Battery control device and battery control method

Abstract

This battery control device comprises a battery controller 10 that manages the state of a battery 1 on the basis of a detection value from a sensor connected to the battery 1 and controls charging and discharging of the battery 1. The battery controller 10 detects charge / discharge switching for switching the battery 1 from charging to discharging, sets a dischargeable amount in accordance with the state of the battery 1 at the time of charge / discharge switching, and prohibits discharging of the battery 1 when the discharge amount of the battery 1 from the time of charge / discharge switching reaches the dischargeable amount.

Description

Battery control device and battery control method

[0001] The present invention relates to a battery control device and a battery control method.

[0002] Conventionally, there has been known a power supply control device that supplies power to a group of auxiliaries using a main battery and a sub-battery that is an auxiliary power source (for example, see Patent Document 1). In the power supply control device described in Patent Document 1, when the main battery is not deteriorated, the user is prompted to select one of a fuel economy priority mode, a balanced mode, and a functionality priority mode, and the lower limit SOC of the sub-battery is set to one of an emergency lower limit value, an intermediate value, and a maximum value SCO depending on the mode selected by the user.

[0003] JP 2015-126574 A

[0004] In the power supply control device described in Patent Document 1, when the SOC difference between the current SOC of the sub-battery and the set lower limit SOC is large, when the sub-battery is discharged to the lower limit SOC, the discharge amount increases, accelerating deterioration of the sub-battery.

[0005] An object of the present invention is to provide a battery control device and a battery control method that prevent deterioration of a battery.

[0006] The present invention solves the above problem by detecting a charge / discharge switchover when the battery switches from charging to discharging, setting the dischargeable amount according to the state of the battery at the time of the charge / discharge switchover, and prohibiting battery discharge when the amount of discharge from the battery since the charge / discharge switchover reaches the dischargeable amount.

[0007] According to the present invention, deterioration of the battery can be prevented.

[0008] Fig. 1 is a block diagram of a battery control system according to an embodiment of the present invention. Fig. 2 is a graph showing the relationship between energy obtained by engine operation and energy consumed by auxiliary devices, etc. Fig. 3 is a flowchart showing a control flow of a battery control method according to this embodiment. Fig. 4 is a graph showing SOC characteristics during charging before a charge / discharge switching point and discharging after a charge / discharge switching point.

[0009] An embodiment of a battery control device and a battery control method according to the present invention will be described below with reference to the drawings. Fig. 1 is a block diagram of a battery control system according to an embodiment of the present invention. The battery control system 100 is mounted on a vehicle equipped with an engine, and is a system that manages the state of a battery 1 and controls the charging and discharging of the battery 1. Note that a device including a battery controller 10 corresponds to the "battery control device" of the present invention, and the battery control method executed by the battery controller 10 corresponds to the "battery control method" of the present invention.

[0010] As shown in FIG. 1, the battery control system 100 includes a battery 1, a current sensor 2, a voltage sensor 3, an alternator 4, an engine (ENG) 5, an inverter 6, a DC-DC converter 7, a starter motor 8, a relay switch 9, a battery controller 10, an idle stop (IS) controller 20, an energy management controller 30, and loads 41 and 42.

[0011] The battery (low-voltage battery) 1 is a low-voltage power source for operating the starter motor 8 and the load 41. The battery 1 is a battery of 50 volts or less, for example, a 12 V battery. The battery 1 is a secondary battery such as a lithium-ion battery or a lead battery. The battery 1 is electrically connected to the alternator 4, the starter motor 8, and the load 41. A lower limit SOC for preventing over-discharge is set in advance for the battery 1. The lower limit SOC is determined in advance based on the materials contained in the battery 1, the battery performance, etc.

[0012] The current sensor 2 and the voltage sensor 3 are connected to the battery 1. The current sensor 2 detects the charge / discharge current flowing through the battery 1. The voltage sensor 3 detects the terminal voltage of the battery 1. The current sensor 2 and the voltage sensor 3 output their detected values ​​to a battery controller 10. The alternator 4 is electrically connected to the battery 1 via an inverter 6 and a DC / DC converter 7. The alternator 4 charges the battery 1 by supplying generated power to the battery 1. The alternator 4 generates electricity using energy obtained from the engine 5. The alternator 4 is connected to the engine 5 via a gear unit, and generates electricity when the rotor included in the alternator 4 rotates due to the output torque (engine torque) of the engine 5.

[0013] The inverter 6 is a power converter that converts the power generated by the alternator 4 into DC power. The DC-DC converter 7 is connected between the battery 1 and the inverter 6, converts the output voltage of the inverter 6, and outputs it as a charging voltage for the battery 1. The DC-DC converter 7 also outputs power to the load 41.

[0014] The starter motor 8 is a motor for cranking the engine. When the relay switch 9 is turned on, power is supplied from the battery 1 to the starter motor 8, driving the starter motor 8. The relay switch 9 is connected between the battery 1 and the starter motor 8, and switches between electrical connection and disconnection from the battery 1 to the starter motor 8. The relay switch 9 is switched on and off by a control command from the IS controller 20.

[0015] The load 41 is operated by power output from the low-voltage battery 1 and / or the alternator 4, and is, for example, a fan included in an air conditioner, audio equipment such as a speaker, a lamp, etc. The load 42 is operated by power from the engine 5, and is, for example, a compressor included in an air conditioner, a transmission, etc.

[0016] The battery controller 10 manages the status of sensors (current sensor 2 and / or voltage sensor 3) connected to the battery 1 and controls the charging and discharging of the battery 1. The battery controller 10 is a processor for executing various functions, such as the function of managing the status of the battery 1, the function of controlling the charging and discharging of the battery 1, and the function of setting the dischargeable amount, and executes programs stored in the memory in the control unit. The battery controller 10 has, as functional blocks, a battery management unit 11, a charge and discharge control unit 12, and a dischargeable amount setting unit 13. Note that the battery controller 10 may have other functions in addition to the functions of each functional block such as the battery management unit 11.

[0017] The battery management unit 11 calculates the SOC (state of charge) of the battery 1 based on the current detected by the current sensor 2 and the voltage detected by the voltage sensor 3. When the battery 1 is in an unloaded state, the battery management unit 11 acquires the voltage detected by the voltage sensor 3 as the open-circuit voltage and calculates the SOC by referring to a map showing the correlation between the open-circuit voltage and the SOC of the battery 1. When the battery 1 is in a loaded state, the battery management unit 11 calculates the charge or discharge amount of the battery 1 by integrating the charge / discharge current of the battery 1 using the current detected by the current sensor 2. The battery management unit 11 calculates the current battery capacity by adding the calculated charge or discharge amount to the battery capacity (remaining capacity) at the start of charging or discharging the battery 1. The battery management unit 11 then calculates the current SOC by dividing the current battery capacity by the full charge capacity of the battery 1. Note that other methods may be used to calculate the SOC of the battery 1. The battery management unit 11 also detects a switch from charging to discharging of the battery 1 (hereinafter also referred to as a "charge / discharge switch"). Specifically, the battery management unit 11 detects a charge / discharge switch by determining whether the change in the SOC of the battery 1 has switched from an increase to a decrease, or whether the current of the battery 1 has changed from a charge current to a discharge current. When the battery management unit 11 detects a charge / discharge switch, it calculates the amount of discharge of the battery from the time of the charge / discharge switch. The charge / discharge switch time corresponds to the timing when the state of the battery 1 switches from charge to discharge.

[0018] The charge / discharge control unit 12 outputs control commands to the inverter 6 and the DC / DC converter 7 to control the charging current output from the alternator 4 to the battery 1. Furthermore, the charge / discharge control unit 12 stops charging the battery 1 when the battery 1 is fully charged. The charge / discharge control unit 12 controls the discharge current of the battery 1 when power is supplied from the battery 1 to the load 41. When the SOC of the battery 1 decreases due to discharge and reaches a lower limit SOC of the battery 1, the charge / discharge control unit 12 stops discharging from the battery 1. Furthermore, when the battery management unit 11 detects a charge / discharge switch, the charge / discharge control unit 12 stops discharging the battery 1 when the amount of discharge from the time of charge / discharge switch reaches the dischargeable amount. After the discharge of the battery 1 is stopped, discharging of the battery 1 is prohibited until the SOC of the battery 1 reaches the SOC at the time of charge / discharge switch. In other words, the charge / discharge control unit 12 prohibits discharging of the battery 1 when the amount of discharge from the time of charge / discharge switch reaches the dischargeable amount.

[0019] The dischargeable amount setting unit 13 sets the dischargeable amount according to the state of the battery 1 at the time of switching between charging and discharging. The dischargeable amount indicates the amount of discharge of the battery 1 that can be discharged from the time of switching between charging and discharging. The dischargeable amount setting unit 13 sets the chargeable and dischargeable amount according to the SOC or remaining capacity of the battery 1 at the time of switching between charging and discharging. For example, the dischargeable amount setting unit 13 sets the chargeable and dischargeable amount so that the larger the SOC or remaining capacity of the battery 1 at the time of switching between charging and discharging, the larger the dischargeable amount. For example, the dischargeable amount setting unit 13 may calculate the dischargeable amount by multiplying the remaining capacity of the battery 1 by a predetermined percentage (e.g., 1%). In this case, the dischargeable amount setting unit 13 may set the predetermined percentage to a value corresponding to the SOC or remaining capacity of the battery 1. Furthermore, when setting the dischargeable amount at the time of switching between charging and discharging, the dischargeable amount setting unit 13 may set the dischargeable amount so that the SOC when the discharge amount of the battery 1 reaches the dischargeable amount is higher than a lower limit SOC that prevents over-discharge of the battery 1. This makes it possible to suppress deterioration of the battery 1 .

[0020] The dischargeable amount setting unit 13 may also set the dischargeable amount based on the vehicle environment and / or the operating conditions of the loads 41, 42 at the time of switching. The vehicle environment is represented by the temperature and / or humidity of the vehicle's surrounding environment (exterior or interior environment). The temperature and / or humidity are used to predict operating requirements for the loads 41, 42, such as an air conditioner. For example, when the outside temperature is low in winter or high in summer, the air conditioner is expected to be used. If the difference between the current outside temperature and the comfortable temperature is large, the air conditioner's airflow rate may be increased. If the output torque of the engine 5 is insufficient when the air conditioner is used, the charge capacity of the battery 1 is used to operate the air conditioner. In such cases, it is preferable to increase the dischargeable amount of the battery 1 to satisfy the operating requirements for the air conditioner. That is, the dischargeable amount setting unit 13 may increase the dischargeable amount if it is possible to predict a situation in which the air conditioner will be used based on the vehicle environment at the time of switching.

[0021] Furthermore, when the operating conditions of the loads 41, 42 indicate that a large amount of energy obtained from the output torque of the engine 5 is being used for operating the loads 41, 42, the alternator 4, etc., and then attempting to operate another load 41, 42, an energy shortage occurs. When such an energy shortage occurs, it is preferable to compensate for the energy shortage by discharging the battery 1. That is, the dischargeable amount setting unit 13 may increase the dischargeable amount if it can predict that the output torque of the engine 5 will be insufficient energy based on the operating conditions of the loads 41, 42 at the time of switching. Note that the dischargeable amount setting unit 13 may increase the dischargeable amount depending on the vehicle environment and / or the operating conditions of the loads 41, 42 at the time of switching between charge and discharge when the SOC or remaining capacity of the battery 1 is sufficiently high (e.g., SOC: 70 to 80% or more). That is, the dischargeable amount setting unit 13 may increase the dischargeable amount when the battery 1 is in a state in which discharging the battery 1 will not accelerate deterioration of the battery 1.

[0022] The IS controller 20 performs an idling stop when an idling stop condition is satisfied. The idling stop condition is defined by the vehicle speed, whether the brakes are applied, the engine rotation speed, etc. For example, the idling stop condition is when the vehicle speed is zero, the brakes are applied, and the engine rotation speed is less than a predetermined rotation speed threshold. The idling stop period (the period during which the engine is stopped) is predetermined, such as one minute. The IS controller 20 cancels the idling stop when the elapsed time of the idling stop reaches the idling stop period, or when the vehicle state during the idling stop does not satisfy the idling stop condition. When canceling the idling stop, the IS controller 20 turns on the relay switch 9 to drive the starter motor 8.

[0023] During idling stop, the engine 5 is stopped and the loads 41 and 42 operate on the power of the battery 1. That is, before idling stop, the engine 5 is running, so the battery 1 is charged with the power generated by the alternator 4. When idling stop is performed, the battery 1 switches from charging to discharging. The battery management unit 11 then detects the switch between charging and discharging that occurs due to idling stop.

[0024] The EM controller 30 is a control unit that controls an energy management system in a vehicle. The energy management system is a system that is installed in a vehicle and controls energy for auxiliary devices. The energy management system distributes the output torque of the engine 5 to energy for operating the loads 41, 42 and the alternator 4.

[0025] With reference to Figure 2, the distribution of energy executed by the energy management system while the vehicle is running will be described. Figure 2 is a graph showing the relationship between the energy obtained by engine operation and the energy consumed by accessories, etc. In Figure 2, "ENG torque" indicates the energy obtained from the output torque of the engine 5, "TM load" indicates the energy required to operate the transmission included in the load 42, "AC load" indicates the energy required to obtain from the output torque of the engine 5 in order to operate the air conditioner, and "generator load" indicates the energy required to operate the alternator 4 and the load 41.

[0026] As shown in FIG. 2(a), even if the energy of the "ENG torque" is distributed to the "TM load," "AC load," and "power generation load" during "normal" operation, there is a torque surplus (engine torque surplus) equivalent to energy (Ea). The engine torque surplus is used to charge the battery 1. When, for example, the output of the air conditioner increases from the "normal" state, much of the energy of the "ECG torque" is consumed by the "AC load." Therefore, as shown in FIG. 2(b), the EM controller 30 is unable to distribute the energy of the "ENG torque" to the "power generation load," resulting in a shortage of engine torque equivalent to energy (Eb). As shown in FIG. 2(b), when the energy of the "ENG torque" is insufficient to cover the energy required by the load that requires engine torque, i.e., when a so-called engine torque balance is reached, the "power generation load" is reduced and the output from the alternator 4 is temporarily limited. However, if the output from the alternator 4 is limited, the power from the alternator 4 will not be supplied sufficiently to the load 41, and for example, the fan of an air conditioner included in the load 41 will stop operating, resulting in a decrease in the output performance of the air conditioner.

[0027] 2B, the EM controller 30 switches the battery 1 from charging to discharging, and supplements the engine torque equivalent to the energy (Eb) with the discharged power of the battery 1. In other words, the EM controller 30 limits the output from the alternator 4 to reduce the "power generation load," and obtains energy equivalent to the shortfall in engine torque by discharging the battery 1.

[0028] Although the above describes an example in which engine torque becomes insufficient due to an increase in the energy of the "AC load," engine torque may also become insufficient when the energy of the "power generation load" increases. For example, when the engine torque balance is balanced, if the energy required to operate the load 41 increases, engine torque becomes insufficient. The EM controller 30 switches the battery 1 from charging to discharging, and uses the discharged power of the battery 1 to make up for the engine torque deficiency.

[0029] That is, when the output torque of the engine 5 is insufficient for the energy required to operate the load 41 and / or the alternator 4, the energy management system compensates for the energy shortage by discharging the battery 1. This makes it possible to supply power to the load 41 while maintaining the engine torque balance.

[0030] As described above, when the EM controller 30 distributes the energy of the "ENG torque" to the "TM load," "AC load," and "power generation load" while the vehicle is running, if there is surplus engine torque (state of FIG. 2(a)), the alternator 4 is driven by the output torque of the engine 5 to charge the battery 1, and energy equivalent to the surplus engine torque is used to charge the battery 1. In this state, if, for example, the AC load increases and the engine torque balance becomes unbalanced, the EM controller 30 outputs a control command to the battery controller 10 to switch the battery 1 from charging to discharging. The charge / discharge control unit 12 of the battery controller 10 switches the battery 1 from charging to discharging. The battery management unit 11 then detects the switch between charging and discharging, which occurs due to the supplementation of the energy shortage.

[0031] Next, the control flow of the battery control method will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the control flow of the battery control method. The battery controller 10 starts the control flow when the vehicle starts running (the ignition switch is turned on). Note that the control flow shown in Fig. 3 shows the flow from when the vehicle starts running, when the battery 1 switches from charging to discharging, and until discharging is prohibited. Note that the control flow in Fig. 3 may be executed while the vehicle is running, or may be executed while the vehicle is stopped.

[0032] In step S1, the battery management unit 11 calculates the current SOC (present SOC) of the battery 1 based on the detected current of the current sensor 2 and / or the detected voltage of the voltage sensor 3. In step S2, the battery management unit 11 calculates the difference (ΔSOC) between the previous SOC and the current SOC by subtracting the previous SOC from the current SOC. The current SOC corresponds to the current SOC. The previous SOC corresponds to the SOC calculated in the control flow of step S1 in the previous control flow loop.

[0033] In step S3, the battery management unit 11 calculates the current value of the SOC difference (ΔSOC ｎ ) and the previous value of the SOC difference (ΔSOC ｎ―１ ) is compared. The current value of the SOC difference corresponds to the SOC calculated in the control flow of step S2 in the current control flow loop. The previous value of the SOC difference corresponds to the SOC calculated in the control flow of step S2 in the previous control flow loop. The current value of the SOC difference (ΔSOC ｎ ) is the previous value (ΔSOC ｎ―１ ), the change in the SOC of the battery 1 has switched from increasing to decreasing, and the battery management unit 11 detects the switch between charging and discharging of the battery 1. ｎ ) is the previous value (ΔSOC ｎ―１ ) or greater, control flow returns to step S1.

[0034] When a charge / discharge switch is detected, the dischargeable capacity setting unit 13 sets the dischargeable capacity according to the state of the battery 1 at the time of the charge / discharge switch (step S4). The charge / discharge control unit 12 switches the battery 1 from charging to discharging and starts discharging the battery 1 (step S5). In step S6, the battery management unit 11 calculates the discharged capacity of the battery 1. In step S7, the battery management unit 11 compares the discharged capacity from the time of the charge / discharge switch to the present with the dischargeable capacity. If the discharged capacity is equal to or less than the dischargeable capacity, the control flow returns to step S6. If the discharged capacity is greater than the dischargeable capacity, in step S8, the battery management unit 11 determines that the discharged capacity of the battery 1 has reached the dischargeable capacity and prohibits discharging of the battery 1. Then, the battery controller 10 ends the control flow shown in FIG. 3.

[0035] After discharging is prohibited, the charge / discharge control unit 12 may charge the battery 1 until the SOC of the battery 1 reaches the SOC at the start of discharging (the SOC when the control flow of step S5 is executed).

[0036] Next, the SOC characteristics of the battery 1 controlled by the battery control system according to this embodiment will be described in comparison with a reference example. Fig. 4 is a graph showing SOC characteristics during charging before the charge / discharge switching point and discharging after the charge / discharge switching point. In Fig. 4, the charge start SOC indicates the SOC at the start of charging before the charge / discharge switching point. The charge completion SOC indicates the SOC at the charge / discharge switching point. Discharge SOC а indicates the SOC when the discharge amount of the battery 1 reaches the dischargeable amount in the battery control system according to this embodiment. ｂ indicates the SOC (SOC at the end of discharge) when the discharge amount of the battery 1 reaches the dischargeable amount in the battery control system according to the reference example. In the reference example, the dischargeable amount is set so that the SOC at the end of discharge after switching between charge and discharge is 1% lower than the SOC at the start of charge.

[0037] As shown by the arrow a in Fig. 4, in this embodiment, the dischargeable capacity is set to be a drop of about several percent (for example, about 1%) from the discharge start SOC, and the SOC when the dischargeable capacity of the battery 1 is reached is set to be higher than the charge start SOC in the charge immediately before the switch. Therefore, the dischargeable capacity allowed by the dischargeable capacity is significantly reduced compared to the charge amount immediately before the charge / discharge switch. Therefore, in area D in Fig. 4 а On the other hand, in the reference example, when the discharge immediately after the charge / discharge switching point is completed, the SOC at the end of the discharge ｂ is lower than the SOC at the start of discharge (corresponding to the SOC at the end of charge), and the decrease in SOC from the start of discharge to the end of discharge is large. ｂ That is, in this embodiment, the discharge amount immediately after the charge / discharge switching point is suppressed compared to the reference example, and deterioration of the battery 1 can be prevented.

[0038] As described above, in the battery control device and battery control method according to this embodiment, the battery controller 10 detects a charge / discharge switch, sets the dischargeable amount according to the state of the battery 1 at the time of the charge / discharge switch, and when the discharge amount of the battery 1 from the time of the charge / discharge switch reaches the dischargeable amount, prohibits discharging of the battery 1. This suppresses the discharge amount of the battery 1 after the charge / discharge switch, and prevents deterioration of the battery 1.

[0039] In this embodiment, the battery controller 10 detects the charge / discharge switch caused by the idling stop, thereby suppressing the discharge amount of the battery 1 during the idling stop, and preventing the battery 1 from deteriorating.

[0040] In this embodiment, the vehicle is equipped with an energy management system that distributes the output torque of the engine 5 to energy for operating the vehicle loads 41, 42 and / or the alternator 4. When the output torque of the engine 5 is insufficient for the energy required to operate the loads 41, 42 and / or the alternator 4, the energy management system compensates for the energy shortage by discharging the battery 1, and the battery controller 10 detects a switch between charging and discharging caused by the compensation of the energy shortage. As a result, when the battery 1 is discharged by energy management, the amount of discharge of the battery 1 is suppressed, and deterioration of the battery 1 can be prevented.

[0041] In this embodiment, the battery controller 10 sets the dischargeable amount depending on the vehicle environment and / or the operating conditions of the loads 41, 42 at the time of switching between charge and discharge. As a result, in a situation where the engine torque is insufficient when operating auxiliary devices such as an air conditioner at a high output due to the vehicle environment, the energy shortage can be compensated for by discharging the battery 1. In addition, in a situation where the energy required to operate the loads 41, 42 is large and the engine torque is insufficient, the energy shortage can be compensated for by discharging the battery 1.

[0042] In this embodiment, the battery controller 10 sets the dischargeable amount so that the SOC when the discharge amount of the battery 1 reaches the dischargeable amount is higher than the lower limit SOC that prevents over-discharge of the battery 1. This makes it possible to prevent deterioration of the battery 1.

[0043] The battery controller 10, IS controller 20, and EM controller 30 do not necessarily have to be configured as a single ECU, but may be configured as multiple ECUs. Multiple ECUs mounted on the vehicle may have the functions of the battery controller 10, IS controller 20, and EM controller 30. For example, the IS controller 20 determines whether to execute or cancel idling stop based on control commands from each ECU, as follows: If the idling stop conditions are not met, the ECU sends a control command to the IS controller 20 indicating that the idling stop conditions are not met. The idling stop conditions include multiple conditions, such as vehicle speed and engine rotation speed, and the determination of whether the idling stop conditions are met is made by multiple ECUs, such as the ECUs. Then, when the IS controller 20 receives a control command from at least one ECU indicating that the idling stop conditions are not met, it cancels the idling stop. The "battery controller 10" in this embodiment corresponds to the "controller" of the present invention.

[0044] REFERENCE SIGNS LIST 1 Battery 2 Current sensor 3 Voltage sensor 4 Alternator 5 Engine 6 Inverter 7 DCDC converter 8 Starter motor 9 Relay switch 10 Battery controller 11 Battery management unit 12 Charge / discharge control unit 13 Dischargeable capacity setting unit 20 IS controller 30 EM controller 41, 42 Load 100 Battery control system

Claims

1. A battery control device that controls a battery mounted on a vehicle, comprising: a controller that manages the state of the battery based on the detection value of a sensor connected to the battery and controls charging and discharging of the battery, wherein the controller detects a charge / discharge switchover from charging to discharging of the battery, sets a dischargeable amount according to the state of the battery at the time of the charge / discharge switchover, and prohibits discharging of the battery when the discharged amount of the battery from the time of the charge / discharge switchover reaches the dischargeable amount.

2. A battery control device according to claim 1, wherein the battery is charged by power generated by an alternator connected to an engine, and the controller detects the switching between charging and discharging caused by an idling stop.

3. A battery control device according to claim 1, wherein the battery is charged by power generated by an alternator connected to an engine, the vehicle is equipped with an energy management system that distributes the output torque of the engine to energy for operating the load of the vehicle and / or the alternator, the energy management system supplements the energy shortage by discharging the battery when the output torque is insufficient for the energy required to operate the load and / or the alternator, and the controller detects the charge / discharge switch that occurs as a result of the supplementation of the energy shortage.

4. A battery control device according to any one of claims 1 to 3, wherein the controller sets the dischargeable amount according to the environment of the vehicle and / or the operating conditions of the load on the vehicle at the time of switching between charging and discharging.

5. A battery control device according to any one of claims 1 to 4, wherein the controller sets the dischargeable amount so that the SOC when the discharge amount of the battery reaches the dischargeable amount is higher than a lower limit SOC that prevents over-discharge of the battery.

6. A battery control method executed by a controller for controlling a battery mounted on a vehicle, wherein the controller manages the state of the battery based on the detection value of a sensor connected to the battery 1, and includes a controller for controlling charging and discharging of the battery 1, detects a charge / discharge switchover from charging to discharging of the battery, sets a dischargeable amount according to the state of the battery at the time of the charge / discharge switchover, and prohibits discharging of the battery when the discharge amount of the battery from the time of the charge / discharge switchover reaches the dischargeable amount.

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