Protection control device for secondary battery

Abstract

This protection control device for a secondary battery is provided with: a current load calculation unit that calculates, for each predetermined calculation interval, an average absolute value of current values of a current that has flowed through the secondary battery during charging and discharging; an overload suppression determination unit that determines whether or not the average absolute value of the current values calculated for each calculation interval exceeds a predetermined suppression determination threshold value for each temperature of the secondary battery; a suppression current value calculation unit that calculates a suppression current value of the current flowing through the secondary battery when it is determined that the average absolute value of the current values calculated for each calculation interval exceeds the suppression determination threshold value; and a current value suppression unit that suppresses the current value of the current flowing through the secondary battery so that the current flowing through the secondary battery is equal to or less than the suppression current value.

Description

Secondary battery protection control device

[0001] The present disclosure relates to a protection and control device for a secondary battery.

[0002] Patent document 1 describes a battery control device that controls current so that the average value of the absolute value of the current calculated for each time window width falls within the upper limit of the average value for each time window width indicated in the allowable average current characteristic information.

[0003] International Publication No. 2013 / 094057

[0004] In the battery control device described in Patent Document 1, the upper limit of the average value for each time window width indicated in the allowable average current characteristic information is not determined for each battery temperature. Therefore, the battery control device described in Patent Document 1 ignores the internal resistance of the battery, which varies with battery temperature, and is unable to suppress metal deposition (electrodeposition) on the negative electrode surface.

[0005] In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a protection and control device for a secondary battery that can suppress metal deposition on the surface of a negative electrode.

[0006] (1) A protection control device for a secondary battery according to at least one embodiment of the present invention is a protection control device for a secondary battery that repeatedly charges and discharges, and includes: a current value measurement unit that measures the current value of the current flowing through the secondary battery; a battery temperature measurement unit that measures the temperature of the secondary battery; a current load calculation unit that calculates the average absolute value of the current value of the current flowing through the secondary battery during charging and discharging for each predetermined calculation interval; an overload suppression determination unit that determines whether the average absolute value of the current value calculated for each calculation interval exceeds a predetermined suppression determination threshold for each temperature of the secondary battery; a suppression current value calculation unit that calculates a suppression current value of the current flowing through the secondary battery when it is determined that the average absolute value of the current value calculated for each calculation interval exceeds the suppression determination threshold; and a current value suppression unit that suppresses the current value of the current flowing through the secondary battery so that the current flowing through the secondary battery is equal to or less than the suppression current value.

[0007] According to the above configuration (1), when the overload suppression determination unit determines that the average absolute value of the current values ​​calculated for each calculation interval exceeds the suppression determination threshold, the suppression current value calculation unit calculates a suppression current value of the current flowing to the secondary battery, and the current value suppression unit suppresses the current value of the current flowing to the secondary battery so that the current flowing to the secondary battery is equal to or less than the suppression current value, thereby suppressing metal deposition on the negative electrode surface.

[0008] (2) In some embodiments, the configuration of (1) above includes a suppression release determination unit that, when the current value of the current flowing through the secondary battery is limited, determines whether the average absolute value of the current value calculated for each calculation interval is equal to or less than a suppression release threshold value that is predetermined for each temperature of the secondary battery, and a current value suppression release unit that releases the suppression of the current value of the current flowing through the secondary battery when it is determined that the average absolute value of the current value calculated for each calculation interval is equal to or less than the suppression release threshold value.

[0009] According to the configuration (2) above, when the suppression release determination unit determines that the average absolute value of the current value calculated for each calculation interval is equal to or less than the suppression release threshold, the current value suppression release unit releases the suppression of the current value of the current flowing to the secondary battery, thereby increasing the current value of the current flowing to the secondary battery (the output of the secondary battery).

[0010] (3) In some embodiments, in the configuration of (1) or (2) above, the current value suppression unit has a change rate limiting unit that limits the current value so that the change rate of the current value is equal to or less than a predetermined change rate.

[0011] According to the configuration (3) above, the change rate limiting unit limits the current value so that the rate of change of the current value is equal to or less than a predetermined rate of change, thereby suppressing a sudden decrease in the current value (output of the secondary battery).

[0012] (4) In some embodiments, in the configuration of (1) or (2) above, the current load calculation unit calculates the average absolute value of the current value by a weighted average.

[0013] According to the configuration (4) above, the current load calculation unit calculates the absolute average of the current value using a weighted average, so that the calculation load of the current load calculation unit can be reduced compared to when the current load calculation unit calculates the absolute average using a moving average.

[0014] (5) In some embodiments, in the configuration of (1) or (2) above, the secondary battery is a lithium ion battery.

[0015] According to the above configuration (5), the secondary battery is a lithium ion battery, so that the energy density can be increased.

[0016] According to at least one embodiment of the present invention, the protection and control device for a secondary battery can suppress metal deposition on the surface of the negative electrode.

[0017] The present invention relates to a battery management unit for a vehicle, a method for controlling a vehicle, and a vehicle driving method, and to a battery management unit for controlling a vehicle.

[0018] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0019] The secondary battery repeatedly charged and discharged according to the embodiment is, for example, a lithium-ion battery mounted on an electric vehicle, but is not limited thereto. Electric vehicles on which the lithium-ion battery according to the embodiment is mounted include, for example, electric vehicles (EVs), hybrid vehicles (HVs), and fuel cell vehicles (FCVs). Hybrid vehicles include plug-in hybrid vehicles (PHVs, PHEVs) that can be charged (externally charged) from an external device (e.g., a quick charger) while parked, and plug-in hybrid vehicles (PHEVs) that can be externally charged while parked and can supply power (externally powered) to an external device (e.g., a general household) while parked.

[0020] [Battery Pack] As shown in FIG. 1 , a plurality (a large number) of lithium-ion batteries 1 (hereinafter referred to as "battery cells 1") mounted on an electric vehicle are connected in series and housed in a single container 3 to form a drive battery 5 (hereinafter referred to as "battery pack 5") for the electric vehicle. However, the plurality of battery cells 1 may also be connected in parallel. All of the battery cells 1 housed in the battery pack 5 are grouped into several groups, and the plurality of battery cells 1 included in a group constitute one battery module 7. The battery module 7 is provided with a voltage measurement unit 11 and a temperature measurement unit 13. The voltage measurement unit 11 measures the voltage of each battery cell 1, and the temperature measurement unit 13 measures the temperature of each battery cell 1. A circuit 15 in which the plurality of battery cells 1 are connected in series is provided with a current measurement unit 17 (e.g., a current sensor) and a leakage current measurement unit 19 (e.g., a leakage current sensor), which measure the current value of the current flowing through the circuit 15 (battery cells 1).

[0021] The battery module 7 is connected to a battery management unit (BMU) 23. The battery management unit 23 is configured by, for example, a processor configured by an arithmetic unit, registers for storing instructions and information, peripheral circuits, etc., memories such as ROM (Read Only Memory) and RAM (Random Access Memory), and an input interface. The battery management unit 23 determines the state of the battery cells 1 based on the current measured by the current measurement unit 17 and the leakage measurement unit 19, and the voltage and temperature of each battery cell 1, and transmits the necessary information to a vehicle integrated controller (EV-ECU) 27 via a vehicle CAN (Vehicle-CAN) 25.

[0022] [Battery Management Unit (Protection and Control Device)] As shown in FIG. 2 , the battery management unit 23 is provided with a current load calculation unit 29, an overload suppression determination unit 31, a suppression current value calculation unit 33, and a current value suppression unit 35.

[0023] The current load calculation unit 29 is a part that calculates the average absolute value of the current value flowing through the battery cell 1 (circuit 15) during charging and discharging for each predetermined calculation interval. The current value measured by the current measurement unit 17 is input to the current load calculation unit 29. The calculation interval is set appropriately within a range from several seconds to several tens of hours, but the calculation interval may be multiple and is not limited to one. The current load calculation unit 29 calculates the average absolute value of the current value using a weighted average, but this is not limited to this and the calculation may also be performed using a moving average, for example.

[0024] The overload suppression determination unit 31 is a part that determines whether the average absolute value of the current value calculated for each calculation interval exceeds a suppression determination threshold that is predetermined for each temperature of the battery module 7 (battery cell 1). The overload suppression determination unit 31 receives as input the degree of deterioration (internal resistance or state of health (SOH (State of Health))) and the battery cell temperature. The suppression determination threshold is determined for each temperature of the battery cell 1 and for each calculation interval. The suppression determination threshold is set, for example, by checking the presence or absence of metal deposition on the negative electrode surface in a verification test, and the suppression determination threshold is corrected based on the degree of deterioration (internal resistance or state of health).

[0025] The suppression current value calculation unit 33 is a part that calculates a suppression current value of the current flowing through the battery cell 1 when it is determined that the average absolute value of the current values ​​calculated for each calculation interval exceeds the suppression determination threshold. The suppression current value calculation unit 33 receives input of the degradation level (internal resistance or health level) and the battery cell temperature as well as the allowable discharge current (or allowable input current). The allowable discharge current and the allowable input current are calculated by the battery management unit 23 based on information such as the temperature of the battery cell 1, the charging rate (SOC (State of Charge)) of the battery cell 1, and the degradation level (internal resistance, health level).

[0026] The current value suppression unit 35 is a part that suppresses the current value of the current flowing through the battery module 7 (battery cell 1) so that the current flowing through the battery module 7 (battery cell 1) is equal to or less than the suppressed current value.

[0027] As shown in FIG. 2, the current value suppression unit 35 has a change rate limiting unit 37 that limits the current value so that the rate of change of the current value is equal to or less than a predetermined change rate, but the change rate limiting unit 37 is not essential.

[0028] As shown in FIG. 3 , the battery management unit 23 is provided with a restriction release determination unit 39 and a current value restriction release unit 41 .

[0029] The suppression release determination unit 39 is a part that determines whether the average absolute value of the current value calculated for each calculation interval is equal to or less than a suppression release threshold value predetermined for each battery cell temperature when the current value of the current flowing through the battery module 7 (battery cell 1) is limited. The suppression release determination unit 39 receives input of the deterioration level (internal resistance or health level) and the battery cell temperature. The suppression release threshold value is determined for each temperature of the battery cell 1 and for each calculation interval. The suppression release threshold value is set, for example, by a verification test. In the verification test, conditions for electrodeposition (NG line) and conditions for no electrodeposition (OK line) are confirmed, and this OK line becomes the suppression determination threshold value, and the suppression release threshold value has hysteresis relative to the OK line.

[0030] The current value suppression release unit 41 is a part that releases the suppression of the current value of the current flowing to the battery module 7 (battery cell 1) when it is determined that the absolute value average of the current value calculated for each calculation interval is below the suppression release threshold.

[0031] As shown in FIG. 3, the current value suppression cancellation unit 41 has a change rate limiting unit 43 that limits the current value so that the rate of change of the current value is equal to or less than a predetermined change rate, but the change rate limiting unit 43 is not essential.

[0032] [Effects of Battery Management Unit (Protection Control Device)] According to the battery management unit 23 of the embodiment, when the overload suppression determination unit 31 determines that the average absolute value of the current values ​​calculated for each calculation interval exceeds the suppression determination threshold, the suppression current value calculation unit 33 calculates the suppression current value of the current flowing to the battery module 7 (battery cell 1), and the current value suppression unit 35 suppresses the current value of the current flowing to the battery module 7 (battery cell 1) so that the current flowing to the battery module 7 (battery cell 1) is equal to or less than the suppression current value, thereby suppressing metal deposition on the negative electrode surface.

[0033] Furthermore, since the current load calculation unit 29 calculates the absolute average of the current values ​​using a weighted average, the calculation load on the current load calculation unit 29 can be reduced compared to when calculation is performed using a moving average.

[0034] In addition, the change rate limiting unit 37 limits the current value so that the rate of change of the current value is equal to or less than a predetermined rate of change, thereby suppressing a sudden decrease in the current value (output of the battery cell 1).

[0035] When the suppression release determination unit 39 determines that the average absolute value of the current value calculated for each calculation interval is below the suppression release threshold, the current value suppression release unit 41 releases the suppression of the current value of the current flowing to the battery module 7 (battery cell 1), thereby increasing the current value (output of battery cell 1) of the current flowing to the battery module 7 (battery cell 1).

[0036] The change rate limiting unit 43 limits the current value so that the rate of change of the current value is equal to or less than a predetermined rate of change, thereby suppressing a sudden increase in the current value (output of the battery cell 1).

[0037] Furthermore, since the secondary battery according to the embodiment is a lithium ion battery, the energy density can be increased.

[0038] The present invention is not limited to the above-described embodiments, and includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0039] REFERENCE SIGNS LIST 1 Battery cell (lithium ion battery) 3 Container 5 Battery pack (driving battery) 7 Battery module 11 Voltage measurement unit 13 Temperature measurement unit 15 Circuit 17 Current measurement unit 19 Leakage measurement unit 23 Battery management unit (BMU) 25 Vehicle CAN 27 Vehicle integrated control controller (EV-ECU) 29 Current load calculation unit 31 Overload suppression determination unit 33 Suppression current value calculation unit 35 Current value suppression unit 37 Change rate limiting unit 39 Suppression release determination unit 41 Current value suppression release unit 43 Change rate limiting unit

Claims

1. A protection control device for a secondary battery that is repeatedly charged and discharged, comprising: a current value measurement unit that measures the current value of the current flowing to the secondary battery; a battery temperature measurement unit that measures the temperature of the secondary battery; a current load calculation unit that calculates an average absolute value of the current value of the current flowing to the secondary battery during charging and discharging for each predetermined calculation interval; an overload suppression judgment unit that judges whether the average absolute value of the current value calculated for each calculation interval exceeds a predetermined suppression judgment threshold for each temperature of the secondary battery; a suppression current value calculation unit that calculates a suppression current value of the current flowing to the secondary battery when it is judged that the average absolute value of the current value calculated for each calculation interval exceeds the suppression judgment threshold; and a current value suppression unit that suppresses the current value of the current flowing to the secondary battery so that the current flowing to the secondary battery is equal to or less than the suppression current value.

2. A protection and control device for a secondary battery as described in claim 1, comprising: a suppression release determination unit that determines whether the average absolute value of the current value calculated for each calculation interval is equal to or less than a suppression release threshold predetermined for each temperature of the secondary battery when the current value of the current flowing to the secondary battery is limited; and a current value suppression release unit that releases the suppression of the current value of the current flowing to the secondary battery when it is determined that the average absolute value of the current value calculated for each calculation interval is equal to or less than the suppression release threshold.

3. A protection and control device for a secondary battery as described in claim 1 or 2, wherein the current value suppression unit has a change rate limiting unit that limits the current value so that the change rate of the current value is equal to or less than a predetermined change rate.

4. The protection and control device for a secondary battery according to claim 1 or 2, wherein the current load calculation unit calculates the average absolute value of the current value by a weighted average.

5. The protection and control device for a secondary battery according to claim 1 or 2, wherein the secondary battery is a lithium ion battery.

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