JP2021061719A - Battery management device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently raise a temperature of a battery in a battery management device. A battery management device disclosed here is a device that controls a battery 4 including a plurality of batteries 2 and a balancer circuit 3 used for equalizing the voltage of each battery 2. This device includes a battery temperature sensor 7 that detects the temperature of the battery 4 and a control device 10. The control device 10 performs balancer temperature rise control for operating the balancer circuit 3 to raise the temperature of the battery 4 when the battery temperature is lower than a predetermined temperature. In the balancer temperature rise control, the lower the battery temperature, the greater the number of batteries 2 to be discharged. [Selection diagram] Fig. 1

Description

The present invention relates to a battery management device that controls a battery incorporating a plurality of batteries and a balancer circuit.

Conventionally, in a battery having a plurality of cells (batteries) built-in, a battery having a built-in balancer circuit (voltage equalization circuit) for eliminating the variation in voltage of each cell is known. The balancer circuit includes a passive circuit and an active circuit. The former is a method of equalizing the voltage by intentionally consuming the electric power stored in the cell having a high voltage. On the other hand, the latter is a method of equalizing the voltage by transferring power from a cell having a high voltage to a cell having a low voltage. The control for equalizing the cell voltage using the balancer circuit is called voltage equalization control or balancer control (see Patent Documents 1 to 3).

Japanese Unexamined Patent Publication No. 11-283678 Japanese Unexamined Patent Publication No. 2006-210244 Japanese Unexamined Patent Publication No. 2013-013236

In voltage equalization control, heat is generated by the power consumption of the internal resistance of the resistor or cell. This heat can be used to warm up the battery and raise the temperature. However, it is difficult to raise the temperature of the battery efficiently because the implementation status of the voltage equalization control is greatly affected by the degree of variation in the voltage of each cell. For example, when the voltage variation is extremely large, the amount of heat generated tends to increase, which may lead to excessive temperature rise of the battery. On the contrary, when the voltage variation is small, the amount of heat generated tends to be insufficient, and the warm-up of the battery may be insufficient.

One of the purposes of this case was devised in view of the above-mentioned problems, and by providing a battery management device capable of efficiently raising the temperature of the battery while eliminating the variation in the cell voltage. is there. Not limited to this purpose, it is also possible to exert an action / effect derived from each configuration shown in the “mode for carrying out the invention” described later, which cannot be obtained by the conventional technique. It can be positioned as a purpose.

The battery management device disclosed here controls a battery including a plurality of batteries and a balancer circuit used for equalizing the voltage of each battery. This device includes a battery temperature sensor that detects the temperature of the battery and a control device. When the temperature is lower than a predetermined temperature, the control device operates a balancer circuit to raise the temperature of the batteries, and controls to increase the number of batteries to be discharged as the temperature is lower.

When warming up the battery using the balancer circuit, the calorific value can be optimized by increasing the number of cells to be discharged as the temperature becomes lower. As a result, the temperature of the battery can be efficiently raised while eliminating the variation in the cell voltage.

It is a schematic diagram of the battery management device applied to a vehicle. It is a perspective view which shows the inside of a battery. It is a circuit diagram which shows the circuit structure of a battery. It is a block diagram of a battery management device. It is a graph which shows the relationship between the battery temperature and the number of cells to be discharged. It is a figure which shows the variation of a cell voltage. It is a figure which shows the variation of a cell temperature. It is a figure which shows the variation of the distance to the side surface of a casing. It is a figure which shows the variation of a cell temperature, (A) is a figure corresponding to an outer cell, (B) is a figure corresponding to an inner cell. It is a flowchart for demonstrating the control content of a battery management apparatus. It is a sequence diagram which shows the flow of the conventional heater control. It is a sequence diagram which shows the flow of the balancer temperature rise control of this case.

[1. apparatus]
A battery management device as an embodiment applied to the vehicle 1 equipped with the battery 4 will be described with reference to FIGS. 1 to 12. The vehicle 1 is an electric vehicle such as an electric vehicle or a hybrid vehicle. The vehicle 1 is equipped with a traveling motor M for driving the driving wheels, a battery 4, and an inverter 5. A device (gasoline engine, diesel engine, generator, etc.) that serves as a drive source other than the traveling motor M can also be mounted on the vehicle 1.

The battery 4 is a secondary battery that stores electric power for driving the traveling motor M, and is, for example, a lithium ion battery or a nickel hydrogen battery. Inside the battery 4, a plurality of cells 2 (battery, cell) and a balancer circuit 3 are provided. The cells 2 are connected to each other inside the battery 4. As shown in FIG. 2, a plurality of battery modules 20 (combined batteries) in which a plurality of cells 2 are housed in one casing may be arranged inside the battery 4.

Of the plurality of cells 2, the cell 2 arranged inside the casing of the battery 4 (position near the center) is called the inner cell 21 (inner battery), and the cell 2 arranged outside the cell 2 is called the outer cell 2. It is called cell 22 (outer battery). In the present embodiment, as shown in FIG. 2, the cell 2 having a relatively long distance from the side surface of the casing is referred to as an inner cell 21, and the cell 2 having a relatively short distance is referred to as an outer cell 22. The outer cell 22 is more susceptible to the influence of the outside air temperature than the inner cell 21, and has a property that the temperature tends to be lower than that of the inner cell 21 particularly in a cold environment.

The balancer circuit 3 is a circuit used to equalize the voltage of each cell 2. The balancer circuit 3 includes a passive type circuit and an active type circuit. The former equalizes the voltage of each cell 2 by consuming the electric power stored in the cell 2 having a relatively high voltage among the plurality of cells 2 with a resistor, and the latter is relative. By moving the electric power of the high-voltage cell 2 to the low-voltage cell 2, the voltage of each cell 2 is equalized. In the present embodiment, the former balancer circuit 3 will be described in detail, but the latter balancer circuit 3 can also be used.

The inverter 5 converts electric power between direct current and alternating current, and is interposed in a power supply line connecting the traveling motor M and the battery 4. The inverter 5 has a function of converting the DC power of the battery 4 into AC power and supplying it to the traveling motor M, and a function of converting the regenerated power generated by the traveling motor M into DC power and supplying it to the battery 4. Also has. The inverter 5 contains switch elements such as IGBTs (Insulated Gate Bipolar Transistor) and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor), their control circuits, rectifier circuits (condensers), transformer circuits (transformers), and the like. ..

As shown in FIG. 1, a power switch 6 is provided in the vehicle interior of the vehicle 1. The power switch 6 is a button-type changeover switch for turning on the main power of the vehicle 1, and each time the button is pressed, the main power is switched to either an on or off state. When the vehicle 1 is in use (for example, when the driver gets on the vehicle 1), the power switch 6 is turned on so that the vehicle 1 can travel. When the vehicle 1 is not in use (for example, when the vehicle 1 is parked), the main power supply of the vehicle 1 is turned off by turning off the power switch 6.

The battery 4 is provided with a battery temperature sensor 7 that detects the battery temperature. The battery temperature sensor 7 is provided in the casing of the battery 4, for example, and detects the air temperature (atmospheric temperature) in the casing, the casing temperature, and the like. The control configuration may be such that the battery temperature is estimated based on the cell temperature detected by the cell temperature sensor 9, which will be described later. The battery temperature information detected here is transmitted to the control device 10.

FIG. 3 shows the circuit structure of the battery 4. Here, an example in which a plurality of cells 2 are arranged in series is illustrated. When distinguishing individual cells 2, the numbers (# 1, # 2, ..., #N) assigned in the order of arrangement are used. A cell voltage sensor 8 and a cell temperature sensor 9 are connected to each cell 2. The cell voltage sensor 8 is a sensor that detects the voltage (cell voltage) of each cell 2, and the cell temperature sensor 9 is a sensor that detects the temperature (cell temperature) of each cell 2. Information on the cell voltage and the cell temperature is transmitted to the control device 10.

A balancer circuit 3 is provided in each cell 2. The balancer circuit 3 is connected in parallel to both electrodes of each cell 2. A resistor 11 and a cell switch 12 are interposed in series in the balancer circuit 3 of each cell 2. The cell switch 12 is basically controlled to be disconnected (off). On the other hand, when the cell switch 12 is connected (on), the power of the cell 2 corresponding to the cell switch 12 is consumed by the resistor 11, and the voltage of the cell 2 gradually decreases. Therefore, by connecting only the cell switch 12 connected to the cell 2 having a relatively high voltage, the voltage of the cell 2 approaches the voltage of another cell 2, and the variation of the overall cell voltage becomes small. ..

The resistor 11 may be a fixed resistor having a predetermined resistance value, or a variable resistor having a variable resistance value. When a variable resistor is used, the resistance value may be increased as the battery temperature is lower. That is, the lower the battery temperature, the more the calorific value may be increased to efficiently raise the temperature of the battery 4. As a specific example of the variable resistor, an IC or a digital potentiometer incorporating a series array of fixed resistors and a semiconductor switch can be used.

The battery 4 shown in FIG. 3 is connected to the inverter 5 via a contactor 16 (electromagnetic switch). The contactor 16 is a relay device for preventing the hot-line exposure of the high-voltage circuit extending from the battery 4, and is connected (closed) only when the vehicle 1 is used and disconnected (opened) when the vehicle 1 is not used. To. The open / closed state of the contactor 16 is controlled to correspond to, for example, the state of the power switch 6. Even if the power switch 6 is on, the contactor 16 may be disconnected if the power of the battery 4 is not used.

A direct connection circuit 13 is connected to the lead wire connecting the battery 4 and the contactor 16. The direct connection circuit 13 is formed so as to connect the negative electrode side of the cell # 1 shown in FIG. 3 and the positive electrode side of the cell # N. A direct-coupled resistor 14 and a direct-coupled switch 15 are interposed in series in the direct-coupled circuit 13. The direct-coupled resistor 14 is a resistor that generates a larger amount of heat than the resistor 11 of the balancer circuit 3, and is used when it is desired to quickly raise the temperature of the entire battery 4 or when the outside air temperature is low. The direct connection switch 15 is a two-position changeover switch for connecting and disconnecting the energization of the direct connection resistor 14.

The direct connection switch 15 is basically controlled to be disconnected (off). On the other hand, when the direct connection switch 15 is connected (on), the electric power of the plurality of cells 2 is consumed by the direct connection resistor 14, and the temperature of the battery 4 rises. Further, since the direct connection circuit 13 is connected to the side closer to the cell 2 than the contactor 16, it can be used even when the contactor 16 is disconnected.

The control device 10 is an electronic control device (computer) for managing the state of the battery 4, and is also called a BMU (Battery Management Unit). The control device 10 includes a processor (central processing unit), a memory (main memory), a storage device (storage), an interface, and the like. As shown in FIG. 4, a power switch 6, a battery temperature sensor 7, a cell voltage sensor 8, and a cell temperature sensor 9 are connected to the input side of the control device 10, and a cell switch 12 and a direct connection switch 15 are connected to the output side. Will be done.

The control device 10 controls the switches 12 and 15 based on the information from the input side to control the temperature of the battery 4. The content of this control is recorded as an application program on the storage device of the control device 10. The program is expanded in memory as needed and executed by the processor. This control is a control that efficiently raises the temperature of the battery 4 by using the balancer circuit 3. Hereinafter, this control is also referred to as "balancer temperature rise control".

[2. Balancer temperature rise control]
The balancer temperature rise control is carried out on condition that the battery temperature is at least lower than a predetermined temperature. The predetermined temperature referred to here is set to, for example, a temperature near the lower limit of the temperature range in which the battery 4 operates stably. Further, the balancer temperature rise control shall be performed regardless of the running state of the vehicle 1 and the disconnection state of the main power supply. For example, when the battery temperature drops below a predetermined temperature while the vehicle 1 in which the power switch 6 is turned off is parked, the balancer temperature rise control is automatically performed without turning on the main power supply. And.

The balancer temperature rise control of the present embodiment shall be carried out when the battery temperature is equal to or higher than the second predetermined temperature. The second predetermined temperature is a temperature lower than the predetermined temperature. When the battery temperature is lower than the second predetermined temperature, the control device 10 connects the direct connection switch 15 and raises the temperature of the battery 4 by utilizing the heat generated by the direct connection resistor 14. Therefore, the range of the battery temperature at which the balancer temperature rise control of the present embodiment is carried out is a range of the second predetermined temperature or higher and lower than the predetermined temperature.

The smaller the standby power consumed by the control device 10 when the main power is off, the more preferable. Therefore, the confirmation of the battery temperature by the control device 10 is performed intermittently in a somewhat long time cycle, and most of the time is in a hibernation state (sleep state) with low power consumption. The control device 10 shall intermittently check the battery temperature even during the balancer temperature rise control, and the operating state of the cell switch 12 and the direct connection switch 15 shall be maintained even when the control device 10 is in a dormant state. And.

When the battery temperature is lower than the predetermined temperature, the control device 10 determines the number of cells to be discharged according to the battery temperature. As shown in the graph of FIG. 5, the relationship between the battery temperature and the number of cells is such that the number of cells increases as the battery temperature decreases. A in the graph represents a temperature corresponding to a predetermined temperature. The control device 10 executes the balancer temperature rise control by operating the balancer circuits 3 having the same number of cells as the number of cells determined here. As described above, as the battery temperature is lower, the number of cells to be discharged is increased to optimize the calorific value, and the excessive temperature rise of the battery 4 and the prolongation of the warm-up time are suppressed.

Examples of specific selection methods for the cell 2 to be discharged are listed below. Any one of these methods may be used, or a plurality of methods may be used in combination.
・ Method 1. Select in order from the one with the highest cell voltage ・ Method 2. Select in order from the one with the lowest cell temperature ・ Method 3. Preferentially select the outer cell 22 over the inner cell 21

The method 1 is a method in which each cell 2 is arranged in the order of cell voltage, and cells 2 having a number of cells to be discharged or more are selected in order from the high voltage side. For example, when the total number of cells is 20, and the cell voltages show the distribution as shown in FIG. 6, the cells 2 to be discharged are selected in order from the right side in FIG. When there are a plurality of cells 2 having substantially the same cell voltage, all of them may be selected, or the numbers (# 1, # 2, ..., #N) of each cell 2 are selected in ascending order. You may. Specifically, when the number of cells determined according to the battery temperature is 3, # 17, # 13, # 23 in FIG. 6 may be targeted for discharge, or # 17, # 13, # 23 and # 26 may be discharged targets.

The method 2 is a method in which each cell 2 is arranged in the order of cell temperature, and cells 2 having a number of cells to be discharged or more are selected in order from the low temperature side. For example, when the total number of cells is 20, and the cell temperatures show the distribution shown in FIG. 7, the cells 2 to be discharged are selected in order from the left side in FIG. 7. If there are a plurality of cells 2 having substantially the same cell temperature, all of them may be selected, or the numbers (# 1, # 2, ..., #N) of each cell 2 may be selected in ascending order (or # N). You may select in descending order). Specifically, when the number of cells determined according to the battery temperature is 6, even if # 28, # 23, # 27, # 5, # 11, # 13 in FIG. 7 are to be discharged. Alternatively, # 28, # 23, # 27, # 5, # 11, # 13, # 19, # 20 may be discharged.

In the method 3, each cell 2 is arranged according to the susceptibility to the outside air temperature (easiness to cool), and the cells 2 having more than the number of cells to be discharged are selected in order from the one most susceptible to the outside air temperature. It is a method to do. For example, when the total number of cells is 20, and the distance to the side surface of the casing shows the distribution as shown in FIG. 8, the cells 2 to be discharged are selected in order from the left side in FIG. If there are a plurality of cells 2 having substantially the same distance to the side surface of the casing, all of them may be selected, or the numbers (# 1, # 2, ..., #N) of each cell 2 may be selected. You may select in ascending order (or in descending order). Specifically, when the number of cells determined according to the battery temperature is 4, # 1 to # 4 in FIG. 8 may be targeted for discharge, and # 1 to # 5 may be targeted for discharge. May be good.

The selection method when the method 2 and the method 3 are combined will be described with reference to FIGS. 9A and 9B. FIG. 9A is a diagram illustrating the distribution of the cell temperature of the outer cell 22, and FIG. 9B is a diagram illustrating the distribution of the cell temperature of the inner cell 21. The cells 2 to be discharged are selected in order from the left side in FIG. 9A. If there are a plurality of outer cells 22 having substantially the same cell temperature, all of them may be selected, or the numbers (# 1, # 2, ..., #N) of each outer cell 22 may be selected in ascending order. You may select (or in descending order). Specifically, when the number of cells determined according to the battery temperature is 3, # 14, # 5, # 10 in FIG. 9A may be the discharge targets, or # 14, # 5, # 10, and # 12 may be discharged targets.

[3. flowchart]
FIG. 10 is a flowchart for explaining a flow of balancer temperature rise control performed by the control device 10 while the vehicle 1 in which the power switch 6 is off is parked. In step A1, it is determined whether or not the power switch 6 is off. If the power switch 6 is on, the process proceeds to step A6, and the cell switch 12 and the direct connection switch 15 are controlled to be off (disconnected state). That is, when the vehicle user operates the power switch 6 on during the balancer temperature rise control, the balancer temperature rise control ends. On the other hand, if the power switch 6 is off in step A1, the process proceeds to step A2.

In step A2, it is determined whether or not a timer, which will be described later, is set. If the timer is set, the process proceeds to step A3, it is determined whether or not the current time has passed the timer start time, and if the timer start time is reached, the process proceeds to step A4. Further, even if the timer is not set in step A2, the process proceeds to step A4. If the timer start time has not been reached in step A3, the control of the control cycle ends.

In step A4, the battery temperature information is acquired. In the following step A5, it is determined whether or not the battery temperature is lower than the predetermined temperature. If this condition is not satisfied, the balancer temperature rise control is unnecessary, and the process proceeds to step A6. On the other hand, if the battery temperature is lower than the predetermined temperature, the process proceeds to step A7, and it is determined whether or not the battery temperature is lower than the second predetermined temperature.

If the condition of step A7 is satisfied, the process proceeds to step A8, the direct connection switch 15 is controlled to be on, and all cell switches 12 are controlled to be off. As a result, the electric power of each cell 2 is consumed by the direct-coupled resistor 14 to generate heat, and the temperature of the battery 4 rises as a whole. After that, in step A9, the timer start time (next start time of the control device 10) is set, and the control device 10 is put into hibernation state. In the hibernation state, the measurement of the current time is continued with a small amount of power consumption, and the states of the direct connection switch 15 and the cell switch 12 are maintained.

If the condition of step A7 is not satisfied, the process proceeds to step A10, and the direct connection switch 15 is controlled to be off. In the following step A11, the cell voltage information and the cell temperature information of each cell 2 are acquired. Further, in step A12, the number of cells to be discharged is determined based on the battery temperature. The number of cells to be discharged increases as the battery temperature becomes lower. Further, in step A13, the cell 2 to be discharged is selected, and the cell switch 12 corresponding to the selected cell 2 is controlled to be turned on. After that, in step A9, the timer start time (next start time of the control device 10) is set, and the control device 10 is put into hibernation state.

The timer start time set in step A9 is referred to in the control cycle from the next time onward. Once the timer is set, step A4 is not executed until the set timer start time is reached, and the dormant state of the control device 10 is maintained unless the power switch 6 is turned on. When the set timer start time is reached, the process proceeds to step A4, and the battery temperature is confirmed again. When the battery temperature becomes equal to or higher than the predetermined temperature by the balancer temperature rise control, the process proceeds to step A6, and the balancer temperature rise control ends.

[4. Action, effect]
FIG. 11 is a sequence diagram showing a conventional flow of heater control. The conventional heater control is a control for raising the temperature of the battery 4 by a heating device (PTC heater, heat pump, etc.) provided in the casing of the battery 4. When the conventional heater control is performed while the vehicle 1 in which the power switch 6 is off is performed, the contactor 16 is connected after the control device 10 is activated, or another control device (for connecting the contactor 16) is used. For example, it is necessary to activate an electronic control device (electronic control device higher than the control device 10) such as PHEV-ECU and EV-ECU. Further, since the control device 10 continues to operate even after the heater is operated and the control device 10 is stopped after the heater control is completed, the power consumption tends to increase.

On the other hand, FIG. 12 is a sequence diagram showing a flow of balancer temperature rise control according to the present embodiment. In the balancer temperature rise control, it is not necessary to connect the contactor 16 and it is not necessary to activate another control device. Further, by setting the timer start time and intermittently monitoring the battery temperature, it is possible to suspend the control device 10 during the execution of the balancer temperature rise control. In this way, by using the balancer temperature rise control, the power consumption is significantly reduced as compared with the conventional heater control.

(1) In the above battery management device, when the battery temperature is lower than a predetermined temperature, the balancer temperature rise control for operating the balancer circuit 3 by increasing the number of cells 2 to be discharged as the battery temperature is lower. Is carried out. In this way, when warming up the battery 4 using the balancer circuit 3, the calorific value of the balancer circuit 3 can be optimized by increasing the number of discharge cells as the battery temperature becomes lower, and the battery 4 can be warmed up. It is possible to suppress excessive temperature rise and lengthening of warm-up time. Therefore, it is possible to efficiently raise the temperature of the battery 4 while eliminating the variation in the cell voltage.

(2) When selecting the cell 2 to be discharged, by selecting the discharge target in order from the one having the highest cell voltage, the electric power stored in the high voltage cell can be preferentially consumed. As a result, the temperature of the battery 4 can be efficiently raised while reducing the variation in the cell voltage. Further, since the number of high-voltage cells 2 is reduced, the variation in cell voltage can be constantly reduced, and the time and power loss required for normal voltage equalization control can be reduced.

(3) When selecting the cell 2 to be discharged, by selecting the discharge target in order from the one with the lowest cell temperature, the temperature of the low temperature cell can be raised preferentially, and the temperature of the battery can be efficiently increased in a short time. Can be raised. Further, since the minimum temperature of each cell 2 can be easily secured, the progress of low temperature deterioration of the battery 4 can be suppressed.
(4) Further, when selecting the cell 2 to be discharged, the outer cell 22 whose cell temperature tends to decrease is preferentially discharged, so that the heating efficiency of the battery 4 can be improved.

(5) As shown in FIG. 3, by providing the direct connection circuit 13, the direct connection resistor 14, and the direct connection switch 15, the temperature of the entire battery 4 can be rapidly raised. Further, the temperature of the battery 4 can be raised even when the contactor 16 is disconnected. By using the direct-coupled resistor 14 which generates a larger amount of heat than the resistor 11 of the balancer circuit 3, the temperature of the battery 4 can be raised efficiently.
(6) Further, when the resistor 11 of the balancer circuit 3 is used as a variable resistor and control is performed to increase the resistance value as the battery temperature is lower, the temperature rising efficiency of the battery 4 can be further improved. it can.

[5. Modification example]
The above embodiment is merely an example, and there is no intention of excluding the application of various modifications and techniques not specified in the present embodiment. Each configuration of the present embodiment can be variously modified and implemented without departing from the gist thereof. In addition, it can be selected as needed, or can be combined as appropriate. For example, in the above-described embodiment, the passive type balancer circuit 3 has been described in detail, but it is also possible to carry out the same control as the above-mentioned balancer temperature rise control in the active type balancer circuit 3.

Further, in the above-described embodiment, the energized state is controlled by using each cell 2 as a control unit, but the control unit is not limited to this. For example, the battery module 20 can be used as a control unit to perform the same control as the balancer temperature rise control described above. At least, as the battery temperature is lower, the number of batteries to be discharged is increased, so that the same effect as that of the above-described embodiment can be obtained.

1 vehicle 2 cells (battery)
3 Balancer circuit 4 Battery 5 Inverter 6 Power switch (main power supply)
7 Battery temperature sensor 8 Cell voltage sensor (battery voltage sensor)
9 Cell temperature sensor (battery temperature sensor) 10 Control device 11 Resistor 12 Cell switch 13 Direct connection circuit 14 Direct connection resistor 15 Direct connection switch 16 Contactor 20 Battery module 21 Inner cell (inner battery)
22 Outer cell (outer battery) M Driving motor

Claims (6)

A battery management device that controls a battery containing a plurality of batteries and a balancer circuit used to equalize the voltage of each battery.
A battery temperature sensor that detects the temperature of the battery and
A control device that operates the balancer circuit to raise the temperature of the battery when the temperature is lower than a predetermined temperature, and controls to increase the number of batteries to be discharged as the temperature is lower. When,
A battery management device characterized by being equipped with. Equipped with a voltage sensor that detects the battery voltage of each battery
The battery management device according to claim 1, wherein the control device selects the discharge target in order from the one having the highest battery voltage. Equipped with a battery temperature sensor that detects the battery temperature of each battery
The battery management device according to claim 1 or 2, wherein the control device selects the discharge target in order from the one having the lowest battery temperature. The plurality of batteries include an inner battery arranged inside the casing and an outer battery arranged outside the inner battery.
The battery management device according to any one of claims 1 to 3, wherein the control device preferentially selects the discharge target over the inner battery. A direct connection circuit built into the battery and connecting between the positive electrode terminal and the negative electrode terminal,
A direct-coupled resistor interposed in the direct-coupled circuit and
The battery management device according to any one of claims 1 to 4, further comprising a direct connection switch for connecting and disconnecting the direct connection resistor. The balancer circuit has a variable resistor connected to each battery.
The battery management device according to any one of claims 1 to 5, wherein the control device increases the resistance value of the variable resistor as the temperature becomes lower.

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