Power storage device

Abstract

To suppress increase in time taken for charging batteries while simultaneously charging the batteries provided in each of a plurality of power storage devices as much as possible.SOLUTION: A power storage device terminates constant current constant voltage charge control by transmitting a current command value to a first charger Ch and a second charger Ch so that voltage of a battery B is maintained as fixed voltage Vc and current flowing to the battery B gradually falls when the voltage of the battery B becomes the fixed voltage or higher after starting the constant current constant voltage charge control, transmitting the current command value to the first charger Ch so that the voltage of the battery B is maintained as the fixed voltage Vc and the current flowing to the battery B gradually falls when the current flowing to the battery B becomes a current threshold Ith or lower and transmitting the current command value to the first charger Ch so that the current flowing to the battery B becomes zero when the current flowing to the battery B becomes termination current If or lower.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electricity storage device. [Background technology]

[0002] As an electric storage device, there is a device that rapidly charges a battery by supplying electric power output from a plurality of chargers to the battery.

[0003] When a plurality of power storage devices are present, there is a demand for simultaneously charging the batteries provided in the respective power storage devices.

[0004] In view of this, it may be possible to simultaneously charge the batteries by using different chargers for each battery.

[0005] However, when each charger is used to charge each battery, the current flowing to each battery may be lower and the charging time for each battery may be longer than when multiple chargers are used to charge a single battery. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7155056 Summary of the Invention [Problem to be solved by the invention]

[0007] An object according to one aspect of the present invention is to charge batteries provided in a plurality of power storage devices as simultaneously as possible while suppressing an increase in the time required to charge the batteries. [Means for solving the problem]

[0008] An energy storage device according to one embodiment of the present invention includes a battery to which power output from one or more first chargers and one or more second chargers is supplied, and a control unit that, after starting constant current constant voltage charging control, when the voltage of the battery becomes equal to or greater than a certain voltage, sends a current command value to the first and second chargers so that the voltage of the battery is maintained at the constant voltage and the current flowing to the battery gradually decreases, when the current flowing to the battery becomes equal to or less than a current threshold, sends a current command value to the first charger so that the voltage of the battery is maintained at the constant voltage and the current flowing to the battery gradually decreases, and when the current flowing to the battery becomes equal to or less than a termination current which is smaller than the current threshold, terminates the constant current constant voltage charging control by sending a current command value to the first charger so that the current flowing to the battery becomes zero.

[0009] This adjusts the current threshold so that the current flowing through the battery does not decrease before and after the current flowing through the battery becomes equal to or less than the current threshold, thereby suppressing an increase in the time required to charge the battery after the current flowing through the battery becomes equal to or less than the current threshold. Also, after the current flowing through the battery becomes equal to or less than the current threshold, the second charger can be used to charge a battery provided in another power storage device. In other words, it is possible to suppress an increase in the time required to charge the batteries provided in the multiple power storage devices while simultaneously charging the batteries provided in the respective multiple power storage devices as much as possible.

[0010] The control unit may also be configured to transmit current command values ​​to the two or more first chargers so that a current flowing from a first charger that is a current limiting target among the two or more first chargers to the battery is reduced, and a current flowing from a first charger that is not a current limiting target among the two or more first chargers to the battery is increased.

[0011] As a result, even if the current output from the first charger is limited, a decrease in the current flowing through the battery can be suppressed, and therefore an increase in the time required to charge the battery can be suppressed.

[0012] Furthermore, the control unit may be configured such that, when receiving data from the first charger indicating that the temperature is equal to or higher than a temperature threshold, the control unit designates the first charger as a first charger to be limited in current.

[0013] In addition, during constant voltage charging control, when the rate of decrease per unit time of the current flowing to the battery when a current command value is sent to the first and second chargers becomes equal to the rate of decrease per unit time of the current flowing to the battery when a current command value is sent only to the first charger, the maximum value of the current output from the first charger may be set as the current threshold value.

[0014] The control unit may be configured to, when the current flowing to the battery becomes equal to or less than the current threshold, send a current command value to the first charger so that the voltage of the battery is maintained at the constant voltage and the current flowing to the battery gradually decreases, and to set the current command value to the second charger to zero, thereby stopping output. Effect of the Invention

[0015] According to the present invention, it is possible to charge the batteries provided in the plurality of power storage devices simultaneously as much as possible, while suppressing an increase in the time required for charging the batteries. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram illustrating an example of a power storage device according to an embodiment. [Diagram 2] 5A and 5B are diagrams illustrating an example of a current flowing through a battery and a voltage of the battery during constant-current constant-voltage charging control. [Diagram 3] 10 is a flowchart showing an example of an operation of a control unit. [Figure 4] FIG. 4 is a diagram illustrating an example of an output current of each charger in the first embodiment. [Diagram 5] FIG. 11 is a diagram illustrating an example of an output current of each charger in the second embodiment. [Figure 6]FIG. 11 is a diagram illustrating an example of an output current of each charger in the third embodiment. [Figure 7] 10 is a flowchart showing a modified example of the operation of the control unit. [Figure 8] FIG. 13 is a diagram showing an example of an output current of each charger in the fourth embodiment. [Figure 9] FIG. 13 is a diagram showing an example of an output current of each charger in the fifth embodiment. [Figure 10] FIG. 23 is a diagram showing an example of an output current of each charger in the sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0018] FIG. 1 is a diagram illustrating an example of a power storage device according to an embodiment.

[0019] The power storage device 1 shown in FIG. 1 includes a battery B, and sends current command values ​​to a plurality of chargers Ch (chargers Ch1 to Ch4) provided outside the power storage device 1 to control the currents flowing from the plurality of chargers Ch to the battery B, thereby charging the battery B. The battery B is formed of a secondary battery such as a lithium-ion battery. The power storage device 1 is mounted on a vehicle such as an industrial vehicle, e.g. a forklift, or an electric vehicle, and supplies power from the battery B to a load, e.g. a loading device and a driving motor. The power storage device 1 is capable of passing a relatively large current through the battery B, and is therefore suitable for a case where it is desired to relatively shorten the time required for charging the battery B.

[0020] Moreover, the chargers Ch1 to Ch4 are, for example, charging stands, and are independent of each other. Moreover, the chargers Ch1 to Ch4 convert AC power supplied from a commercial power source PW into DC power, and supply the DC power to the power storage device 1. Moreover, the chargers Ch1 to Ch4 may each be configured to output AC power. In such a configuration, the power storage device 1 has a function of converting each of the AC powers supplied from the chargers Ch1 to Ch4 into DC power. Moreover, the number of chargers Ch capable of supplying power to the power storage device 1 is not particularly limited as long as it is two or more.

[0021] In addition to the battery B, the power storage device 1 also includes a plurality of connectors C (connectors C1 to C4), a plurality of switches SW (switches SW1 to SW4), a plurality of diodes D (diodes D1 to D3), a voltage detection unit 2, a current detection unit 3, and a control unit 4. The number of connectors C, switches SW, and diodes D is changed according to the number of chargers Ch capable of supplying power to the battery B. For example, as shown in FIG. 1, when the number of chargers Ch capable of supplying power to the battery B is four, the number of connectors C and switches SW is four, and the number of diodes D is three. When the number of chargers Ch capable of supplying power to the battery B is two, the number of connectors C and switches SW is two, and the number of diodes D is one.

[0022] The connectors C1 to C4 are configured to be connectable to plugs PL provided in the chargers Ch1 to Ch4, respectively. In the example shown in Fig. 1, the plug PL provided in the charger Ch1 is connected to the connector C1, the plug PL provided in the charger Ch2 is connected to the connector C2, the plug PL provided in the charger Ch3 is connected to the connector C3, and the plug PL provided in the charger Ch4 is connected to the connector C4.

[0023] The switches SW1 to SW4 are, for example, electromagnetic relays or semiconductor relays, and are put into a cutoff state or a conductive state by the control unit 4 controlling their operation. One terminal of the switch SW1 is connected to one terminal of the connector C1, and the other terminal of the switch SW1 is connected to the anode terminal of the diode D1. One terminal of the switch SW2 is connected to one terminal of the connector C2, and the other terminal of the switch SW2 is connected to the connection point between the cathode terminal of the diode D1 and the anode terminal of the diode D2. One terminal of the switch SW3 is connected to one terminal of the connector C3, and the other terminal of the switch SW3 is connected to the connection point between the cathode terminal of the diode D2 and the anode terminal of the diode D3. One terminal of the switch SW4 is connected to one terminal of the connector C4, and the other terminal of the switch SW4 is connected to the cathode terminal of the diode D3 and the positive terminal of the battery B. The negative terminal of the battery B is connected to the other terminals of the connectors C1 to C4.

[0024] When the plug PL of the charger Ch1 is connected to the connector C1 and the switch SW1 is in a conductive state, the charger Ch1 can supply power to the battery B via the connector C1, the switch SW1, and the diodes D1 to D3. When the plug PL of the charger Ch2 is connected to the connector C2 and the switch SW2 is in a conductive state, the charger Ch2 can supply power to the battery B via the connector C2, the switch SW2, and the diodes D2 and D3. When the plug PL of the charger Ch3 is connected to the connector C3 and the switch SW3 is in a conductive state, the charger Ch3 can supply power to the battery B via the connector C3, the switch SW3, and the diode D3. When the plug PL of the charger Ch4 is connected to the connector C4 and the switch SW4 is in a conductive state, the charger Ch4 can supply power to the battery B via the connector C4 and the switch SW4.

[0025] The voltage detection unit 2 is configured, for example, by a plurality of voltage dividing resistors, detects the voltage of the battery B, and sends the detected voltage to the control unit 4.

[0026] The current detection unit 3 is configured with a shunt resistor or a Hall element, detects the current flowing through the battery B, and sends the detected current to the control unit 4.

[0027] The control unit 4 is configured by a processor or a programmable device (such as a field programmable gate array (FPGA) or a programmable logic device (PLD)).

[0028] The control unit 4 is also provided in the power storage device 1, and transmits and receives data to and from a charger Ch connected to the connector C. For example, as shown in Fig. 1, when a plug PL included in the charger Ch1 is connected to the connector C1, a plug PL included in the charger Ch2 is connected to the connector C2, a plug PL included in the charger Ch3 is connected to the connector C3, and a plug PL included in the charger Ch4 is connected to the connector C4, the control unit 4 and the chargers Ch1 to Ch4 are in a state in which they can transmit and receive data to and from each other. Note that the communication between the control unit 4 and the chargers Ch may be wired communication or wireless communication.

[0029] Furthermore, the control unit 4 charges the battery B by performing constant current / constant voltage charging control. During constant current / constant voltage charging control, the control unit 4 determines a current command value to be transmitted to each charger Ch depending on the number of chargers Ch connected to the connector C. For example, when four chargers Ch (chargers Ch1 to Ch4) are connected to the power storage device 1 and a constant current Ic is made to flow through the battery B, the control unit 4 transmits a current command value I* indicating a quarter of the constant current Ic to each of the chargers Ch1 to Ch4. When receiving the current command value I*, each of the chargers Ch1 to Ch4 outputs a quarter of the constant current Ic.

[0030] FIG. 2(a) is a diagram showing an example of a current flowing through battery B during constant current / constant voltage charging control, and FIG. 2(b) is a diagram showing an example of a voltage of battery B during constant current / constant voltage charging control. Note that the horizontal axis of the two-dimensional coordinate system shown in FIG. 2(a) indicates time, and the vertical axis indicates current. Also, the solid line shown in FIG. 2(a) indicates a current flowing through battery B. Also, the horizontal axis of the two-dimensional coordinate system shown in FIG. 2(b) indicates time, and the vertical axis indicates voltage. Also, the solid line shown in FIG. 2(b) indicates the voltage of battery B.

[0031] First, at time t0, constant-current constant-voltage charging control starts, and a constant current Ic flows to the battery B. While the constant current Ic flows to the battery B, the voltage of the battery B gradually increases.

[0032] Next, at time t1, when the voltage of battery B becomes equal to or higher than the constant voltage Vc, from time t1 onwards, the current flowing through battery B gradually decreases while the voltage of battery B is maintained at the constant voltage Vc.

[0033] Then, at time t3, when the current flowing through battery B becomes equal to or lower than the end current If, the current flowing through battery B becomes zero, and the constant-current constant-voltage charging control ends.

[0034] The charging control of battery B during the period from time t0 to time t1 is constant current charging control, and the charging control of battery B during the period from time t1 to time t3 is constant voltage charging control.

[0035] FIG. 3 is a flowchart showing an example of the operation of the control unit 4.

[0036] First, the control unit 4 checks the connection state between the plug PL of the charger Ch and the connector C, and then when it receives a charging instruction from a vehicle-side control unit that controls the driving of the vehicle (step ST1: Yes), it starts constant-current constant-voltage charging control and turns on the switch SW corresponding to the connector C to which the plug PL of the charger Ch is connected, thereby performing constant-current charging control on the first charger Ch and the second charger Ch (step ST2). For example, when the plugs PL of the chargers Ch1 to Ch4 are connected to the connectors C1 to C4, the control unit 4 regards the chargers Ch1 and Ch2 as the first charger Ch and the chargers Ch3 and Ch4 as the second charger Ch.

[0037] Next, when the control unit 4 is performing constant current charging control on the first charger Ch and the second charger Ch, if the voltage of the battery B becomes equal to or higher than a certain voltage Vc (step ST3: Yes), the control unit 4 performs constant voltage charging control on the first charger Ch and the second charger Ch (step ST4).

[0038] Next, when the current flowing to the battery B becomes equal to or less than the current threshold Ith while the control unit 4 is performing the constant voltage charging control for the first charger Ch and the second charger Ch (step ST5: Yes), the control unit 4 performs the constant voltage charging control for only the first charger Ch and turns off the switch SW corresponding to the connector C to which the second charger Ch is connected (step ST6). For example, during the constant voltage charging control, when the decrease width per unit time Δt of the current flowing to the battery B while the control unit 4 is sending a current command value to the first charger Ch and the second charger Ch becomes equal to the decrease width per unit time Δt of the current flowing to the battery B while the control unit 4 is sending a current command value only to the first charger Ch, the maximum value of the current output from the first charger Ch is set as the current threshold Ith. By setting the current threshold Ith in this manner, when the current flowing to the battery B becomes equal to or less than the current threshold Ith, that is, when the constant voltage charging control using the first charger Ch and the second charger Ch is shifted to the constant voltage charging control using only the first charger Ch, the fluctuation of the current flowing to the battery B can be suppressed. Furthermore, by setting the current threshold Ith in this manner, it is possible to prevent the rate of decrease in the current flowing through battery B per unit time Δt from becoming small after the current flowing through battery B becomes equal to or lower than the current threshold Ith, thereby suppressing an increase in the time required to charge battery B after the current flowing through battery B becomes equal to or lower than the current threshold Ith. Note that in step ST6, the second charger Ch may be configured to display on a display (not shown) that the second charger Ch can be used to charge battery B of another power storage device 1.

[0039] Then, when the current flowing through battery B becomes equal to or less than the termination current If (step ST7: Yes), the control unit 4 terminates the constant-current constant-voltage charging control and turns off the switch SW corresponding to the connector C to which the first charger Ch is connected.

[0040] In this manner, the energy storage device 1 of the embodiment is configured to perform constant voltage charging control only on the first charger Ch when the current flowing through the battery B becomes equal to or lower than the current threshold Ith while performing constant voltage charging control on the first charger Ch and the second charger Ch. Therefore, after the current flowing through the battery B becomes equal to or lower than the current threshold Ith, the second charger Ch can be used to charge the battery B of another energy storage device 1.

[0041] Furthermore, according to the power storage device 1 of the embodiment, even if the battery B is charged using only the first charger Ch during constant-current constant-voltage charging control, an increase in the time required to charge the battery B can be suppressed.

[0042] That is, according to the power storage device 1 of the embodiment, it is possible to simultaneously charge the batteries B provided in the respective power storage devices 1 as much as possible, while suppressing an increase in the time required for charging the batteries B.

[0043] Furthermore, according to the power storage device 1 of the embodiment, there is no need to provide each charger Ch with a control unit for integrating the chargers Ch, so that an increase in the manufacturing cost of the chargers Ch can be suppressed.

[0044] <Example 1> In the first embodiment, the chargers Ch1 and Ch2 are the first chargers Ch, the chargers Ch3 and Ch4 are the second chargers Ch, the constant current Ic is 200 [A], the current threshold Ith is 100 [A], the end current If is 50 [A], and the maximum output current of the chargers Ch1 to Ch4 is 50 [A]. Note that FIG. 4(a) shows the current output from the charger Ch1 during constant current constant voltage charging control in the first embodiment, FIG. 4(b) shows the current output from the charger Ch2 during constant current constant voltage charging control in the first embodiment, FIG. 4(c) shows the current output from the charger Ch3 during constant current constant voltage charging control in the first embodiment, and FIG. 4(d) shows the current output from the charger Ch4 during constant current constant voltage charging control in the first embodiment. The horizontal axis of the two-dimensional coordinates shown in FIG. 4(a) to (d) indicates time, and the vertical axis indicates current. The solid line in Figure 4(a) indicates the current output from charger Ch1, the solid line in Figure 4(b) indicates the current output from charger Ch2, the solid line in Figure 4(c) indicates the current output from charger Ch3, and the solid line in Figure 4(d) indicates the current output from charger Ch4.

[0045] First, during constant current charging control from time t0 to time t1, the control unit 4 transmits a current command value indicating a quarter current (50 [A]) of the constant current Ic (200 [A]) to each of the chargers Ch1 to Ch4. Then, as shown in Fig. 4(a) to Fig. 4(d), a current of 50 [A] is output from each of the chargers Ch1 to Ch4 during the period from time t0 to time t1.

[0046] Next, when the voltage of battery B becomes equal to or higher than the constant voltage Vc at time t1, the control unit 4 gradually reduces the current command value sent to each of the chargers Ch1-Ch4 from 50[A] to 25[A] so as to maintain the voltage of battery B at the constant voltage Vc during the constant voltage charging control from time t1 to time t2. Then, as shown in Fig. 4(a) to Fig. 4(d), the current output from each of the chargers Ch1-Ch4 gradually decreases from 50[A] to 25[A] during the period from time t1 to time t2.

[0047] Next, when the currents output from the chargers Ch1 to Ch4 become 25 [A] or less at time t2, causing the current flowing through the battery B to become the current threshold Ith (100 [A]) or less, the control unit 4 sets the current command values ​​sent to the chargers Ch3 and Ch4 to zero after time t2, and gradually reduces the current command values ​​sent to the chargers Ch1 and Ch2 from 50 [A] to 25 [A] so that the voltage of the battery B is kept at a constant voltage Vc during the constant voltage charging control from time t2 to time t3. Then, as shown in Fig. 4(a) to Fig. 4(d), the currents output from the chargers Ch3 and Ch4 become zero after time t2, and the currents output from the chargers Ch1 and Ch2 gradually reduce from 50 [A] to 25 [A] during the period from time t2 to time t3. That is, at time t2, the control unit 4 reduces the current command value transmitted to each of the chargers Ch3 and Ch4 from 25 [A] to zero, and increases the current command value transmitted to each of the chargers Ch1 and Ch2 from 25 [A] to 50 [A], thereby continuing charging of the battery B using the chargers Ch1 and Ch2 even after the output of the chargers Ch3 and Ch4 is stopped. In this way, in the first embodiment, the chargers Ch1 and Ch2 out of the chargers Ch1 to Ch4 are used to charge the battery B after time t2, so that the chargers Ch3 and Ch4 can be used to charge the battery B of another power storage device 1.

[0048] Then, at time t3, when the currents output from the chargers Ch1 and Ch2 reach 25 [A] and the current flowing through the battery B falls to or below the end current If (50 [A]), the control unit 4 sets the current command values ​​transmitted to the chargers Ch1 and Ch2 to zero. Then, as shown in Figures 4(a) and 4(b), at time t3, the currents output from the chargers Ch1 and Ch2 reach zero.

[0049] <Example 2> In the second embodiment, the charger Ch1 is the first charger Ch, the chargers Ch2 to Ch4 are the second chargers Ch, the constant current Ic is 200 [A], the current threshold Ith is 100 [A], the end current If is 50 [A], the maximum output current of the charger Ch1 is 100 [A], and the maximum output current of the chargers Ch2 to Ch4 is 50 [A]. Note that FIG. 5(a) shows the current output from the charger Ch1 during constant current constant voltage charging control in the second embodiment, FIG. 5(b) shows the current output from the charger Ch2 during constant current constant voltage charging control in the second embodiment, FIG. 5(c) shows the current output from the charger Ch3 during constant current constant voltage charging control in the second embodiment, and FIG. 5(d) shows the current output from the charger Ch4 during constant current constant voltage charging control in the second embodiment. The horizontal axis of the two-dimensional coordinates shown in FIG. 5(a) to (d) indicates time, and the vertical axis indicates current. The solid line in Fig. 5(a) indicates the current output from charger Ch1, the solid line in Fig. 5(b) indicates the current output from charger Ch2, the solid line in Fig. 5(c) indicates the current output from charger Ch3, and the solid line in Fig. 5(d) indicates the current output from charger Ch4. Also, the currents flowing through chargers Ch1-Ch4 from time t0 to time t2 in Fig. 5(a) to Fig. 5(d) are similar to the currents flowing through chargers Ch1-Ch4 from time t0 to time t2 in Fig. 4(a) to Fig. 4(d), so the description will begin from time t2.

[0050] When the currents output from the chargers Ch1 to Ch4 become 25 [A] or less at time t2, causing the current flowing through the battery B to become the current threshold Ith (100 [A]) or less, the control unit 4 sets the current command values ​​sent to the chargers Ch2 to Ch4 to zero after time t2, and increases the current command value sent to the charger Ch1 to 100 [A] and then gradually decreases it from 100 [A] to 50 [A] during the constant voltage charging control from time t2 to time t3 so that the voltage of the battery B is kept at a constant voltage Vc. Then, as shown in Fig. 5(a) to Fig. 5(d), the currents output from the chargers Ch2 to Ch4 become zero after time t2, and the current output from the charger Ch1 gradually decreases from 100 [A] to 50 [A] during the period from time t2 to time t3. That is, at time t2, the control unit 4 reduces the current command value sent to each of the chargers Ch2 to Ch4 from 25 [A] to zero, and increases the current command value sent to the charger Ch1 from 25 [A] to 100 [A], thereby continuing charging of the battery B using the charger Ch1 even after the output of the chargers Ch2 to Ch4 is stopped. In this way, in the second embodiment, the charger Ch1 of the chargers Ch1 to Ch4 is used to charge the battery B after time t2, so that the chargers Ch2 to Ch4 can be used to charge the battery B of another power storage device 1.

[0051] Then, at time t3, when the current output from the charger Ch1 becomes 50 [A] and the current flowing through the battery B becomes equal to or less than the end current If (50 [A]), the control unit 4 sets the current command value to be sent to the charger Ch1 to zero. Then, as shown in Fig. 5(a), at time t3, the current output from the charger Ch1 becomes zero.

[0052] <Example 3> In the third embodiment, the charger Ch1 is the first charger Ch, the charger Ch2 is the second charger Ch, the constant current Ic is 200 [A], the current threshold Ith is 100 [A], the end current If is 50 [A], and the maximum output current of the chargers Ch1 and Ch2 is 100 [A]. FIG. 6(a) shows the current output from the charger Ch1 during constant current / constant voltage charging control in the third embodiment, and FIG. 6(b) shows the current output from the charger Ch2 during constant current / constant voltage charging control in the third embodiment. The horizontal axis of the two-dimensional coordinate system shown in FIG. 6(a) and FIG. 6(b) shows the time, and the vertical axis shows the current. The solid line shown in FIG. 6(a) shows the current output from the charger Ch1, and the solid line shown in FIG. 6(b) shows the current output from the charger Ch2. In the third embodiment, in the period from time t0 to time t3, chargers Ch1 and Ch2 out of chargers Ch1 to Ch4 are used to charge battery B, so that chargers Ch3 and Ch4 can be used to charge battery B of another power storage device 1.

[0053] First, the control unit 4 transmits a current command value indicating a current (100[A]) that is half the constant current Ic (200[A]) to each of the chargers Ch1 and Ch2 during constant current charging control from time t0 to time t1. Then, as shown in Fig. 6(a) and Fig. 6(b), a current of 100[A] is output from each of the chargers Ch1 and Ch2 during the period from time t0 to time t1.

[0054] Next, when the voltage of battery B becomes equal to or higher than the constant voltage Vc at time t1, the control unit 4 gradually reduces the current command values ​​sent to the chargers Ch1 and Ch2 from 100 [A] to 50 [A] so that the voltage of battery B is kept at the constant voltage Vc during the constant voltage charging control from time t1 to time t2. Then, as shown in Figures 6(a) and 6(b), the currents output from the chargers Ch1 and Ch2 gradually reduce from 100 [A] to 50 [A] during the period from time t1 to time t2.

[0055] Next, when the currents output from the chargers Ch1 and Ch2 become 50 [A] or less at time t2, causing the current flowing through the battery B to become equal to or less than the current threshold Ith (100 [A]), the control unit 4 sets the current command value sent to the charger Ch2 to zero after time t2, and increases the current command value sent to the charger Ch1 to 100 [A] during the constant voltage charging control from time t2 to time t3 so that the voltage of the battery B is kept at a constant voltage Vc, and then gradually decreases it from 100 [A] to 50 [A]. Then, as shown in Figures 6(a) and 6(b), after time t2, the current output from the appliance Ch2 becomes zero, and during the period from time t2 to time t3, the current output from the charger Ch1 gradually decreases from 100 [A] to 50 [A]. That is, at time t2, the control unit 4 reduces the current command value sent to the charger Ch2 from 50 [A] to zero, and increases the current command value sent to the charger Ch1 from 50 [A] to 100 [A], thereby continuing charging of the battery B using the charger Ch1 even after the output of the charger Ch2 is stopped. In this way, in the third embodiment, the charger Ch1 of the chargers Ch1 and Ch2 is used to charge the battery B after time t2, so that the charger Ch2 can also be used to charge the battery B of another power storage device 1.

[0056] Then, at time t3, when the current output from the charger Ch1 becomes 50 [A] and the current flowing through the battery B becomes equal to or less than the end current If (50 [A]), the control unit 4 sets the current command value to be sent to the charger Ch1 to zero. Then, as shown in Fig. 6(a), at time t3, the current output from the charger Ch1 becomes zero.

[0057] FIG. 7 is a flowchart showing another example of the operation of the control unit 4. In FIG.

[0058] First, the control unit 4 checks the connection state between the plug PL of the charger Ch and the connector C, and then when it receives a charging instruction from a vehicle-side control unit that controls the driving of the vehicle (step ST1: Yes), it starts constant-current constant-voltage charging control, turns on the switch SW corresponding to the connector C to which the charger Ch is connected, and determines whether or not there is a first charger Ch that is to be output-limited among the first chargers Ch connected to the connector C (step ST1'). For example, when the control unit 4 receives data from the first charger Ch indicating that the temperature of the first charger Ch is equal to or higher than the temperature threshold, it sets the first charger Ch as a charger Ch that is to be output-limited. Alternatively, when the control unit 4 receives data from the first charger Ch indicating that the maximum value of the output current needs to be limited from 50 [A] to 25 [A], it sets the first charger Ch as a charger Ch that is to be output-limited.

[0059] Next, if the control unit 4 does not receive data regarding output limitation from the first charger Ch connected to the connector C and determines that there is no first charger Ch that is subject to output limitation (step ST1': No), it performs constant current charging control on the first charger Ch and the second charger Ch (step ST2).

[0060] On the other hand, when the control unit 4 determines that there is a first charger Ch that is subject to output limiting (step ST1': Yes), it performs constant current charging control on the first charger Ch and the second charger Ch, while transmitting a current command value to the first charger Ch that is subject to output limiting and the first charger Ch that is not subject to output limiting so that the current output from the first charger Ch that is subject to output limiting is reduced and the current output from the first charger Ch that is not subject to output limiting is increased by the amount of the reduction in the output current of the first charger Ch that is subject to output limiting (step ST2').

[0061] Next, when the control unit 4 is performing constant current charging control on the first charger Ch and the second charger Ch, if the voltage of the battery B becomes equal to or higher than a certain voltage Vc (step ST3: Yes), it determines whether or not there is a first charger Ch that is subject to output limiting among the first chargers Ch connected to the connector C (step ST3').

[0062] Next, when the control unit 4 determines that there is no first charger Ch that is the output limit target (step ST3': No), it performs constant voltage charging control on the first charger Ch and the second charger Ch (step ST4).

[0063] On the other hand, when the control unit 4 determines that there is a first charger Ch that is subject to output limiting (step ST3': Yes), it performs constant voltage charging control on the first charger Ch and the second charger Ch, and transmits a current command value to the first charger Ch that is subject to output limiting and the first charger Ch that is not subject to output limiting so that the current output from the first charger Ch that is subject to output limiting is reduced and the current output from the first charger Ch that is not subject to output limiting is increased by the amount of the reduction in the output current of the first charger Ch that is subject to output limiting (step ST4').

[0064] Next, when the control unit 4 is performing constant voltage charging control on the first charger Ch and the second charger Ch, if the current flowing through the battery B becomes equal to or lower than the current threshold Ith (step ST5: Yes), the control unit 4 determines whether or not there is a first charger Ch that is subject to output limiting among the first chargers Ch connected to the connector C (step ST5').

[0065] When the control unit 4 determines that there is no first charger Ch that is subject to output limiting (step ST5': No), it performs constant voltage charging control only on the first charger Ch and turns off the switch SW corresponding to the connector C to which the second charger Ch is connected (step ST6).

[0066] On the other hand, when the control unit 4 determines that there is a first charger Ch that is subject to output limiting (step ST5': Yes), it performs constant voltage charging control only on the first charger Ch, turns off the switch SW corresponding to the connector C to which the second charger Ch is connected, and sends a current command value to the first charger Ch that is subject to output limiting and the first chargers Ch that are not subject to output limiting so that the current output from the first charger Ch that is subject to output limiting decreases and the current output from the first charger Ch that is not subject to output limiting is increased by the amount of the decrease in output current of the first charger Ch that is subject to output limiting (step ST6').

[0067] Then, when the current flowing through battery B becomes equal to or less than the termination current If (step ST7: Yes), the control unit 4 terminates the constant-current constant-voltage charging control and turns off the switch SW corresponding to the connector C to which the first charger Ch is connected.

[0068] In this way, even if the current output from the charger Ch is limited, the magnitude of the current flowing to the battery B can be prevented from changing, thereby preventing an increase in the time required to charge the battery B.

[0069] <Example 4> In the fourth embodiment, the chargers Ch1 and Ch2 are the first chargers Ch, the chargers Ch3 and Ch4 are the second chargers Ch, the constant current Ic is 200 [A], the current threshold Ith is 100 [A], the end current If is 50 [A], the maximum output current of the chargers Ch1, Ch3, and Ch4 is 50 [A], and the maximum output current of the charger Ch2 is 100 [A]. Note that FIG. 8(a) shows the current output from the charger Ch1 during constant current constant voltage charging control in the fourth embodiment, FIG. 8(b) shows the current output from the charger Ch2 during constant current constant voltage charging control in the fourth embodiment, FIG. 8(c) shows the current output from the charger Ch3 during constant current constant voltage charging control in the fourth embodiment, and FIG. 8(d) shows the current output from the charger Ch4 during constant current constant voltage charging control in the fourth embodiment. The horizontal axis of the two-dimensional coordinates shown in FIG. 8(a) to (d) indicates time, and the vertical axis indicates current. The solid line in Figure 8(a) indicates the current output from charger Ch1, the solid line in Figure 8(b) indicates the current output from charger Ch2, the solid line in Figure 8(c) indicates the current output from charger Ch3, and the solid line in Figure 8(d) indicates the current output from charger Ch4.

[0070] First, during constant current charging control from time t0 to time t1', the control unit 4 transmits a current command value indicating a quarter current (50 [A]) of the constant current Ic (200 [A]) to each of the chargers Ch1 to Ch4. Then, as shown in Fig. 8(a) to Fig. 8(d), a current of 50 [A] is output from each of the chargers Ch1 to Ch4 during the period from time t0 to time t1'.

[0071] Next, when the control unit 4 determines at time t1' that it is necessary to limit the maximum value of the output current of the charger Ch1 from 50 [A] to 25 [A], during the constant current charging control from time t1' to time t1, it transmits a current command value indicating 25 [A] to the charger Ch1, a current command value indicating 75 [A] to the charger Ch2, and a current command value indicating 50 [A] to the chargers Ch3 and Ch4. Then, as shown in Fig. 8(a) to Fig. 8(d), during the period from time t1' to time t1, a current of 25 [A] is output from the charger Ch1, a current of 75 [A] is output from the charger Ch2, and a current of 50 [A] is output from each of the chargers Ch3 and Ch4.

[0072] Next, when the voltage of battery B becomes equal to or higher than the constant voltage Vc at time t1, the control unit 4 transmits a current command value indicating 25 [A] to the charger Ch1, gradually reduces the current command value transmitted to the charger Ch2 from 75 [A] to 25 [A], and gradually reduces the current command values ​​transmitted to the chargers Ch3 and Ch4 from 50 [A] to 25 [A] so that the voltage of battery B is kept at the constant voltage Vc during the constant voltage charging control from time t1 to time t2. Then, as shown in Fig. 8(a) to Fig. 8(d), during the period from time t1 to time t2, a current of 25 [A] is output from the charger Ch1, the current output from the charger Ch2 gradually decreases from 75 [A] to 25 [A], and the currents output from the chargers Ch3 and Ch4 gradually decrease from 50 [A] to 25 [A]. In this manner, in the fourth embodiment, in the period from time t1' to time t2, the output current of the charger Ch1 is limited, and the charger Ch2 can compensate for this, so that an increase in the charging time of the battery B can be suppressed.

[0073] Next, when the currents output from the chargers Ch1 to Ch4 become 25 [A] at time t2, and the current flowing through the battery B becomes equal to or less than the current threshold Ith (100 [A]), the control unit 4 sets the current command values ​​to be sent to the chargers Ch3 and Ch4 to zero after time t2, and gradually reduces the current command value to be sent to the charger Ch1 from 25 [A] to 0 [A] and gradually reduces the current command value to be sent to the charger Ch2 from 75 [A] to 50 [A] so that the voltage of the battery B is kept at a constant voltage Vc during the constant voltage charging control from time t2 to time t3. Then, as shown in FIG. 8(a) to FIG. 8(d), the currents output from the chargers Ch3 and Ch4 become zero after time t2, and during the period from time t2 to time t3, the current output from the charger Ch1 gradually decreases from 25 [A] to 0 [A] and the current output from the charger Ch2 gradually decreases from 75 [A] to 50 [A]. That is, at time t2, the control unit 4 reduces the current command value sent to each of the chargers Ch3 and Ch4 from 25 [A] to zero, and increases the current command value sent to the charger Ch2 from 25 [A] to 75 [A], thereby continuing charging of the battery B using the chargers Ch1 and Ch2 even after the output of the chargers Ch3 and Ch4 is stopped. In this way, in the fourth embodiment, since the chargers Ch1 and Ch2 out of the chargers Ch1 to Ch4 are used to charge the battery B after time t2, the chargers Ch3 and Ch4 can be used to charge the battery B of another power storage device 1.

[0074] Then, at time t3, when the current output from charger Ch1 becomes 0 [A] and the current output from charger Ch2 becomes 50 [A], causing the current flowing through battery B to become equal to or less than the end current If (50 [A]), the control unit 4 sets the current command value to be sent to charger Ch2 to zero. Then, as shown in Fig. 8(a) and Fig. 8(b), at time t3, the currents output from chargers Ch1 and Ch2 each become zero.

[0075] <Example 5> In the fifth embodiment, the chargers Ch1 and Ch2 are the first chargers Ch, the chargers Ch3 and Ch4 are the second chargers Ch, the constant current Ic is 200 [A], the current threshold Ith is 100 [A], the end current If is 50 [A], the maximum output current of the chargers Ch1, Ch3, and Ch4 is 50 [A], and the maximum output current of the charger Ch2 is 100 [A]. Note that FIG. 9(a) shows the current output from the charger Ch1 during constant current constant voltage charging control in the fifth embodiment, FIG. 9(b) shows the current output from the charger Ch2 during constant current constant voltage charging control in the fifth embodiment, FIG. 9(c) shows the current output from the charger Ch3 during constant current constant voltage charging control in the fifth embodiment, and FIG. 9(d) shows the current output from the charger Ch4 during constant current constant voltage charging control in the fifth embodiment. The horizontal axis of the two-dimensional coordinates shown in FIG. 9(a) to (d) indicates time, and the vertical axis indicates current. The solid line in Fig. 9(a) indicates the current output from charger Ch1, the solid line in Fig. 9(b) indicates the current output from charger Ch2, the solid line in Fig. 9(c) indicates the current output from charger Ch3, and the solid line in Fig. 9(d) indicates the current output from charger Ch4. Also, the currents flowing through chargers Ch1-Ch4 from time t0 to time t1 in Fig. 9(a) to Fig. 9(d) are similar to the currents flowing through chargers Ch1-Ch4 from time t0 to time t1 in Fig. 4(a) to Fig. 4(d), so the explanation will begin from time t1 onwards.

[0076] When the voltage of battery B becomes equal to or higher than the constant voltage Vc at time t1, the control unit 4 gradually reduces the current command value transmitted to each of the chargers Ch1-Ch4 during the constant voltage charging control from time t1 to time t2' so that the voltage of battery B is kept at the constant voltage Vc. Then, as shown in Fig. 9(a) to Fig. 9(d), the current output from each of the chargers Ch1-Ch4 gradually decreases during the period from time t1 to time t2'.

[0077] Next, when the control unit 4 determines at time t2' that the maximum value of the output current of the charger Ch1 needs to be limited to 25 [A], during the constant voltage charging control from time t2' to time t2, it transmits a current command value indicating 25 [A] to the charger Ch1, increases the current command value transmitted to the charger Ch2 by an amount corresponding to the decrease in the current command value of the charger Ch1, and then gradually decreases it, and gradually decreases the current command values ​​transmitted to the chargers Ch3 and Ch4. Then, as shown in Fig. 9(a) to Fig. 9(d), during the period from time t2' to time t2, a current of 25 [A] is output from the charger Ch1, the current output from the charger Ch2 increases by an amount corresponding to the decrease in the output current of the charger Ch1, and then gradually decreases it, and the currents output from the chargers Ch3 and Ch4 each gradually decrease.

[0078] Next, when the currents output from the chargers Ch1 to Ch4 become 25 [A] at time t2, and the current flowing through the battery B becomes equal to or less than the current threshold Ith (100 [A]), the control unit 4 sets the current command values ​​to be sent to the chargers Ch3 and Ch4 to zero after time t2, and transmits a current command value indicating 25 [A] to the charger Ch1 and increases the current command value to be sent to the charger Ch2 to 75 [A] so that the voltage of the battery B is kept at a constant voltage Vc during the constant voltage charging control from time t2 to time t3, and then gradually reduces the current command value from 75 [A] to 25 [A]. Then, as shown in Fig. 9(a) to Fig. 9(d), the currents output from the chargers Ch3 and Ch4 become zero after time t2, and during the period from time t2 to time t3, a current of 25 [A] is output from the charger Ch1, and a current output from the charger Ch2 gradually reduces from 75 [A] to 25 [A]. That is, at time t2, the control unit 4 reduces the current command values ​​transmitted to the chargers Ch3 and Ch4 from 25 [A] to zero, and increases the current command value transmitted to the charger Ch2 from 25 [A] to 75 [A], thereby allowing the chargers Ch1 and Ch2 to continue charging the battery B even after the output of the chargers Ch3 and Ch4 is stopped. In this manner, in the fifth embodiment, the chargers Ch1 and Ch2 out of the chargers Ch1 to Ch4 are used to charge the battery B after time t2, so that the chargers Ch3 and Ch4 can be used to charge the battery B of another power storage device 1. In addition, in the fifth embodiment, the charger Ch2 can compensate for the limited output current of the charger Ch1 during the period from time t2' to time t3, and therefore an increase in the charging time of the battery B can be suppressed.

[0079] Then, at time t3, when the current output from charger Ch1 becomes 25 [A] and the current output from charger Ch2 becomes 25 [A], causing the current flowing through battery B to become equal to or less than the end current If (50 [A]), the control unit 4 sets the current command values ​​transmitted to chargers Ch1 and Ch2 to zero. Then, as shown in Figures 9(a) and 9(b), at time t3, the currents output from chargers Ch1 and Ch2 become zero.

[0080] <Example 6> In the sixth embodiment, the chargers Ch1 and Ch2 are the first chargers Ch, the chargers Ch3 and Ch4 are the second chargers Ch, the constant current Ic is 200 [A], the current threshold Ith is 100 [A], the end current If is 50 [A], the maximum output current of the chargers Ch1, Ch3, and Ch4 is 50 [A], and the maximum output current of the charger Ch2 is 100 [A]. Note that FIG. 10(a) shows the current output from the charger Ch1 during constant current constant voltage charging control in the sixth embodiment, FIG. 10(b) shows the current output from the charger Ch2 during constant current constant voltage charging control in the sixth embodiment, FIG. 10(c) shows the current output from the charger Ch3 during constant current constant voltage charging control in the sixth embodiment, and FIG. 10(d) shows the current output from the charger Ch4 during constant current constant voltage charging control in the sixth embodiment. The horizontal axis of the two-dimensional coordinates shown in FIG. 10(a) to (d) indicates time, and the vertical axis indicates current. The solid line in Fig. 10(a) indicates the current output from charger Ch1, the solid line in Fig. 10(b) indicates the current output from charger Ch2, the solid line in Fig. 10(c) indicates the current output from charger Ch3, and the solid line in Fig. 10(d) indicates the current output from charger Ch4. Also, the currents flowing through chargers Ch1-Ch4 from time t0 to time t2 in Fig. 10(a) to Fig. 10(d) are similar to the currents flowing through chargers Ch1-Ch4 from time t0 to time t2 in Fig. 4(a) to Fig. 4(d), so the description will begin from time t2.

[0081] When the currents output from the chargers Ch1 to Ch4 reach 25 [A] at time t2, causing the current flowing through battery B to fall below the current threshold Ith (100 [A]), the control unit 4 sets the current command values ​​sent to the chargers Ch3 and Ch4 to zero after time t2, and gradually reduces the current command values ​​sent to the chargers Ch1 and Ch2 during the constant voltage charging control from time t2 to time t3' so that the voltage of battery B is maintained at a constant voltage Vc. Then, as shown in Figures 10(a) to 10(d), the currents output from the chargers Ch3 and Ch4 reach zero after time t2, and the currents output from the chargers Ch1 and Ch2 gradually decrease during the period from time t2 to time t3'. That is, at time t2, the control unit 4 reduces the current command value transmitted to each of the chargers Ch3 and Ch4 from 25 [A] to zero, and increases the current command value transmitted to each of the chargers Ch1 and Ch2 from 25 [A] to 50 [A], thereby continuing charging of the battery B using the chargers Ch1 and Ch2 even after the output of the chargers Ch3 and Ch4 is stopped. In this way, in the sixth embodiment, the chargers Ch1 and Ch2 out of the chargers Ch1 to Ch4 are used to charge the battery B after time t2, so that the chargers Ch3 and Ch4 can be used to charge the battery B of another power storage device 1.

[0082] Next, when the control unit 4 determines that the maximum value of the output current of the charger Ch1 needs to be limited to 25 [A] at time t3', it transmits a current command value indicating 25 [A] to the charger Ch1 during the constant voltage charging control from time t3' to time t3, and increases the current command value transmitted to the charger Ch2 by an amount corresponding to the decrease in the current command value of the charger Ch1, and then gradually decreases the current command value to 25 [A]. Then, as shown in FIG. 10(a) and FIG. 10(b), in the period from time t3' to time t3, a current of 25 [A] is output from the charger Ch1, and a current output from the charger Ch2 increases by an amount corresponding to the decrease in the output current of the charger Ch1, and then gradually decreases to 25 [A]. In this way, in the sixth embodiment, the charger Ch2 can be made to compensate for the amount of the limit on the output current of the charger Ch1 during the period from time t3' to time t3, and therefore it is possible to suppress an increase in the charging time of the battery B.

[0083] Then, at time t3, when the current output from charger Ch1 becomes 25 [A] and the current output from charger Ch2 becomes 25 [A], causing the current flowing through battery B to become equal to or less than the end current If (50 [A]), the control unit 4 sets the current command values ​​transmitted to chargers Ch1 and Ch2 to zero. Then, as shown in Figures 10(a) and 10(b), at time t3, the currents output from chargers Ch1 and Ch2 become zero.

[0084] The present invention is not limited to the above-described embodiment, and various improvements and modifications are possible without departing from the gist of the present invention.

[0085] <Modification> In the above embodiment, the output current of the charger Ch is limited (reduced) when the temperature of the charger Ch becomes relatively high, but the output current of the charger Ch may be limited when an abnormality occurs in the charger Ch. An abnormality occurring in the charger Ch is, for example, an abnormality in a current sensor that detects the output current of the charger Ch, which causes the output current of the charger Ch to be limited. [Explanation of symbols]

[0086] 1. Energy storage device 2 Voltage detection section 3 Current detection section 4. Control section PW Commercial power supply Ch1~Ch4 charger PL plug C1~C4 Connectors SW1~SW4 Switches D1~D4 Diodes B Battery

Claims

1. a battery to which power output from one or more first chargers and one or more second chargers are supplied; a control unit which, after starting constant-current constant-voltage charging control, when the voltage of the battery becomes equal to or higher than a certain voltage, transmits current command values ​​to the first and second chargers so that the voltage of the battery is maintained at the constant voltage and the current flowing to the battery is gradually reduced, and, when the current flowing to the battery becomes equal to or lower than a current threshold, transmits a current command value to the first charger so that the voltage of the battery is maintained at the constant voltage and the current flowing to the battery is gradually reduced, and, when the current flowing to the battery becomes equal to or lower than a termination current which is smaller than the current threshold, terminates the constant-current constant-voltage charging control by transmitting a current command value to the first charger so that the current flowing to the battery becomes zero; A power storage device comprising:

2. The power storage device according to claim 1 , The control unit transmits current command values ​​to the two or more first chargers so that a current flowing from a first charger that is a current limit target among the two or more first chargers to the battery is reduced and a current flowing from a first charger that is a current limit target among the two or more first chargers to the battery is increased. Energy storage device.

3. The power storage device according to claim 2, When the control unit receives data from the first charger indicating that the temperature is equal to or higher than a temperature threshold, the control unit sets the first charger as a first charger to be subject to the current limit. Energy storage device.

4. The power storage device according to claim 1 , During constant voltage charging control, when a decrease in a current flowing to the battery per unit time when a current command value is sent to the first and second chargers becomes equal to a decrease in a current flowing to the battery per unit time when a current command value is sent only to the first charger, a maximum value of a current output from the first charger is set as the current threshold value. Energy storage device.

5. The power storage device according to claim 1 , When the current flowing to the battery becomes equal to or less than the current threshold, the control unit transmits a current command value to the first charger so that the voltage of the battery is maintained at the constant voltage and the current flowing to the battery gradually decreases, and sets a current command value to the second charger to zero to stop output. Energy storage device.

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