Power supply device

Abstract

To dissolve voltage difference between a plurality of battery modules in a short time while suppressing generation of arc in a relay when the battery modules are connected in parallel.SOLUTION: A power supply device comprises: a first battery module and a second battery module capable of being charged by an external power supply; a connection circuit having a plurality of relays, and selectively forming a series circuit in which the first battery module and the second battery module are connected in series and a parallel circuit in which the first battery module and the second battery module are connected in parallel; a variable resistor provided in the connection circuit, and disposed between the first battery module and the second battery module in the parallel circuit; and a controller for controlling opening / closing of the plurality of relays and a resistance value of the variable resistor. After the controller controls the plurality of relays to form the parallel circuit, it can execute current regulating processing for continuously or stepwisely reducing the resistance value of the variable resistor.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a power supply device. [Background technology]

[0002] Patent Document 1 describes a power supply device. This power supply device includes two battery modules that can be charged by an external power source, a connection circuit having multiple relays and selectively forming a series circuit in which the two battery modules are connected in series and a parallel circuit in which the two battery modules are connected in parallel, and a control device that controls the opening and closing of the multiple relays. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-118221 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the power supply device as described above, when two battery modules connected in series are charged and discharged over a long period of time, a difference in the state of charge (SOC) may occur between the battery modules. In this case, a voltage difference occurs between the two battery modules, and therefore, when the battery modules are connected in parallel, a circulating current occurs in which a current circulates between the battery modules. Depending on the voltage difference, an arc may occur at the contacts of the relay, or an excessive circulating current may flow. Therefore, in order to prevent the occurrence of an arc or an excessive circulating current, it is necessary to prohibit the parallel connection of the battery modules according to the voltage difference between the battery modules.

[0005] However, if the parallel connection of the battery modules is frequently prohibited, problems such as the loss of functionality and convenience of the power supply device may occur. Therefore, when two battery modules are connected in parallel, it is possible to interpose a resistor between the two battery modules. This makes it possible to suppress the occurrence of arcs in the relay and the magnitude of circulating current in response to the voltage difference between the battery modules, and significantly reduces the frequency with which the parallel connection of the battery modules is prohibited. On the other hand, since the circulating current is suppressed by the resistor, it takes longer for the voltage difference between the battery modules to be eliminated. In this case, as a result, the functionality and convenience of the power supply device are still impaired.

[0006] This specification takes into consideration the above-mentioned trade-off problem and provides a technology that can quickly eliminate the voltage difference (also referred to as the difference in charging rate) between battery modules while suppressing the occurrence of arcs in relays when two battery modules are connected in parallel. [Means for solving the problem]

[0007] The technology disclosed in this specification is embodied in a power supply device. In a first aspect, the power supply device includes a first battery module and a second battery module that can be charged by an external power source, a connection circuit having a plurality of relays and selectively forming a series circuit in which the first battery module and the second battery module are connected in series and a parallel circuit in which the first battery module and the second battery module are connected in parallel, a variable resistor provided in the connection circuit and interposed between the first battery module and the second battery module in the parallel circuit, and a control device that controls opening and closing of the plurality of relays and the resistance value of the variable resistor. The control device is configured to be able to execute a current adjustment process that continuously or stepwise reduces the resistance value of the variable resistor after controlling the plurality of relays to form the parallel circuit. The number of battery modules provided in the power supply device does not necessarily need to be two, and may be three or more.

[0008] In the above-mentioned configuration, a variable resistor is interposed in the parallel circuit in which two battery modules are connected in parallel. The resistance value of the variable resistor can be controlled to decrease continuously or stepwise after the parallel circuit is formed. In this way, when two battery modules are connected in parallel, the generation of an arc in the relay and the magnitude of the circulating current can be suppressed by interposing a relatively high resistance. Therefore, even if the voltage difference between the battery modules is relatively large, it is possible to allow the parallel connection of the battery modules, and the frequency with which the parallel connection is prohibited can be reduced.

[0009] Thereafter, as the circulating current flows, the voltage difference between the battery modules is gradually eliminated, and the circulating current naturally becomes smaller. In this case, by lowering the resistance value of the variable resistor and relaxing the restrictions on the circulating current, the voltage difference (or the difference in charging rate) between the battery modules can be quickly eliminated. Note that the smaller the voltage difference between the battery modules, the greater the allowable circulating current value for the relay, battery module, and variable resistor. For this reason, the resistance value of the variable resistor may be significantly lowered so that the circulating current increases over time.

[0010] In a second aspect, in the first aspect, the control device may be configured to estimate or detect at least one of an open circuit voltage difference between the first battery module and the second battery module and a circulating current flowing between the first battery module and the second battery module, and determine a resistance value of the variable resistor based on at least one of the open circuit voltage difference and the circulating current. The amount of heat generated by the circulating current in the relay, the battery module, and the variable resistor depends on the voltage difference between the battery modules and the magnitude of the circulating current. Since the voltage difference and the magnitude of the circulating current are correlated, one can be estimated from the other. Therefore, the circulating current can be appropriately adjusted by determining the resistance value of the variable resistor based on at least one of the voltage difference and the circulating current.

[0011] In a third aspect, in the first or second aspect, the control device may determine the resistance value of the variable resistor so that the product of the voltage difference and the circulating current is equal to or less than a predetermined threshold. More precisely, the amount of heat generated by the circulating current in the relay, the battery module, and the variable resistor depends on the product of the voltage difference between the battery modules and the magnitude of the circulating current (i.e., power). Therefore, by determining the resistance value of the variable resistor so that the product of the voltage difference and the circulating current is equal to or less than a threshold that the relay, the battery module, and the variable resistor can tolerate, the circulating current can be appropriately suppressed.

[0012] In a fourth aspect, in any one of the first to third aspects, the connection circuit may include a bypass circuit that bypasses the variable resistor via at least one of the multiple relays. In this case, the control device may electrically open the bypass circuit during the current adjustment process and conduct the bypass circuit after the current adjustment process is completed. With this configuration, for example, after the voltage difference between the battery modules is sufficiently eliminated, unnecessary current flow to the variable resistor can be avoided by shorting the variable resistor with the bypass circuit.

[0013] In any of the above-described aspects, the connection circuit may have a system main relay that connects and disconnects the first battery module and the second battery module to the load. In this case, the variable resistor may be a pre-charge resistor provided in the system main relay. That is, by adopting a variable resistor as the pre-charge resistor provided in the system main relay, the pre-charge resistor can also be used as the variable resistor during the above-described parallel connection.

[0014] In a fifth aspect, the vehicle may include a motor for driving a wheel, a power supply device according to any one of the first to fourth aspects for supplying power to the motor, and a charging inlet configured to allow an external power supply to be detachably attached. In this case, the control device may be configured to connect the first battery module and the second battery module in series to the motor by configuring a series circuit in the connection circuit when the power supply device supplies power to the motor, and to connect the first battery module and the second battery module in parallel to the charging inlet by configuring a parallel circuit in the connection circuit when the power supply device is charged by the external power supply. With this configuration, when the power supply device supplies power to the motor, the first battery module and the second battery module are connected in series, so that power can be supplied at a high voltage. Also, when the power supply device is charged by the external power supply, the first battery module and the second battery module are connected in parallel, so that the output voltage required of the external power supply can be reduced. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a schematic configuration of a power supply device 10 according to an embodiment and a vehicle 100 on which the power supply device is mounted. [Diagram 2] FIG. 4 is a circuit diagram showing a series circuit formed by a connection circuit 16. [Diagram 3] FIG. 4 is a circuit diagram showing a parallel circuit formed by a connection circuit 16. [Figure 4] FIG. 4 shows the time-dependent changes in various indices in the current adjustment process. FIG. 4(A) shows the resistance value R of the second pre-charge resistor 44. FIG. 4(B) shows the detected value of the charging rate SOC1 of the first battery module 12 and the detected value of the charging rate SOC2 of the second battery module 14. FIG. 4(C) shows the open circuit voltage V1 of the first battery module 12, the open circuit voltage V2 of the second battery module 14, and the open circuit voltage difference dV therebetween. FIG. 4(D) shows the circulating current I. FIG. 4(E) shows the product W of the open circuit voltage difference and the circulating current between the battery modules 12, 14, which indicates the amount of heat (power) caused by the circulating current. [Diagram 5]A modified example of the manner in which the resistance value R of the second pre-charge resistor 44 is changed in the current adjustment process will be described. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A power supply device 10 according to an embodiment and a vehicle 100 in which the power supply device 10 is used will be described with reference to the drawings. The power supply device 10 is a device that supplies power to a plurality of motors 102, 104, 106, and 108 of the vehicle 100. The power supply device 10 in this embodiment includes a plurality of battery modules 12 and 14, and may be referred to as a battery pack. Each of the battery modules 12 and 14 is configured to be rechargeable. The vehicle 100 referred to here is an electric vehicle that runs on a road surface, and is a so-called battery electric vehicle (BEV). However, the vehicle 100 is not limited to an electric vehicle, and may be a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a fuel cell electric vehicle (FCEV). The motors 102, 104, 106, and 108 in this embodiment are examples of loads mounted on the vehicle 100.

[0017] As shown in FIG. 1, the vehicle 100 includes a plurality of motors 102, 104, 106, 108 and a plurality of inverters 110, 112, 114, 116. Each of the motors 102, 104, 106, 108 is a traction motor that drives the wheels of the vehicle 100. The plurality of motors 102, 104, 106, 108 includes a first motor 102, a second motor 104, a third motor 106, and a fourth motor 108. The first motor 102 drives the right front wheel, the second motor 104 drives the left front wheel, the third motor 106 drives the right rear wheel, and the fourth motor 108 drives the left rear wheel. Each of the inverters 110, 112, 114, 116 is a device that performs DC-AC power conversion between the power supply device 10 and the corresponding motor 102, 104, 106, 108. The multiple inverters 110, 112, 114, 116 include a first inverter 110, a second inverter 112, a third inverter 114, and a fourth inverter 116. The first inverter 110 is provided between the power supply device 10 and the first motor 102, and can convert DC power from the power supply device 10 into three-phase AC power and supply it to the first motor 102. The first inverter 110 can also convert three-phase AC power from the first motor 102 into DC power and supply it to the power supply device 10. The configurations of the second inverter 112, the third inverter 114, and the fourth inverter 116 are similar to that of the first inverter 110, so a description thereof will be omitted. Although not particularly limited, if the rated voltage of the power supply device 10 and the rated voltages of the motors 102, 104, 106, and 108 are different from each other, a DC-DC converter may be further provided between the power supply device 10 and each of the inverters 110, 112, 114, and 116.

[0018] It should be noted that each of the motors 102, 104, 106, 108 does not necessarily have to drive only one wheel. For example, one motor may drive a pair of front or rear wheels. Therefore, the number of motors 102, 104, 106, 108 provided in the vehicle 100 is not limited to four, but may be one or more. In addition, the number of inverters 110, 112, 114, 116 can be appropriately changed depending on the number and arrangement of the motors 102, 104, 106, 108.

[0019] As shown in FIG. 1, the vehicle 100 further includes a charging inlet 118. The charging inlet 118 is configured to allow an external power source to be attached and detached. For example, when charging the battery modules 12, 14 of the power source device 10 mounted on the vehicle 100, the external power source and the charging inlet 118 of the vehicle 100 are connected via a power supply connector. This allows AC power from the external power source to be supplied to the battery modules 12, 14. In this manner, the vehicle 100 can charge the battery modules 12, 14 using the external power source. As an example, the external power source is a power source that supplies AC power, such as a commercial power source for home use or a charging station. Although not limited thereto, the charging inlet 118 is connected to the power source device 10 via charging relays 120, 122.

[0020] As described above, the power supply device 10 includes a first battery module 12 and a second battery module 14. Each of the battery modules 12, 14 includes a plurality of battery cells arranged in a stacked configuration. Each battery cell is a secondary battery cell that can be repeatedly charged and discharged, such as a lithium-ion battery cell, an all-solid-state battery cell, or a nickel-metal hydride battery cell. The specific number of the plurality of battery cells is not particularly limited, and can be changed as appropriate according to the output voltage required for each of the battery modules 12, 14. The number of battery modules included in the power supply device 10 does not necessarily need to be two, and may be three or more.

[0021] 1, the power supply device 10 further includes a connection circuit 16 and a control device 18. The connection circuit 16 includes a plurality of relays 20, 22, 24, 26, 28, 30, 32, 34, 36, and 38. The control device 18 controls the opening and closing of the plurality of relays 20-38.

[0022] The multiple relays 20-38 include a first relay 20, a second relay 22, and a third relay 24. These relays 20, 22, and 24, together with a first pre-charge resistor 40, constitute a first system main relay 42. The third relay 24 and the first pre-charge resistor 40 are connected in series, and are connected in parallel to the second relay 22. In this manner, the first system main relay 42 is provided with the first pre-charge resistor 40 to avoid an excessively large inrush current. The first system main relay 42 is interposed between the battery modules 12, 14 and the first motor 102, and can electrically connect and disconnect the battery modules 12, 14 and the first motor 102. The first system main relay 42 is also interposed between the battery modules 12, 14 and the second motor 104, and can electrically connect and disconnect the battery modules 12, 14 and the second motor 104. In addition, when the first system main relay 42 electrically connects the battery modules 12, 14 and the motors 102, 104, an excessive inrush current can be avoided by interposing the pre-charge resistor 40 between them.

[0023] The plurality of relays 20-38 further includes a fourth relay 26, a fifth relay 28, and a sixth relay 30. These relays 26, 28, and 30, together with a second pre-charge resistor 44, constitute a second system main relay 46. The second pre-charge resistor 44 is a variable resistor. The resistance value of the second pre-charge resistor 44 is controlled by the control device 18. The sixth relay 30 and the second pre-charge resistor 44 are connected in series, and are connected in parallel to the fifth relay 28. That is, the second system main relay 46 is also provided with the second pre-charge resistor 44 to avoid an excessive inrush current, similar to the first system main relay 42. The second system main relay 46 is interposed between the battery modules 12, 14 and the third motor 106, and can electrically connect and disconnect the battery modules 12, 14 and the third motor 106. The second system main relay 46 is also interposed between the battery modules 12, 14 and the fourth motor 108, and can electrically connect and disconnect the battery modules 12, 14 and the fourth motor 108. In addition, when the second system main relay 46 electrically connects the battery modules 12, 14 and the motors 106, 108, it is possible to avoid an excessive inrush current by interposing the second pre-charge resistor 44 between them.

[0024] The relays 20-38 further include a seventh relay 32, an eighth relay 34, a ninth relay 36, and a tenth relay 38. These relays 32, 34, 36, and 38 are provided to switch the connection mode between the first battery module 12 and the second battery module 14. That is, the control device 18 is configured to selectively form the series circuit shown in FIG. 2 and the parallel circuit shown in FIG. 3 in the connection circuit 16 by controlling the opening and closing of the relays 20-38. In detail, when the control device 18 closes the relays 20, 22, 26, 30, and 32 and opens the other relays, the connection circuit 16 forms the series circuit shown in FIG. 2. In this series circuit, the first battery module 12 and the second battery module 14 are connected in series. Furthermore, the first battery module 12 and the second battery module 14 connected in series are electrically connected to four inverters 110, 112, 114, 116 and four motors 102, 104, 106, 108.

[0025] On the other hand, when the control device 18 closes the relays 26, 30, 34, and 36 and opens the other relays, the connection circuit 16 forms a parallel circuit as shown in FIG. 3. In this parallel circuit, the first battery module 12 and the second battery module 14 are connected in parallel. Furthermore, the first battery module 12 and the second battery module 14 connected in parallel are electrically connected to the charging inlet 118 via the charging relays 120 and 122. As a result, when an external power source is connected to the charging inlet 118 via a power supply connector, the two battery modules 12 and 14 can be charged by the external power source. Furthermore, in the parallel circuit shown in FIG. 3, a second pre-charge resistor 44 is interposed between the first battery module 12 and the second battery module 14. As described above, the second pre-charge resistor 44 is a variable resistor, and the resistance value of the second pre-charge resistor 44 is controlled by the control device 18.

[0026] The control device 18 monitors the state of charge (SOC) of the first battery module 12 and the state of charge of the second battery module 14. The method is not particularly limited. For example, the control device 18 can calculate the state of charge of the first battery module 12 by integrating the charging current and discharging current of the first battery module 12 over time. The same is true for the second battery module 14. The control device 18 estimates the open circuit voltage of the first battery module 12 based on the state of charge of the first battery module 12, and estimates the open circuit voltage of the second battery module 14 based on the state of charge of the second battery module 14. Then, the control device 18 uses these two open circuit voltages to estimate the open circuit voltage difference between the first battery module 12 and the second battery module 14 and the circulating current flowing between the first battery module 12 and the second battery module 14 in the parallel circuit (see FIG. 3). In addition, since the resistance value of the entire parallel circuit (i.e., the internal resistance values ​​of the battery modules 12, 14, the resistance value of the second pre-charge resistor 44, and the resistance values ​​of the other circuit components) is known, the circulating current can be calculated by dividing the open-circuit voltage difference by the resistance value.

[0027] 1, the open circuit voltage of the first battery module 12, the open circuit voltage of the second battery module 14, and the circulating current between the two battery modules 12, 14 may be directly detected by voltage sensors 48, 58 and a current sensor 52, or may be estimated from the detected values. Alternatively, the control device 18 may use these sensors 48, 50, 52 to calculate the charging rate described above.

[0028] With the above configuration, when the vehicle 100 runs, the power supply device 10 is electrically connected to the motors 102, 104, 106, and 108. In this case, the control device 18 causes the connection circuit 16 to configure a series circuit as shown in FIG. 2. As a result, the first battery module 12 and the second battery module 14 are connected in series to the multiple motors 102, 104, 106, and 108. This allows the power supply device 10 to supply power at a relatively high voltage to the multiple motors 102, 104, 106, and 108. On the other hand, when the power supply device 10 is charged by an external power source, the power supply device 10 is electrically connected to the charging inlet 118. In this case, the control device 18 causes the connection circuit 16 to configure a parallel circuit as shown in FIG. 3. As a result, the first battery module 12 and the second battery module 14 are connected in parallel to the charging inlet 118. This allows the power supply device 10 to be charged at a relatively low charging voltage, and the output voltage required of the external power source can be reduced.

[0029] As described above, the power supply device 10 of the present embodiment can switch the connection of the two battery modules 12, 14 between a series connection and a parallel connection. However, when the two battery modules 12, 14 connected in series are charged and discharged over a long period of time, a difference in the charging rate between the battery modules 12, 14 may occur. In this case, an open circuit voltage difference (hereinafter simply referred to as a voltage difference) occurs between the two battery modules 12, 14, and therefore, when the battery modules 12, 14 are connected in parallel, a circulating current occurs in which a current circulates between the battery modules 12, 14. At this time, depending on the voltage difference, an arc may occur at the contacts of the relay 20-38 or an excessive circulating current may flow. For this reason, the control device 18 is configured to prohibit the parallel connection of the battery modules 12, 14 according to the voltage difference between the two battery modules 12, 14 in order to prevent the occurrence of an arc or an excessive circulating current.

[0030] However, if the parallel connection of the battery modules 12, 14 is frequently prohibited, the function and convenience of the power supply device 10, for example, may be impaired. Therefore, in the power supply device 10 of this embodiment, when the connection circuit 16 forms the parallel circuit shown in FIG. 3, the second pre-charge resistor 44, which is a variable resistor, is interposed between the two battery modules 12, 14. This suppresses the occurrence of an arc in the relay 20-38 and the magnitude of the circulating current with respect to the voltage difference between the battery modules 12, 14. As a result, the frequency with which the parallel connection of the battery modules 12, 14 is prohibited is significantly reduced. In addition, the control device 18 is configured to be able to execute the current adjustment process shown in FIG. 4 after controlling the multiple relays 20-38 to form the parallel circuit. As shown in FIG. 4(A), in the current adjustment process, the control device 18 continuously reduces the resistance value (R) of the second pre-charge resistor 44. This avoids excessive restriction on the circulating current (I). As a result, as shown in FIGS. 4(B) and 4(C), the difference in charging rate (SOC1, SOC2) between the battery modules 12, 14 and the voltage difference (dV) between the battery modules 12, 14 are quickly eliminated.

[0031] That is, at time t0 when the two battery modules 12, 14 are connected in parallel, the difference in the charging rate between the battery modules 12, 14 and the voltage difference between the battery modules 12, 14 are relatively large. In contrast, the resistance value of the second pre-charge resistor 44 is set relatively high. Therefore, as shown in Fig. 4(D), the magnitude of the circulating current is suppressed, and the occurrence of an arc in the relay 20-38 is also suppressed.

[0032] Thereafter, as the circulating current flows, the difference in the charging rate and the voltage difference between the battery modules 12, 14 are gradually eliminated, as shown in Fig. 4(B) and Fig. 4(C). In parallel with this, the resistance value of the second pre-charge resistor 44 is continuously decreased. As the restriction on the circulating current is relaxed, the voltage difference between the battery modules 12, 14 is eliminated sooner. Note that, as the voltage difference between the battery modules 12, 14 decreases, the allowable value of the circulating current for the relay 20-38, the battery modules 12, 14, and the second pre-charge resistor 44 increases. For this reason, the resistance value of the second pre-charge resistor 44 may be significantly decreased so that the circulating current increases over time, as shown in Fig. 4(D).

[0033] 4(E), as an example, the control device 18 of this embodiment determines the resistance value of the second pre-charge resistor 44 so that the product (W) of the voltage difference and the circulating current is equal to or less than a predetermined threshold. The amount of heat generated by the circulating current in the relay 20-38, the battery modules 12, 14, and the second pre-charge resistor 44 depends on the product (i.e., power) of the voltage difference between the battery modules 12, 14 and the magnitude of the circulating current. Therefore, by determining the resistance value of the second pre-charge resistor 44 so that the product (W) of the voltage difference and the circulating current is equal to or less than a threshold that the relay 20-38, the battery modules 12, 14, and the second pre-charge resistor 44 can tolerate, the circulating current can be appropriately suppressed.

[0034] In another embodiment, the control device 18 may determine the resistance value of the second pre-charge resistor 44 based on at least one of the voltage difference and the circulating current. The amount of heat generated by the circulating current in the relay 20-38, the battery modules 12, 14, and the second pre-charge resistor 44 depends on the voltage difference between the battery modules 12, 14 and the magnitude of the circulating current. Since the voltage difference and the magnitude of the circulating current are correlated, one can be estimated from the other. Therefore, by determining the resistance value of the second pre-charge resistor 44 based on at least one of the voltage difference and the circulating current, the circulating current can be appropriately adjusted.

[0035] As yet another embodiment, the resistance value of the second pre-charge resistor 44 may be set in advance based on an allowable value for the amount of heat generated by the circulating current of the relay 20-38, the battery modules 12, 14, and the second pre-charge resistor 44.

[0036] In the parallel circuit shown in FIG. 3, when the control device 18 closes the tenth relay 38 and opens the sixth relay 30, the second pre-charge resistor 44 is bypassed. This allows the connection circuit 16 to connect the two battery modules 12, 14 in parallel while bypassing the second pre-charge resistor 44. That is, the connection circuit 16 has a bypass circuit that bypasses the second pre-charge resistor 44 via the tenth relay 38. As an example, the control device 18 in this embodiment electrically opens the bypass circuit during the execution of the current adjustment process described above, and conducts the bypass circuit after the current adjustment process is completed. In detail, the control device 18 closes the sixth relay 30 and opens the tenth relay 38 during the execution of the current adjustment process, thereby interposing the second pre-charge resistor 44 between the two battery modules 12, 14. After completing the current adjustment process, the control device 18 closes the tenth relay 38 and opens the sixth relay 30, thereby bypassing the second pre-charge resistor 44. With this configuration, for example, after the voltage difference between the battery modules 12, 14 falls below a predetermined value and the voltage difference between the battery modules 12, 14 is sufficiently eliminated, the second pre-charge resistor 44 can be short-circuited by the bypass circuit, and unnecessary current flow through the second pre-charge resistor 44 can be avoided.

[0037] As shown in Fig. 4(A), the control device 18 of this embodiment executes a current adjustment process in which the resistance value of the second pre-charge resistor 44 is continuously decreased in the current adjustment process. As another embodiment, the control device 18 may decrease the resistance value of the second pre-charge resistor 44 in a stepwise manner in the current adjustment process, as shown in Fig. 5. Even with this configuration, when the two battery modules 12, 14 are connected in parallel, the voltage difference between the battery modules 12, 14 can be eliminated in a short time while suppressing the occurrence of arcing in the relay 20-38.

[0038] Although several specific examples have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical usefulness alone or in combination. [Explanation of symbols]

[0039] 10: power supply device, 12: first battery module, 14: second battery module, 16: connection circuit, 18: control device, 20-38: relay, 40: first pre-charge resistor, 42: first system main relay, 44: second pre-charge resistor, 46: second system main relay, 48, 50: voltage sensor, 52: current sensor, 100: vehicle, 102-108: motor, 110-116: inverter, 118: charging inlet, 120, 112: charging relay

Claims

1. a first battery module and a second battery module that are chargeable by an external power source; a connection circuit having a plurality of relays, selectively forming a series circuit in which the first battery module and the second battery module are connected in series and a parallel circuit in which the first battery module and the second battery module are connected in parallel; a variable resistor provided in the connection circuit and interposed between the first battery module and the second battery module in the parallel circuit; A control device that controls opening and closing of the plurality of relays and the resistance value of the variable resistor; Equipped with The control device is configured to be capable of executing a current adjustment process for continuously or stepwise decreasing a resistance value of the variable resistor after controlling the plurality of relays to form the parallel circuit. power supply.

2. The control device includes: Estimating or detecting at least one of an open circuit voltage difference between the first battery module and the second battery module and a circulating current flowing between the first battery module and the second battery module; The power supply device according to claim 1 , configured to determine a resistance value of the variable resistor based on at least one of the open-circuit voltage difference and the circulating current.

3. The power supply device according to claim 2 , wherein the control device determines a resistance value of the variable resistor such that a product of an open-circuit voltage difference and the circulating current is equal to or smaller than a predetermined threshold value.

4. the connection circuit includes a bypass circuit that bypasses the variable resistor via at least one of the plurality of relays; The power supply device according to claim 1 , wherein the control device electrically opens the bypass circuit while the current adjustment process is being performed, and electrically opens the bypass circuit after the current adjustment process is completed.

5. A motor that drives the wheels; The power supply device according to claim 1 , which supplies power to the motor; a charging inlet configured to allow the external power source to be detachably attached; The control device includes: when the power supply device supplies power to the motor, the first battery module and the second battery module are connected in series to the motor by configuring the series circuit in the connection circuit, When the power supply device is charged by the external power supply, the first battery module and the second battery module can be connected in parallel to the charging inlet by configuring the parallel circuit in the connection circuit. Electric car.

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