Power supply device

Abstract

To avoid prohibition of processing involving opening / closing of a relay when charging is completed.SOLUTION: A power supply device comprises: a connection circuit that forms a parallel circuit that connects a first battery module and a second battery module in parallel when charging them; a variable resistor disposed between the first battery module and the second battery module connected in parallel in the connection circuit; and a control device capable of executing resistance adjustment processing for adjusting a resistance value of the variable resistor when charging the first battery module and the second battery module. The resistance adjustment processing includes processing of: calculating a circulation current generatable between the battery modules on the basis of an open circuit voltage difference being a difference between an open circuit voltage of the first battery module and an open circuit voltage of the second battery module; calculating a heat generation quantity generatable in the variable resistor by multiplying the calculated circulation current by the open circuit voltage difference; and adjusting the resistance value of the variable resistor so as to allow the calculated heat generation quantity to become less than a prescribed allowable value.SELECTED DRAWING: Figure 4

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 that connects the two battery modules in parallel, and a control device. [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 are charged by an external power source, it is possible to connect the battery modules in parallel. This can lower the output voltage required for the external power source and shorten the time required to charge the battery modules. However, since there are individual differences between the two battery modules, even if charging is performed at the same charging voltage, a difference in the state of charge (SOC) may occur between the battery modules. In this case, when charging is completed (specifically, when the flow of charging current is stopped), an open circuit voltage difference occurs between the two battery modules, and a circulating current occurs in which a current circulates between the battery modules. If the relay is opened and closed in a situation where a circulating current occurs, an arc occurs at the contact of the relay, which may damage the relay. For this reason, it is necessary to prohibit processes involving opening and closing of the relay until the open circuit voltage difference between the battery modules is eliminated, which impairs the function and convenience of the power supply device.

[0005] In consideration of the above circumstances, this specification provides a technique for avoiding the prohibition of processes involving opening and closing of a relay when charging is terminated. [Means for solving the problem]

[0006] The technology disclosed in this specification is embodied in 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 forming a parallel circuit that connects the first battery module and the second battery module in parallel when the first battery module and the second battery module are charged, a variable resistor that is provided in the connection circuit and is interposed between the first battery module and the second battery module that are connected in parallel, and a control device that is capable of executing a resistance adjustment process that adjusts a resistance value of the variable resistor when the first battery module and the second battery module are charged. The resistance adjustment process includes a process of calculating a circulating current that may be generated between the first battery module and the second battery module based on an open circuit voltage difference that is a difference between an open circuit voltage of the first battery module and an open circuit voltage of the second battery module, a process of calculating a heat amount that may be generated in the variable resistor by multiplying the open circuit voltage difference by the calculated circulating current, and a process of adjusting the resistance value of the variable resistor so that the calculated heat amount is below a predetermined allowable value.

[0007] In the above-mentioned configuration, the resistance adjustment process is repeatedly executed while the first battery module and the second battery module are being charged. In the resistance adjustment process, for example, the open circuit voltage difference between the first battery module and the second battery module is monitored based on the charging rate of each of the battery modules. If an open circuit voltage difference occurs between the battery modules, if charging is terminated at that point (specifically, the flow of the charging current is stopped), a circulating current will occur between the battery modules, which will cause heat generation in the variable resistor. Therefore, in the resistance adjustment process, the circulating current that may occur between the battery modules is calculated based on the open circuit voltage difference, and the amount of heat that may be generated in the variable resistor is calculated. Then, the resistance value of the variable resistor is adjusted so that the amount of heat generated in the variable resistor falls below a predetermined allowable value. The predetermined allowable value here is, for example, a value that can withstand the flow of current for an unlimited time when the amount of heat generated in the variable resistor is smaller than that value. With this configuration, the occurrence of an open circuit voltage difference between the battery modules is suppressed while the two battery modules are being charged. This makes it possible to avoid prohibiting a process involving opening and closing of the relay after the end of charging.

[0008] In a second aspect, in the first aspect, the resistance adjustment process may include a process of calculating a first correction voltage by correcting the open circuit voltage of the first battery module by a voltage change caused by the circulating current, a process of calculating a second correction voltage by correcting the open circuit voltage of the second battery module by a voltage change caused by the circulating current, and a process of adjusting the resistance value of the variable resistor so that the first correction voltage and the second correction voltage are within a predetermined allowable range. With this configuration, the open circuit voltage difference between the two battery modules is suppressed so that the circulating current that may occur between the two battery modules is within an allowable range for each battery module.

[0009] In a third aspect, in the first or second aspect, the resistance adjustment process may further include a process of estimating an open-circuit voltage of the first battery module based on a charging rate of the first battery module, and a process of estimating an open-circuit voltage of the second battery module based on a charging rate of the second battery module.

[0010] In a fourth aspect, in any one of the first to third aspects, the control device may set the resistance value of the variable resistor to approximately the maximum value when charging of the first battery module and the second battery module is completed, and then execute a process involving opening and closing of a plurality of relays. With this configuration, even if an open circuit voltage difference occurs between the two battery modules when charging is completed, the resistance value of the variable resistor is set to approximately the maximum value, so that the circulating current flowing between the battery modules is significantly reduced. This allows the control device to quickly execute a process involving opening and closing of the relays after charging is completed, without waiting for the open circuit voltage difference to be eliminated.

[0011] The technology disclosed in this specification may also be embodied in other power supply devices. 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 parallel circuit that connects the first battery module and the second battery module in parallel and a series circuit that connects the first battery module and the second battery module in series, a variable resistor provided in the connection circuit and interposed between the first battery module and the second battery module that are connected in parallel, and a control device that controls opening and closing of the plurality of relays and adjusts the resistance value of the variable resistor. The control device is configured to be able to execute a process of controlling the plurality of relays to form the parallel circuit in the connection circuit when charging of the first battery module and the second battery module starts, a process of setting the resistance value of the variable resistor to an approximately maximum value when charging of the first battery module and the second battery module ends, and a process of controlling the plurality of relays to form the series circuit in the connection circuit after setting the resistance value of the variable resistor to the approximately maximum value.

[0012] In the above configuration, when charging starts, two battery modules are connected in parallel, and when charging ends, the resistance value of the variable resistor between the two battery modules connected in parallel is set to approximately the maximum value. As a result, even if an open circuit voltage difference occurs between the two battery modules at the end of charging, the resistance value of the variable resistor is set to approximately the maximum value, so that the circulating current flowing between the battery modules is significantly reduced. As a result, the power supply device can connect the two battery modules in series without waiting for the open circuit voltage difference to be eliminated after charging ends. [Brief description of the drawings]

[0013] [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 schematic diagram of a series circuit formed by a connection circuit 16. [Diagram 3] FIG. 4 is a circuit diagram showing a schematic diagram of a parallel circuit formed by a connection circuit 16. [Figure 4] 4 is a flow chart showing an example of a resistance adjustment process executed by a control device 18. FIG. [Diagram 5] FIG. 5 shows the change over time of various indices in the resistance adjustment process. FIG. 5(A) shows the resistance value RV of the second pre-charge resistor 42. FIG. 5(B) shows the open circuit voltage OCV1 of the first battery module 12, the open circuit voltage OCV2 of the second battery module 14, the closed circuit voltage CCV1 of the first battery module 12, and the closed circuit voltage CCV2 of the second battery module 14. FIG. 5(C) shows the open circuit voltage difference (OCV1-OCV2) between the open circuit voltage OCV1 of the first battery module 12 and the open circuit voltage OCV2 of the second battery module 14. FIG. 5(D) shows the charging current I1 flowing through the first battery module 12 and the charging current I2 flowing through the second battery module 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (Example 1) A power supply device 10 of an example and a vehicle 100 in which the power supply device 10 is adopted 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, 108 of the vehicle 100. The power supply device 10 in this example includes a plurality of battery modules 12, 14, and may be referred to as a battery pack. Each of the battery modules 12, 14 is configured to be rechargeable. The vehicle 100 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 vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a fuel cell electric vehicle (FCEV). The motors 102, 104, 106, 108 in this example are examples of loads mounted on the vehicle 100.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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, and 36. The control device 18 controls the opening and closing of the plurality of relays 20-36.

[0020] 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 38, constitute a first system main relay 40. The third relay 24 and the first pre-charge resistor 38 are connected in series, and are connected in parallel to the second relay 22. In this manner, the first system main relay 40 is provided with the first pre-charge resistor 38 to avoid an excessively large inrush current. The first system main relay 40 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 40 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 40 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 38 between them.

[0021] The plurality of relays 20-36 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 42, constitute a second system main relay 44. The second pre-charge resistor 42 is a variable resistor. The resistance value of the second pre-charge resistor 42 is controlled by the control device 18. The sixth relay 30 and the second pre-charge resistor 42 are connected in series, and are connected in parallel to the fifth relay 28. That is, the second system main relay 44 is also provided with the second pre-charge resistor 42 to avoid an excessive inrush current, similar to the first system main relay 40. The second system main relay 44 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 44 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 44 electrically connects the battery modules 12, 14 and the motors 106, 108, it can avoid an excessive inrush current by interposing the second pre-charge resistor 42 between them.

[0022] The relays 20-36 further include a seventh relay 32, an eighth relay 34, and a ninth relay 36. These relays 32, 34, and 36 are provided to switch the connection state 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 20-36. 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, and 116 and four motors 102, 104, 106, and 108.

[0023] 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, the second pre-charge resistor 42 is interposed between the first battery module 12 and the second battery module 14 connected in parallel. As described above, the second pre-charge resistor 42 is a variable resistor, and the resistance value of the second pre-charge resistor 42 is controlled by the control device 18.

[0024] 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 42, 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.

[0025] 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.

[0026] Next, the resistance adjustment process executed by the control device 18 will be described with reference to Figs. 4 and 5. In this resistance adjustment process, the resistance value RV of the second pre-charge resistor 42 is adjusted. The control device 18 repeatedly executes the resistance adjustment process while the first battery module 12 and the second battery module 14 are being charged. Prior to the resistance adjustment process shown in Fig. 4, the control device 18 controls the opening and closing of multiple relays 20-36 at the start of charging the first battery module 12 and the second battery module 14, thereby forming a parallel circuit shown in Fig. 3 in the connection circuit 16. In this parallel circuit, the first battery module 12 and the second battery module 14 are connected in parallel, and the second pre-charge resistor 42 is interposed between them.

[0027] As shown in FIG. 4, the control device 18 determines whether the difference (|SOC1-SOC2|) between the charging rate SOC1 of the first battery module 12 and the charging rate SOC2 of the second battery module 14 is greater than a predetermined charging rate difference dSOC (step S10). As described above, the control device 18 monitors the charging rate SOC1 of the first battery module 12 and the charging rate SOC2 of the second battery module 14. If the answer is YES in step S10, the control device 18 sets the resistance value RV of the second pre-charge resistor 42 to an initial resistance value RV0 (step S12). Although not particularly limited, the initial resistance value RV0 here is zero. On the other hand, if the answer is NO in step S10, the control device 18 ends the resistance adjustment process shown in FIG. 4.

[0028] Next, the control device 18 calculates a circulating current (|I|) that may occur between the first battery module 12 and the second battery module 14 (step S14). The circulating current that may occur between the first battery module 12 and the second battery module 14 here means a circulating current that may occur due to an open circuit voltage difference occurring between the two battery modules 12, 14 if charging is terminated at that time (specifically, the flow of the charging current is stopped). The control device 18 estimates an open circuit voltage OCV1 of the first battery module 12 based on the charging rate SOC1 of the first battery module 12, and estimates an open circuit voltage OCV2 of the second battery module 14 based on the charging rate SOC2 of the second battery module 14. Here, the resistance value R1 of the first battery module 12, the resistance value R2 of the second battery module 14, the resistance value RV of the second pre-charge resistor 42, and the resistance value RT of the other circuit components are known, and the sum of these is the resistance value of the entire parallel circuit. Therefore, the control device 18 can calculate the circulating current (|I|) that may occur between the first battery module 12 and the second battery module 14 by dividing the open circuit voltage difference (|OCV1-OCV2|), which is the difference between the open circuit voltage OCV1 of the first battery module 12 and the open circuit voltage OCV2 of the second battery module 14, by the resistance value of the entire parallel circuit (R1+R2+RV+RT).

[0029] Then, the control device 18 determines whether the first correction voltage of the first battery module 12 and the second correction voltage of the second battery module 14 are within a predetermined tolerance range (step S16). The first correction voltage of the first battery module 12 is calculated by correcting the open circuit voltage OCV1 of the first battery module 12 by the voltage change caused by the circulating current. Similarly, the second correction voltage of the second battery module 14 is calculated by correcting the open circuit voltage OCV2 of the second battery module 14 by the voltage change caused by the circulating current.

[0030] For example, when charging is stopped, if the open circuit voltage OCV1 of the first battery module 12 is higher than the open circuit voltage OCV2 of the second battery module 14, a circulating current may be generated from the first battery module 12 to the second battery module 14. Therefore, the first correction voltage of the first battery module 12 is calculated by subtracting a voltage change amount, which is the product of the resistance value R1 of the first battery module 12 and the circulating current (|I|), from the open circuit voltage OCV1 of the first battery module 12. The second correction voltage of the second battery module 14 is calculated by adding a voltage change amount, which is the product of the resistance value R2 of the second battery module 14 and the integrated circulating current (|I|), to the open circuit voltage OCV2 of the second battery module 14. These correction voltages substantially correspond to the closed circuit voltages (CCV1, CCV2 in FIG. 5).

[0031] When the first correction voltage of the first battery module 12 and the second correction voltage of the second battery module 14 are greater than the predetermined allowable lower limit Vmin and smaller than the predetermined allowable upper limit Vmax, the control device 18 judges YES in step S16 and proceeds to processing in step S20. On the other hand, when the judgment in step S16 is NO, the control device 18 increases the resistance value RV of the second pre-charge resistor 42 by a predetermined resistance value dRV from the initial resistance value RV0 (step S18) and returns to the processing in step S14. As a result, the processing in steps S14 to S18 is repeated until the judgment in step S16 is YES, and the resistance value RV of the second pre-charge resistor 42 increases. In this way, the resistance value RV of the second pre-charge resistor 42 is adjusted so that the first correction voltage and the second correction voltage are within the predetermined allowable range.

[0032] Next, the control device 18 calculates the amount of heat W that can be generated in the second pre-charge resistor 42 (step S20). This amount of heat W is calculated by multiplying the open circuit voltage difference (|OCV1-OCV2|) between the two battery modules 12, 14 by the circulating current (|I|) calculated in step S14. If the amount of heat W that can be generated in the second pre-charge resistor 42 falls below a predetermined allowable value Wmax (YES in step S22), the control device 18 ends the resistance adjustment process shown in FIG. 4. On the other hand, if NO in step S22, similar to the case of NO in step S16, the control device 18 increases the resistance value RV of the second pre-charge resistor 42 from the initial resistance value RV0 by a predetermined resistance value dRV (step S18) and returns to the process of step S14. Therefore, the resistance value RV of the second pre-charge resistor 42 increases until YES is determined in step S16 and YES is determined in step S22. In this manner, the resistance value RV of the second pre-charge resistor 42 is adjusted so that the amount of heat W that can be generated in the second pre-charge resistor 42 falls below a predetermined allowable value Wmax. The predetermined allowable value Wmax here is, for example, a value that can withstand the passage of current for an unlimited period of time when the amount of heat generated in the second pre-charge resistor 42 is smaller than that value.

[0033] When charging of the first battery module 12 and the second battery module 14 is completed, the control device 18 sets the resistance value RV of the second pre-charge resistor 42 to approximately the maximum value, and then executes a process involving opening and closing the multiple relays 20-36. Approximately the maximum value here means the maximum value to which the resistance value RV of the second pre-charge resistor 42 can be set, or a value that is 70% or more of the maximum value. In addition, the process involving opening and closing the multiple relays 20-36 includes, for example, a process for forming a series circuit shown in FIG. 2 in the connection circuit 16, and a process for opening the second system main relay 44 and the like to shut down the power supply device 10.

[0034] In the above-mentioned configuration, the resistance adjustment process shown in FIG. 4 is repeatedly performed during charging of the first battery module 12 and the second battery module 14, and the resistance value RV of the second pre-charge resistor 42 is adjusted as shown in FIG. 5(A). In the resistance adjustment process, the open circuit voltages OCV1, OCV2 and the closed circuit voltages CCV1, CCV2 of the first battery module 12 and the second battery module 14 are estimated or calculated based on the charging rates SOC1, SOC2 of the first battery module 12 and the second battery module 14 as shown in FIG. 5(B). As a result, the open circuit voltage difference (OCV1-OCV2) between the battery modules 12, 14 is monitored as shown in FIG. 5(C). If an open circuit voltage difference (OCV1-OCV2) occurs between the battery modules 12, 14, if charging is terminated at that time (more specifically, if the flow of the charging current is stopped), a circulating current I is generated between the battery modules 12, 14, which generates heat in the second pre-charge resistor 42. Therefore, in the resistance adjustment process, the circulating current I that may occur between the battery modules 12, 14 is calculated based on the open circuit voltage difference (OCV1-OCV2), and further the amount of heat W that may occur in the second pre-charge resistor 42 is calculated. Then, the resistance value RV of the second pre-charge resistor 42 is adjusted so that the amount of heat W in the second pre-charge resistor 42 falls below a predetermined allowable value Wmax.

[0035] That is, as shown in FIG. 5(C), at the time t0 when charging of the two battery modules 12, 14 is started, the open circuit voltage difference (OCV1-OCV2) between the open circuit voltage OCV1 of the first battery module 12 and the open circuit voltage OCV2 of the second battery module 14 is relatively large. In contrast, the resistance value of the second pre-charge resistor 42 is adjusted to increase once after charging starts and then decrease, as shown in FIG. 5(A). Therefore, as shown in FIG. 5(D), after charging starts, the charging current I2 flowing through the second battery module 14 is larger than the charging current I1 flowing through the first battery module 12 connected in series with the second pre-charge resistor 42. When the open circuit voltage difference between the two battery modules 12, 14 is eliminated due to the difference between these charging currents I1 and I2, the resistance value of the second pre-charge resistor 42 is set small (for example, a resistance value close to zero), and the charging current I2 flowing through the first battery module 12 and the charging current I2 flowing through the second battery module 14 become approximately equal. As described above, while the two battery modules 12, 14 are being charged, the occurrence of an open-circuit voltage difference between the battery modules 12, 14 is suppressed. This makes it possible to avoid prohibiting processes involving opening and closing of the relay 20-36 after charging is completed.

[0036] As one example, the control device 18 of the first embodiment adjusts the resistance value RV of the second pre-charge resistor 42 in the resistance adjustment process so that the first correction voltage and the second correction voltage are within a predetermined allowable range (i.e., greater than a predetermined allowable lower limit value Vmin and smaller than a predetermined allowable upper limit value Vmax) as shown in Fig. 4. With this configuration, the open circuit voltage difference (OCV1-OCV2) between the two battery modules 12, 14 is suppressed so that the circulating current I that may occur between the two battery modules 12, 14 is within an allowable range for each of the battery modules 12, 14.

[0037] The control device 18 of the first embodiment estimates the open circuit voltage OCV1 of the first battery module 12 based on the charging rate SOC1 of the first battery module 12, and estimates the open circuit voltage OCV2 of the second battery module 14 based on the charging rate SOC1 of the second battery module 14. Note that in other embodiments, the control device 18 may directly detect the open circuit voltages OCV1, OCV2 of each battery module 12, 14 using a voltage sensor.

[0038] As one example, the control device 18 of the first embodiment sets the resistance value RV of the second pre-charge resistor 42 to approximately the maximum value when charging of the first battery module 12 and the second battery module 14 is completed, and then executes processing involving opening and closing of the multiple relays 20-36. With this configuration, even if an open-circuit voltage difference (OCV1-OCV2) occurs between the two battery modules 12, 14 when charging is completed, the resistance value RV of the second pre-charge resistor 42 is set to approximately the maximum value, so that the circulating current I flowing between the battery modules 12, 14 is significantly reduced. This allows the control device 18 to quickly execute processing involving opening and closing of the relays 20-36 after charging is completed, without waiting for the open-circuit voltage difference (OCV1-OCV2) to be eliminated.

[0039] (Embodiment 2) Next, a power supply device of embodiment 2 will be described. The power supply device of embodiment 2 is characterized in that, compared with the power supply device 10 of embodiment 1, the control device 18 executes the following series of processes instead of the resistance adjustment process shown in FIG.

[0040] The control device 18 of the second embodiment controls the multiple relays 20-36 at the start of charging the first battery module 12 and the second battery module 14 to form a parallel circuit in the connection circuit 16 as shown in FIG. 3. This allows the two battery modules 12, 14 to be charged in a state in which they are connected in parallel. Then, at the end of charging the first battery module 12 and the second battery module 14, the control device 18 sets the resistance value of the second pre-charge resistor 42 to approximately the maximum value. The approximately maximum value here means the maximum value to which the resistance value RV of the second pre-charge resistor 42 can be set, or a value that is 70% or more of the maximum value. After setting the resistance value of the second pre-charge resistor 42 to approximately the maximum value, the control device 18 controls the multiple relays 20-36 to form a series circuit in the connection circuit 16 as shown in FIG. 2.

[0041] In the above-mentioned configuration, the second pre-charge resistor 42 is also interposed between the two battery modules 12, 14 connected in parallel in the parallel circuit shown in FIG. 3. Therefore, even if an open circuit voltage difference occurs between the two battery modules 12, 14 at the end of charging, the resistance value of the second pre-charge resistor 42 is set to approximately the maximum value, so that the circulating current flowing between the battery modules 12, 14 can be significantly reduced. For example, it is assumed that the accuracy of the open circuit voltage estimated for the battery modules 12, 14 is low depending on the type of the battery modules 12, 14 or the charging rate of the battery modules 12, 14. Even in such a case, the power supply device of the second embodiment can connect the two battery modules 12, 14 in series without waiting for the open circuit voltage difference to be eliminated after the end of charging. In addition, since the resistance value of the second pre-charge resistor 42 can be set to zero during charging of the battery modules 12, 14, the charging power supplied from the external power source can be used as the charging power for the battery modules 12, 14 without being consumed by the second pre-charge resistor 42.

[0042] 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]

[0043] 10: power supply device, 12: first battery module, 14: second battery module, 16: connection circuit, 18: control device, 20-36: relay, 38: first pre-charge resistor, 40: first system main relay, 42: second pre-charge resistor, 44: second system main relay, 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 including a plurality of relays and forming a parallel circuit that connects the first battery module and the second battery module in parallel when the first battery module and the second battery module are charged; a variable resistor provided in the connection circuit and interposed between the first battery module and the second battery module connected in parallel; a control device capable of executing a resistance adjustment process for adjusting a resistance value of the variable resistor when the first battery module and the second battery module are charged; Equipped with The resistance adjustment process includes: A process of calculating a circulating current that may occur between the first battery module and the second battery module based on an open circuit voltage difference that is a difference between an open circuit voltage of the first battery module and an open circuit voltage of the second battery module; A process of calculating an amount of heat that may be generated in the variable resistor by multiplying the open circuit voltage difference by the calculated circulating current; and adjusting a resistance value of the variable resistor so that the calculated amount of heat generation falls below a predetermined allowable value. power supply.

2. The resistance adjustment process includes: calculating a first corrected voltage by correcting the open circuit voltage of the first battery module by a voltage change caused by the circulating current; calculating a second corrected voltage by correcting the open circuit voltage of the second battery module by a voltage change caused by the circulating current; The power supply device according to claim 1 , further comprising a process of adjusting a resistance value of the variable resistor so that the first correction voltage and the second correction voltage are within a predetermined tolerance range.

3. The resistance adjustment process includes: estimating the open circuit voltage of the first battery module based on a charging rate of the first battery module; The power supply device according to claim 1 , further comprising: a process for estimating the open circuit voltage of the second battery module based on a charging rate of the second battery module.

4. 4. The power supply device according to claim 1, wherein the control device sets a resistance value of the variable resistor to an approximate maximum value when charging of the first battery module and the second battery module is completed, and then executes a process involving opening and closing the plurality of relays.

5. 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 parallel circuit that connects the first battery module and the second battery module in parallel and a series circuit that connects the first battery module and the second battery module in series; a variable resistor provided in the connection circuit and interposed between the first battery module and the second battery module connected in parallel; a control device that controls opening and closing of the plurality of relays and adjusts the resistance value of the variable resistor; Equipped with The control device includes: a process of controlling the plurality of relays to form the parallel circuit in the connection circuit when charging of the first battery module and the second battery module starts; setting the resistance value of the variable resistor to a substantially maximum value when charging of the first battery module and the second battery module is completed; and after setting the resistance value of the variable resistor to the substantially maximum value, controlling the plurality of relays to form the series circuit in the connection circuit. power supply.

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