BATTERY DEVICE

A battery device has a storage unit, a calculation unit, a level shifter, and an AD conversion unit. The storage unit stores battery information including a closed circuit voltage of a plurality of battery cells electrically connected to each other. The setting unit that sets an acquisition range of the closed circuit voltage based on the battery information. The level shifter and the AD conversion unit convert the closed circuit voltage into a digital signal within the acquisition range set by the calculation unit. The calculation unit changes the acquisition range when the closed circuit voltage is outside the acquisition range.

TECHNICAL FIELD

The disclosure provided herein relates to a battery device.

BACKGROUND

A conceivable technique teaches a capacity adjustment device that equalizes the SOCs of a plurality of lithium secondary batteries.

SUMMARY

According to an example, a battery device may have a storage unit, a calculation unit, a level shifter, and an AD conversion unit. The storage unit stores battery information including a closed circuit voltage of a plurality of battery cells electrically connected to each other. The setting unit that sets an acquisition range of the closed circuit voltage based on the battery information. The level shifter and the AD conversion unit convert the closed circuit voltage into a digital signal within the acquisition range set by the calculation unit. The calculation unit changes the acquisition range when the closed circuit voltage is outside the acquisition range.

DETAILED DESCRIPTION

The closed path voltage of lithium secondary batteries is used to equalize the SOCs of a plurality of lithium secondary batteries. Therefore, it is necessary to avoid a situation that the closed path voltage becomes undetectable.

An object of the present embodiments is to provide a battery device that suppresses the closed path voltage from becoming undetectable.

A battery device according to an aspect of the present embodiments includes:a storage unit that stores battery information including a closed path voltage of a plurality of electrically connected battery cells;a setting unit that sets an acquisition range of the closed path voltage based on the battery information; anda conversion unit that converts the closed path voltage into a digital signal within the acquisition range set by the setting unit.

The setting unit changes the acquisition range when the closed path voltage is one of the upper limit value and the lower limit value of the acquisition range.

According to this, as a result of restrictively narrowing the acquisition range, it is suppressed that the closed path voltage cannot be detected.

The reference numerals in parentheses above indicate only a correspondence relationship with the configuration described in the embodiment to be described later, and do not limit the technical range in any way.

The following will describe embodiments for carrying out the present disclosure with reference to the drawings. In each of embodiments, parts/configurations corresponding to the elements described in the preceding embodiments are denoted by the same reference numerals, and redundant explanation may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration.

When, in each embodiment, it is specifically described that combination of parts is possible, the parts can be combined. In a case where any obstacle does not especially occur in combining the parts of the respective embodiments, it is possible to partially combine the embodiments, the embodiment and the modification, or the modifications even when it is not explicitly described that combination is possible.

First Embodiment

A first embodiment will be described with reference toFIGS.1to8.

FIG.1shows a battery device100and an assembled battery200. The battery device100and the assembled battery200are mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle. The electric vehicles include passenger cars, buses, construction vehicles, agricultural machinery vehicles, and the like.

The battery device100monitors and controls the state of the assembled battery200. The assembled battery200supplies electric power to various in-vehicle devices such as an electric motor that provides driving force to the electric vehicle.

The assembled battery200has a plurality of battery stacks210. Each of the plurality of battery stacks210has a plurality of battery cells220electrically connected in series. As the battery cell220, a secondary battery such as a lithium-ion secondary battery, a nickel-hydrogen secondary battery, or an organic radical battery can be employed. The output voltage of the battery cells220connected in series is the output voltage of the battery stack210. InFIG.1, a plurality of battery cells220included in one battery stack210are shown surrounded by dashed lines.

A plurality of battery stacks210are electrically connected in series or in parallel. In this embodiment, a plurality of battery stacks210are electrically connected in series. The output voltage of the assembled battery200is the sum of the output voltages of the plurality of battery stacks210connected in series. The power source electric power depending on this output voltage is supplied to various in-vehicle devices.

Each of the plurality of battery stacks210is provided with a physical quantity sensor230that detects the physical quantity of the battery cell220. The physical quantities detected by the physical quantity sensor230include, for example, the temperature and the current of the battery cell220.

The physical quantity detected by the physical quantity sensor230is used for estimating the SOC of each of the battery cell220, the battery stack210, and the assembled battery200, and the like. The SOC is an abbreviation for state of charge. The SOC corresponds to the charge amount.

The SOC is reduced by supplying the above power source electric power to various in-vehicle devices. Also, the battery cell220self-discharges. Therefore, the SOC decreases even when the power source electric power is not supplied.

This decrease in the SOC is improved by supplying the charging power to the assembled battery200from a charging device such as an electric station disposed outside the vehicle, for example. The supply of charging the electric power from the charging device to the assembled battery200is controlled by the battery device100. The battery device100controls the charging of the assembled battery200while transmitting and receiving a CPLT signal to and from the charging device via a wiring (not shown).

Note that the quality and environment of the plurality of battery cells220are not uniform. Therefore, the SOCs of the plurality of battery cells220may vary. This variation is improved by an equalization process, which will be described later.

The battery cell220has an internal resistance. Therefore, there is a difference of a voltage drop between the actual cell voltage according to the SOC of the battery cell220and the cell voltage detected by the monitor unit10, and the voltage drop corresponds to the internal resistance and the current flowing through the battery cell220.

Hereinafter, the actual cell voltage corresponding to the SOC of the battery cell220will be referred to as an open path voltage OCV as required. A cell voltage detected by the monitor unit10is indicated as a closed path voltage CCV. The internal resistance R is the resistance in the battery cell220and the actual current I is the current that actually flows through the battery cell220. OCV is an abbreviation for Open Circuit Voltage. CCV is an abbreviation for Closed Circuit Voltage.

A relationship between the closed circuit voltage CCV and the open circuit voltage OCV is expressed as CCV=OCV±I×R. When the battery cell220is discharged, the above relationship is expressed as CCV=OCV−I×R. When the battery cell220is charged, the above relationship is expressed as CCV=OCV+I×R.

<Characteristics of SOC and OCV>

The battery cell220has SOC and OCV characteristics.FIG.2shows SOC and OCV characteristic data when the battery cell220is a lithium ion battery.

As shown inFIG.2, in the over-discharge region where the SOC is close to 0%, the rate of change of OCV with respect to SOC is high. In the over-charge region where the SOC is close to 100%, the rate of change of OCV with respect to SOC is high.

On the other hand, in the charge/discharge region between the over-discharge region and the over-charge region, the rate of change of OCV with respect to SOC is low. The battery cell220is mainly used in this charge/discharge region. InFIG.2, as an example, the values of the SOC and the OCV between the over-discharge region and the charge/discharge region are expressed as SOC1and OCV1. The values of the SOC and the OCV between the charge/discharge region and the over-charge region are denoted as SOC2and OCV2.

The characteristic data shown inFIG.2are temperature dependent. Therefore, the rate of change of OCV with respect to SOC changes depending on the temperature. Along with this, the values of SOC1, SOC2, OCV1and OCV2also change.

The battery device100has a monitor unit10and a control unit30. The battery device100has the same number of monitor units10as the battery stacks210. The plurality of monitor units10detect battery information related to the state of each of the plurality of battery stacks210.

The control unit30acquires battery information detected by the multiple monitor units10. The control unit30also acquires vehicle information input from various other ECUs and various sensors (not shown). When a charging device is connected to the electric vehicle, the control unit30acquires charging information input from the charging device. The input of the vehicle information and charging information to the control unit30, and the output of the processing result of the control unit30to various ECUs, the charging device and the like are indicated by white arrows inFIG.1.

The control unit30determines the state of the assembled battery200based on the acquired information. At the same time, the control unit30executes processing for the assembled battery200. The processing for the assembled battery200includes, for example, charge/discharge of the assembled battery200, equalization processing for equalizing the SOCs of the plurality of battery cells220included in the assembled battery200, and the like.

Each of the plurality of monitor units10is individually provided for each of the plurality of battery stacks210. One monitor unit10detects the inter-terminal voltage (i.e., the closed circuit voltage) between the positive and negative electrodes of each of the plurality of battery cells220included in one battery stack210. Also, the monitor unit10acquires the physical quantity detected by the physical quantity sensor230. The monitor unit10executes processing based on instruction signals input from the control unit30.

As shown inFIG.1, the monitor unit10has a multiplexer11, a level shifter12, an AD conversion unit13, a monitor control unit14and a monitor communication unit15. In the drawing, the multiplexer11is written as MUX. The level shifter12is written as LS. The AD conversion unit13is written as AD. The monitor control unit14is written as MCU. The monitor communication unit15is written as MCS.

The multiplexer11is connected to the positive and negative electrodes of each of the plurality of battery cells220included in one battery stack210. As a result, the multiplexer11receives the closed circuit voltages of the plurality of battery cells220.

Also, the multiplexer11is connected to the physical quantity sensor230. Thereby, the physical quantity is input to the multiplexer11.

The multiplexer11sequentially selects and detects a plurality of input closed circuit voltages. The multiplexer11sequentially outputs the detected closed circuit voltages to the level shifter12. The multiplexer11also sequentially selects and detects a plurality of input physical quantities. The multiplexer11also sequentially outputs the detected physical quantities to the level shifter12.

The level shifter12includes an operational amplifier and multiple feedback circuits connected in parallel between an input terminal and an output terminal of the operational amplifier. This feedback circuit includes a switch and a capacitor connected in series. The capacitances of the capacitors included in the multiple feedback circuits may be the same or different.

The switches of the plurality of feedback circuits of the level shifter12are selectively controlled to turn on and off by the monitor control unit14. As a result, the number of capacitors connected between the input terminal and the output terminal of the operational amplifier changes. The capacitance between the input terminal and the output terminal of the operational amplifier changes. In addition, the resistance between the input terminal and the output terminal of the operational amplifier changes. As a result, the gain and the offset of the level shifter12are controlled.

The analog signals of the closed circuit voltage and the physical quantity whose gain and offset are adjusted is input from the level shifter12to the AD conversion unit13. The AD conversion unit13has a clamp circuit for limiting the input range. This clamp circuit is controlled by the monitor control unit14. The input range of the AD conversion unit13is thereby controlled.

By limiting the input range of the AD conversion unit13and adjusting the gain and the offset of the level shifter12, the voltage range of the analog signal converted from analog to digital by the AD conversion unit13is controlled. The voltage ranges of the closed circuit voltage and the physical quantity that are analog-to-digital converted by the AD conversion unit13are controlled. As a result, the acquisition ranges of the closed circuit voltage and the physical quantity are controlled. Note that it is not necessary to particularly control the acquisition range of the physical quantity. The level shifter12and the AD conversion unit13correspond to the converter.

The AD conversion unit13intermittently samples continuous analog signals. Then, the AD conversion unit13quantizes the sampled values and converts them into discrete digital signals. Due to such conversion, there may be an error (i.e., the quantization error) between the analog signal and the digital signal.

This quantization error becomes smaller as the number of quantization bits of the AD conversion unit13increases. However, the number of quantization bits is fixed. Therefore, for example, when the acquisition range of the closed circuit voltage is between 0.0V and 5.0V, the resolution of the AD conversion unit13is the value obtained by dividing this range between 0.0V and 5.0V by the number of quantization bits.

On the other hand, for example, when the acquisition range of the closed circuit voltage is between 3.0 V and 3.5 V, which is 1/10 of the above range, the resolution of the AD conversion unit13is the value obtained by dividing the range between 3.0 V and 3.5 V by the number of quantization bits. In this case, the resolution of the AD conversion unit13is increased by about ten times. By limiting the acquisition range in this way, the detection accuracy of the closed circuit voltage is improved.

The monitor control unit14has a processor and a non-transitional tangible storage medium that non-transitory stores a program readable by the processor. A digital signal input from the AD conversion unit13and an instruction signal input from the control unit30are stored in this non-transitory tangible storage medium. The processor of the monitor control unit14controls the multiplexer11, the level shifter12, and the AD conversion unit13based on the instruction signal.

The instruction signal input to the monitor control unit14includes the acquisition range of the closed circuit voltage of the battery cell220as a detection target. The monitor control unit14controls the gain and the offset of the level shifter12when the multiplexer11selects the closed circuit voltage as the detection target. The monitor control unit14limits the input range of the AD conversion unit13. This controls the acquisition range of the closed circuit voltage.

The digital signals of the closed circuit voltage and the physical quantity are input to the monitor communication unit15. The monitor communication unit15outputs this digital signal to the control unit30.

As shown inFIG.1, the control unit30has a control communication unit31, a storage unit32and a calculation unit33. In the drawing, the control communication unit31is denoted as CCU. The storage unit32is referred to as MU. The calculation unit33is referred to as OP. The calculation unit33corresponds to the setting unit.

Various information is input to the control communication unit31. This information includes the closed circuit voltage and the physical quantity acquired by the monitor unit10. In addition, this information includes vehicle information and charging information. The vehicle information includes the running state of the electric vehicle and the current time. The charging information includes charging electric power.

Note that vehicle information and charging information may be input to a communication unit (not shown). And when the control unit30has RTC, the present time does not need to be included in the vehicle information. RTC stands for Real Time Clock.

The storage unit32is a non-transitory tangible storage medium that non-transitory stores programs that can be read by a computer or a processor. The storage unit32includes a volatile memory and a nonvolatile memory. Various information input to the control communication unit31and processing results of the calculation unit33are stored in the storage unit32.

In addition, the storage unit32stores in advance programs and reference values for the calculation unit33to perform calculation processing. The reference values include, for example, the temperature dependence of SOC and OCV characteristic data of various secondary batteries, an equalization determination value for determining execution of equalization processing, manufacturing dates of the plurality of battery cells220, and deterioration determination value, and the like.

The calculation unit33has a processor. The calculation unit33stores various information input to the control communication unit31in the storage unit32. The calculation unit33executes various calculation processes based on the information stored in the storage unit32. An electrical signal including the result of this calculation processing is output to the monitor unit10via the control communication unit31. An electric signal including the result of the calculation processing is output to various ECUs and the charging device via the control communication unit31or a communication unit (not shown).

As a specific example of the calculation process, the calculation unit33estimates the SOC of the battery cell220based on the information stored in the storage unit32. The calculation unit33generates an instruction signal for instructing the operation of the monitor unit10based on the estimated SOC and the information stored in the storage unit32. This instruction signal includes the acquisition range of the closed circuit voltage of the battery cell220as the detection target. Note that if the battery information for estimating the SOC is not stored in the storage unit32, the calculation unit33sets the acquisition range of the closed circuit voltage to a possible range of the closed circuit voltage of the battery cell220.

In addition to determining the acquisition range of the closed circuit voltage, the calculation unit33determines execution of an equalization process for reducing variations in the SOCs of the plurality of battery cells220. The calculation unit33outputs an instruction signal including equalization processing for each of the plurality of battery stacks210to the monitor unit10.

The calculation unit33calculates the difference between the maximum value and the minimum value of the closed circuit voltage input from the monitor unit10. When this difference exceeds the equalization determination value, the calculation unit33determines to execute the equalization process. This equalization process may be performed, for example, only in the battery stack210in which at least one of the maximum value and the minimum value of the closed circuit voltage is detected. The equalization process may be performed on all battery stacks210.

Although not clearly shown in the drawing, the monitor unit10has a plurality of switches that bridge a plurality of wires connecting the multiplexer11and the positive and negative electrodes of the plurality of battery cells220, respectively. The monitor control unit14selectively controls the plurality of switches between the energization state and the cut-off state based on the instruction signal input from the calculation unit33. As a result, the battery cell220with a relatively high SOC among the plurality of electrically connected battery cells220is discharged. Conversely, a battery cell220with relatively low SOC is charged. As a result, the SOCs of the plurality of battery cells220are equalized.

<Acquisition of Closed Circuit Voltage>

Due to the SOC and OCV characteristics of the battery cell220shown inFIG.2, when the SOC drops due to discharge, the OCV also drops. Along with this, the closed circuit voltage CCV of the battery cell220also decreases. Conversely, when the SOC increases due to the supply of charging electric power from the charging device, the closed circuit voltage of battery cell220also increases.

FIG.3shows the time change of the closed circuit voltage. The vertical axis is an arbitrary unit. The horizontal axis is time. The arbitrary unit is indicated by a. u. The time is indicated by T.

In addition to the closed circuit voltage,FIG.3shows the driving state of the battery device100, the actual current flowing through the assembled battery200, and the closed circuit voltage of one battery cell220. The driving state of the battery device100is described as DS. For the sake of simplicity, the behavior of the closed circuit voltage of the battery cell220and the behavior of the closed circuit voltage of the assembled battery200shown in the drawings are assumed to be the same. In order to clarify the behavior, the drawing shows that the closed circuit voltage of the battery cell220changes significantly in a short time.

In the initial state at time0, the battery device100is in a non-driving state. The storage unit32does not store battery information such as the closed circuit voltage and the physical quantity. The system main relay that controls the conduction state between the assembled battery200and various in-vehicle devices is in the cutoff state. Therefore, no current is substantially flowing through the assembled battery200. The closed circuit voltage of the battery cell220has a value in the charge/discharge region.

Even when no current is flowing through the battery cell220, the SOC of the battery cell220decreases due to self-discharge. Therefore, in the initial state of time0, the closed circuit voltage of the battery cell220tends to decrease in a small amount.

At time t0, the battery device100changes from the non-driving state to the driving state. The system main relay changes from the cutoff state to the energization state. As a result, the supply of power source electric power from the assembled battery200to various in-vehicle devices is started. The actual current begins to flow in the assembled battery200. The rate of decrease in the SOC of the battery cell220increases. Along with this configuration, the rate of decrease in the closed circuit voltage of the battery cell220also increases.

At time t1, the calculation unit33acquires the closed circuit voltage of the battery cell220. At this time, the battery information is not stored in the storage unit32. Therefore, the calculation unit33sets the acquisition range of the closed circuit voltage at the time t1to a possible range that the battery cell220can take. That is, the calculation unit33sets the acquisition range of the closed circuit voltage between 0.0V and 5.0V.

At time t2, the calculation unit33again acquires the closed circuit voltage of the battery cell220. At this time, the calculation unit33determines the center value of the acquisition range of the closed circuit voltage at the time t2based on the closed circuit voltage of the battery cell220acquired at the time t1. Further, the calculation unit33determines the range width a of the acquisition range of the closed circuit voltage.

The acquisition range is indicated by the width of the solid double-ended arrow shown inFIG.3. The difference between the center value and the upper or lower limit value of the acquisition range is set to the range width a. The range width a is a value greater than the detection error of the closed circuit voltage. The range width a is a value smaller than half of the difference between the OCV1and the OCV2shown inFIG.2. The difference between the center value and the upper limit value and the difference between the center value and the lower limit value may be the same or different. In this embodiment, the range width a is a fixed value. The range width a is pre-stored in the storage unit32. As such, the acquisition range is determined substantially based on the closed circuit voltage. The calculation unit33sets a limited acquisition range based on the range width a and the acquired closed circuit voltage. The calculation unit33sets the acquisition range at time t2between 2.8V and 3.2V, for example. The calculation unit33acquires the closed circuit voltage detected by the monitor unit10in the acquisition range at this time t2.

Strictly speaking, since the battery device100performs a calculation process, the timing of determining the acquisition range and the timing of acquiring the closed circuit voltage around time t2are not the same. The determination timing is before the acquisition timing. However, the difference between these two timings is small. Therefore, these two timings are substantially regarded as the same and described.

The calculation unit33acquires the closed circuit voltage at the acquisition cycle. This acquisition cycle is an expected time interval in which the SOC of the battery cell220does not suddenly change unless the charge or discharge state of the battery cell220suddenly changes due to rapid charging or the like. The acquisition cycle is a time interval in which it is expected that the amount of change in the closed circuit voltage of the battery cell220does not exceed the range width a. When the acquisition cycle elapses from the time t1, the time becomes t2.

At time t3after the acquisition cycle has elapsed from time t2, the calculation unit33determines the acquisition range of the closed circuit voltage based on the closed circuit voltage at time t2. The calculation unit33sets the acquisition range at time t3between 2.6V and 3.0V, for example. Then, the calculation unit33acquires the closed circuit voltage of the battery cell220detected by the monitor unit10in this acquisition range.

When the time t3changes to the time tc1, the driving state of the vehicle changes. The actual current is reduced. Along with this configuration, the reduction rate of the closed circuit voltage is also reduced.

At time t4after the acquisition cycle has elapsed from time t3, the calculation unit33determines the acquisition range of the closed circuit voltage based on the closed circuit voltage at time t3. The calculation unit33sets the acquisition range at time t4between 2.4V and 2.8V, for example. Then, the calculation unit33acquires the closed circuit voltage of the battery cell220detected by the monitor unit10in this acquisition range. As shown inFIG.3, even if the reduction rate of the closed circuit voltage decreases at time tc1, in this example, the closed circuit voltage detected at time t4is within the acquisition range.

At tc2elapsed from time t4, the charging device is connected to the electric vehicle. The assembled battery200is rapidly charged by the charging device. As a result, the actual current rises sharply. The calculation unit33acquires such information from vehicle information or charging information. At this time, the calculation unit33sets the acquisition range of the closed circuit voltage to a possible range that the battery cell220can take.

At time t5after the acquisition period has passed from time t4, the calculation unit33acquires the closed circuit voltage of the battery cell220detected by the monitor unit10within the acquisition range set to the possible range of the closed circuit voltage. Due to the change in the acquisition range, as shown inFIG.3, even when the closed circuit voltage suddenly rises from the time tc2, the closed circuit voltage detected at the time t5is within the acquisition range.

When the time t5changes to the time tc3, the output voltage of the assembled battery200reaches the target voltage. When detecting this, the calculation unit33terminates the rapid charging by the charging device. The calculation unit33causes the charging device to perform full charging.

The amount of current supply differs between the quick charge and the full charge. The quick charge has a larger supply current than the full charge.

As described above, there is a difference of the voltage drop of I×R between the closed circuit voltage CCV and the open circuit voltage OCV. During the charging, an expression of “CCV=OCV+I×R” is established. Therefore, even if the maximum output voltage of the assembled battery200is detected as the closed circuit voltage CCV, the open circuit voltage OCV does not reach the maximum output voltage. The SOC of the assembled battery200has not reached the full charge capacity.

The above target voltage is a value based on the maximum output voltage of the assembled battery200. When the calculation unit33determines that the output voltage of the assembled battery200has reached the target voltage, it causes the charging device to perform full charging. In full charging, the charging power is supplied to the assembled battery200while maintaining the output voltage of the assembled battery200at the target voltage in order to bring the SOC of the assembled battery200closer to the full charge amount with avoiding over-charging. The target voltage and the maximum output voltage are stored in advance in the storage unit32.

At time t6after the acquisition period has passed from time t5, the calculation unit33acquires the closed circuit voltage of the battery cell220detected by the monitor unit10within the acquisition range set to the possible range of the battery cell220. At this time, it may be expected that the output voltage of the assembled battery200has reached the target voltage. Therefore, the closed circuit voltage may be detected in the acquisition range based on this target voltage.

FIG.3shows an example in which the closed circuit voltage is detected within the acquisition range. However, it may happen that the closed circuit voltage is not detected within the acquisition range, for example as shown inFIGS.4to6.

In the example shown inFIG.4, the calculation unit33sets the acquisition range of the closed circuit voltage at time t5based on the closed circuit voltage detected at time t4without considering rapid charging of the assembled battery200. With such settings, the closed circuit voltage is outside the acquisition range due to rapid charging. The closed circuit voltage detected by the monitor unit10becomes the upper limit of the acquisition range. The calculation unit33acquires this upper limit value.

When the upper limit value of the acquisition range is acquired in this manner, the calculation unit33resets the acquisition range of the closed circuit voltage to a possible range that the closed circuit voltage can take. By expanding the acquisition range in this way, it becomes possible to detect the closed circuit voltage at time t6.

In the example shown inFIG.5, the calculation unit33sets the acquisition range of the closed circuit voltage at time t3based on the closed circuit voltage acquired at time t2. However, if a ground fault occurs at time to between time t2and time t3, the closed circuit voltage detected by monitor unit10at time t3is out of the acquisition range. The closed circuit voltage acquired by the calculation unit33becomes the lower limit value of the acquisition range.

When the lower limit value of the acquisition range is acquired in this manner, the calculation unit33resets the acquisition range of the closed circuit voltage to a possible range that the closed circuit voltage can take. By expanding the acquisition range in this way, it becomes possible to detect the closed circuit voltage at time t4.

If the ground fault is not temporary, the monitor unit10detects 0.0 V at times t3, t4, t5, and t6after time ta, as shown inFIG.5. The calculation unit33acquires 0.0V multiple times. When the number of acquisitions of 0.0 V is equal to or greater than the failure determination value, the calculation unit33determines that a ground fault has occurred. In this embodiment, the failure determination value is set to 3 times. Note that the value of the failure determination value is not particularly limited. A failure determination value is stored in the storage unit32.

In the example shown inFIG.6, the calculation unit33sets the acquisition range of the closed circuit voltage at time t3based on the closed circuit voltage acquired at time t2. However, if a power fault occurs at time ta between time t2and time t3, the closed circuit voltage detected by monitor unit10at time t3is out of the acquisition range. The closed circuit voltage acquired by the calculation unit33becomes the upper limit value of the acquisition range.

When the upper limit value of the acquisition range is acquired in this way, the calculation unit33resets the acquisition range of the closed circuit voltage to a possible range that the closed circuit voltage can take, as described with reference toFIGS.4and5.

If the power fault is not temporary, the monitor unit10detects 5.0 V at times t3, t4, t5, and t6after time ta, as shown inFIG.6. The calculation unit33acquires 5.0V multiple times. When the number of acquisitions of 5.0 V is equal to or greater than the failure determination value, the calculation unit33determines that a power fault has occurred.

Next, the voltage detection processing of the calculation unit33will be described with reference toFIG.7. The calculation unit33executes this voltage detection process as a cycle task. The execution interval of this voltage detection process corresponds to the acquisition period described above.

In step S10, the calculation unit33determines whether or not the closed circuit voltage is stored in the storage unit32. When the closed circuit voltage is stored in the storage unit32, the calculation unit33proceeds to step S20. If the closed circuit voltage is not stored in the storage unit32, the calculation unit33proceeds to step S30.

When proceeding to step S20, the calculation unit33calculates the acquisition range of the closed circuit voltage based on the closed circuit voltage stored in the storage unit32and the range width a. The calculation unit33stores this acquisition range in the storage unit32. Then, the calculation unit33transmits an instruction signal including the limited acquisition range to the monitor unit10as a limited range signal. After this process, in the calculation unit33, the process proceeds to step S40.

When proceeding to step S40, the calculation unit33acquires the closed circuit voltage detected by the monitor unit10. After this process, in the calculation unit33, the process proceeds to step S50.

When proceeding to step S50, the calculation unit33determines whether or not the closed circuit voltage is the upper limit value or the lower limit value of the acquisition range. That is, the calculation unit33determines whether or not the closed circuit voltage is a value excluding the upper limit value and the lower limit value of the acquisition range. If the closed circuit voltage is the upper limit value or the lower limit value of the acquisition range, the calculation unit33proceeds to step S60. When the closed circuit voltage is a value excluding the upper limit value and the lower limit value of the acquisition range, the calculation unit33proceeds to step S70.

When proceeding to step S60, the calculation unit33increments its own counter by one. After this process, in the calculation unit33, the process proceeds to step S80.

When proceeding to step S80, the calculation unit33determines whether or not the value of the counter is smaller than the failure determination value. The failure determination value of this embodiment is 3. If the counter value is smaller than the failure determination value, the calculation unit33proceeds to step S90. When the value of the counter is equal to or greater than the failure determination value, the calculation section33proceeds to step S100.

When proceeding to step S90, if the limited range signal has been transmitted in step S20, the calculation unit33sends an instruction signal including an acquisition range different from the acquisition range included in the limited range signal to the monitor unit10as a range signal. In the case of this embodiment, the calculation unit33causes the range signal to include the possible range of the closed circuit voltage. If a full-range signal, which will be described later, has been transmitted in step S30, the calculation unit33transmits an instruction signal equivalent to that to the monitor unit10. Alternatively, the calculation unit33stops outputting the instruction signal. After this process, in the calculation unit13, the process proceeds to step S110.

When proceeding to step S110, the calculation unit33acquires the closed circuit voltage detected by the monitor unit10. After this process, the calculation unit110returns to the step S50.

When a ground fault or a power fault occurs as shown inFIGS.5and6, the calculation unit33repeats steps S50, S60, S80, S90, and S110. It is repeated that the closed circuit voltage becomes the upper limit value or the lower limit value of the acquisition range. As a result, the value of the counter becomes equal to or greater than the failure determination value.

When the value of the counter does not exceed the failure determination value and the closed circuit voltage is stored in the storage unit32, the calculation unit33estimates the SOC based on the stored closed circuit voltage. Then, the calculation unit33executes calculation processing based on the estimation result.

When it is determined in step S80that the value of the counter is equal to or greater than the failure determination value and the process proceeds to step S100, the calculation unit33determines that a failure such as a ground fault or a power fault has occurred. Then, the calculation unit33terminates the voltage detection process.

Returning the flow, when it is determined in step S50that the closed circuit voltage is neither the upper limit value nor the lower limit value of the acquisition range and the process proceeds to step S70, the calculation unit33clears the counter. The calculation unit33sets the value of the counter to zero. Then, in the calculation unit33, the process proceeds to step S120.

When proceeding to step S120, the calculation unit33determines that the battery cell220is normal. Then, in the calculation unit33, the process proceeds to step S130.

When proceeding to step S130, the calculation unit33stores the acquired closed circuit voltage in the storage unit32. Then, the calculation unit33terminates the voltage detection process.

Returning the flow, when it is determined in step S10that the closed circuit voltage is not stored in the storage unit32and the process proceeds to step S30, the calculation unit33transmits the instruction signal including the possible acquisition range of the closed circuit voltage to the monitor unit10as a full range signal. After this process, in the calculation unit33, the process proceeds to step S40.

The voltage detection process will be described based onFIG.6, and at time t1, the calculation unit33executes steps S30and S130. The calculation unit33detects the closed circuit voltage within a possible acquisition range and stores the closed circuit voltage in the storage unit32.

At time t2, the calculation unit33executes steps S20and S130. The calculation unit33detects the closed circuit voltage in a limited acquisition range and stores the closed circuit voltage in the storage unit32.

After time t3, the calculation unit33repeatedly executes steps S50, S60, S80, S90, and S110. Then, the calculation unit33executes step S100. The calculation unit33repeatedly acquires the closed circuit voltage while changing the acquisition range. Then, the calculation unit33performs failure determination.

As described above, when the closed circuit voltage is outside the acquisition range, the calculation unit33changes the acquisition range of the closed circuit voltage. The calculation unit33changes the acquisition range so that the closed circuit voltage is detected. The calculation unit33of the present embodiment changes the acquisition range to a possible acquisition range of the closed circuit voltage.

According to this, as a result of narrowing the acquisition range, it is suppressed that the closed circuit voltage cannot be detected.

For example, the calculation unit33changes the acquisition range of the closed circuit voltage from a possible acquisition range of 0.0V to 5.0V to a limited acquisition range of 3.0V to 3.5V. In this limited acquisition range, the analog closed circuit voltage is converted into a digital signal by the AD conversion unit13. This reduces the quantization error of the AD conversion unit13. Detection accuracy of the closed circuit voltage is improved.

The calculation unit33determines that a failure has occurred when the number of acquisitions of the lower limit value or the upper limit value of the acquisition range of the closed circuit voltage is equal to or greater than the failure determination value. Specifically, when the number of acquisitions of 0.0 V is 3 or more, the calculation unit33determines that a ground fault has occurred. When the number of acquisitions of 5.0 V is 3 or more, the calculation unit33determines that a power fault has occurred.

This suppresses erroneous determination of failure. A ground fault and a power fault can be separately detected.

Second Embodiment

Next, a second embodiment will be described with reference toFIGS.8and9.

In the first embodiment, when the closed circuit voltage of the upper limit value or the lower limit value of the acquisition range is acquired, the calculation unit33resets the acquisition range of the closed circuit voltage to a possible range of the closed circuit voltage. Then, an example has been shown in which the acquisition of the closed circuit voltage is continued within a possible range. On the other hand, in this embodiment, when the closed circuit voltage of the upper limit value or the lower limit value is acquired in the possible range, the calculation unit33narrows the acquisition range to the vicinity of the acquired closed circuit voltage.

As shown inFIG.8, when the closed circuit voltage of the lower limit value is acquired in the possible range that the closed circuit voltage can take, the calculation unit33sets the acquisition range of the closed circuit voltage to the vicinity including the closed circuit voltage. The calculation unit33sets the acquisition range to around 0.0V. The calculation unit33sets the width of the acquisition range to a value smaller than the range width a stored in the storage unit32. Thereby, a ground fault can be detected with high accuracy.

As shown inFIG.9, when the closed circuit voltage of the upper limit value is acquired in the possible range that the closed circuit voltage can take, the calculation unit33sets the acquisition range of the closed circuit voltage to the vicinity including the closed circuit voltage. The calculation unit33sets the acquisition range to around 5.0V. The calculation unit33sets the width of the acquisition range to a value smaller than the range width a. Thereby, a power fault can be detected with high accuracy.

Third Embodiment

Next, a third embodiment will be described with reference toFIG.10.

In the first embodiment, when the closed circuit voltage of the upper limit value or the lower limit value of the acquisition range is acquired, the calculation unit33resets the acquisition range of the closed circuit voltage to a possible range of the closed circuit voltage. On the other hand, in this embodiment, each time the closed circuit voltage of the upper limit value or the lower limit value of the acquisition range is acquired, the calculation unit33gradually expands the acquisition range of the closed circuit voltage as shown inFIG.10.

Fourth Embodiment

Next, a fourth embodiment will be described with reference toFIGS.11and12.

In the second embodiment, the calculation unit33gradually expands the acquisition range of the closed circuit voltage every time the closed circuit voltage of the upper limit value or the lower limit value of the acquisition range is acquired. In contrast, in the present embodiment, each time the closed circuit voltage at the lower limit of the acquisition range is acquired, the calculation unit33gradually shifts the acquisition range of the closed circuit voltage to 0.0 V as shown inFIG.11. Each time the closed circuit voltage of the upper limit value of the acquisition range is acquired, the calculation unit33gradually shifts the acquisition range of the closed circuit voltage to 5.0 V as shown inFIG.12.

The calculation unit33determines that a ground fault has occurred when 0.0V is obtained in the acquisition range including 0.0V. When the calculation unit33obtains 5.0V in the acquisition range including 5.0V, it determines that a power fault has occurred.

Fifth Embodiment

Next, a fifth embodiment will be described with reference toFIGS.13and14.

In the first embodiment, when the closed circuit voltage of the upper limit value or the lower limit value of the acquisition range is acquired, the calculation unit33resets the acquisition range of the closed circuit voltage to a possible range of the closed circuit voltage. On the other hand, in this embodiment, when the closed circuit voltage is the upper limit value or the lower limit value of the acquisition range, the calculation unit33sets the acquired closed circuit voltage to the new lower limit value or upper limit value of the acquisition range.

When the closed circuit voltage is the lower limit value of the acquisition range, the calculation unit33sets the upper limit value of the new acquisition range to the acquired closed circuit voltage, as indicated by the dashed-dotted line inFIG.13. Then, the calculation unit33sets the lower limit value of the new acquisition range to the lower limit value of the possible range.

When the closed circuit voltage is the upper limit value of the acquisition range, the calculation unit33sets the lower limit value of the new acquisition range to the acquired closed circuit voltage, as indicated by the dashed-dotted line inFIG.14. Then, the calculation unit33sets the upper limit value of the new acquisition range to the upper limit value of the possible range.

According to this, deterioration in detection accuracy of the closed circuit voltage due to resetting of the acquisition range is suppressed.

Other Modifications

In this embodiment, an example is shown in which one control unit30is provided for a plurality of monitor units10. Alternatively, a configuration in which a plurality of controllers30are provided individually for a plurality of monitor units10may also be adopted.

In this embodiment, an example of setting the acquisition range of the closed circuit voltage of each of the plurality of battery cells220has been described. Alternatively, it may be also possible to employ a configuration in which the acquisition range of the closed circuit voltage of each of the plurality of battery stack210is set. It may be also possible to employ a configuration in which a common closed circuit voltage acquisition range is set for each of the plurality of battery cells220included in one battery stack210. In such a modification, the assembled battery200has at least two battery stacks210.

Although the present disclosure has been described in accordance with the embodiment, it is understood that the present disclosure is not limited to the embodiment and the structure. To the contrary, the present disclosure is intended to cover various modification and equivalent arrangements. In addition, while various combinations and modes are described in the present disclosure, other combinations and modes including only one element, more elements, or less elements therein are also within the scope and spirit of the present disclosure.

The controllers and methods described in the present disclosure may be implemented by a special purpose computer created by configuring a memory and a processor programmed to execute one or more particular functions embodied in computer programs. Alternatively, the controllers and methods described in the present disclosure may be implemented by a special purpose computer created by configuring a processor provided by one or more special purpose hardware logic circuits. Alternatively, the controllers and methods described in the present disclosure may be implemented by one or more special purpose computers created by configuring a combination of a memory and a processor programmed to execute one or more particular functions and a processor provided by one or more hardware logic circuits. The computer programs may be stored, as instructions being executed by a computer, in a tangible non-transitory computer-readable medium.