Power supply device

Abstract

The invention provides a power supply device. The power supply device includes: a first battery module and a second battery module that can be charged by an external power supply; a connection circuit having a plurality of relays and selectively forming a series circuit connecting the first battery module and the second battery module in series and a parallel circuit connecting the first battery module and the second battery module 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 the opening and closing of the plurality of relays and the resistance value of the variable resistor. The control device is configured so as to be able to execute a current adjustment process for continuously or stepwise reducing the resistance value of the variable resistor after controlling the plurality of relays to form a parallel circuit.

Description

Technical Field

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

[0002] Japanese Patent Application Laid-Open No. 2019-118221 discloses a power supply device. The power supply device has two battery modules that can be charged using an external power supply and a plurality of relays. The power supply device comprises: a connection circuit that selectively forms a series circuit that connects the two battery modules in series and a parallel circuit that connects the two battery modules in parallel; and a control device that controls the opening and closing of the plurality of relays. Summary of the invention

[0003] In the power supply device as described above, when two battery modules connected in series are charged and discharged for a long time, a difference in the charge rate (State of Charge: SOC) may occur between these battery modules. In this case, a voltage difference is generated between the two battery modules, so when these battery modules are connected in parallel, a circulating current is generated in which the current circulates between these battery modules. At this time, depending on the voltage difference, there is a possibility that an arc will be generated at the contacts of the relay, or an excessive circulating current will flow. Therefore, in order to prevent the generation of arcs and excessive circulating currents in advance, it is necessary to prohibit the parallel connection of battery modules according to the voltage difference between the battery modules.

[0004] However, when the parallel connection of battery modules is frequently prohibited, it may cause problems such as impairment of the function and convenience of the power supply device. Therefore, when connecting two battery modules in parallel, consider placing a resistor between the two battery modules. As a result, it is possible to suppress the arc and circulating current generated in the relay in response to the voltage difference between the battery modules, and the frequency of prohibition of the parallel connection of the battery modules can be significantly reduced. On the other hand, by suppressing the circulating current with resistance, the time until the voltage difference between the battery modules is eliminated becomes longer. In this case, as a result, the function and convenience of the power supply device will still be impaired.

[0005] This specification takes the above-mentioned trade-off into consideration and provides a technique that can eliminate the voltage difference (also called the difference in charging rate) between the battery modules in a short time while suppressing arcing or the like in the relay when two battery modules are connected in parallel.

[0006] The technology disclosed in this specification is embodied as a power supply device. In a first aspect, the power supply device includes:

[0007] The first battery module and the second battery module can be charged by an external power source;

[0008] A connecting circuit having a plurality of relays selectively forming a series circuit and a parallel circuit;

[0009] 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

[0010] The control device controls the opening and closing of the plurality of relays and the resistance value of the variable resistor.

[0011] The series circuit is a circuit in which the first battery module and the second battery module are connected in series. The parallel circuit is a circuit in which the first battery module and the second battery module are connected in parallel. The control device is configured to perform 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. In addition, the power supply device does not necessarily have to have two battery modules, but may have three or more.

[0012] In the above structure, a variable resistor is interposed in the parallel circuit connecting two battery modules in parallel. Moreover, the resistance value of the variable resistor can be controlled in a manner of continuously or stepwise reduction after the parallel circuit is formed. Therefore, when the two battery modules are connected in parallel, the arc generated in the relay and the size of the circulating current can be suppressed due to the relatively high resistance. Therefore, even if the voltage difference between the battery modules is relatively large, the parallel connection of the battery modules can be allowed, and the frequency of the parallel connection being prohibited can be reduced.

[0013] Afterwards, due to the flow of circulating current, the voltage difference between the battery modules is gradually eliminated, and the circulating current naturally becomes smaller. In this case, the resistance value of the variable resistor is reduced, and the restriction on the circulating current is relaxed, so that the voltage difference (or the difference in charging rate) between the battery modules can be eliminated early. In addition, the smaller the voltage difference between the battery modules, the larger the allowable value of the circulating current for the relay, battery module and variable resistor becomes. Therefore, the resistance value of the variable resistor can also be greatly reduced in a way that the circulating current increases over time.

[0014] In the second aspect, in the first aspect, the

[0015] Controls:

[0016] 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,

[0017] The resistance value of the variable resistor is determined based on at least one of the open circuit voltage difference and the circulating current.

[0018] The amount of heat generated by the circulating current of the relay, battery module, and variable resistor depends on the voltage difference between the battery modules and the magnitude of the circulating current. Moreover, the voltage difference and the magnitude of the circulating current are related, so the other can be inferred from one of them. Therefore, by determining the resistance value of the variable resistor based on at least one of the voltage difference and the circulating current, the circulating current can be appropriately adjusted.

[0019] A third aspect is the first aspect or the second aspect,

[0020] The control device determines the resistance value of the variable resistor so that the product of the voltage difference and the circulating current becomes equal to or less than a predetermined threshold value.

[0021] More precisely, the amount of heat generated by the circulating current of the relay, battery module, and 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 below the threshold value that the relay, battery module, and variable resistor can tolerate, the circulating current can be suppressed without excess or deficiency.

[0022] According to 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 plurality of relays.

[0023] In this case, the control device may electrically disconnect the bypass circuit during the execution of the current adjustment process, and may electrically connect the bypass circuit after the current adjustment process is completed.

[0024] According to such a configuration, for example, after the voltage difference between the battery modules is sufficiently eliminated, the variable resistor is short-circuited by the bypass circuit, thereby avoiding unnecessary energization of the variable resistor.

[0025] In any of the above-mentioned embodiments, the connection circuit may include 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 using a variable resistor in the pre-charge resistor provided in the system main relay, the pre-charge resistor can also be used as the variable resistor in the above-mentioned parallel connection.

[0026] In a fifth aspect, the electric vehicle may include:

[0027] Motor, driving the wheels;

[0028] The power supply device according to any one of the first to fourth aspects supplies electric power to a motor; and

[0029] The charging socket is configured to be able to attach and detach an external power source.

[0030] In this case, the device can also be controlled:

[0031] When the power supply device supplies electric power to the motor, the connection circuit forms a series circuit, thereby connecting the first battery module and the second battery module in series to the motor.

[0032] When the power source device is charged by the external power source, the connection circuit is configured to form a parallel circuit, so that the first battery module and the second battery module can be connected in parallel to the charging socket.

[0033] According to such a structure, 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. In addition, when the power supply device is charged by an external power supply, the first battery module and the second battery module are connected in parallel, so that the output voltage required for the external power supply can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0035] Figure 1 1 is a diagram schematically showing the configuration of a power supply device 10 according to the embodiment and a vehicle 100 equipped with the power supply device 10.

[0036] Figure 2 is a circuit diagram schematically showing a series circuit formed by connecting the circuits 16 .

[0037] Figure 3 is a circuit diagram schematically showing a parallel circuit formed by the connecting circuit 16 .

[0038] Figure 4A The following diagram shows the change over time of the resistance value R of the second precharge resistor 44 during the current adjustment process.

[0039] Figure 4B The following diagrams show changes over time in the detected value of the charge rate SOC1 of the first battery module 12 and changes over time in the detected value of the charge rate SOC2 of the second battery module 14 during the current adjustment process.

[0040] Figure 4C The temporal change of the open circuit voltage V1 of the first battery module 12 and the temporal change of the open circuit voltage V2 of the second battery module 14 during the current adjustment process, and the temporal change of the open circuit voltage difference dV are respectively shown.

[0041] Figure 4D The graph shows the change over time of the circulating current I in the current adjustment process.

[0042] Figure 4E The product W of the open circuit voltage difference and the circulating current between the battery modules 12 and 14 during the current adjustment process is shown, and the change over time in the amount of heat (electric power) generated by the circulating current is shown.

[0043] Figure 5 A modification example of a method of changing the resistance value R of the second precharge resistor 44 in the current adjustment process is shown. DETAILED DESCRIPTION

[0044] The power supply device 10 of the embodiment and the vehicle 100 using the same are described with reference to the accompanying drawings. The power supply device 10 is a device that supplies power to multiple motors 102, 104, 106, and 108 of the vehicle 100. The power supply device 10 in this embodiment includes multiple battery modules 12 and 14, which are sometimes called battery packs. Each battery module 12 and 14 is configured to be rechargeable. The vehicle 100 referred to here is an electric vehicle that travels on the road, a so-called battery electric vehicle (BEV: Battery Electric Vehicle). However, the vehicle 100 is not limited to a battery electric vehicle, and may also be a hybrid electric vehicle (HEV: Hybrid Electric Vehicle), a plug-in hybrid electric vehicle (PHEV: Plug-in Hybrid Electric Vehicle), or a fuel cell electric vehicle (FCEV: Fuel Cell Electric Vehicle). In addition, the motors 102, 104, 106, and 108 in this embodiment are an example of a load mounted on the vehicle 100.

[0045] like Figure 1As shown, the vehicle 100 includes a plurality of motors 102, 104, 106, 108 and a plurality of inverters 110, 112, 114, 116. Each motor 102, 104, 106, 108 is a driving motor that drives the wheels of the vehicle 100. The plurality of motors 102, 104, 106, 108 include 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 inverter 110, 112, 114, 116 is a device that performs power conversion between DC and AC between the power supply device 10 and the corresponding motor 102, 104, 106, 108. The plurality of inverters 110, 112, 114, and 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 is capable of converting the DC power from the power supply device 10 into three-phase AC power and supplying it to the first motor 102. In addition, the first inverter 110 is also capable of converting the three-phase AC power from the first motor 102 into DC power and supplying it to the power supply device 10. The configurations of the second inverter 112, the third inverter 114, and the fourth inverter 116 are the same as those of the first inverter 110, and thus description thereof is omitted. Although not particularly limited, when the rated voltage of the power supply device 10 and the rated voltage of each motor 102 , 104 , 106 , 108 are different from each other, a DC-DC converter may be further provided between the power supply device 10 and each inverter 110 , 112 , 114 , 116 .

[0046] In addition, each motor 102, 104, 106, 108 does not necessarily drive only one wheel. For example, one motor may drive a pair of front wheels or rear wheels. Therefore, the number of motors 102, 104, 106, 108 provided in the vehicle 100 is not limited to four, and may be one or more. In addition, the number of the plurality of inverters 110, 112, 114, 116 can be appropriately changed according to the number and arrangement of the plurality of motors 102, 104, 106, 108.

[0047] like Figure 1As shown, the vehicle 100 also has a charging socket 118. The charging socket 118 is configured to be able to load and unload an external power source. For example, when charging the battery modules 12 and 14 of the power supply device 10 mounted on the vehicle 100, the external power source and the charging socket 118 of the vehicle 100 are connected via a power supply connector. As a result, AC power from the external power source is supplied to the battery modules 12 and 14. In this way, the vehicle 100 can charge the battery modules 12 and 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 household use, a charging station, etc. Although not particularly limited, the charging socket 118 is connected to the power supply device 10 via charging relays 120 and 122.

[0048] As described above, the power supply device 10 includes a first battery module 12 and a second battery module 14. Each battery module 12, 14 has a plurality of battery cells arranged in a stacked manner. Each battery cell is, for example, a secondary battery cell that can be repeatedly charged and discharged, such as a lithium-ion battery cell, a solid-state battery cell, or a nickel-hydrogen battery cell. In addition, the specific number of the plurality of battery cells is not particularly limited and can be appropriately changed according to the output voltage required for each battery module 12, 14. In addition, the power supply device 10 does not necessarily have to have two battery modules, but may also have three or more.

[0049] like Figure 1 As shown, 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.

[0050] Among the multiple relays 20-38, there are a first relay 20, a second relay 22, and a third relay 24. These relays 20, 22, 24 together with the first pre-charging resistor 40 constitute a first system main relay 42. The third relay 24 and the first pre-charging resistor 40 are connected in series, and they are connected in parallel with respect to the second relay 22. In this way, in the first system main relay 42, a first pre-charging resistor 40 is provided for avoiding excessive inrush current. The first system main relay 42 is located 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. In addition, the first system main relay 42 is also located 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. Furthermore, when the first system main relay 42 electrically connects the battery modules 12 and 14 and the motors 102 and 104 , an excessive inrush current can be avoided by interposing the precharge resistor 40 therebetween.

[0051] The plurality of relays 20-38 also include a fourth relay 26, a fifth relay 28, and a sixth relay 30. These relays 26, 28, 30 together with the 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 they are connected in parallel with the fifth relay 28. That is, in the second system main relay 46, as in the first system main relay 42, a second pre-charge resistor 44 is provided for avoiding excessive inrush current. The second system main relay 46 is located 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. In addition, 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, the second pre-charge resistor 44 is interposed between them, thereby avoiding excessive inrush current.

[0052] The plurality of relays 20-38 also 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 connection circuit 16 by controlling the opening and closing of the plurality of relays 20-38. Figure 2 The series circuit shown and Figure 3 Specifically, when the control device 18 closes the relays 20, 22, 26, 30, and 32 and opens the other relays, the connection circuit 16 forms Figure 2 In the 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.

[0053] 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 Figure 3The parallel circuit shown. 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 socket 118 via charging relays 120 and 122. Thus, when an external power source is connected to the charging socket 118 via a power supply connector, the two battery modules 12 and 14 can be charged using the external power source. Furthermore, in Figure 3 In the parallel circuit shown, the second precharge resistor 44 is interposed between the first battery module 12 and the second battery module 14. As described above, the second precharge resistor 44 is a variable resistor, and the resistance value of the second precharge resistor 44 is controlled by the control device 18.

[0054] The control device 18 monitors the charge rate (State of Charge: SOC) of the first battery module 12 and the charge rate of the second battery module 14, respectively. The method is not particularly limited. For example, the control device 18 can calculate the charge rate of the first battery module 12 by accumulating the charge current and discharge 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 charge rate of the first battery module 12, and estimates the open circuit voltage of the second battery module 14 based on the charge rate of the second battery module 14. Furthermore, 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. 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 in the parallel circuit (refer to Figure 3 ) is the circulating current flowing between the first battery module 12 and the second battery module 14. In addition, the resistance value of the entire parallel circuit (i.e., the internal resistance values ​​of the battery modules 12 and 14, the resistance value of the second pre-charge resistor 44, and the resistance values ​​of other circuit components) is known. Therefore, the circulating current can be obtained by dividing the open circuit voltage difference by the resistance value.

[0055] In addition, if Figure 1 As shown, 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 can be directly detected by the voltage sensors 48, 58 and the current sensor 52, or can be estimated based on their detection values. Alternatively, the control device 18 can also calculate the above-mentioned charging rate using these sensors 48, 50, 52.

[0056] With the above configuration, when the vehicle 100 is running, the power supply device 10 is electrically connected to the motors 102, 104, 106, and 108. In this case, the control device 18 configures the connection circuit 16 to Figure 2As a result, the first battery module 12 and the second battery module 14 are connected in series to the plurality of motors 102, 104, 106, 108. Thus, the power supply device 10 can supply power to the plurality of motors 102, 104, 106, 108 at a relatively high voltage. 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 socket 118. In this case, the control device 18 causes the connection circuit 16 to form Figure 3 As a result, the first battery module 12 and the second battery module 14 are connected in parallel to the charging socket 118. Thus, the power supply device 10 can be charged at a relatively low charging voltage, and the output voltage required for the external power supply can be reduced.

[0057] As described above, the power supply device 10 of the present embodiment is capable of switching the connection mode of the two battery modules 12 and 14 between series connection and parallel connection. However, when the two battery modules 12 and 14 connected in series are charged and discharged for a long time, a difference in charging rate may occur between these battery modules 12 and 14. In this case, an open circuit voltage difference (hereinafter referred to as voltage difference) is generated between the two battery modules 12 and 14, so when these battery modules 12 and 14 are connected in parallel, a circulating current is generated in which current circulates between these battery modules 12 and 14. At this time, due to the voltage difference, there is a possibility that an arc will be generated at the contact of the relay 20-38 or an excessive circulating current will flow. Therefore, the control device 18 is configured to prohibit the parallel connection of the battery modules 12 and 14 according to the voltage difference between the two battery modules 12 and 14 in order to prevent the generation of arcs and excessive circulating currents in advance.

[0058] However, when the parallel connection of the battery modules 12 and 14 is frequently prohibited, for example, the function and convenience of the power supply device 10 are impaired. Figure 3 In the parallel circuit shown in FIG. 1 , the second pre-charge resistor 44 as a variable resistor is interposed between the two battery modules 12 and 14. As a result, the voltage difference between the battery modules 12 and 14 suppresses the arc generated in the relay 20-38 and the magnitude of the circulating current. As a result, the frequency of prohibiting the parallel connection of the battery modules 12 and 14 is significantly reduced. In addition, the control device 18 is configured to be able to execute after controlling the plurality of relays 20-38 to form a parallel circuit. FIG. 4A to FIG. 4E The current regulation process is shown in FIG. Figure 4A As shown in FIG. 1 , in the current regulation process, the control device 18 continuously reduces the resistance value (R) of the second pre-charging resistor 44. Thus, excessive restriction of the circulating current (I) is avoided. As a result, Figure 4B as well as Figure 4CAs shown, the difference in the charge rate (SOC1, SOC2) between the battery modules 12, 14 and the voltage difference (dV) between the battery modules 12, 14 are eliminated at an early stage.

[0059] That is, at time t0 when the two battery modules 12 and 14 are connected in parallel, the difference in charge rate between the battery modules 12 and 14 and the voltage difference between the battery modules 12 and 14 are relatively large. In contrast, the resistance value of the second pre-charge resistor 44 is set relatively high. Figure 4D As shown, the magnitude of the circulating current is suppressed, and the arc generated in the relay 20-38 is also suppressed.

[0060] Afterwards, due to the circulating current, Figure 4B as well as Figure 4C As shown, the difference in charge rate and voltage difference between the battery modules 12 and 14 are gradually eliminated. In parallel, the resistance value of the second pre-charge resistor 44 is continuously reduced. By relaxing the restriction on the circulating current, the voltage difference between the battery modules 12 and 14 is eliminated early. In addition, the smaller the voltage difference between the battery modules 12 and 14, the larger the allowable value of the circulating current for the relays 20-38, the battery modules 12, 14 and the second pre-charge resistor 44 becomes. Therefore, it is also possible as shown in Figure 4D As shown in FIG. 2 , the resistance value of the second precharge resistor 44 is greatly reduced so that the circulating current increases with time.

[0061] As an example, Figure 4E As shown, the control device 18 of this embodiment determines the resistance value of the second pre-charge resistor 44 in such a way that the product of the voltage difference and the circulating current (W) becomes less than a predetermined threshold value. 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 depends on the product of the voltage difference between the battery modules 12, 14 and the magnitude of the circulating current (i.e., power). Therefore, by determining the resistance value of the second pre-charge resistor 44 in such a way that the product of the voltage difference and the circulating current (W) becomes less than a threshold value that the relay 20-38, the battery modules 12, 14, and the second pre-charge resistor 44 can tolerate, the circulating current can be suppressed without excess or deficiency.

[0062] As another embodiment, the control device 18 may also 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 of 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. Moreover, the voltage difference and the magnitude of the circulating current are related, so the other can be inferred based on one of them. 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.

[0063] As still another embodiment, the resistance value of the second pre-charging resistor 44 may be set in advance according to the allowable value of the amount of heat generated by the circulating current of the relays 20 - 38 , the battery modules 12 , 14 , and the second pre-charging resistor 44 .

[0064] exist Figure 3 In the parallel circuit shown, when the control device 18 closes the 10th relay 38 and opens the 6th relay 30, the 2nd pre-charge resistor 44 is bypassed. Thus, the connection circuit 16 can connect the two battery modules 12 and 14 in parallel while bypassing the 2nd pre-charge resistor 44. That is, the connection circuit 16 has a bypass circuit that bypasses the 2nd pre-charge resistor 44 via the 10th relay 38. As an example, the control device 18 of this embodiment electrically disconnects the bypass circuit during the execution of the above-mentioned current adjustment process, and turns on the bypass circuit after the current adjustment process is completed. In detail, the control device 18 interposes the 2nd pre-charge resistor 44 between the two battery modules 12 and 14 by closing the 6th relay 30 and opening the 10th relay 38 during the execution of the current adjustment process. Moreover, after the current adjustment process is completed, the control device 18 closes the 10th relay 38 and opens the 6th relay 30, thereby bypassing the 2nd pre-charge resistor 44. According to such a configuration, for example, when the voltage difference between the battery modules 12 and 14 is lower than a predetermined value and the voltage difference between the battery modules 12 and 14 is sufficiently eliminated, the second precharge resistor 44 can be short-circuited by the bypass circuit. Therefore, unnecessary energization of the second precharge resistor 44 can be avoided.

[0065] The control device 18 of this embodiment is as follows Figure 4A As shown in FIG. 1 , in the current adjustment process, the current adjustment process is performed to continuously reduce the resistance value of the second pre-charge resistor 44. As another embodiment, the control device 18 may also be as follows Figure 5As shown, in the current adjustment process, the resistance value of the second pre-charge resistor 44 is gradually reduced. Even in such a structure, when the two battery modules 12 and 14 are connected in parallel, the voltage difference between the battery modules 12 and 14 can be eliminated in a short time while suppressing the arc generated in the relay 20-38.

[0066] Several specific examples are described in detail above, but these are only examples and do not limit the claims. The technology described in the claims includes examples obtained by making various deformations and changes to the specific examples illustrated above. The technical elements described in this specification or the drawings exert technical usefulness alone or in combination.

Claims

1. A power supply device comprising: The first battery module and the second battery module can be charged by an external power source; A connecting circuit having a plurality of relays selectively forming a series circuit and a parallel circuit, wherein The series circuit is a circuit in which the first battery module and the second battery module are connected in series, and the parallel circuit is a circuit in which the first battery module and the second battery module are connected in parallel; a variable resistor, disposed in the connection circuit and between the first battery module and the second battery module in the parallel circuit; as well as a control device for controlling the opening and closing of the plurality of relays and the resistance value of the variable resistor, The control device is configured to be capable of executing a current adjustment process for continuously or stepwise reducing a resistance value of the variable resistor after controlling the plurality of relays to form the parallel circuit.

2. The power supply device according to claim 1, wherein: The control device is composed of: 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 resistance value of the variable resistor is determined 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 the resistance value of the variable resistor so that the product of the open circuit voltage difference and the circulating current becomes equal to or less than a predetermined threshold value.

4. The power supply device according to claim 1, wherein: The connection circuit includes a bypass circuit for bypassing the variable resistor via at least one of the plurality of relays. The control device electrically disconnects the bypass circuit during execution of the current adjustment process, and electrically connects the bypass circuit after completion of the current adjustment process.

5. An electric vehicle comprising: Motor, driving the wheels; The power supply device according to any one of claims 1 to 4, which supplies electric power to the motor; and The charging socket is configured to be able to attach and detach the external power source. The control device: When the power supply device supplies electric power to the motor, the connection circuit forms the series circuit, thereby connecting the first battery module and the second battery module in series to the motor. When the power source device is charged by the external power source, the connection circuit is configured to form the parallel circuit so that the first battery module and the second battery module can be connected in parallel to the charging socket.

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