set by increasing the estimation error margin of the degradation pattern. Thus, in the foregoing case, as shown in the lower right diagram ofFIG.20, the correction limit width is set in the region2001to be broader than the second embodiment, and the points on the SOC-OCVpattern, fixedshown in the diagram will fall within the range of the correction limit width. Consequently, the correction of the SOC-OCVpatternis performed, and the SOC-OCVtempis overwritten. Accordingly, this embodiment is able to obtain a more accurate SOC.

According to the third embodiment of the present invention explained above, the following operation and effect are yielded in addition to those explained in the first and second embodiments.

(7) As shown inFIG.19andFIG.20, the correction limit width designation unit520bchanges the correction limit width according to the use history of the battery.

Specifically, the correction limit width designation unit520bchanges the correction limit width according to the use history of the battery by selecting one among a plurality of correction limit widths stored in advance in the correction limit width library521based on the SOC-OCVpattern. As a result of adopting the foregoing configuration, since it is possible to change the correction limit width according to changes in the determination error of the degradation pattern that occurs according to the operating history of the battery, the SOC can be operated with a higher degree of accuracy.

Fourth Embodiment

The fourth embodiment of the present invention is now explained. The foregoing first to third embodiments explained an example of the pattern calling unit510determining the degradation pattern of the battery by using the SOH as the use history information of the battery, calling the SOC-OCV characteristic corresponding to that degradation pattern, and outputting the SOC-OCVpattern. Meanwhile, the following fourth embodiment explains an example of determining the degradation pattern by using a plurality of pieces of information, and not only the SOH, as the use history information of the battery.

FIG.21is a diagram showing the functional configuration of the SOC-OCV correction unit151according to the fourth embodiment of the present invention. The SOC-OCV correction unit151in this embodiment is configured in the same manner as the first embodiment other than the point of comprising a pattern calling unit510cin substitute for the pattern calling unit510.

The pattern calling unit510cuses a plurality of pieces of information, such as the SOH, the current history, the temperature history and the SOC history, as the user history information of the battery as the inputs, determines the degradation pattern of the battery based on the foregoing information, and calls the SOC-OCV characteristic corresponding to that degradation pattern among a plurality of SOC-OCV characteristics stored in advance. The pattern calling unit510csubsequently outputs the information of the called SOC-OCV characteristic as the SOC-OCVpattern.

FIG.22is a diagram showing the configuration of the pattern calling unit510caccording to the fourth embodiment of the present invention. The pattern calling unit510cincludes a pattern determination unit511c, and an SOC-OCV library512c.

The pattern determination unit511cperforms pattern determination based on each piece of information that was input as the use history information of the battery; that is, based on the input SOH, current history, temperature history and SOC history, and calls the SOC-OCV characteristic corresponding to that pattern determination result by searching the SOC-OCV library512c. The pattern determination unit511csubsequently generates the SOC-OCVpatternfrom the called SOC-OCV characteristic and outputs the generated SOC-OCVpattern.

The SOC-OCV library512chas a database of the SOC-OCV characteristics for each combination of the values of each piece of information input to the pattern determination unit511c; that is, the values of the SOH, the current history, the temperature history and the SOC history. For example, the foregoing information is associated respectively with four axes, and the result of associating the SOC-OCV characteristics for each coordinate value expressed with the four axes is stored as the database of the SOC-OCV characteristics. In the foregoing case, the pattern determination unit511cacquires the SOC-OCV characteristic corresponding to the input use history information by identifying the coordinate value based on the pattern determination result and calling the SOC-OCV characteristic corresponding to the coordinate value by searching the SOC-OCV library512c.

FIG.23is a diagram showing an example of the SOC-OCV characteristics of the SOC-OCV library512caccording to the fourth embodiment of the present invention.FIG.23shows that, in each case where the value of the SOH is 100%, 120%, 140%, . . . , respectively different SOC-OCV characteristics are stored in the SOC-OCV library512cfor each combination of values of the current history, the temperature history and the SOC history. Here, the SOC-OCV library512ccan be realized, for example, by conducting a degradation test of each single battery111by respectively changing the four conditions of the SOH, the current, the temperature, and the SOC and acquiring in advance the relationship of the SOC and the OCV when the degradation of each single battery111advances, and compiling a database of the relationship.

Note that, in the foregoing explanation, while a case was explained where the pattern calling unit510ccalls the SOC-OCVpatterncorresponding to the state of health of the battery by using the SOH, the current history, the temperature history and the SOC history as the use history information of the battery, it is not necessary to use all of the foregoing information. In other words, the pattern calling unit510ccan call the SOC-OCVpatterncorresponding to the state of health of the battery by using at least one piece of use history information of the battery among the SOH, the current history, the temperature history and the SOC history. Note that the SOC-OCV library512cmay store the SOC-OCV characteristics for each combination of information that is input to the pattern calling unit510cas the use history information of the battery and used for the pattern determination in the pattern determination unit511c. Here, the pattern calling unit510explained in the first embodiment corresponds to the case of using only the SOH as the use history information of the battery. Moreover, information other than the SOH, the current history, the temperature history and the SOC history may also be used as the use history information of the battery.

FIG.24is a diagram explaining the effect based on the fourth embodiment of the present invention in comparison to the effect of the first embodiment. Here, considered is a case where, in the first embodiment and the fourth embodiment, a different SOC-OCVpatternhas been called as respectively shown in the center diagram and the right diagram ofFIG.24relative to the SOC-OCV true value shown with a double line in the left diagram ofFIG.24.

In this embodiment, since a plurality of pieces of information are used as the use history information of the battery, the operating history of the battery can be captured in detail. Thus, as evident fromFIG.24, a SOC-OCVpatternthat is closer to the SOC-OCV true value can be called in comparison to the first embodiment. Note that, since the SOC-OCVpattern, fixedis acquired from the SOC-OCVpatternwith at least one point as the origin, generally speaking, these will not coincide if the SOC-OCVpatternis different. Accordingly, as shown in the respective points of the center diagram and the right diagram ofFIG.24, the SOC-OCVpattern, fixedis different in the first embodiment and in this embodiment.

In this embodiment, as a result of using a plurality of pieces of information as the use history information of the battery, it is possible to conduct a more detailed prediction of the degradation pattern, and call an SOC-OCVpatternthat is closer to the true value. Thus, it is possible to set the correction limit width by reducing the estimation error margin of the degradation pattern, and cause the correction limit width to be narrow. Accordingly, even when an operational error occurs in which the points on the SOC-OCVpattern, fixedfall within the range of the correction limit width and the SOC-OCVtempis consequently overwritten in the first embodiment, this embodiment is able to prevent the overwriting of the SOC-OCVtemp. Consequently, this embodiment is able to obtain a more accurate SOC.

According to the fourth embodiment of the present invention explained above, the following operation and effect are yielded in addition to those explained in the first to third embodiments.

(8) As explained inFIG.23andFIG.24, the pattern calling unit510ccalls the SOC-OCVpatternby using at least one among the state of health (SOH), the current history, the temperature history and the state of charge (SOC) history of the battery as the use history information of the battery. As a result of adopting the foregoing configuration, since it is possible to call a more appropriate SOC-OCVpatternaccording to the state of health of the battery, the SOC can be operated with a higher degree of accuracy.

Fifth Embodiment

The fifth embodiment of the present invention is now explained. The foregoing first to fourth embodiments explained an example of the direct detection correction unit530determining whether the SOC-OCVpattern, fixed, which was obtained by correcting the SOC-OCVpatternbased on the OCV and the SOC obtained based on direct detection, is within the correction limit width, and overwriting the SOC-OCVtempwhen the SOC-OCVpattern, fixedis within the correction limit width. Meanwhile, the following fifth embodiment explains a case of determining whether to overwrite the SOC-OCVtempby giving further consideration to the difference in comparison to the SOC-OCVtempbeing used in the present control.

FIG.25is a diagram showing the functional configuration of the SOC-OCV correction unit151according to the fifth embodiment of the present invention. The SOC-OCV correction unit151in this embodiment is configured in the same manner as the first embodiment other than the point of comprising a correction limit width designation unit520dand a direct detection correction unit530din substitute for the correction limit width designation unit520and the direct detection correction unit530, respectively.

As with the correction limit width designation unit520in the first embodiment, the correction limit width designation unit520dcalls and acquires the correction limit width corresponding to the degradation pattern of the battery among a plurality of correction limit widths stored in advance. The correction limit width designation unit520dsubsequently outputs, to the direct detection correction unit530d, the acquired correction limit width as the correction limit width (pattern). In addition, the correction limit width designation unit520doutputs, as the correction limit width (previous value), the correction limit width when the SOC-OCVtempwas overwritten in the previous processing. This correction limit width (previous value) is used as an index for detecting, in the direct detection correction unit530d, the occurrence of a large fluctuation on a short-term basis due to a sensor error in the OCV and the SOC acquired based on direct detection or other reasons.

The direct detection correction unit530dcorrects the SOC-OCVpatternoutput from the pattern calling unit510according to the correction limit width (pattern) and the correction limit width (previous value) designated by the correction limit width designation unit520dbased on the current I and the OCV. The direct detection correction unit530dsubsequently outputs the correction result as the SOC-OCVtemp.

FIG.26is a diagram showing the functional configuration of the direct detection correction unit530daccording to the fifth embodiment of the present invention. The direct detection correction unit530dis configured in the same manner as the direct detection correction unit530explained in the first embodiment other than the point of comprising an SOC-OCV overwrite determination unit533din substitute for the SOC-OCV overwrite determination unit533.

The SOC-OCV overwrite determination unit533ddetermines the overwrite timing of the SOC-OCV characteristics by using the correction limit width (pattern) and the correction limit width (previous value) input from the correction limit width designation unit520d, the sequence Ncountrepresenting the correction count at the respective points input from the SOC-OCV direct detection correction unit532, and the SOC-OCVtemp, z-1as the value of the SOC-OCVtempin the previous processing. When it is determined that the overwrite timing has arrived, the SOC-OCV overwrite determination unit533doverwrites the SOC-OCVtempwith the SOC-OCVpattern, fixedand outputs the result.

The SOC-OCV overwrite determination unit533dis now explained in detail with reference to the flowchart shown inFIG.27.FIG.27is a flowchart showing the processing flow of the SOC-OCV correction unit151according to the fifth embodiment of the present invention.

In steps601to609, the same processing as the flowchart ofFIG.12explained in the first embodiment is performed. Here, in correction limit width determination step609, the SOC-OCV overwrite determination unit533dperforms the determination explained in the first embodiment by using the correction limit width (pattern) input from the correction limit width designation unit520d. Consequently, the processing is advanced to step619when it is determined that the SOC-OCVpattern, fixedis within the range of the correction limit width (pattern), and the processing is advanced to step610when it is determined that the SOC-OCVpattern, fixedis outside the range of the correction limit width (pattern).

In previous correction limit width determination step619, the SOC-OCV overwrite determination unit533ddetermines whether the SOC-OCVpattern, fixedis within the range of the correction limit width (previous value). Here, for example, upon substituting the OCV′pattern, iof Evaluation Formula (6) explained in the first embodiment with the OCV′temp, z-1, i, with regard to a point on the SOC-OCVpattern, fixedand the intersection point of the perpendicular line drawn downward from such point and the line segment connecting two points on the SOC-OCVtemp, z-1, the squared difference of the OCV of these points is evaluated by being compared with the correction limit width (previous value) based on Evaluation Formula (7) below. Note that the value of the OCV′temp, z-1, iin Evaluation Formula (7) represents the value of the OCV of the foregoing intersection point.

When it is determined in step619that the SOC-OCVpattern, fixedis outside the range of the correction limit width (previous value), the processing is advanced to calculation reset step610, the previously obtained values of the SOC-OCVpattern, fixedand the Ncountare reset in step610, and the operation is thereafter re-performed from step607. Meanwhile, the processing is advanced to subsequent step611when the SOC-OCVpattern, fixedis within the range of the correction limit width (previous value). In step611onward, the same processing as the flowchart ofFIG.12explained in the first embodiment is performed.

In this embodiment, by performing the foregoing processing in step619, whether the SOC-OCVpattern, fixedobtained based on direct detection has changed considerably from the SOC-OCVtemp, z-1; that is, the SOC-OCVtempobtained in the previous processing is determined. When the SOC-OCVpattern, fixedhas changed considerably, it is determined that the SOC-OCV characteristic has fluctuated due to reasons that are not based on the state of the battery that arose from a sensor error or the like, and the processing is returned to step607and the operation is re-performed without executing SOC-OCV characteristic overwrite step611. It is thereby possible to suppress the divergence of the operation result of the SOC even when the SOC-OCV characteristic changes suddenly in comparison to the first embodiment.

Note that, when the battery is not used for a long period, it is anticipated that the state of the battery will change considerably from the time that the previous processing was performed. Thus, when the elapsed time from the previous processing is longer than a predetermined threshold, the processing of step619may be omitted.

FIG.28is a diagram explaining the effect based on the fifth embodiment of the present invention. Here, considered is a case where the SOC-OCV characteristic shown with a broken line in the left diagram ofFIG.28has been obtained in the previous processing relative to the SOC-OCV true value shown with a double line, and is used as the SOC-OCVtemp, z-1. Moreover, considered is a case where, in a region having a high SOC shown with reference numeral2801in the left diagram ofFIG.28, a combination of the OCV and the SOC having a higher OCV than the SOC-OCVtemp, z-1has been detected as the SOC-OCVpattern, fixedas respectively shown with the respective points of the center diagram and right diagram ofFIG.28.

As shown in the center diagram ofFIG.28, when the points on the SOC-OCVpattern, fixedare within the range of the correction limit width (pattern), in the first to fourth embodiments, the correction of the SOC-OCVpatternis performed and the SOC-OCVtempis overwritten. Accordingly, if an OCV containing a gross error is detected in the foregoing region2801for some reason, the operational precision of the SOC in that region will deteriorate in comparison to the case of using the SOC-OCVtemp, z-1obtained in the previous processing.

Meanwhile, in this embodiment, since the processing of step619explained inFIG.27is additionally performed, whether the points on the SOC-OCVpattern, fixedare within the range of the correction limit width (previous value) for the SOC-OCVtemp, z-1is determined. Consequently, as shown in the right diagram ofFIG.28, when the points on the SOC-OCVpattern, fixedare outside the range of the correction limit width (previous value), the correction of the SOC-OCVpatternis not performed, and the SOC-OCVtempis not overwritten. Accordingly, this embodiment is able to improve the operational precision of the SOC.

According to the fifth embodiment of the present invention explained above, the following operation and effect are yielded in addition to those explained in the first to fourth embodiments.

(9) The correction limit width designation unit520ddesignates the correction limit width (previous value) for prescribing the tolerance level of the correction to the SOC-OCVtemp, z-1, which is the SOC-OCVtempcreated by the direct detection correction unit530din the past (previously). As explained inFIG.27andFIG.28, the direct detection correction unit530dcreates the SOC-OCVtempby using the correction limit width (pattern) designated by the correction limit width designation unit520dfor the present SOC-OCVpattern, and the correction limit width (previous value) designated by the correction limit width designation unit520dfor the past SOC-OCVtemp, z-1. As a result of adopting the foregoing configuration, since it is possible to suppress the divergence of the operation result of the SOC even when the SOC-OCV characteristic changes suddenly due to a sensor error or other reasons, the SOC can be operated with a higher degree of accuracy.

Sixth Embodiment

The sixth embodiment of the present invention is now explained. The foregoing first to fifth embodiments explained an example of resetting the calculation result and re-performing the operation when the SOC-OCVpattern, fixed, which was obtained from the OCV and the SOC obtained based on direct detection, is outside the range of the correction limit width. Meanwhile, the following sixth embodiment explains an example of determining that there was an error in the determination of the degradation pattern of the battery when the SOC-OCVpattern, fixedis converging outside the range of the correction limit width, and updating the operating history of the battery.

FIG.29is a diagram showing the functional configuration of the SOC-OCV correction unit151according to the sixth embodiment of the present invention. The SOC-OCV correction unit151in this embodiment is configured in the same manner as the first embodiment other than the point of comprising a direct detection correction unit530ein substitute for the direct detection correction unit530.

As with the direct detection correction unit530in the first embodiment, the direct detection correction unit530ecorrects the SOC-OCVpatternoutput from the pattern calling unit510according to the correction limit width designated by the correction limit width designation unit520dbased on the current I and the OCV. The direct detection correction unit530esubsequently outputs the correction result as the SOC-OCVtemp. In addition, the direct detection correction unit530edetermines whether the SOC-OCVpattern, fixeddetermined to be outside the range of the correction limit width satisfies a predetermined convergence condition, and updates the operating history of the battery upon determining that the SOC-OCVpattern, fixeddetermined to be outside the range of the correction limit width satisfies a convergence condition.

FIG.30is a diagram showing the functional configuration of the direct detection correction unit530eaccording to the sixth embodiment of the present invention. The direct detection correction unit530eis configured in the same manner as the direct detection correction unit530explained in the first embodiment other than the point of additionally comprising an SOC-OCV convergence determination unit534.

Input to the SOC-OCV convergence determination unit534are, among the SOC-OCVpattern, fixedoutput from the SOC-OCV direct detection correction unit532, those determined to be outside the range of the correction limit width by the SOC-OCV overwrite determination unit533. The SOC-OCV convergence determination unit534stores the input SOC-OCVpattern, fixeda plurality of times, and determines whether these satisfy a predetermined convergence condition. When it is consequently determined that the convergence condition is satisfied, the SOC-OCV convergence determination unit534updates the SOH as the use history information of the battery based on the stored SOC-OCVpattern, fixed, and outputs the updated SOH. Note that, as explained in the fourth embodiment, when information other than the SOH such as the current history, the temperature history, and the SOC history is to be used as the use history information of the battery, such information may also be updated.

FIG.31is a diagram showing the functional configuration of the SOC-OCV convergence determination unit534. The SOC-OCV convergence determination unit534includes an out-of-width count unit535and an operating history determination unit536.

The out-of-width count unit535stores, a predetermined number of times, the immediate SOC-OCVpattern, fixeddetermined to be outside the range of the correction limit width by the SOC-OCV overwrite determination unit533. The out-of-width count unit535subsequently counts the consecutive storage of the SOC-OCVpattern, fixed; that is, the consecutive count Nerrorin which the SOC-OCVpattern, fixedwas determined to be outside the range of the correction limit width, and, when this consecutive count Nerrorexceeds a predetermined threshold, the average and variance of previously stored multiple SOC-OCVpattern, fixedare calculated, and the respective calculation results thereof are output as the average SOC-OCVpattern, fixedand the variance SOC-OCVpattern, fixed.

With the average SOC-OCVpattern, fixedand the variance SOC-OCVpattern, fixedcalculated and output by the out-of-width count unit535as the inputs, the operating history determination unit536outputs the updated use history information (for example, SOH) of the battery based on the foregoing inputs. Specifically, the operating history determination unit536determines whether the variance SOC-OCVpattern, fixedis within a predetermined threshold and, when it is within the threshold, determines that the SOC-OCVpattern, fixedis converging outside the range of the correction limit width. The operating history determination unit536subsequently searches for the SOC-OCV characteristic that is most similar to the average SOC-OCVpattern, fixedfrom the SOC-OCV library512, and outputs the SOH corresponding to that SOC-OCV characteristic as the updated use history information. Here, the search of the SOC-OCV characteristic that is most similar to the average SOC-OCVpattern, fixedcan be performed, for example, based on the same method as Evaluation Formula (6) explained in the first embodiment. In other words, the SOC-OCV characteristic that is most similar to the average SOC-OCVpattern, fixedcan be obtained by searching the SOC-OCV library512for the SOC-OCV characteristic in which the square sum of the OCV differences at the respective SOC points becomes smallest relative to the average SOC-OCVpattern, fixed.

The SOC-OCV convergence determination unit534is now explained in detail with reference to the flowchart shown inFIG.32.FIG.32is a flowchart showing the processing flow of the SOC-OCV correction unit151according to the sixth embodiment of the present invention.

In steps601to609, the same processing as the flowchart ofFIG.12explained in the first embodiment is performed. The processing is advanced to step611when it is determined in correction limit width determination step609that the SOC-OCVpattern, fixedis within the range of the correction limit width, and the processing is advanced to step617when it is determined in correction limit width determination step609that the SOC-OCVpattern, fixedis outside the range of the correction limit width. Upon proceeding to step611, in step611onward, the same processing as the flowchart ofFIG.12explained in the first embodiment is performed.

In convergence determination step617, the out-of-width count unit535and the operating history determination unit536determine whether the SOC-OCVpattern, fixedhas converged outside the range of the correction limit width. Here, convergence determination step617is performed using the convergence condition described above. In other words, the out-of-width count unit535compares the consecutive count Nerror, which is the number of times that the SOC-OCVpattern, fixedWas consecutively determined as being outside the range of the correction limit width, with a predetermined threshold, and determines that the convergence condition has been satisfied when the consecutive count Nerrorexceeds the threshold. Moreover, the operating history determination unit536compares the variance SOC-OCVpattern, fixedcalculated by the out-of-width count unit535with a predetermined threshold, and determines that the convergence condition has been satisfied when the variance SOC-OCVpattern, fixedis within the threshold. Consequently, the processing is advanced to step618when the convergence condition is satisfied, and the processing is advanced to step610when the convergence condition is not satisfied. Upon advancing to step610, the previously obtained values of the SOC-OCVpattern, fixedand the Ncountare reset in step610, and the operation is thereafter re-performed from step607.

In operating history change step618, the operating history determination unit536changes the use history information representing the operating history of the battery. Here, as described above, the use history information is changed by searching for the SOC-OCV characteristic that is most similar to the average SOC-OCVpattern, fixedcalculated by the out-of-width count unit535and outputting the SOH corresponding to that SOC-OCV characteristic. Once the change of the use history information is completed in step618, the processing is returned to pattern SOC-OCV reading step605, the SOC-OCV characteristic searched in step618is stored in the memory as the SOC-OCVpattern, and the processing of step606onward is thereafter repeated.

In this embodiment, by performing the foregoing processing in step617and step618, whether the SOC-OCVpattern, fixedis converging outside the range of the correction limit width is determined. Consequently, when the SOC-OCVpattern, fixedis converging outside the range of the correction limit width, it is determined that there was an error in the determination of the degradation pattern of the battery, and the operating history of the battery is updated. It is thereby possible to correct the estimation error of the degradation pattern of the battery while suppressing the divergence of the operation result of the SOC in comparison to the first embodiment. Moreover, as a result of adopting this method, it is possible to detect an unexpected degradation of the battery based on the difference between the degradation pattern of the battery determined from the operating history and the operating history anticipated from the SOC-OCVpattern, fixed. Thus, it is possible to use this for determining the malfunction of a battery.

FIG.33is a diagram explaining the effect based on the sixth embodiment of the present invention. Here, considered is a case where, in a region having a high SOC shown with reference numeral3301in the left diagram ofFIG.33, a combination of the OCV and the SOC outside the range of the correction limit width has been detected as the SOC-OCVpattern, fixedrelative to the SOC-OCV true value shown with a double line.

As shown in the center diagram ofFIG.33, when the points on the SOC-OCVpattern, fixedare outside the range of the correction limit width, in the first to fifth embodiments, the correction of the SOC-OCVpatternis not performed, and the SOC-OCVtempis not overwritten. Here, when the difference between the SOC-OCVpatternand the SOC-OCVpattern, fixedwas not caused by a short-term fluctuation due to a measurement error or other reasons and was rather caused by a determination error of the degradation pattern caused by an error or insufficiency of the operating history of the battery, a negative determination will be repeatedly obtained in step609inFIG.12andFIG.27. Consequently, the cycle of steps607to610will be repeated, and this may result in the suspension of the update of the SOC-OCVtemp.

Meanwhile, in this embodiment, when a negative determination is obtained in step609, whether the SOC-OCVpattern, fixedhas converged outside the range of the correction limit width is determined as a result of the processing of step617explained inFIG.32being performed. As a result of the processing of step618being additionally performed when it is determined that the SOC-OCVpattern, fixedhas converged outside the range of the correction limit width, the operating history of the battery is updated based on the previously detected SOC-OCVpattern, fixed. Consequently, as shown in the right diagram ofFIG.33, the SOC-OCVpattern, fixedwill fall within the range of the correction limit width that was set according to the updated operating history, the SOC-OCVtempis updated, and the operation of the SOC can be continued.

Note that the SOC-OCVpattern, fixedis acquired with at least one point on the SOC-OCVpatternas the origin. Thus, generally speaking, the SOC-OCVpattern, fixedwill not coincide before the update and after the update of the operating history. Accordingly, the SOC-OCV characteristic can be corrected based on the update of the operating history, and the operational precision of the SOC can thereby be improved.

According to the sixth embodiment of the present invention explained above, the following operation and effect are yielded in addition to those explained in the first to fifth embodiments.

(10) The direct detection correction unit530eupdates the use history information of the battery based on the SOC-OCVpatternafter correction including parts outside the range of the correction limit width; that is, based on the SOC-OCVpattern, fixed. Specifically, as explained inFIG.32andFIG.33, the direct detection correction unit530edetermines whether the SOC-OCVpattern, fixedis within the range of the correction limit width (step609), and, when the SOC-OCVpattern, fixeddetermined to be outside the range of the correction limit width satisfies a predetermined convergence condition (step617: YES), updates the use history information of the battery (step618). As a result of adopting the foregoing configuration, since the SOC-OCV characteristics can be corrected and the operation of the SOC can be continued even when the degradation pattern of the battery is erroneously determined, the operational precision of the SOC can be improved.

(11) The convergence condition used in the determination of step617includes at least one of either a first condition in which a number of times that the SOC-OCVpattern, fixedwas continuously determined to be outside the range of the correction limit width is equal to or greater than a predetermined number of times, or a second condition in which a variance in the SOC-OCVpattern, fixed(variance SOC-OCVpattern, fixed) is equal to or less than a predetermined threshold. As a result of adopting the foregoing configuration, it is possible to accurately determine whether the SOC-OCVpattern, fixeddetermined to be outside the range of the correction limit width satisfies a predetermined convergence condition.

Note that the respective embodiments and various modified examples explained above are merely examples, and the present invention is not limited to the subject matter thereof so as long as the features of the present invention are not impaired. Moreover, the respective embodiments explained above may also be used by being arbitrarily combined. In addition, while various embodiments and modified examples were explained above, the present invention is not limited to the subject matter thereof. Other modes considered to fall within the scope of the technical concept of the present invention are also included in the scope of the present invention.

The disclosure of the following priority application is incorporated herein by reference. Japanese Patent Application No. 2018-201527 (filed on Oct. 26, 2018)

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