Battery Management System, Battery Management Method, Battery Pack, and Electric Vehicle

A battery management system includes a sensing unit to generate a sensing signal indicating a battery voltage and a battery current of a battery, a memory unit to store a charge map recording first to nth reference currents, first to nth reference voltage ranges, first to nth reference states of charge (SOCs) and first to nth reference voltage curves for multi-stage constant-current charging, and a control unit to command constant-current charging to a charging circuit using a kth reference current corresponding to a kth reference voltage range to which the battery voltage belongs, and update the charge map by comparing a kth measured voltage curve indicating a correlation between the battery voltage and the SOC of the battery over a charging period of the constant-current charging with a kth reference voltage curve in response to the battery voltage having reached an upper limit of the kth reference voltage range.

TECHNICAL FIELD

The present disclosure relates to battery charge control.

BACKGROUND ART

Recently, there has been a rapid increase in the demand for portable electronic products such as laptop computers, video cameras and mobile phones, and with the extensive development of electric vehicles, accumulators for energy storage, robots and satellites, many studies are being made on high performance batteries that can be recharged repeatedly.

Currently, commercially available batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium batteries and the like, and among them, lithium batteries have little or no memory effect, and thus they are gaining more attention than nickel-based batteries for their advantages that recharging can be done whenever it is convenient, the self-discharge rate is very low and the energy density is high.

In the constant-current charging of a battery, when the current rate of the charge current is low, it takes a very long time to fully charge the battery. In contrast, when the current rate of the charge current is too high, the battery degrades fast.

One of charge protocols proposed to solve this problem is ‘multi-stage constant-current charging’, namely, stepwise adjustment of the current rate of the charge current according to the State Of Charge (SOC) or voltage of the battery during charging. The current rate is a value obtained by dividing the charge current by the maximum capacity of the battery, and may be referred to as ‘C-rate’, and it's unit is ‘C’. A multi-stage constant-current charge map includes at least one data array recording a correlation between a plurality of voltage ranges and a plurality of C-rates. A charging procedure using the multi-stage constant-current charge map includes repeating the process of supplying the charge current of the next C-rate to the battery each time the voltage of the battery reaches the upper limit value of each voltage range.

As the battery degrades from Beginning Of Life (BOL), degradation by the same C-rate may be accelerated. For example, when constant-current charging is performed using the same C-rate over a specific voltage range, as the battery degrades, more lithium deposition occurs.

However, the charging procedure using the multi-stage constant-current charge map according to the related art does not consider the operational state (for example, degradation) of the battery that changes over time.

SUMMARY

Technical Problem

The present disclosure is designed to solve the above-described problem, and therefore the present disclosure is directed to providing a battery management system, a battery management method, a battery pack and an electric vehicle, in which a multi-stage constant-current charge map is updated according to the operational state of a battery based on the voltage and current of the battery monitored during charging using the multi-stage constant-current charge map.

The present disclosure is further directed to providing a battery management system, a battery management method, a battery pack and an electric vehicle, in which even though the charging procedure is not completed across all of a plurality of voltage ranges, the C-rate associated with the remaining voltage range having not undergone constant-current charging is updated based on the update result of the C-rate associated with at least one voltage range having undergone constant-current charging.

These and other objects and advantages of the present disclosure may be understood by the following description and will be apparent from the embodiments of the present disclosure. In addition, it will be readily understood that the objects and advantages of the present disclosure may be realized by the means set forth in the appended claims and a combination thereof.

Technical Solution

A battery management system according to an aspect of the present disclosure includes a voltage sensor configured to generate a voltage signal indicating a battery voltage of a battery, a current sensor configured to generate a current signal indicating a battery current of the battery, memory configured to store a charge map recording a correlation between first to nthreference currents, first to nthreference voltage ranges, first to nthreference states of charge (SOCs) and first to nthreference voltage curves for multi-stage constant-current charging of the battery, and a controller, the memory having instructions programmed thereon that, when executed, are configured to cause the controller to determine a SOC of the battery based on at least one of the voltage signal or the current signal, in response to a charge start command, command constant-current charging to a charging circuit connected to the battery using a kthreference current corresponding to a kthreference voltage range to which the battery voltage belongs, and in response to the battery voltage having reached an upper limit of the kthreference voltage range, update the charge map by comparing a kthmeasured voltage curve indicating a correlation between the battery voltage and the SOC of the battery over a charging period of the constant-current charging with a kthreference voltage curve of the charge map. n is a natural number equal to 2 or greater, and k is a natural number of n or smaller.

The instructions may be configured to cause the controller to update the kthreference current based on a ratio of an average SOC of the kthmeasured voltage curve to an average SOC of the kthreference voltage curve.

The instructions may be configured to cause the controller to update the kthreference current based on a ratio of an average voltage of the kthreference voltage curve to an average voltage of the kthmeasured voltage curve.

The instructions may be configured to cause the controller to update the kthreference current based on a first ratio of an average SOC of the kthmeasured voltage curve to an average SOC of the kthreference voltage curve and a second ratio of an average voltage of the kthreference voltage curve to an average voltage of the kthmeasured voltage curve.

The instructions may be configured to cause the controller to update the kthreference current based on a ratio of a SOC of interest to a kthreference SOC. The SOC of interest is the SOC of the battery at a point in time when the battery voltage reaches the upper limit of the kthreference voltage range.

The instructions may be configured to cause the controller to update each remaining reference current except the kthreference current based on a ratio of the updated kthreference current to the kthreference current.

The instructions may be configured to cause the controller to command constant-voltage charging to the charging circuit using the upper limit of the kthreference voltage range in response to the battery voltage having reached the upper limit of the kthreference voltage range.

A battery pack according to another aspect of the present disclosure includes the battery management system of any of the embodiments described herein.

An electric vehicle according to still another aspect of the present disclosure includes the battery pack.

A battery management method according to yet another aspect of the present disclosure includes in response to a charge start command, commanding, by the controller, constant-current charging using a kthreference current corresponding to a kthreference voltage range to which a battery voltage of a battery belongs to a charging circuit connected to the battery, using a charge map recording a correlation between first to nthreference currents, first to nthreference voltage ranges, first to nthreference states of charge (SOCs) and first to nthreference voltage curves for multi-stage constant-current charging of the battery, and in response to the battery voltage having reached an upper limit of the kthreference voltage range, updating, by the controller, the charge map by comparing a kthmeasured voltage curve indicating a correlation between the battery voltage and a SOC of the battery over a charging period of the constant-current charging with a kthreference voltage curve of the charge map. n is a natural number equal to 2 or greater, and k is a natural number of n or smaller.

Updating the charge map may include updating the kthreference current based on a ratio of an average SOC of the kthmeasured voltage curve to an average SOC of the kthreference voltage curve.

Advantageous Effects

According to at least one of the embodiments of the present disclosure, it is possible to update a multi-stage constant-current charge map according to the operational state of a battery based on the voltage and current of the battery monitored during charging using the multi-stage constant-current charge map.

Additionally, according to at least one of the embodiments of the present disclosure, even though the charging procedure is not completed across all of a plurality of voltage ranges, the C-rate associated with the remaining voltage range having not undergone constant-current charging may be updated based on the update result of the C-rate associated with at least one voltage range having undergone constant-current charging.

The effects of the present disclosure are not limited to the effects mentioned above, and these and other effects will be clearly understood by those skilled in the art from the appended claims.

DETAILED DESCRIPTION

Hereinafter, the preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to the description, it should be understood that the terms or words used in the specification and the appended claims should not be construed as being limited to general and dictionary meanings, but rather interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define the terms appropriately for the best explanation.

Therefore, the embodiments described herein and the illustrations shown in the drawings are just a most preferred embodiment of the present disclosure, but not intended to fully describe the technical aspects of the present disclosure, so it should be understood that a variety of other equivalents and modifications could have been made thereto at the time that the application was filed.

Unless the context clearly indicates otherwise, it will be understood that the term “comprises” when used in this specification, specifies the presence of stated elements, but does not preclude the presence or addition of one or more other elements. Additionally, the term “control unit” refers to a processing unit of at least one function or operation, and this may be implemented by hardware and software either alone or in combination.

In addition, throughout the specification, it will be further understood that when an element is referred to as being “connected to” another element, it can be directly connected to the other element or intervening elements may be present.

FIG.1is a diagram exemplarily showing a configuration of an electric vehicle1according to the present disclosure.

Referring toFIG.1, the electric vehicle1includes a battery pack10, an inverter30, an electric motor40and a charging circuit50.

The battery pack10includes a battery B, a switch20and a battery management system100.

The battery B includes at least one battery cell. Each battery cell is not limited to a particular type, and may include any battery cell that can be repeatedly recharged such as, for example, a lithium ion cell. The battery B may be coupled to the inverter30and/or the charging circuit50through a pair of power terminals provided in the battery pack10.

The switch20is connected in series to the battery B. The switch20is installed on a current path for the charge/discharge of the battery B. The on/off of the switch20is controlled in response to a switching signal from the battery management system100. The switch20may be a mechanical relay that is turned on/off by the electromagnetic force of a coil or a semiconductor switch such as a Metal Oxide Semiconductor Field Effect transistor (MOSFET).

The inverter30is provided to convert the direct current (DC) from the battery B to alternating current (AC) in response to a command from the battery management system100. The electric motor40may be, for example, a three-phase AC motor. The electric motor40works using the AC power from the inverter30.

The battery management system100may be responsible for the general control related to the charge/discharge of the battery B.

The battery management system100includes a sensing unit110, a memory unit120and a control unit140. The battery management system100may further include at least one of an interface unit130or a switch driver150.

The sensing unit110includes a voltage sensor111and a current sensor112. The sensing unit110may further include a temperature sensor113.

The voltage sensor111is connected in parallel to the battery B and configured to detect a battery voltage across the battery B and generate a voltage signal indicating the detected battery voltage. The current sensor112is connected in series to the battery B through the current path. The current sensor112is configured to detect a battery current flowing through the battery B and generate a current signal indicating the detected battery current. The temperature sensor113is configured to detect a temperature of the battery B and generate a temperature signal indicating the detected temperature.

The memory unit120may include at least one type of storage medium of flash memory type, hard disk type, Solid State Disk (SSD) type, Silicon Disk Drive (SDD) type, multimedia card micro type, random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM) or programmable read-only memory (PROM). The memory unit120may store data and programs required for the computation operation by the control unit140. The memory unit120may store data indicating the result of the computation operation by the control unit140.

The memory unit120stores a charge map. The charge map may be pre-stored in the memory unit120before the battery management system100is loaded, or may be received from, for example, a battery manufacturer, or a high-level controller2through the interface unit130. The data recorded in the charge map may be preset based on test and/or simulation results of a sample battery having the same specification as the battery B.

The charge map is used in a charging procedure for multi-stage constant-current charging of the battery B. The charge map records a correlation between (i) first to nthreference currents, (ii) first to nthreference voltage ranges, (iii) first to nthreference state of charges (SOCs) and (iv) first to nthreference voltage curves for multi-stage constant-current charging. n is a natural number of 2 or greater. The later reference current may be smaller than the earlier reference current. Each reference voltage range may be referred to as ‘stage’.

The interface unit130may include a communication circuit configured to support wired or wireless communication between the control unit140and the high-level controller2(for example, an Electronic Control Unit (ECU)). The wired communication may be, for example, controller area network (CAN) communication, and the wireless communication may be, for example, Zigbee or Bluetooth communication. The communication protocol is not limited to a particular type, and may include any communication protocol that supports the wired/wireless communication between the control unit140and the high-level controller2. The interface unit130may include an output device (for example, a display, a speaker) to provide the information received from the control unit140and/or the high-level controller2in a recognizable format. The high-level controller2may control the inverter30based on battery information (for example, voltage, current, temperature, SOC) collected through the communication with the battery management system100. The high-level controller2may transmit a charge start command or charge stop command to the battery management system100in response to the vehicle's user input.

The control unit140may be operably coupled to the high-level controller2, the switch20, the charging circuit50, the sensing unit110, the memory unit120, the interface unit130and/or the switch driver150. Operably coupled refers to directly/indirectly connected to transmit and receive a signal in one or two directions.

The switch driver150is electrically coupled to the control unit140and the switch SW. The switch driver150is configured to selectively turn on/off the switch SW in response to a command from the control unit140. The control unit140may command the switch driver150to turn on the switch SW during the charging procedure.

The control unit140may collect a sensing signal from the sensing unit110. The sensing signal indicates the detected voltage signal, the detected current signal and/or the detected temperature signal in synchronization.

The control unit140may be referred to as a ‘battery controller’, and may be implemented in hardware using at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), microprocessors or electrical units for performing the other functions.

The interface unit130may relay the bi-directional communication between the control unit140and the charging circuit50and the bi-directional communication between the control unit140and the high-level controller2. The charging circuit50is configured to supply a charge current of a C-rate requested from the battery management system100to the battery B. The charging circuit50may be configured to supply a charge voltage having a voltage level requested from the battery management system100to the battery B. The control unit140is configured to start the charging procedure using the charge map in response to receiving the charge start command through the interface unit130. The control unit140may terminate the charging procedure using the charge map in response to receiving the charge stop command through the interface unit130.

The control unit140may determine a SOC indicating the remaining capacity of the battery B based on the sensing signal. In determining the SOC, a well-known algorithm such as ampere counting, an open circuit voltage (OCV)-SOC curve and a Kalman filter may be used. The SOC of the battery B may be referred to as a ‘battery SOC’.

FIG.2is a diagram exemplarily showing the correlation between the reference current and the reference voltage range recorded in the charge map, andFIG.3is a diagram exemplarily showing the correlation between the reference voltage range and the reference SOC recorded in the charge map. For convenience of description,FIGS.2and3show n=4, that is, the charge map defining the correlation between four reference currents, four reference voltage ranges and four reference SOCs.

A current profile210shown inFIG.2indicates the correlation between the first to fourth reference currents I1˜I4and the first to fourth reference voltage ranges ΔV1˜ΔV4for the battery B at Beginning Of Life (BOL). The current profile210may be recorded in the charge map in the format of a data table. When k (may be referred to as a ‘charge index’) is a natural number of n or smaller, Vk−1and Vkis the lower limit and upper limit of the kthreference voltage range Vk, respectively.

The first to fourth reference voltage ranges ΔV1˜ΔV4are consecutive in a sequential order. Accordingly, when i is a natural number of (n−1) or smaller, Viis the upper limit of the ithreference voltage range ΔVi, and the lower limit of the (i+1)threference voltage range ΔVi+1. For example, each of the upper limit of ΔV2and the lower limit of ΔV3is V2and equal to each other. Hereinafter, Vkmay be referred to as a ‘kthreference voltage’.

When the battery voltage of the battery B is found in the ithreference voltage range ΔVi, the control unit140may command constant-current charging using the ithreference current Iito the charging circuit50.

During the constant-current charging using the ithreference current Ii, when the SOC of the battery B reaches the upper limit Viof the ithreference voltage range ΔVi, the control unit140may command constant-current charging using the (i+1)threference current Ii+1to the charging circuit50. That is, the control unit140may change from the constant-current charging using the ithreference current Iito the constant-current charging using the (i+1)threference current Ii+1.

During the constant-current charging using the nthreference current In, when the SOC of the battery B reaches the upper limit Vnof the nthreference voltage range ΔVn, the control unit140may terminate the multi-stage constant-current charging using the charge map and command constant-voltage charging using the upper limit Vnto the charging circuit50. That is, the control unit140may change from the constant-current charging using the nthreference current Into the constant-voltage charging using the upper limit Vn.

A first voltage profile310shown inFIG.3shows the correlation between the first to fourth reference SOCs S1˜S4and the first to fourth reference voltages ΔV1˜ΔV4for the battery B at BOL. The first voltage profile310may be recorded in the charge map in the format of a data table. The first voltage profile310includes first to fourth reference voltage curves. The kthreference voltage curve is part corresponding to the kthreference voltage range ΔVkin the first voltage profile310.

Skindicates the SOC of the battery B when the battery voltage of the battery B at BOL reaches the kthreference voltage Vkby the constant-current charging using the kthreference current Ik.

Meanwhile, as the battery B gradually degrades, the capacity loss of the battery B increases, and thus the voltage rise by the same charge capacity increases compared to when the battery B is at BOL. Accordingly, the battery voltage having reached the kthreference voltage Vkbefore the SOC reaches the kthreference SOC Skduring the constant-current charging using the kthreference current Ikof the charge map indicates that the battery B degraded compared to when the battery B is at BOL A second voltage profile320shown inFIG.3indicates the correlation between a change history of battery voltage and a change history of SOC, monitored through the constant-current charging process of the degraded battery B using the first to fourth reference currents I1˜I4in a sequential order for each of the first to fourth reference voltage ranges ΔV1˜ΔV4without applying the battery management method (seeFIG.4) according to the present disclosure. Referring to the second voltage profile320, Zkis the battery SOC when the battery voltage of the degraded battery B reaches the kthreference voltage Vk, and is found lower than the kthreference SOC Sk. That is, S1>Z1, S2>Z2, S3>Z3, S4>Z4.

During the constant-current charging using the kthreference current Ik, the battery voltage having reached the kthreference voltage Vkbefore the SOC of the battery B reaches the kthreference SOC Skindicates that it is necessary to reduce the kthreference current Ikin the next multi-stage constant-current charging procedure. The decrease in the kthreference current Ikmay be determined considering the voltage history and/or SOC history monitored during charging by the kthreference current Ik.

A third voltage profile330shown inFIG.3indicates the correlation between the change history of battery voltage and the change history of SOC monitored through the process of charging the degraded battery B by applying a battery management method (seeFIG.4) according to the present disclosure, respectively. The third voltage profile330includes first to fourth measured voltage curves. The kthmeasured voltage curve is part corresponding to the kthreference voltage range ΔVkin the third voltage profile330.

Referring to the third voltage profile330, the control unit140monitors the battery voltage, the battery current and the SOC at a preset time interval (for example, 0.001 sec) during the constant-current charging using the kthreference current Ik. The control unit140may change from the constant-current charging using the kthreference current Ikto constant-voltage charging using the kthreference voltage Vkin response to the battery voltage having reached the kthreference voltage Vkbefore the SOC of the battery B reaches the kthreference SOC Sk. Accordingly, the battery B is charged at constant-voltage of the kthreference voltage Vkfrom the time when the battery voltage reaches the kthreference voltage Vkto the time when the SOC of the battery B reaches the kthreference SOC Sk. For example, after the constant-current charging using the second reference current I2is performed over the voltage range of V1˜V2, the constant-voltage charging of the battery B is performed with the same charge voltage as the kthreference voltage V2until the SOC of the battery B reaches the second reference SOC S2. During the constant-voltage charging using the kthreference voltage range ΔVk, the battery voltage gradually increases and the battery current gradually reduces. During the constant-voltage charging using the kthreference voltage range ΔVk, the control unit140may monitor the battery voltage, the battery current and the SOC at the predetermined time interval.

The control unit140may update the kthreference current Ikof the charge map including the current profile210ofFIG.2and the first voltage profile310ofFIG.3based on the battery voltage, the battery current and the SOC monitored during charging over the kthreference voltage range ΔVk. Each current I11˜I14of the current profile230ofFIG.2may be the result of updating the reference currents I1˜I4of the charge map.

Specifically, the control unit140may determine at least one of an average voltage or an average SOC of the kthreference voltage curve. The average voltage of the kthreference voltage curve is an average battery voltage over the kthreference voltage range ΔVkin the first voltage profile310. The average SOC of the kthreference voltage curve is an average SOC over the kthreference voltage range ΔVkin the first voltage profile310.

The control unit140may determine at least one of an average voltage or an average SOC of the kthmeasured voltage curve. The average voltage of the kthmeasured voltage curve is an average battery voltage over the kthreference voltage range ΔVkin the third voltage profile330. The average SOC of the kthmeasured voltage curve is an average SOC over the kthreference voltage range ΔVkin the third voltage profile330.

Subsequently, the control unit140may update the kthreference current Ikof the charge map based on at least one of the average voltage or the average SOC of the kthreference voltage curve and at least one of the average voltage or the average SOC of the kthmeasured voltage curve.

The control unit140may update the kthreference current Ikbased on a first ratio (less than 1) of the average SOC of the kthmeasured voltage curve to the average SOC of the kthreference voltage curve. For example, the control unit140may update the kthreference current Ikto be equal to the multiplication of the first ratio and the kthreference current Ik.

Alternatively, the control unit140may update the kthreference current Ikbased on a second ratio (less than 1) of the average voltage of the kthreference voltage curve to the average voltage of the kthmeasured voltage curve. For example, the control unit140may update the kthreference current Ikto equal to the multiplication of the second ratio and the kthreference current Ik.

Alternatively, the control unit140may update the kthreference current Ikbased on the first ratio and the second ratio. For example, the control unit140may update the kthreference current Ikto be equal to the multiplication of the first ratio, the second ratio and the kthreference current Ik.

Alternatively, the control unit140may update the kthreference current Ikbased on a third ratio (less than 1) of a SOC of interest to the kthreference SOC Sk. For example, the control unit140may update the kthreference current Ikto be equal to the multiplication of the third ratio and the kthreference current Ik. The SOC of interest may be equal to the SOC Uk of the battery B at the time when the battery voltage reaches the kthreference voltage Vk.

Meanwhile, the charging procedure according to the battery management method described above is often not performed in part of the reference voltage range ΔV1˜ΔV4. For example, referring toFIGS.2and3, in case that the charging procedure using the charge map starts when the battery voltage is higher than V0, it is impossible to obtain the first measured voltage curve over the entire first reference voltage range ΔV1, and the above-described method cannot update the first reference current I1. In another example, when the vehicle user separates a charging cable from the electric vehicle1before the battery voltage reaches V4, it is impossible to obtain the fourth measured voltage curve over the entire fourth reference voltage range ΔV4, so it is impossible to update the fourth reference current I4.

To solve the above-described problem, in case that charging starts when the battery voltage is larger than V0, or charging ends when the battery voltage is smaller than V4, the control unit140may update the reference current associated with each of the remaining reference voltage ranges based on the update information of at least one reference voltage range in which the measured voltage curve is obtained among all the reference voltage ranges ΔV1˜ΔV4.

Assume that only the kthreference current Ikcorresponding to the kthreference voltage range ΔVkwas updated to I1kaccording to the above-described battery management method. The control unit140may determine a ratio of I1kto Ik, and update each of the remaining reference currents based on the determined ratio. For example, when the second reference current I2is updated from 120 A to 100 A, the control unit140may update the first reference current I1, the third reference current I3and the fourth reference current I4by multiplying each of the first reference current I1, the third reference current I3and the fourth reference current I4by 100/120=⅚.

Assume that each of i and j is a natural number, i≤j, i is 2 or greater or j is less than n=4. Only the ithto jthreference currents Ii˜Ijcorresponding to the ithto jthreference voltage ranges ΔVi˜ΔVjare updated to according to the battery management method (seeFIG.4), respectively, and the charging procedure may end. Then, the control unit140may update each of the remaining reference currents using the following equation.

In the above equation, x is a natural number of n or smaller except i to j, Ixis the reference current before update, and I1xis the updated reference current. μavgis an average ratio of the ithto jthupdated reference currents I1i˜I1jto the ithto jthreference currents Ii˜Ij.

FIG.4is a flowchart exemplarily showing a battery management method according to a first embodiment of the present disclosure. The method ofFIG.4may start in response to the charge start command from the vehicle user.

Referring toFIGS.1to4, in step S410, the control unit140selects the kthreference current Ikcorresponding to the kthreference voltage range ΔVkto which the battery voltage of the battery B belongs, from the charge map. For example, when the battery voltage is equal to or higher than V1and less than V2, the second reference current I2is selected.

In step S420, the control unit140commands constant-current charging using the kthreference current Ikto the charging circuit50. Accordingly, the charging circuit50starts the constant-current charging using the kthreference current Ikby supplying the kthreference current Ikas the charge current to the battery B.

In step S430, the control unit140determines whether the battery voltage reached the kthreference voltage Vkbefore the battery SOC reaches the kthreference SOC Sk. When a value of the step S430is “YES”, step S450is performed. When the value of the step S430is “NO”, the step S430is performed again after the lapse of a predetermined time.

In step S440, the control unit140commands constant-voltage charging using the kthreference voltage Vkto the charging circuit50. Accordingly, the charging circuit50terminates the constant-current charging using the kthreference current Ik, and at the same time, supplies the charge voltage that is equal to the kthreference voltage Vkto the battery B.

In the step S450, the control unit140determines whether the battery SOC reached the kthreference SOC Sk. When a value of the step S450is “YES”, step S460is performed. When the value of the step S450is “NO”, the step S450is performed again after the lapse of a predetermined time.

In the step S460, the control unit140determines the kthmeasured voltage curve. The kthmeasured voltage curve indicates the correlation between the battery voltage and the battery SOC over the charging period of the constant-current charging using the kthreference current Ik.

In step S470, the control unit140determines whether the voltage range of the kthmeasured voltage curve is equal to the kthreference voltage range ΔVk. When a value of the step S470is “YES”, step S480is performed. When the value of the step S470is “NO”, step S490may be performed. For example, when constant-current charging with the first reference current I1is performed from the time when the battery voltage is higher than Vo and lower than V1, the value of the step S470is “NO”.

In the step S480, the control unit140updates the charge map based on the kthreference voltage curve and the kthmeasured voltage curve.

In the step S490, the control unit140determines whether the charge index k is equal to n. That is, the control unit140determines whether charging for the last reference voltage range ΔVndefined by the charge map was completed. When a value of the step S490is “NO”, the charge index k may be increased by 1 in the step S492, and the method may return to the step S430. When the value of the step S490is “YES”, the method ofFIG.4may end.

The method ofFIG.4may start in response to the charge start command when a predetermined update condition is satisfied. The update condition is for preventing the unnecessarily frequent updates of the charge map. The update condition indicates an increase in the degree of degradation of the battery B over a predetermined level, and may be, for example, an increase in the accumulated capacity of the battery B by at least a first threshold (for example, 100 Ah[ampere-hour]) than the accumulated capacity at the previous update time, an increase in the cycle number of the battery B by at least a second threshold (for example, 50 times) than the cycle number at the previous update time, a reduction in the capacity retention rate of the battery B by at least a third threshold (for example, 5%) than the capacity retention rate at the previous update time, and a lapse of at least a threshold time (for example, a month) from the previous update time.

FIG.5is a flowchart exemplarily showing a battery management method according to a second embodiment of the present disclosure. When only the ithto jthreference currents Ii˜Ijamong the first to nthreference currents I1˜Inare updated through the method ofFIG.4, the method ofFIG.5may be used to update each of the remaining reference currents. That is, the method ofFIG.5may be performed when the battery B is charged over only part of the voltage range of V0˜Vnby the method ofFIG.4. As described above, each of i and j is a natural number, i<j, and i is 2 or greater, or j is less than n (for example, 4).

In step S510, the control unit140calculates the average ratio of the ithto jthupdated reference currents I1i˜I1jto the ithto jthreference currents Ii˜Ij(see μavgof the above equation).

In step S520, the control unit140updates each of the remaining reference currents except the ithto jthreference currents I1˜Ijamong the first to nthreference currents I1˜Inby multiplying each of the remaining reference currents by the average ratio.

The embodiments of the present disclosure described hereinabove are not implemented only through the apparatus and method, and may be implemented through programs that perform functions corresponding to the configurations of the embodiments of the present disclosure or recording media having the programs recorded thereon, and such implementation may be easily achieved by those skilled in the art from the disclosure of the embodiments previously described.

Additionally, as many substitutions, modifications and changes may be made to the present disclosure described hereinabove by those skilled in the art without departing from the technical aspects of the present disclosure, the present disclosure is not limited by the above-described embodiments and the accompanying drawings, and some or all of the embodiments may be selectively combined to allow various modifications.