Battery control device, method for controlling battery unit, and recording medium

Abstract

This battery control device for executing a cell balancing process determines whether an inrush current, which is generated when a maximum-capacity battery module is connected to a booster circuit having a capacitor, exceeds a predetermined allowable current upper limit value. When it is determined that the inrush current exceeds the allowable current upper limit value, the battery control device selects a battery module of which the inrush current does not exceed the allowable current upper limit value among battery modules other than the maximum-capacity battery module and connects the selected battery module to the booster circuit, thereby performing a charging process for preventing the inrush current generated when the maximum-capacity battery module is connected to the booster circuit from exceeding the allowable current upper limit value.

Description

Battery control device, method for controlling a battery unit, and recording medium

[0001] The present disclosure relates to a battery control device, a method for controlling a battery unit, and a recording medium.

[0002] In a vehicle that includes a plurality of battery modules and supplies the power output from each battery module to a driving power source to run, a voltage difference may occur between the battery modules. For example, in an electric vehicle in which battery modules can be replaced at a battery station or the like, when only some of the battery modules are replaced, the remaining capacity (SOC: State Of Charge) may be different between the replaced battery modules and the non-replaced battery modules. When the vehicle is run by connecting a plurality of battery modules in series in such a state, the power supply to the driving power source becomes impossible when the power of the battery module with a low remaining capacity runs out, and the power of other battery modules cannot be used up.

[0003] On the other hand, a technique for connecting a plurality of battery modules in parallel and equalizing the remaining capacities of the plurality of battery modules is known. When connecting a plurality of battery modules in parallel to equalize the remaining capacities of the plurality of battery modules, the processing time can be shortened by boosting the voltage using a boost circuit.

[0004] For example, in Patent Document 1, a power supply system is disclosed that includes a plurality of rechargeable batteries, a plurality of voltage converters whose primary sides are connected to any one of the plurality of batteries, whose secondary sides are connected in parallel to each other, and that convert the voltage of the battery connected to the primary side at an arbitrary conversion ratio and output the converted voltage to the secondary side, and a plurality of ammeters each connected to the primary sides of the plurality of voltage converters and measuring the current flowing through the primary sides. For each of the plurality of voltage converters, the conversion ratio is set so that the current measured by the ammeter connected to the primary side falls within a first range between the maximum discharge current value of the battery connected to the primary side and the maximum charge current value of the battery.

[0005] International Publication No. 2020 / 054828

[0006] However, in the power supply system disclosed in Patent Document 1, after connecting multiple batteries to a voltage converter, the current flowing while equalizing the remaining capacity of the multiple batteries is set to fall between the maximum discharge current and the maximum charge current of the batteries. Nevertheless, there is a risk that the current generated when connecting the batteries to the voltage converter (inrush current) may become excessive. For example, when connecting a battery to a boost circuit, if the difference between the battery voltage and the voltage of the boost circuit's capacitor is large, an excessive inrush current may occur, potentially exceeding the maximum discharge current of the battery.

[0007] This disclosure is made in view of the above circumstances and aims to provide a technology that can suppress the generation of excessive inrush current when equalizing the remaining capacity of multiple battery modules, and that can shorten the time required for equalization.

[0008] To solve the above problems, in view of the present disclosure, a battery control device is provided for controlling a battery unit having a plurality of battery modules, which, when the remaining capacities of the plurality of battery modules differ, performs a process to connect the plurality of battery modules in parallel and equalize the remaining capacities of the plurality of battery modules, wherein the battery control device determines whether the inrush current generated when the maximum capacity battery module, which has the largest remaining capacity, is connected to a boost circuit having a capacitor exceeds a predetermined allowable current upper limit; if it is determined that the inrush current exceeds the allowable current upper limit, it selects a battery module other than the maximum capacity battery module whose inrush current generated when connected to the boost circuit does not exceed the allowable current upper limit and connects it to the boost circuit, thereby performing a charge process so that the inrush current generated when the maximum capacity battery module is connected to the boost circuit does not exceed the allowable current upper limit; and after the charge process, connects the maximum capacity battery module to the input side of the boost circuit and connects the battery modules other than the maximum capacity battery module in parallel to the output side of the boost circuit, thereby equalizing the remaining capacities of the plurality of battery modules.

[0009] To solve the above problems, according to another aspect of this disclosure, a battery unit control method is provided which, when the remaining capacities of the multiple battery modules of a battery unit having multiple battery modules differ, performs a process to connect the multiple battery modules in parallel and equalize the remaining capacities of the multiple battery modules, the method comprising: determining whether the inrush current generated when the largest capacity battery module, which has the largest remaining capacity, is connected to a boost circuit having a capacitor exceeds a predetermined allowable current limit; if it is determined that the inrush current exceeds the allowable current limit, selecting a battery module other than the largest capacity battery module whose inrush current generated when connected to the boost circuit does not exceed the allowable current limit and connecting it to the boost circuit, thereby performing a charge process so that the inrush current generated when the largest capacity battery module is connected to the boost circuit does not exceed the allowable current limit; and after the charge process, connecting the largest capacity battery module to the input side of the boost circuit and connecting the battery modules other than the largest capacity battery module in parallel to the output side of the boost circuit, thereby equalizing the remaining capacities of the multiple battery modules.

[0010] To solve the above problem, according to another aspect of this disclosure, a program causes a computer to perform a process to equalize the remaining capacities of multiple battery modules in a power system having multiple battery modules when the remaining capacities of the multiple battery modules differ, wherein the program causes the computer to determine whether the inrush current generated when the largest capacity battery module with the largest remaining capacity is connected to a boost circuit having a capacitor exceeds a predetermined allowable current limit, and if it is determined that the inrush current exceeds the allowable current limit, then among the battery modules other than the largest capacity battery module, A non-temporary tangible recording medium is provided, which records a program that performs the following actions: selecting a battery module whose inrush current generated when connected to the boost circuit does not exceed the allowable current limit and connecting it to the boost circuit, thereby performing a charge process so that the inrush current generated when the maximum capacity battery module is connected to the boost circuit does not exceed the allowable current limit; and after the charge process, connecting the maximum capacity battery module to the input side of the boost circuit and connecting the battery modules other than the maximum capacity battery module in parallel to the output side of the boost circuit to equalize the remaining capacities of the multiple battery modules.

[0011] According to one embodiment of the present disclosure, it is possible to suppress the generation of excessive inrush current when equalizing the remaining capacity of multiple battery modules, and to shorten the time required for equalization.

[0012] This is a schematic diagram showing an example of the configuration of a vehicle equipped with a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing an example of the configuration of a battery unit equipped with a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing an example of the configuration of a boost circuit provided in a battery unit equipped with a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing a battery unit equipped with a plurality of replaceable battery modules according to one embodiment of the present disclosure. This is a block diagram showing the configuration of a battery control device according to one embodiment of the present disclosure. This is a flowchart showing an example of the operation of a battery control device according to one embodiment of the present disclosure. This is a flowchart showing an example of the operation of a battery control device according to one embodiment of the present disclosure. This is a flowchart showing an example of the operation of a battery control device according to one embodiment of the present disclosure. This is a flowchart showing an example of the operation of a battery control device according to one embodiment of the present disclosure. This is a flowchart showing an example of the operation of a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure. This is a schematic diagram showing the connection state of a battery module to a boost circuit by a battery control device according to one embodiment of the present disclosure.

[0013] Preferred embodiments of this disclosure will be described in detail below with reference to the attached drawings. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions will be omitted.

[0014] <1. Overall Vehicle Configuration> Referring to Figure 1, an example of the overall configuration of a vehicle 1 equipped with a battery control device 50 according to one embodiment of the present disclosure will be described.

[0015] The illustrated vehicle 1 is a two-wheel drive four-wheeled vehicle that transmits the drive torque output from a drive motor 11, which acts as a driving force source to generate drive torque, to the left and right front wheels 3LF and 3RF. However, the combination of drive wheels and the drive method are not limited. For example, vehicle 1 may be a rear-wheel drive vehicle or a four-wheel drive vehicle. Also, vehicle 1 may be an electric vehicle equipped with two drive motors, including a front-wheel drive motor and a rear-wheel drive motor. Furthermore, vehicle 1 may be an electric vehicle equipped with a drive motor corresponding to each wheel.

[0016] The drive motor 11 outputs drive torque transmitted to the front wheels 3LF and 3RF via the differential mechanism 7 and the front wheel drive shafts 5L and 5R. The drive motor 11 may be, for example, a three-phase AC motor. In this case, a rotor (not shown) rotates due to a rotating magnetic field formed by the supply of a three-phase AC current to a stator (not shown), and drive torque is output. The drive motor 11 may also have a function to perform regenerative power generation by receiving rotational torque from the front wheels 3LF and 3RF transmitted via the front wheel drive shafts 5L and 5R when a three-phase AC current is not supplied to the stator, causing the rotor to rotate.

[0017] The power system 10 installed in vehicle 1 includes an inverter 13, a battery unit 20, a power control device 15, and a battery control device 50.

[0018] The inverter 13 converts at least the DC power supplied from the battery unit 20 into three-phase AC power and supplies it to the drive motor 11. The inverter 13 also converts the three-phase AC power generated by the regeneration of the drive motor 11 into DC power and supplies it to the battery unit 20. The operation of the inverter 13 is controlled by the power control device 15.

[0019] The battery unit 20 is a power source for the drive motor 11 and comprises multiple rechargeable battery modules, such as lithium-ion batteries or solid-state batteries. Here, "battery module" corresponds to a so-called battery pack, which is composed of multiple battery cells connected together. The battery unit 20 is configured by connecting cartridge-type battery modules that can be replaced with charged battery modules at, for example, a battery exchange station. That is, each battery module is detachably housed in a case mounted on the vehicle 1. The rated output voltage of the battery unit 20 is, for example, 200V to 800V. However, the rated voltage and type are not particularly limited.

[0020] Figure 2 is a schematic diagram showing an example of the configuration of a battery unit. The illustrated battery unit 20 comprises a first battery module 21a to a fourth battery module 21d (hereinafter collectively referred to as battery module 21 unless otherwise specified), a positive terminal 23a, a negative terminal 23b, a circuit board 31, a connection switching circuit 32, a boost circuit 33, and a battery control device 50. The circuit board 31 has a connection switching circuit 32 that switches the connection state of the multiple battery modules 21 to any connection state, such as series connection or parallel connection. The connection switching circuit 32 comprises multiple switching elements (not shown). The battery control device 50 switches the connection state of the multiple battery modules 21 by switching the on / off state of each switching element.

[0021] Multiple battery modules 21 are essentially connected in series while supplying power to the drive motor 11. In this case, the terminal voltage between the positive terminal 23a and the negative terminal 23b of the battery unit 20 is the sum of the terminal voltages of each of the multiple battery modules 21.

[0022] Furthermore, the circuit board 31 is equipped with a boost circuit 33. The boost circuit 33 boosts the voltage of the input power to a desired required voltage and outputs it. When the battery control device 50 equalizes the remaining capacity of multiple battery modules 21, it connects the battery module 21 with the largest remaining capacity to the input terminal of the boost circuit 33 and connects one or more battery modules 21 with the smallest remaining capacity to the output terminal of the boost circuit 33, thereby shortening the time required to equalize the remaining capacity.

[0023] Figure 3 is a schematic diagram showing an example configuration of a boost circuit 33. The boost circuit 33 shown is a known DC-DC converter that outputs DC power at a higher voltage than the input DC power voltage. The boost circuit 33 includes a coil 35, a diode 36, a capacitor 37, and a switching element 38 between the input terminal 34a and the output terminal 34b. When the switching element 38 of the boost circuit 33 is turned on, electrical energy is stored in the coil 35, and when the switching element 38 is turned off, the electrical energy stored in the coil 35 is released, and the boosted power charges the capacitor 37. By repeatedly turning the switching element 38 on and off, the voltage can be boosted to any desired value.

[0024] Furthermore, the circuit board 31 is equipped with a plurality of voltage sensors (not shown) for measuring the terminal voltage values ​​of the battery unit 20 and the terminal voltage values ​​of each battery module 21. In addition, the circuit board 31 is equipped with a plurality of current sensors (not shown) for measuring the charge and discharge current values ​​of the battery unit 20 and the charge and discharge current values ​​of each battery module 21.

[0025] The battery control device 50 comprises one or more processors, one or more memories, and peripheral components. When the remaining capacities of the multiple battery modules 21 differ, the battery control device 50 connects the multiple battery modules 21 in parallel and performs cell balancing to equalize the remaining capacities of the multiple battery modules 21. By equalizing the remaining capacities of the multiple battery modules 21, the battery control device 50 delays the time at which discharge from the battery unit 20 becomes impossible due to a decrease in the remaining capacity of any of the battery modules 21. This extends the driving range of the vehicle 1.

[0026] Figure 4 is a schematic diagram showing a battery unit 20 equipped with multiple replaceable battery modules 21. In Figure 4, the remaining capacity level of each battery module 21 is indicated by the height of the shaded area within the container. The terminal voltage value of each battery module 21 is proportional to the remaining capacity.

[0027] In the illustrated example, the remaining capacity of the first battery module 21a has decreased. When multiple battery modules 21 are connected in series, once the remaining capacity of the first battery module 21a falls below a predetermined lower limit, it becomes impossible to discharge from the battery unit 20, even though the remaining capacities of the other battery modules 21 are still high. On the other hand, since each battery module 21 is replaceable, the first battery module 21a can be replaced with a fully charged fifth battery module 21e, allowing the battery unit 20 to continue to be used and extending the driving range of the vehicle 1.

[0028] However, if the first battery module 21a is replaced with the fifth battery module 21e, even if the remaining capacity of the fifth battery module 21e is greater than the remaining capacity of the other battery modules 21, the battery unit 20 will not be able to discharge when the remaining capacity of the battery module 21 with the smallest remaining capacity among the series-connected battery modules 21 falls below a predetermined lower limit. For this reason, the battery control device 50 performs a process to equalize the remaining capacities when the remaining capacities of the multiple battery modules 21 are different.

[0029] Here, when the battery module 21 is connected to the input terminal 34a or output terminal 34b of the boost circuit 33 described above, an inrush current is generated. For example, suppose a battery module 21 with voltage V is connected to the output terminal 34b of the boost circuit 33. If, before connecting the battery module 21, the capacitor 37 is not charged (voltage of capacitor 37 = 0), then when the battery module 21 is connected to the output terminal 34b, an inrush current flows through the capacitor 37 at the moment of connection. If the internal resistance of the battery module 21 is r, then the value of the inrush current I at this time is I = V / r.

[0030] After connecting the battery module 21, the amount of current flowing decreases as the power stored in the capacitor 37 increases, and the current becomes zero when the voltage of the capacitor 37 equals the voltage of the battery module 21. Considering the moment of connection, in the case of a single battery module 21, the voltage V is on the order of tens of volts, and in the case of a lithium-ion battery, for example, the internal resistance r is generally on the order of a few milliohms, so there is a risk that an inrush current exceeding the allowable current upper limit Imax of the battery module 21 will flow immediately after connection. This phenomenon can also occur when the battery module 21 is connected to the input terminal 34a of the boost circuit 33.

[0031] The battery control device 50 is configured to perform a process to suppress the excessive inrush current that occurs when the battery module 21 is connected to the boost circuit 33.

[0032] <2. Battery Control Device> Next, the battery control device 50 according to this embodiment will be described. Note that some or all of the components of the battery control device 50 may be incorporated into a known or arbitrary battery management system (BMS), or it may be provided separately from the battery management system.

[0033] (2-1. Configuration Example) The battery control device 50 functions as a device that performs the cell balancing process described below by having one or more CPUs (Central Processing Units) or other processors execute a computer program. The computer program is a computer program that causes the processor to perform the operations that the battery control device 50 should perform, as described later. The computer program executed by the processor may be recorded on a recording medium that functions as a memory unit 55, as described later, or it may be recorded on a recording medium built into the battery control device 50 or on any recording medium that can be attached externally to the battery control device 50.

[0034] The recording medium for storing computer programs may include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs, DVDs, and Blu-ray®; magneto-optical media such as floppy disks; memory elements such as RAM and ROM; flash memory such as USB memory and SSDs; and other media capable of storing programs.

[0035] Figure 5 is a block diagram showing the configuration of the battery control device 50. The battery control device 50 has a configuration that allows it to acquire sensor signals output from a plurality of voltage sensors (voltage sensor group) 41 and a plurality of current sensors (current sensor group) 43 mounted on the circuit board 31. The battery control device 50 also has a configuration that allows it to output drive signals to the switching elements of the connection switching circuit 32 and the boost circuit 33 provided on the circuit board 31.

[0036] The battery control device 50 comprises a processing unit 51 and a storage unit 55. The processing unit 51 comprises one or more processors such as a CPU and various peripheral components. Part or all of the processing unit 51 may be composed of updatable components such as firmware, or it may be a program module executed by instructions from the CPU, etc. The storage unit 55 is composed of one or more memory elements such as RAM or ROM that are connected to the processing unit 51 in a communicative manner. However, the type and number of storage units 55 are not particularly limited. The storage unit 55 stores information such as computer programs executed by the processing unit 51, various parameters used in arithmetic processing, detection data, and calculation results. Part of the storage unit 55 is used as a work area for the processing unit 51.

[0037] (2-2. Configuration of the Processing Unit) Next, the functional configuration of the processing unit 51 of the battery control device 50 will be described. The processing unit 51 includes a remaining capacity determination unit 52 and a cell balancing processing unit 53. Each of these units is a function realized by the execution of a computer program by one or more processors such as a CPU. However, some or all of the remaining capacity determination unit 52 and the cell balancing processing unit 53 may be configured using analog circuits.

[0038] (Remaining Capacity Determination Unit) The remaining capacity determination unit 52 acquires the remaining capacity of each of the multiple battery modules 21 and determines whether the remaining capacities are different. For example, the remaining capacity determination unit 52 acquires the terminal voltage value of each battery module 21 from a voltage sensor that measures the terminal voltage value of each battery module 21. The remaining capacity determination unit 52 also acquires the charge / discharge current value of each battery module 21 from a current sensor that measures the charge / discharge current value of each battery module 21. Based on the acquired terminal voltage value and charge / discharge current value of each battery module 21, the remaining capacity determination unit 52 calculates the remaining capacity of each battery module 21. The remaining capacity determination unit 52 may calculate the remaining capacity based on the terminal voltage value and charge / discharge current value using a known or arbitrary method.

[0039] Furthermore, the remaining capacity determination unit 52 determines whether the difference between the maximum and minimum values ​​of the calculated remaining capacities of each battery module 21 exceeds a predetermined threshold. The predetermined threshold is a reference value for determining whether or not to perform cell balancing processing, and may be zero or any positive value greater than zero.

[0040] The remaining capacity determination unit 52 may, instead of determining the remaining capacity, determine whether the terminal voltage values ​​of each battery module 21, which are proportional to the remaining capacity, are different.

[0041] (Cell Balancing Processing Unit) If the remaining capacity determination unit 52 determines that the remaining capacities of the multiple battery modules 21 are different, the cell balancing processing unit 53 performs a cell balancing process to equalize the remaining capacities. The cell balancing processing unit 53 connects the multiple battery modules 21 in parallel and distributes power from the battery module 21 with the highest remaining capacity, i.e., the battery module 21 with the highest terminal voltage value, to the battery module 21 with the lowest remaining capacity, thereby equalizing the remaining capacities of the battery modules 21.

[0042] In this process, the cell balancing processing unit 53 connects the battery module 21 with the highest remaining capacity to the input terminal a of the boost circuit 33, and connects the other battery modules 21 in parallel to the output terminal b of the boost circuit 33, thereby shortening the time required for cell balancing. The cell balancing processing unit 53 also performs a process to select the order in which the battery modules 21 are connected to the boost circuit 33 so that the inrush current generated when any of the battery modules 21 are connected to the boost circuit 33 does not exceed the allowable current upper limit Imax of the battery module 21.

[0043] In this embodiment, the battery control device 50 determines whether or not the inrush current generated when the battery module with the largest remaining capacity (maximum capacity battery module) is connected to the boost circuit 33 exceeds a predetermined allowable current upper limit value Imax. Further, when it is determined that the inrush current exceeds the allowable current upper limit value Imax, the battery control device 50 selects, from the battery modules other than the maximum capacity battery module, a battery module whose inrush current generated when connected to the boost circuit 33 does not exceed the allowable current upper limit value Imax and connects it to the boost circuit 33, thereby performing a charging process to ensure that the inrush current generated when the maximum capacity battery module is connected to the boost circuit 33 does not exceed the allowable current upper limit value Imax. Further, after the charging process, the battery control device 50 connects the maximum capacity battery module to the input side of the boost circuit 33 and connects the battery modules other than the maximum capacity battery module in parallel to the output side of the boost circuit 33 to equalize the remaining capacities of the plurality of battery modules.

[0044] (2-3. Operating example of the control device) Next, an operating example of the battery control device 50 according to this embodiment will be described while appropriately referring to the drawings.

[0045] In this operating example, as shown in FIG. 4, an example will be described in which the remaining capacity of the first battery module 21a among the first to fourth battery modules 21a to 21d decreases and the first battery module 21a is replaced with the fifth battery module 21e at the replacement station. However, for ease of understanding of the description, the replaced battery module will be described as the first battery module 21a, and the first battery module 21a will be described as corresponding to the maximum capacity battery module.

[0046] FIGS. 6 to 11 show flowcharts of the operating example of the battery control device 50. FIGS. 12 to 20 are schematic diagrams showing the states in which the respective battery modules 21 are connected to the boost circuit 33.

[0047] In the following example, instead of the remaining capacity of each battery module 21, the battery control device 50 uses the voltage value V between the terminals of the battery module 21 (hereinafter also simply referred to as "voltage") proportional to the remaining capacity to select the order of the battery modules 21 connected to the boost circuit 33. Let the voltage of the replaced first battery module 21a be V1, and the voltages of the second battery module 21b to the fourth battery module 21d that have not been replaced be V2, V3, and V4 respectively (V1 > V2 > V3 > V4).

[0048] The remaining capacity determination unit 52 acquires the voltages V1 to V4 of each of the plurality of battery modules 21 (step S11). As described above, the remaining capacity determination unit 52 may calculate the remaining capacity of each of the plurality of battery modules 21 based on the voltage value between the terminals and the charge / discharge current value.

[0049] Next, the remaining capacity determination unit 52 determines whether the voltages V1 to V4 of the plurality of battery modules 21 acquired in step S11 are different (step S13). For example, when the difference between the maximum value (V1) and the minimum value (V4) of the voltages V1 to V4 of each battery module 21 exceeds a predetermined threshold set in advance, the remaining capacity determination unit 52 determines that the voltages V1 to V4 are different. On the other hand, when the difference between the maximum value (V1) and the minimum value (V4) of the voltages V1 to V4 of each battery module 21 is less than or equal to the predetermined threshold set in advance, the remaining capacity determination unit 52 determines that the voltages V1 to V4 are the same. The predetermined threshold may be, for example, a value of 0 to 5% of the maximum charge capacity of the battery module 21.

[0050] When the remaining capacity determination unit 52 does not determine that the voltages V1 to V4 of the plurality of battery modules 21 are different (S13 / No), since it is not necessary to execute the cell balancing process, the first battery module 21a to the fourth battery module 21d are connected in series (step S27). Thereby, the battery unit 20 can be charged and discharged.

[0051] On the other hand, if the remaining capacity determination unit 52 determines that the voltages V1 to V4 of the multiple battery modules 21 are different (S13 / Yes), the cell balancing processing unit 53 calculates the inrush current Ic_A that occurs when the first battery module 21a with the largest remaining capacity is connected to the boost circuit 33 (step S15). For example, the inrush current Ic_A that occurs due to charge accumulation in the capacitor 37 at the moment the first battery module 21a is connected to the boost circuit 33 with the output terminal b open can be shown by the following formula (1).

[0052] Ic_A = (V1 - Vc) / r (1) V1: Voltage of the first battery module 21a Vc: Voltage of the capacitor 37 r: Resistance in the closed circuit connecting the first battery module 21a and the capacitor 37

[0053] When the first battery module 21a is connected to the input terminal a of the boost circuit 33, the sum of the internal resistances of the coil 35 and diode 36 of the boost circuit 33 and the first battery module 21a may be set to the above resistance value r. Alternatively, for simplicity, it may be assumed that the first battery module 21a is connected to the output terminal b of the boost circuit 33, and the internal resistance of the first battery module 21a may be set to the above resistance value r. The resistance values ​​of the coil 35 and diode 36 of the boost circuit 33, and the internal resistance value of the first battery module 21a may be set in advance. Also, the voltage Vc of the capacitor 37 when the battery module 21 is first connected to the boost circuit 33 can be set to zero. From the above equation (1), the larger the difference between the voltage V1 of the first battery module 21a and the voltage Vc of the capacitor 37, the larger the inrush current.

[0054] Next, the cell balancing processing unit 53 determines whether the calculated inrush current Ic_A is less than or equal to the allowable current upper limit Imax of the battery module 21 (step S17). If the cell balancing processing unit 53 determines that the inrush current Ic_A is less than or equal to the allowable current upper limit Imax (S17 / Yes), it connects the first battery module 21a to the input terminal a of the boost circuit 33, as shown in Figure 12 (step S19). The inrush current Ic_A generated at this time will be less than or equal to the allowable current upper limit Imax.

[0055] Furthermore, as shown in Figure 13, the cell balancing processing unit 53 connects the other second battery modules 21b to the fourth battery modules 21d in parallel to the output terminal b of the boost circuit 33 (step S21). Since charge is already stored in the capacitor 37 when each battery module 21 is connected, the inrush current generated when each battery module 21 is connected to the boost circuit 33 does not exceed the allowable current upper limit Imax. As a result, the charging power of the first battery module 21a begins to be distributed to the second battery modules 21b to the fourth battery modules 21d.

[0056] Next, the cell balancing processing unit 53 starts driving the boost circuit 33 (step S23). This shortens the time required to equalize the remaining capacities of the first battery module 21a to the fourth battery module 21d.

[0057] Next, the cell balancing processing unit 53 acquires the voltages V1 to V4 of each of the first battery module 21a to the fourth battery module 21d and determines whether the remaining capacities of the first battery module 21a to the fourth battery module 21d have become equal (step S25). For example, the cell balancing processing unit 53 determines whether the remaining capacities of the first battery module 21a to the fourth battery module 21d have become equal in accordance with the determination process in step S13.

[0058] If the cell balancing processing unit 53 does not determine that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / No), it continues the cell balancing process and repeats the determination in step S25. On the other hand, if the cell balancing processing unit 53 determines that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / Yes), it connects the first battery module 21a to the fourth battery module 21d in series and allows charging and discharging from the battery unit 20 (step S27).

[0059] On the other hand, in step S17 above, if the cell balancing processing unit 53 does not determine that the inrush current Ic_A is less than or equal to the allowable current upper limit Imax (S17 / No), it calculates the inrush current Ic_B that occurs when the second battery module 21b, which has the highest voltage V2 among the second battery module 21b to the fourth battery module 21d, is connected to the boost circuit 33 (step S31). For example, the cell balancing processing unit 53 can calculate the inrush current Ic_B based on the above formula (1).

[0060] Next, the cell balancing processing unit 53 determines whether the calculated inrush current Ic_B is less than or equal to the allowable current upper limit Imax of the battery module 21 (step S33). If the cell balancing processing unit 53 determines that the inrush current Ic_B is less than or equal to the allowable current upper limit Imax (S33 / Yes), it connects the second battery module 21b to the output terminal b of the boost circuit 33 and performs a charge process to accumulate charge in the capacitor 37, as shown in Figure 14 (step S35). The inrush current Ic_B generated at this time will be less than or equal to the allowable current upper limit Imax.

[0061] Furthermore, as shown in Figure 13, the cell balancing processing unit 53 connects the first battery module 21a to the input side of the boost circuit 33 and connects the third battery module 21c to the fourth battery module 21d in parallel to the output terminal b of the boost circuit 33 (step S37). When the first battery module 21a, which has a maximum voltage V1, is connected to the boost circuit 33, charge has already been accumulated in the capacitor 37, and the difference between the voltage V1 of the first battery module 21a and the voltage Vc of the capacitor 37 becomes small. For this reason, the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 does not exceed the allowable current upper limit Imax. The same applies when the third battery module 21c and the fourth battery module 21d are connected to the boost circuit 33. As a result, the charging power of the first battery module 21a begins to be distributed to the second battery module 21b to the fourth battery module 21d.

[0062] The process then proceeds to step S23, where the cell balancing processing unit 53 starts driving the boost circuit 33 (step S23). If it determines that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / Yes), it connects the first battery module 21a to the fourth battery module 21d in series and allows charging and discharging from the battery unit 20 (step S27).

[0063] On the other hand, in step S33 above, if the cell balancing processing unit 53 does not determine that the inrush current Ic_B is less than or equal to the allowable current upper limit Imax of the battery module 21 (S33 / No), it calculates the inrush current Ic_C that occurs when the third battery module 21c, which has the highest voltage V3 among the third battery module 21c to the fourth battery module 21d, is connected to the boost circuit 33 (step S41). For example, the cell balancing processing unit 53 can calculate the inrush current Ic_C based on the above formula (1).

[0064] Next, the cell balancing processing unit 53 determines whether the calculated inrush current Ic_C is less than or equal to the allowable current upper limit Imax of the battery module 21 (step S43). If the cell balancing processing unit 53 determines that the inrush current Ic_C is less than or equal to the allowable current upper limit Imax (S43 / Yes), it connects the third battery module 21c to the output terminal b of the boost circuit 33 and performs a charge process to accumulate charge in the capacitor 37, as shown in Figure 15 (step S45). The inrush current Ic_C generated at this time will be less than or equal to the allowable current upper limit Imax.

[0065] Next, the cell balancing processing unit 53 calculates the inrush current Ic_A that occurs when the first battery module 21a is connected to the input side of the boost circuit 33 (step S47). For example, if the remaining capacity of the third battery module 21c is low, even if the third battery module 21c is connected to the boost circuit 33 and charge is stored in the capacitor 37, the inrush current Ic_A that occurs when the first battery module 21a is subsequently connected to the input side terminal a of the boost circuit 33 may exceed the allowable current upper limit Imax. For this reason, the cell balancing processing unit 53 calculates the inrush current Ic_A that occurs when the first battery module 21a is connected to the input side terminal a of the boost circuit 33 while the third battery module 21c is connected to the boost circuit 33.

[0066] Next, the cell balancing processing unit 53 determines whether the calculated inrush current Ic_A is less than or equal to the allowable current upper limit Imax of the battery module 21 (step S49). If the cell balancing processing unit 53 determines that the inrush current Ic_A is less than or equal to the allowable current upper limit Imax (S49 / Yes), as shown in Figure 13, it connects the first battery module 21a to the input side of the boost circuit 33 and connects the second battery module 21b and the fourth battery module 21d in parallel to the output terminal b of the boost circuit 33 (step S51). When the first battery module 21a with the maximum voltage V1 is connected to the boost circuit 33, charge has already been accumulated in the capacitor 37, and the difference between the voltage V1 of the first battery module 21a and the voltage Vc of the capacitor 37 becomes small.

[0067] Therefore, the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 does not exceed the allowable current upper limit Imax. The same applies when the second battery module 21b and the fourth battery module 21d are connected to the boost circuit 33. As a result, the charging power of the first battery module 21a begins to be distributed to the second battery module 21b through the fourth battery module 21d.

[0068] The process then proceeds to step S23, where the cell balancing processing unit 53 starts driving the boost circuit 33 (step S23). If it determines that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / Yes), it connects the first battery module 21a to the fourth battery module 21d in series and allows charging and discharging from the battery unit 20 (step S27).

[0069] On the other hand, in step S49 above, if the cell balancing processing unit 53 does not determine that the inrush current Ic_A is less than or equal to the allowable current upper limit Imax (S49 / No), it connects the second battery module 21b in parallel to the output side of the boost circuit 33 and performs a charge process to further accumulate charge in the capacitor 37, as shown in Figure 16 (step S61). When the second battery module 21b is connected to the boost circuit 33, charge has already been accumulated in the capacitor 37, and the difference between the voltage V2 of the second battery module 21b and the voltage Vc of the capacitor 37 becomes small. For this reason, the inrush current Ic_B generated when the second battery module 21b is connected to the boost circuit 33 will not exceed the allowable current upper limit Imax.

[0070] Next, as shown in Figure 13, the cell balancing processing unit 53 connects the first battery module 21a to the input side of the boost circuit 33 and connects the fourth battery module 21d in parallel to the output terminal b of the boost circuit 33 (step S63). When the first battery module 21a with the maximum voltage V1 is connected to the boost circuit 33, charge has already been accumulated in the capacitor 37, and the difference between the voltage V1 of the first battery module 21a and the voltage Vc of the capacitor 37 becomes small.

[0071] Therefore, the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 does not exceed the allowable current upper limit Imax. The same applies when the fourth battery module 21d is connected to the boost circuit 33. As a result, the charging power of the first battery module 21a begins to be distributed to the second battery module 21b through the fourth battery module 21d.

[0072] The process then proceeds to step S23, where the cell balancing processing unit 53 starts driving the boost circuit 33 (step S23). If it determines that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / Yes), it connects the first battery module 21a to the fourth battery module 21d in series and allows charging and discharging from the battery unit 20 (step S27).

[0073] On the other hand, in step S43 above, if the cell balancing processing unit 53 does not determine that the inrush current Ic_C is less than or equal to the allowable current upper limit Imax (S43 / No), it calculates the inrush current Ic_D that occurs when the fourth battery module 21d is connected to the boost circuit 33 (step S71). For example, the cell balancing processing unit 53 can calculate the inrush current Ic_D based on the above formula (1).

[0074] Next, the cell balancing processing unit 53 determines whether the calculated inrush current Ic_D is less than or equal to the allowable current upper limit Imax of the battery module 21 (step S73). If the cell balancing processing unit 53 determines that the inrush current Ic_D is less than or equal to the allowable current upper limit Imax (S73 / Yes), it connects the fourth battery module 21d to the output terminal b of the boost circuit 33 and performs a charge process to accumulate charge in the capacitor 37, as shown in Figure 17 (step S75). The inrush current Ic_D generated at this time will be less than or equal to the allowable current upper limit Imax.

[0075] Subsequently, the cell balancing processing unit 53 proceeds to step S47 and calculates the inrush current Ic_A that occurs when the first battery module 21a is connected to the input side of the boost circuit 33 (step S47). For example, if the remaining capacity of the fourth battery module 21d is low, even if the fourth battery module 21d is connected to the boost circuit 33 and charge is stored in the capacitor 37, the inrush current Ic_A that occurs when the first battery module 21a is then connected to the input side terminal a of the boost circuit 33 may exceed the allowable current upper limit Imax. For this reason, the cell balancing processing unit 53 calculates the inrush current Ic_A that occurs when the first battery module 21a is connected to the input side terminal a of the boost circuit 33 while the fourth battery module 21d is connected to the boost circuit 33.

[0076] Next, the cell balancing processing unit 53 determines whether the calculated inrush current Ic_A is less than or equal to the allowable current upper limit Imax of the battery module 21 (step S49). If the cell balancing processing unit 53 determines that the inrush current Ic_A is less than or equal to the allowable current upper limit Imax (S49 / Yes), as shown in Figure 13, it connects the first battery module 21a to the input side of the boost circuit 33 and connects the second battery module 21b and the third battery module 21c in parallel to the output terminal b of the boost circuit 33 (step S51). When the first battery module 21a with the maximum voltage V1 is connected to the boost circuit 33, charge has already been accumulated in the capacitor 37, and the difference between the voltage V1 of the first battery module 21a and the voltage Vc of the capacitor 37 becomes small.

[0077] Therefore, the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 does not exceed the allowable current upper limit Imax. The same applies when the second battery module 21b and the third battery module 21c are connected to the boost circuit 33. As a result, the charging power of the first battery module 21a begins to be distributed to the second battery module 21b through the fourth battery module 21d.

[0078] The process then proceeds to step S23, where the cell balancing processing unit 53 starts driving the boost circuit 33 (step S23). If it determines that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / Yes), it connects the first battery module 21a to the fourth battery module 21d in series and allows charging and discharging from the battery unit 20 (step S27).

[0079] When the fourth battery module 21d is connected to the boost circuit 33, in step S49, if the cell balancing processing unit 53 does not determine that the inrush current Ic_A is less than or equal to the allowable current upper limit Imax (S49 / No), it connects the second battery module 21b in parallel to the output side of the boost circuit 33, as shown in Figure 18 (step S61). When the second battery module 21b is connected to the boost circuit 33, charge has already been accumulated in the capacitor 37, and the difference between the voltage V2 of the second battery module 21b and the voltage Vc of the capacitor 37 becomes small. For this reason, the inrush current Ic_B generated when the second battery module 21b is connected to the boost circuit 33 will not exceed the allowable current upper limit Imax.

[0080] Next, as shown in Figure 13, the cell balancing processing unit 53 connects the first battery module 21a to the input side of the boost circuit 33 and connects the third battery module 21c in parallel to the output terminal b of the boost circuit 33 (step S63). When the first battery module 21a with the maximum voltage V1 is connected to the boost circuit 33, charge has already been accumulated in the capacitor 37, and the difference between the voltage V1 of the first battery module 21a and the voltage Vc of the capacitor 37 becomes small.

[0081] Therefore, the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 does not exceed the allowable current upper limit Imax. The same applies when the third battery module 21c is connected to the boost circuit 33. As a result, the charging power of the first battery module 21a begins to be distributed to the second battery module 21b to the fourth battery module 21d.

[0082] The process then proceeds to step S23, where the cell balancing processing unit 53 starts driving the boost circuit 33 (step S23). If it determines that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / Yes), it connects the first battery module 21a to the fourth battery module 21d in series and allows charging and discharging from the battery unit 20 (step S27).

[0083] In this way, by selecting the battery module 21 to connect to the boost circuit 33 first, in order of the largest remaining capacity, it becomes possible to keep the inrush current Ic generated when connecting the battery module 21 to the boost circuit 33 below the allowable current upper limit Imax of the battery module 21. However, it is possible that the inrush current Ic_D generated when the fourth battery module 21d, which has the smallest remaining capacity (lowest voltage), is connected to the boost circuit 33 may exceed the allowable current upper limit Imax (in the case of S73 / No).

[0084] Figure 19 shows an example of the configuration of a connection switching circuit 32 that takes such a case into consideration. The connection switching circuit 32 shown in Figure 19 has a first path 47a having a first relay switch 46a and a second path 47b having a second relay switch 46b in the electrical circuit on the positive side of the input terminal a of the boost circuit 33. Of these, an electrical resistor 45 is provided in the first path 47a.

[0085] When the connection switching circuit 32 shown in Figure 19 is used, the processes from steps S11 to S75 described so far are performed with the first relay switch 46a open and the second relay switch 46b connected. That is, when the first battery module 21a is connected to the input terminal a of the boost circuit 33, the current supplied from the first battery module 21a is supplied to the boost circuit 33 without passing through the electrical resistor 45.

[0086] On the other hand, in step S73 above, if the cell balancing processing unit 53 does not determine that the inrush current Ic_D is less than or equal to the allowable current upper limit Imax (S73 / No), it connects the first relay switch 46a of the connection switching circuit 32 shown in Figure 19, while opening the second relay switch 46b, and connects the electrical resistor 45 in series with the first battery module 21a to the input terminal a of the boost circuit 33 (step S81). As a result, the current flowing through the electrical resistor 45 is suppressed, while charge can be accumulated in the capacitor 37. Therefore, the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 can be kept from exceeding the allowable current upper limit Imax.

[0087] Furthermore, since power loss occurs when current flows through the electrical resistor 45, the battery control device 50 according to this embodiment has a configuration that connects the battery module 21 to the boost circuit 33 so that the inrush current Ic does not exceed the allowable current upper limit Imax, without using the electrical resistor 45.

[0088] Next, the cell balancing processing unit 53 determines whether the voltage Vc of the capacitor 37 has reached the voltage V1 of the first battery module 21a (step S83). If the cell balancing processing unit 53 does not determine that the voltage Vc of the capacitor 37 has reached the voltage V1 of the first battery module 21a (S83 / No), it repeats the determination in step S83. On the other hand, if the cell balancing processing unit 53 determines that the voltage Vc of the capacitor 37 has reached the voltage V1 of the first battery module 21a (S83 / Yes), it opens the first relay switch 46a while connecting the second relay switch 46b, disconnecting the electrical resistor 45 from the current path (step S85).

[0089] Next, as shown in Figure 20, the cell balancing processing unit 53 connects the second battery module 21b to the fourth battery module 21d in parallel to the output terminal b of the boost circuit 33 (step S87).

[0090] The process then proceeds to step S23, where the cell balancing processing unit 53 starts driving the boost circuit 33 (step S23). If it determines that the remaining capacities of the first battery module 21a to the fourth battery module 21d are equal (S25 / Yes), it connects the first battery module 21a to the fourth battery module 21d in series and allows charging and discharging from the battery unit 20 (step S27).

[0091] <3. Effects> As described above, the battery control device 50 according to this embodiment performs a process to equalize the remaining capacities of multiple battery modules 21 by connecting them in parallel when the remaining capacities of multiple battery modules 21 are different. The battery control device 50 determines whether the inrush current Ic_A generated when the first battery module 21a, which has the largest remaining capacity, is connected to the boost circuit 33 exceeds a predetermined allowable current upper limit Imax. Furthermore, if the battery control device 50 determines that the inrush current Ic_A exceeds the allowable current upper limit Imax, it performs a charge process to ensure that the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 does not exceed the allowable current upper limit Imax by selecting a battery module 21 other than the first battery module 21a whose inrush current Ic generated when connected to the boost circuit 33 does not exceed the allowable current upper limit Imax and connecting it to the boost circuit 33. Furthermore, after the charging process, the battery control device 50 connects the first battery module 21a to the input terminal a of the boost circuit 33, and connects the battery modules 21 other than the first battery module 21a in parallel to the output terminal b of the boost circuit 33, thereby equalizing the remaining capacity of the multiple battery modules 21.

[0092] This allows the battery module 21 with the largest remaining capacity to be connected to the input terminal a of the boost circuit 33, and the other battery modules 21 to the output terminal b, so that the inrush current Ic does not exceed the allowable current upper limit Imax of the battery module 21. This also shortens the time required for cell balancing.

[0093] Furthermore, in the charging process, the battery control device 50 according to this embodiment selects the battery module 21 with the largest remaining capacity from among the battery modules 21 other than the first battery module 21a which has the largest remaining capacity, and connects it to the boost circuit 33, from among the battery modules 21 whose inrush current Ic does not exceed the allowable current upper limit Imax. As a result, by connecting one battery module 21, the likelihood that the inrush current Ic_A that occurs when the first battery module 21a is connected will not exceed the allowable current upper limit Imax increases, and the time required for cell balancing can be prevented from becoming longer.

[0094] Furthermore, in the charging process, the battery control device 50 estimates the inrush current Ic generated when a battery module 21 other than the first battery module 21a, which has the largest remaining capacity, is connected to the boost circuit 33, in descending order of remaining capacity among the battery modules 21 other than the first battery module 21a, and connects the battery module 21 whose inrush current Ic is determined not to exceed the allowable current upper limit Imax to the boost circuit 33. This makes it possible to minimize the time required to select a battery module 21 that can be connected to the boost circuit 33 without the inrush current Ic exceeding the allowable current upper limit Imax, even if the battery module 21 whose inrush current Ic was initially calculated cannot be connected to the boost circuit 33.

[0095] Furthermore, in the charging process, the battery control device 50 in this embodiment selects the battery module 21 with the largest remaining capacity from among the battery modules 21 other than the first battery module 21a which has the largest remaining capacity, and connects it to the boost circuit 33 to store charge in the capacitor 37. Then, it determines whether the inrush current Ic_A when the first battery module 21a is connected to the boost circuit 33 exceeds the allowable current limit Imax. If it is determined that the inrush current Ic_A exceeds the allowable current limit Imax, it connects yet another battery module 21 to the boost circuit 33 to prevent the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 from exceeding the allowable current limit Imax. This makes it possible to connect one battery module 21 to the boost circuit 33 and store charge in the capacitor 37, while still connecting the first battery module 21a to the boost circuit 33, thereby preventing the inrush current Ic_A from exceeding the allowable current upper limit Imax.

[0096] Furthermore, in this embodiment, if there is no battery module 21 other than the first battery module 21a, which has the largest remaining capacity, whose inrush current Ic generated when connected to the boost circuit 33 does not exceed the allowable current limit Imax, the battery control device 50 connects the first battery module 21a and the electrical resistor 45 in series with the boost circuit 33 to prevent the inrush current Ic_A generated when the first battery module 21a is connected to the boost circuit 33 from exceeding the allowable current limit Imax. After that, the electrical resistor 45 is disconnected, and the battery modules 21 other than the first battery module 21a are connected in parallel to the output terminal b of the boost circuit 33. As a result, even if there is no battery module 21 whose inrush current Ic does not exceed the allowable current limit Imax, the inrush current Ic_A can be prevented from exceeding the allowable current limit Imax by connecting the first battery module 21a to the boost circuit 33 while suppressing the current supplied to the capacitor 37. Furthermore, the battery control device 50 does not connect the electrical resistor 45 until it determines that there are no battery modules 21 in which the inrush current Ic does not exceed the allowable current upper limit Imax, thereby suppressing power loss.

[0097] Furthermore, in this embodiment, the battery unit 20 is provided in the power system 10 of the vehicle 1, the plurality of battery modules 21 are replaceable battery modules 21 for the user of the vehicle 1, and the battery control device 50 performs a process to equalize the remaining capacity of the plurality of battery modules 21 after one or more of the plurality of battery modules 21 have been replaced. This shortens the time required for cell balancing after the replacement of a battery module 21, and shortens the time until the vehicle 1 can be started to operate.

[0098] Preferred embodiments of the present disclosure have been described in detail above with reference to the attached drawings, but the present disclosure is not limited to such examples. It is clear to any person with ordinary skill in the art to which the present disclosure belongs that various modifications or alterations can be conceived within the scope of the technical idea described in the claims, and these will naturally also be understood to fall within the technical scope of the present disclosure. For example, the functions etc. included in each component or each step etc. can be rearranged in a logically consistent manner, and multiple components or steps etc. can be combined into one or divided into two.

[0099] For example, the above embodiment describes an example in which cell balancing is performed after replacing one of the battery modules 21. However, the execution of cell balancing is not limited to after replacing a battery module 21. For example, it is possible to determine whether the remaining capacities of each battery module 21 are different when the power system 10 of the vehicle 1 is stopped, and then perform the cell balancing process described above. In this case, the battery module 21 may be a battery module 21 that cannot be replaced by the user.

[0100] Furthermore, the technology disclosed herein can also be realized as a vehicle 1 equipped with the battery control device 50 described in the above-described embodiment, a control method for the battery unit 20 executed by the battery control device 50, a computer program that causes a computer to function as the above-described battery control device 50, and a non-temporary tangible recording medium on which the computer program is stored.

[0101] 1: Vehicle 10: Power system 20: Battery unit 21, 21a, 21b, 21c, 21d, 21e: Battery module 31: Circuit board 32: Connection switching circuit 33: Boost circuit 34a: Input terminal 34b: Output terminal 37: Capacitor 38: Switching element 45: Electrical resistor 46a: First relay switch 46b: Second relay switch 47a: First path 47b: Second path 50: Battery control device 51: Processing unit 52: Remaining capacity determination unit 53: Cell balancing processing unit

Claims

1. A battery control device for controlling a battery unit having multiple battery modules, wherein when the remaining capacities of the multiple battery modules differ, the battery control device performs a process to connect the multiple battery modules in parallel and equalize the remaining capacities of the multiple battery modules, wherein the battery control device performs the following: determine whether the inrush current generated when the maximum capacity battery module, which has the largest remaining capacity, is connected to a boost circuit having a capacitor exceeds a predetermined allowable current upper limit; if it is determined that the inrush current exceeds the allowable current upper limit, select a battery module from among the battery modules other than the maximum capacity battery module, whose inrush current generated when connected to the boost circuit does not exceed the allowable current upper limit, and connect it to the boost circuit, thereby performing a charge process so that the inrush current generated when the maximum capacity battery module is connected to the boost circuit does not exceed the allowable current upper limit; and after the charge process, connect the maximum capacity battery module to the input side of the boost circuit, and connect the battery modules other than the maximum capacity battery module in parallel to the output side of the boost circuit, thereby equalizing the remaining capacities of the multiple battery modules.

2. The battery control device according to claim 1, wherein in the charging process, among the battery modules other than the maximum capacity battery module, the battery module with the largest remaining capacity is selected from among the battery modules whose inrush current does not exceed the allowable current upper limit and connected to the boost circuit.

3. The battery control device according to claim 2, wherein, in the charging process, the inrush current generated when a battery module other than the maximum capacity battery module is connected to the boost circuit is estimated in order of the remaining capacity of the battery modules other than the maximum capacity battery module, and the battery module whose inrush current is determined not to exceed the allowable current upper limit is connected to the boost circuit.

4. In the charging process, the battery control device according to claim 2, wherein, among the battery modules other than the maximum capacity battery module, the battery module with the largest remaining capacity is selected from among the battery modules whose inrush current does not exceed the allowable current upper limit and connected to the boost circuit to store charge in the capacitor, and then it is determined whether the inrush current when the maximum capacity battery module is connected to the boost circuit exceeds the allowable current upper limit, and if it is determined that the inrush current exceeds the allowable current upper limit, another battery module is connected to the boost circuit to prevent the inrush current generated when the maximum capacity battery module is connected to the boost circuit from exceeding the allowable current upper limit.

5. If, among the battery modules other than the maximum capacity battery module, there is no battery module in which the inrush current generated when connected to the boost circuit does not exceed the allowable current limit, the battery control device according to claim 1, wherein the maximum capacity battery module and an electrical resistor are connected in series with the boost circuit so that the inrush current generated when the maximum capacity battery module is connected to the boost circuit does not exceed the allowable current limit, the electrical resistor is disconnected, and the battery modules other than the maximum capacity battery module are connected in parallel to the output side of the boost circuit.

6. The battery control device according to claim 1, wherein the battery unit is provided in the power system of a vehicle, the plurality of battery modules are replaceable battery modules for the user of the vehicle, and the battery control device performs a process to equalize the remaining capacity of the plurality of battery modules after one or more of the plurality of battery modules have been replaced.

7. A battery unit control method that, when the remaining capacities of the multiple battery modules of a battery unit having multiple battery modules differ, performs a process to connect the multiple battery modules in parallel and equalize the remaining capacities of the multiple battery modules, comprising: determining whether the inrush current generated when the maximum capacity battery module, which has the largest remaining capacity, is connected to a boost circuit having a capacitor exceeds a predetermined allowable current limit; if it is determined that the inrush current exceeds the allowable current limit, selecting a battery module other than the maximum capacity battery module whose inrush current generated when connected to the boost circuit does not exceed the allowable current limit and connecting it to the boost circuit, thereby performing a charge process so that the inrush current generated when the maximum capacity battery module is connected to the boost circuit does not exceed the allowable current limit; and after the charge process, connecting the maximum capacity battery module to the input side of the boost circuit and connecting the battery modules other than the maximum capacity battery module in parallel to the output side of the boost circuit, thereby equalizing the remaining capacities of the multiple battery modules.

8. A non-temporary tangible recording medium that records the program causing a computer to perform a process to equalize the remaining capacities of a plurality of battery modules in a power system having a plurality of battery modules when the remaining capacities of the plurality of battery modules differ, the program to perform the following: determine whether the inrush current generated when the largest capacity battery module with the largest remaining capacity is connected to a boost circuit having a capacitor exceeds a predetermined allowable current limit; if it is determined that the inrush current exceeds the allowable current limit, select a battery module other than the largest capacity battery module whose inrush current generated when connected to the boost circuit does not exceed the allowable current limit and connect it to the boost circuit, thereby performing a charge process so that the inrush current generated when the largest capacity battery module is connected to the boost circuit does not exceed the allowable current limit; and after the charge process, connect the largest capacity battery module to the input side of the boost circuit and connect the battery modules other than the largest capacity battery module in parallel to the output side of the boost circuit, thereby equalizing the remaining capacities of the plurality of battery modules.

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