Charging device

Abstract

To provide a charging device which charges a battery by power supplied from a system, capable of reducing power which becomes waste when estimating a full charge capacity of a battery.SOLUTION: A charging device executes: first charging processing that power is supplied to a first power storage device St1 from a system P until a first battery B1 becomes a full charging state, and power is supplied to the first power storage device St1 from a second power storage device St2; estimation processing that power is supplied from at least the first power storage device St1 to the second power storage device St2 until the first battery B1 becomes a complete discharge state, for estimating an integrated value of current output from the first power storage device St1 as a full charge capacity of the first battery B1 until the first power storage device St1 becomes the complete discharge state from the full charging state; and second charging processing that power is supplied to the first power storage device St1 from the second power storage device St2 until the first battery B1 becomes the full charging state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a charging device that charges a battery with power supplied from a power grid. [Background technology]

[0002] There is a charging device that charges a battery with power supplied from a grid until it is fully charged, and then discharges the battery at a constant current until it is fully discharged, and estimates the full charge capacity of the battery based on the time it takes for the battery to go from the fully charged state to the fully discharged state.

[0003] However, in the above-mentioned charging device, when the battery is fully discharged, there is a concern that the power will be wasted if the power is returned from the battery to the grid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-057184 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object according to one aspect of the present invention is to reduce power wasted when estimating the full charge capacity of a battery in a charging device that charges a battery with power supplied from a power grid. [Means for solving the problem]

[0006] A charging device of one embodiment of the present invention includes a first power converter connected between a grid and a first power storage device, a second power converter connected between the first power converter and a second power storage device, and a control unit that controls operation of the first and second power converters.

[0007] When estimating a full charge capacity of a first battery provided in the first storage device, the control unit executes a first charging process to cause power to be supplied from the grid via the first power converter to the first storage device and to cause power to be supplied from the second storage device via the second power converter to the first storage device until the first battery is in a fully charged state, executes an estimation process to cause power to be supplied from at least the first storage device to the second storage device via the second power converter until the first battery is in a fully discharged state, and estimates as the full charge capacity of the first battery an integrated value of the current output from the first storage device during the time period when the first storage device goes from a fully charged state to a fully discharged state, and executes a second charging process to cause power to be supplied from the second storage device to the first storage device via the second power converter to recharge the first battery.

[0008] This makes it possible to suppress the power supplied from the first power storage device to the grid when the first battery is put into a fully discharged state, thereby reducing the amount of power wasted when estimating the full charge capacity of the first battery.

[0009] In addition, when the first charging process is performed, the control unit may be configured to reduce the power supplied from the grid to the first power storage device and increase the power supplied from the second power storage device to the first power storage device when the power supply and demand of the grid is tight, compared to when the power supply and demand of the grid is not tight.

[0010] As a result, even if the power supply and demand in the grid is tight when the first charging process is performed, the decrease in the current flowing to the first power storage device can be suppressed, thereby suppressing an increase in the time required for the estimation process.

[0011] Furthermore, when the estimation process is performed, if the remaining capacity of the first battery is greater than the available capacity of a second battery provided in the second storage device, the control unit may be configured to supply power from the first storage device to the second storage device via the second power converter until the second battery is fully charged, and then supply power from the first storage device to the system via the first power converter until the first battery is fully discharged.

[0012] The control unit may also be configured to reset the charging rate of the second battery by charging the second battery provided in the second power storage device until the second battery is fully charged after executing the second charging process.

[0013] This makes it possible to improve the accuracy of estimating the state of charge of the second power storage device, and therefore the accuracy of estimating the full charge capacity of the first power storage device. Effect of the Invention

[0014] According to the present invention, in a charging device that charges a battery with power supplied from a power grid, it is possible to reduce the amount of power wasted when estimating the full charge capacity of the battery. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating an example of a charging device according to an embodiment. [Diagram 2] 5 is a flowchart showing an example of the operation of a control unit in the first embodiment. [Diagram 3] 5 is a flowchart showing an example of a first charging process. [Figure 4] 13 is a flowchart illustrating an example of an estimation process. [Diagram 5] 10 is a flowchart showing an example of a second charging process. [Figure 6] 10 is a flowchart showing an example of the operation of a control unit in the second embodiment. [Figure 7]13 is a flowchart illustrating an example of a reset process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the details of the embodiment will be described with reference to the drawings.

[0017] FIG. 1 is a diagram illustrating an example of a charging device according to an embodiment.

[0018] 1 includes a first power converter Cnv1, a second power converter Cnv2, and control units Cntc1 and Cntc2, and charges a first power storage device St1 and a second power storage device St2 with power supplied from a system P. The charging device Chg, the first power storage device St1, and the second power storage device St2 are mounted on a vehicle such as a forklift or an electric vehicle, and the power stored in the first power storage device St1 and the second power storage device St2 is used to drive a driving motor and electrical equipment mounted on the vehicle.

[0019] The first power storage device St1 includes a first battery B1 and a control unit Cntb1.

[0020] The first battery B1 is composed of a chargeable and dischargeable secondary battery such as a lead battery, a nickel-metal hydride battery, or a lithium-ion battery. The first battery B1 is charged by power supplied from the system P to the first power storage device St1 via the first power converter Cnv1. The first battery B1 is charged by power supplied from the second power storage device St2 to the first power storage device St1 via the second power converter Cnv2. When power is supplied from the first power storage device St1 to the system P via the first power converter Cnv1, the first battery B1 is discharged. When power is supplied from the first power storage device St1 to the second power storage device St2 via the second power converter Cnv2, the first battery B1 is discharged.

[0021] The control unit Cntb1 is constituted by a microcomputer or the like, and controls the charging of the first battery B1 when electric power is being supplied to the first power storage device St1.

[0022] For example, the control unit Cntb1 keeps the current flowing to the first battery B1 constant until the voltage of the first battery B1 becomes equal to or higher than a predetermined voltage Vc1, and when the voltage of the first battery B1 becomes equal to or higher than the predetermined voltage Vc1, it gradually reduces the current flowing to the first battery B1 while maintaining the voltage of the first battery B1 at the predetermined voltage Vc1, and when the current flowing to the first battery B1 becomes equal to or lower than the predetermined current Ic1, it determines that the first battery B1 is fully charged and terminates the charging of the first battery B1 (constant current constant voltage charging control).

[0023] Alternatively, the control unit Cntb1 keeps the current flowing to the first battery B1 constant until the voltage of the first battery B1 becomes equal to or higher than a predetermined voltage Vc1, and when the voltage of the first battery B1 becomes equal to or higher than the predetermined voltage Vc1, it determines that the first battery B1 is fully charged and terminates the charging of the first battery B1 (constant current charging control).

[0024] Alternatively, the control unit Cntb1 keeps the current flowing to the first battery B1 constant until the voltage of the first battery B1 becomes equal to or higher than a predetermined voltage Vc1, and when the voltage of the first battery B1 becomes equal to or higher than the predetermined voltage Vc1, gradually reduces the constant current flowing to the first battery B1 each time the voltage of the first battery B1 becomes equal to or higher than the predetermined voltage Vc1, and when the current flowing to the first battery B1 becomes equal to or lower than the predetermined current Ic1, it determines that the first battery B1 is fully charged and terminates the charging of the first battery B1 (multi-stage constant current charging control).

[0025] Furthermore, when power is being output from the first power storage device St1, the control unit Cntb1 determines whether the first battery B1 is in a fully discharged state. For example, when the voltage of the first battery B1 becomes equal to or lower than a predetermined voltage Vd1, the control unit Cntb1 determines that the first battery B1 is in a fully discharged state. Note that the predetermined voltage Vc1 is set to be greater than the predetermined voltage Vd1.

[0026] The control unit Cntb1 also obtains the charging rate of the first battery B1 (the ratio [%] of the remaining capacity to the full charge capacity of the first battery B1). For example, the control unit Cntb1 refers to information indicating the correspondence between the open circuit voltage and the charging rate of the first battery B1, and determines the charging rate corresponding to the open circuit voltage of the first battery B1 measured at a predetermined timing as the charging rate of the first battery B1 at the predetermined timing.

[0027] The second power storage device St2 includes a second battery B2 and a control unit Cntb2.

[0028] The second battery B2 is configured by a chargeable and dischargeable secondary battery such as a lead battery, a nickel-metal hydride battery, or a lithium-ion battery. The full charge capacity of the second battery B2 is assumed to be greater than the full charge capacity of the first battery B1. The second battery B2 is charged by power supplied from the first power storage device St1 to the second power storage device St2 via the second power converter Cnv2. The second battery B2 is charged by power supplied from the system P to the second power storage device St2 via the first power converter Cnv1 and the second power converter Cnv2. When power is supplied from the second power storage device St2 to the first power storage device St1 via the second power converter Cnv2, the second battery B2 is discharged. When power is supplied from the second power storage device St2 to the system P via the second power converter Cnv2 and the first power converter Cnv1, the second battery B2 is discharged.

[0029] The control unit Cntb2 is constituted by a microcomputer or the like, and controls the charging of the second battery B2 when electric power is being supplied to the second power storage device St2.

[0030] For example, the control unit Cntb2 keeps the current flowing to the second battery B2 constant until the voltage of the second battery B2 becomes equal to or higher than a predetermined voltage Vc2, and when the voltage of the second battery B2 becomes equal to or higher than the predetermined voltage Vc2, gradually reduces the current flowing to the second battery B2 while maintaining the voltage of the second battery B2 at the predetermined voltage Vc2, and when the current flowing to the second battery B2 becomes equal to or lower than the predetermined current Ic2, it determines that the second battery B2 is fully charged and terminates the charging of the second battery B2 (constant current constant voltage charging control).

[0031] Alternatively, the control unit Cntb2 keeps the current flowing to the second battery B2 constant until the voltage of the second battery B2 becomes equal to or higher than a predetermined voltage Vc2, and when the voltage of the second battery B2 becomes equal to or higher than the predetermined voltage Vc2, it determines that the second battery B2 is fully charged and terminates the charging of the second battery B2 (constant current charging control).

[0032] Alternatively, the control unit Cntb2 keeps the current flowing to the second battery B2 constant until the voltage of the second battery B2 becomes equal to or higher than a predetermined voltage Vc2, and when the voltage of the second battery B2 becomes equal to or higher than the predetermined voltage Vc2, gradually reduces the constant current flowing to the second battery B2 each time the voltage of the second battery B2 becomes equal to or higher than the predetermined voltage Vc2, and when the current flowing to the second battery B2 becomes equal to or lower than the predetermined current Ic2, it determines that the second battery B2 is fully charged and terminates the charging of the second battery B2 (multi-stage constant current charging control).

[0033] The control unit Cntb2 also obtains the charging rate of the second battery B2 (the ratio [%] of the remaining capacity to the full charge capacity of the second battery B2). For example, the control unit Cntb2 refers to information indicating the correspondence between the open circuit voltage and the charging rate of the second battery B2, and determines the charging rate corresponding to the open circuit voltage of the second battery B2 measured at a predetermined timing as the charging rate of the second battery B2 at the predetermined timing.

[0034] Furthermore, the control unit Cntb2 resets the charging rate of the second battery B2 by setting the charging rate of the second battery B2, which is the rate at which the second battery B2 is charged until it reaches a fully charged state, to 100[%].

[0035] Control units Cntc1, Cntc2, Cntb1, Cntb2, and a control unit (not shown) that controls the power supply and demand of system P transmit and receive output current instructions, charging state information, and the like to each other via any communication means.

[0036] The first power converter Cnv1 is connected between the system P and the first power storage device St1, and converts three-phase AC power output from the system P into DC power and outputs it to the first power storage device St1 and the second power converter Cnv2. The first power converter Cnv1 also converts DC power output from the first power storage device St1 and the second power converter Cnv2 into three-phase AC power and outputs it to the system P.

[0037] The first power converter Cnv1 includes diodes D1 to D6, capacitors C1 to C3, an inductor L, switching elements S1 to S10, and a transformer T1. The switching elements S1 to S10 are, for example, N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The R-phase of the system P is connected to a connection point between an anode terminal of the diode D1 and a cathode terminal of the diode D2, the S-phase of the system P is connected to a connection point between an anode terminal of the diode D3 and a cathode terminal of the diode D4, and the T-phase of the system P is connected to a connection point between an anode terminal of the diode D5 and a cathode terminal of the diode D6. The cathode terminals of the diodes D1, D3, and D5 are connected to one terminal of the capacitor C1, and the anode terminals of the diodes D2, D4, and D6 are connected to the other terminal of the capacitor C1. One terminal of the capacitor C1 is connected to a connection point between the source terminal of the switching element S1 and the drain terminal of the switching element S2 via the inductor L, and the other terminal of the capacitor C1 is connected to the source terminal of the switching element S2. One terminal of the capacitor C2 is connected to the drain terminals of the switching elements S1, S3, and S5, and the other terminal of the capacitor C2 is connected to the source terminals of the switching elements S2, S4, and S6. A connection point between the source terminal of the switching element S3 and the drain terminal of the switching element S4 is connected to one terminal of the primary coil L11 of the transformer T1, and a connection point between the source terminal of the switching element S5 and the drain terminal of the switching element S6 is connected to the other terminal of the primary coil L11. One terminal of the secondary coil L12 of the transformer T1 is connected to a connection point between the source terminal of the switching element S9 and the drain terminal of the switching element S10, and the other terminal of the secondary coil L12 is connected to a connection point between the source terminal of the switching element S7 and the drain terminal of the switching element S8.In addition, the drain terminals of switching elements S7 and S9 are connected to one terminal of capacitor C3, the positive terminal of the first battery B1, and one terminal of capacitor C4 of the second power converter Cnv2 described later, and the source terminals of switching elements S8 and S10 are connected to the other terminal of capacitor C3, the negative terminal of the first battery B1, and the other terminal of capacitor C4.

[0038] The three-phase AC voltage output from the system P is rectified by a rectifier circuit formed of diodes D1-D6, and converted into a DC voltage by being boosted and smoothed by a boost circuit formed of an inductor L, switching elements S1, S2, and a capacitor C2. The DC voltage is then converted into an AC voltage by switching elements S3-S6 and transmitted from the primary coil L11 to the secondary coil L12 of the transformer T1, rectified by switching elements S7-S10 and smoothed by capacitor C3, and converted into a DC voltage, which is then output to the first power storage device St1 and the second power converter Cnv2.

[0039] Moreover, the DC voltage output from the first power storage device St1 and the second power converter Cnv2 is converted to an AC voltage by the switching elements S7-S10, transmitted from the secondary coil L12 to the primary coil L11 of the transformer T1, rectified by the switching elements S3-S6, and smoothed by the capacitor C2 to be converted back to a DC voltage. The voltage converted to DC is then stepped down in a step-down circuit formed of the inductor L, the switching elements S1, S2, and the capacitor C1, and then converted to a three-phase AC voltage by the diodes D1-D6 and output to the system P.

[0040] The second power converter Cnv2 is connected between the first power converter Cnv1 and the second power storage device St2, and converts the DC power output from the first power converter Cnv1 into a predetermined DC power and outputs it to the second power storage device St2. The second power converter Cnv2 also converts the DC power output from the second power storage device St2 into the predetermined DC power and outputs it to the first power storage device St1 or to the system P via the first power converter Cnv1.

[0041] The second power converter Cnv2 includes capacitors C4 and C5, switching elements S11 to S18, and a transformer T2. The switching elements S11 to S18 are, for example, configured with N-channel MOSFETs. One terminal of the capacitor C4 is connected to the drain terminals of the switching elements S11 and S13, and the other terminal of the capacitor C4 is connected to the source terminals of the switching elements S12 and S14. A connection point between the source terminal of the switching element S11 and the drain terminal of the switching element S12 is connected to one terminal of a primary coil L21 of the transformer T2, and a connection point between the source terminal of the switching element S13 and the drain terminal of the switching element S14 is connected to the other terminal of the primary coil L21. One terminal of a secondary coil L22 of the transformer T2 is connected to a connection point between the source terminal of the switching element S17 and the drain terminal of the switching element S18, and the other terminal of the secondary coil L22 is connected to a connection point between the source terminal of the switching element S15 and the drain terminal of the switching element S16. In addition, the drain terminals of switching elements S15 and S17 are connected to one terminal of capacitor C5 and the positive terminal of the second battery B2, and the source terminals of switching elements S16 and S18 are connected to the other terminal of capacitor C5 and the negative terminal of the second battery B2.

[0042] The control unit Cntc1 is configured with a microcomputer or the like, and controls the operation of the first power converter Cnv1, that is, the on / off of the switching elements S1 to S10.

[0043] When the power output from the system P is supplied to the first power storage device St1 or the second power converter Cnv2 via the first power converter Cnv1, the control unit Cntc1 alternately turns on and off the switching elements S1 and S2 to boost the voltage smoothed by the capacitor C1. The control unit Cntc1 also alternately turns on and off the switching elements S3, S6 and the switching elements S4, S5 to convert the voltage applied to the capacitor C2 into an AC voltage and transmits it from the primary coil L11 to the secondary coil L12 of the transformer T1. The control unit Cntc1 also alternately turns on and off the switching elements S7, S10 and the switching elements S8, S9 to rectify the AC voltage transmitted to the secondary coil L12.

[0044] When the power output from the first power storage device St1 or the second power converter Cnv2 is supplied to the system P via the first power converter Cnv1, the control unit Cntc1 alternately turns on and off the switching elements S7, S10 and the switching elements S8, S9 to convert the DC voltage applied to the capacitor C3 into an AC voltage and transmits the AC voltage from the secondary coil L12 to the primary coil L11 of the transformer T1. The control unit Cntc1 alternately turns on and off the switching elements S3, S6 and the switching elements S4, S5 to rectify the AC voltage transmitted to the primary coil L11. The control unit Cntc1 alternately turns on and off the switching elements S1, S2 to step down the voltage smoothed by the capacitor C2.

[0045] The control unit Cntc2 is configured with a microcomputer or the like, and controls the operation of the second power converter Cnv2, that is, the on / off of the switching elements S11 to S18.

[0046] When the power output from the second storage device St2 is supplied to the first storage device St1 or the first power converter Cnv1 via the second power converter Cnv2, the control unit Cntc2 alternately turns on and off the switching elements S15, S18 and the switching elements S16, S17 to convert the DC voltage applied to the capacitor C5 into an AC voltage and transmits the AC voltage from the secondary coil L22 to the primary coil L21 of the transformer T2. The control unit Cntc2 also alternately turns on and off the switching elements S11, S14 and the switching elements S12, S13 to rectify the AC voltage transmitted to the primary coil L21. In this way, not only the power output from the system P but also the power output from the second storage device St2 can be simultaneously supplied to the first storage device St1, so that a relatively large amount of power can be supplied to the first storage device St1 without adding equipment for increasing the output power on the system P side.

[0047] Furthermore, when power output from the first power storage device St1 or the first power converter Cnv1 is supplied to the second power storage device St2 via the second power converter Cnv2, the control unit Cntc2 converts the DC voltage applied to the capacitor C4 into an AC voltage by alternately and repeatedly turning on and off the switching elements S11, S14 and the switching elements S12, S13, and transmits the AC voltage from the primary coil L21 to the secondary coil L22 of the transformer T2. The control unit Cntc2 also rectifies the AC voltage transmitted to the secondary coil L22 by alternately and repeatedly turning on and off the switching elements S15, S18 and the switching elements S16, S17.

[0048] The control unit Cntc1 also estimates the full charge capacity of the first battery B1 (first power storage device St1) at a predetermined timing. The predetermined timing may be, for example, when the vehicle ignition is turned off. The control unit Cnt1 may also be configured to calculate a ratio of the full charge capacity of the first battery B1 estimated at the predetermined timing to the full charge capacity of the first battery B1 at the time of factory shipment or at the start of use as the deterioration level (SOH (State of Health)) of the first battery B1.

[0049] <First Example> FIG. 2 is a flowchart showing an example of the operation of the control unit Cntc1 in the first embodiment.

[0050] First, in step STP1, the control unit Cntc1 executes a first charging process in which power is supplied from the second storage device St to the first storage device St1 via the second power converter Cnv2 until the first battery B1 is fully charged, and power is supplied from the system P to the first storage device St1 via the first power converter Cnv1.

[0051] Next, in step STP2, the control unit Cntc1 causes power to be supplied from the first storage device St1 to the second storage device St2 via the second power converter Cnv2 at least until the first battery B1 is in a completely discharged state, and executes an estimation process to estimate the integrated value of the current output from the first storage device St1 during the time when the first battery B1 goes from a fully charged state to a completely discharged state as the full charge capacity of the first battery B1. As a result, if the free capacity of the second battery B2 is sufficiently large and the remaining capacity of the first battery B1 can be entirely transferred to the second battery B2, there is no need to return power from the first storage device St1 to the system P. Also, even if the free capacity of the second battery B2 is relatively small, some of the remaining capacity of the first battery B1 can be transferred to the second battery B2, so that the power supplied from the first storage device St1 to the system P can be suppressed.

[0052] Then, in step STP3, the control unit Cntc1 executes a second charging process to supply electric power from the second power storage device St2 to the first power storage device St1 via the second power converter Cnv2 until the first battery B1 is fully charged.

[0053] In this way, in the first embodiment, when the first battery B1 is put into a fully discharged state, the power supplied from the first storage device St1 to the system P can be suppressed, thereby reducing the power wasted when estimating the full charge capacity of the first battery B1.

[0054] FIG. 3 is a flowchart showing an example of the first charging process.

[0055] First, the control unit Cntc1 judges whether the power supply and demand of the system P is tight (step STP101). "The power supply and demand of the system P is tight" means that the power supplied from the system P to the charging device Chg is relatively small because a relatively large amount of power is supplied from the system P to loads other than the charging device Chg. For example, the control unit Cntc1 judges whether the power supply and demand of the system P is tight based on information transmitted from a control unit (not shown) that controls the power supply and demand of the system P.

[0056] Next, when the control unit Cntc1 determines that the power supply and demand of the system P is not tight (step STP101: No), it determines whether or not there is a constraint on the second power storage device St2 side (step STP102). "There is a constraint on the second power storage device St2 side" refers to a state in which the remaining capacity of the second battery B2 is relatively small and the second battery B2 may deteriorate if the power output from the second battery B2 is not limited, or a state in which the temperature of the second battery B2 is relatively low or relatively high and the second battery B2 may deteriorate if the power output from the second battery B2 is not limited.

[0057] Next, when the control unit Cntc1 determines that there is no constraint on the second storage device St2 side (STP102: No), it sets the output current of the first power converter Cnv1 when power is supplied from the first power converter Cnv1 to the first storage device St1 to a constant current I1, and sets the output current of the second power converter Cnv2 when power is supplied from the second power converter Cnv2 to the first storage device St1 to a constant current I2 (step STP103), and proceeds to processing of step STP106.

[0058] In addition, when the control unit Cntc1 determines that the power supply and demand of the system P is tight (step STP101: Yes), it sets the output current of the first power converter Cnv1 when power is supplied from the first power converter Cnv1 to the first power storage device St1 to a constant current I1', and sets the output current of the second power converter Cnv2 when power is supplied from the second power converter Cnv2 to the first power storage device St1 to a constant current I2' (step STP104), and proceeds to the processing of step STP106.

[0059] In addition, when the control unit Cntc1 determines that there is a constraint on the second storage device St2 side (step STP102: Yes), it sets the output current of the first power converter Cnv1 when power is supplied from the first power converter Cnv1 to the first storage device St1 to a constant current I1'', and sets the output current of the second power converter Cnv2 when power is supplied from the second power converter Cnv2 to the first storage device St1 to a constant current I2'' (step STP105), and proceeds to processing of step STP106.

[0060] Here, constant current I1″>constant current I1>constant current I1′, and constant current I2″<constant current I2<constant current I2′. Also, constant current I1′ or constant current I2″ may be zero. As a result, when the power supply and demand of the system P is tight, the output current of the second power converter Cnv2 can be increased while the output current of the first power converter Cnv1 is decreased, compared to when the power supply and demand of the system P is not tight. Therefore, even when the power supply and demand of the system P is tight during the execution of the first charging process, a decrease in the current flowing to the first power storage device St1 can be suppressed, so that an increase in the time required for the estimation process can be suppressed. Also, when there is a constraint on the second power storage device St2 side, it is possible to increase the output current of the first power converter Cnv1 while decreasing the output current of the second power converter Cnv2, compared to when there is no constraint on the second power storage device St2 side. Therefore, even if there is a constraint on the second power storage device St2 side when the first charging process is performed, it is possible to suppress a decrease in the current flowing to the first power storage device St1 and to suppress deterioration of the second battery B2.

[0061] Next, if the free capacity of the second battery B2 is equal to or greater than the full charge capacity of the first battery B1 estimated at the previous predetermined timing (step STP106: Yes), the control unit Cntc1 proceeds to the process of step STP107. The "full charge capacity of the first battery B1" is defined as an integrated value of the current flowing through the first battery B1 until the first battery B1 goes from a fully charged state to a fully discharged state. Moreover, the "free capacity of the second battery B2" is defined as the full charge capacity of the second power storage device St2 minus the remaining capacity of the second power storage device St2. For example, if the free capacity of the second battery B2 is equal to or greater than the full charge capacity of the first battery B1 estimated at the previous predetermined timing, all the remaining capacity of the first battery B1 can be transferred to the second battery B2 when the first battery B1 goes from a fully charged state to a fully discharged state.

[0062] Furthermore, in step STP107, the control unit Cntc1 starts power supply from the system P and the second power storage device St2 to the first power storage device St1. For example, when power is supplied to the first power storage device St1, the control unit Cntc1 controls the operation of the first power converter Cnv1 so that the current output from the first power converter Cnv1 becomes a constant current I1, a constant current I1', or a constant current I1", and instructs the control unit Cntc2 to cause the current output from the second power converter Cnv2 to become a constant current I2, a constant current I2', or a constant current I2".

[0063] Next, the control unit Cntc1 judges whether the first battery B1 has reached a fully charged state (step STP108). For example, when the control unit Cntc1 receives information indicating that the first battery B1 has reached a fully charged state, which is transmitted from the control unit Cntb1, the control unit Cntc1 judges that the first battery B1 has reached a fully charged state.

[0064] Next, when the control unit Cntc1 determines that the first battery B1 has reached a fully charged state (step STP108: Yes), it stops the power supply from the system P and the second power storage device St2 to the first power storage device St1 (step STP109) and ends the first charging process at the current predetermined timing. For example, the control unit Cntc1 stops the power supply to the first battery B1 by stopping the first power converter Cnv1 and the second power converter Cnv2.

[0065] Furthermore, when the available capacity of the second battery B2 is smaller than the full charge capacity of the first battery B1 estimated at the previous predetermined timing (step STP106: No), the control unit Cntc1 starts only the power supply from the second power storage device St2 to the first power storage device St1 (step STP110). For example, the control unit Cntc1 instructs the control unit Cntc2 to make the current output from the second power converter Cnv2 constant current I2, constant current I2', or constant current I2" when power is supplied to the first power storage device St1. In this way, by only supplying power from the second power storage device St2 to the first power storage device St1, the available capacity of the second battery B2 can be made to approach the full charge capacity of the first battery B1 estimated at the previous predetermined timing.

[0066] Next, when the control unit Cntc1 determines that the second battery B2 has entered a completely discharged state (step STP111: Yes), it stops the power supply from the second power storage device St2 to the first power storage device St1 (step S112), and then starts the power supply from the system P to the first power storage device St1 (step S113). For example, when the control unit Cntc1 receives information that the second battery B2 has entered a completely discharged state, which is transmitted from the control unit Cntb2, via the control unit Cntc2, it determines that the second battery B2 has entered a completely discharged state.

[0067] Next, when the control unit Cntc1 determines that the first battery B1 has reached a fully charged state (step STP114: Yes), it stops the power supply from the system P to the first storage device St1 (step STP115) and ends the first charging process at the current specified timing.

[0068] On the other hand, when the control unit Cntc1 determines that the first battery B1 has reached a fully charged state (step STP116: Yes), it stops the power supply from the second storage device St2 to the first storage device St1 (step S117) and ends the first charging process at the current specified timing.

[0069] FIG. 4 is a flowchart showing an example of the estimation process.

[0070] First, the control unit Cntc1 judges whether the remaining capacity of the first battery B1 in the fully charged state can be entirely supplied to the second battery B2 (step STP201). For example, the control unit Cntc1 first receives information indicating the remaining capacity Ch1 of the first battery B1 transmitted from the control unit Cntb1, and also receives information indicating the free capacity Ch2 of the second battery B2 transmitted from the control unit Cntb2 via the control unit Cntc2. If the free capacity Ch2 is equal to or greater than the remaining capacity Ch1, the control unit Cntc1 judges that the remaining capacity of the first battery B1 in the fully charged state can be entirely supplied to the second battery B2, and if the free capacity Ch2 is less than the remaining capacity Ch1, the control unit Cntc1 judges that the remaining capacity of the first battery B1 in the fully charged state cannot be entirely supplied to the second battery B2.

[0071] Next, when the control unit Cntc1 determines that the remaining capacity of the fully charged first battery B1 can be fully supplied to the second battery B2 (step STP201: Yes), it starts the supply of power from the first storage device St1 to the second storage device St2 (step STP202).

[0072] Next, when the control unit Cntc1 determines that the first battery B1 has reached a fully discharged state (step STP203: Yes), it stops the power supply from the first storage device St1 to the second storage device St2 (step STP204), estimates the integrated value of the current output from the first storage device St1 during the period when the first battery B1 goes from a fully charged state to a fully discharged state as the full charge capacity of the first battery B1 at the current predetermined timing (step STP205), and ends the estimation process at the current predetermined timing. For example, the control unit Cntc1 calculates the integrated value of the current output from the first storage device St1 during the period when the first battery B1 goes from a fully charged state to a fully discharged state, using information indicating the output current of the first battery B1 transmitted from the control unit Cntb1.

[0073] On the other hand, when the control unit Cntc1 determines that the remaining capacity of the fully charged first battery B1 cannot be supplied entirely to the second battery B2 (step STP201: No), it starts the supply of power from the first storage device St1 to the second storage device St2 (step STP206).

[0074] Next, when the control unit Cntc1 determines that the second battery B2 has reached a fully charged state (step STP207: Yes), it stops the power supply from the first power storage device St1 to the second power storage device St2 (step STP208).

[0075] Next, the control unit Cntc1 stops the power supply from the first power storage device St1 to the second power storage device St2, and then starts the power supply from the first power storage device St1 to the system P (step STP209).

[0076] Then, when the control unit Cntc1 determines that the first battery B1 has reached a fully discharged state (step STP210: Yes), it stops the supply of power from the first storage device St1 to the system P (step STP211), estimates the integrated value of the current output from the first storage device St1 from the fully charged state to the time when the first battery B1 reaches a fully discharged state as the full charge capacity of the first battery B1 at the current specified timing (step STP212), and terminates the estimation process at the current specified timing.

[0077] FIG. 5 is a flowchart showing an example of the second charging process.

[0078] First, the control unit Cntc1 starts the power supply from the second power storage device St2 to the first power storage device St1 (step STP301).

[0079] Next, when the control unit Cntc1 determines that the first battery B1 has reached a fully charged state (step STP302: Yes), it stops the power supply from the second power storage device St2 to the first power storage device St1 (step STP303) and ends the second charging process at the current predetermined timing. Note that, if the deterioration level of the first battery B1 can be estimated by the first charging process and the estimation process, the first battery B1 does not necessarily need to be fully charged in the second charging process, and may be charged, for example, to a charging rate of 80%. It is preferable that the configuration be such that whether the first battery B1 is fully charged or the charging rate is 80% can be set arbitrarily in advance.

[0080] In this way, the capacity transferred from the first battery B1 to the second battery B2 in the estimation process is used to charge the first battery B1 in the second charging process, so that unnecessary power is not drawn from the system P in the second charging process.

[0081] In addition, since the estimation process estimates the full charge capacity of the first battery B1, and then the second charging process brings the first battery B1 into a fully charged state, the vehicle can be driven using the first battery B1 in a fully charged state immediately after the full charge capacity of the first battery B1 is estimated.

[0082] In addition, for the purpose of estimating the next full charge capacity of the first battery B1, the control unit Cntc1 may be configured to charge the second battery B2 so that it has a certain amount of free capacity rather than bringing the second battery B2 to a fully charged state after executing the second charging process.

[0083] <Second Example> Fig. 6 is a flow chart showing an example of the operation of the control unit Cntc1 in the second embodiment. Note that a description of the same operations as those shown in Fig. 2 will be omitted.

[0084] First, at a predetermined timing, the control unit Cntc1 waits until the charging rate of the second battery B2 becomes below a threshold value (step STP1': No), and when it determines that the charging rate of the second battery B2 has become below the threshold value (step STP1': Yes), it executes the first charging process, the estimation process, and the second charging process (steps STP1 to STP3).

[0085] Next, the control unit Cntc1 executes a reset process to reset the charging rate of the second battery B2 (step STP4).

[0086] In this way, in the second embodiment, the charging rate of the second battery B2 is reset by the reset process, so that the accuracy of estimating the full charge capacity of the first battery B1 can be improved when estimating the full charge capacity at a specified timing from the next time onwards.

[0087] FIG. 7 is a flowchart showing an example of the reset process.

[0088] First, the control unit Cntc1 starts the power supply from the system P to the second power storage device St2 (step STP401).

[0089] Next, the control unit Cntc1 judges whether the second battery B2 has reached a fully charged state (step STP402). For example, when the control unit Cntc1 receives, via the control unit Cntc2, information indicating that the second battery B2 has reached a fully charged state, which is transmitted from the control unit Cntb2, the control unit Cntc1 judges that the second battery B2 has reached a fully charged state.

[0090] Then, when the control unit Cntc1 determines that the second battery B2 has reached a fully charged state (step STP402: Yes), it stops the power supply from the system P to the second power storage device St2 (step STP403) and resets the charging rate of the second battery B2 (step STP403). For example, the control unit Cntb2 corrects the open circuit voltage of the second battery B2 when it is determined that the second battery B2 has reached a fully charged state to an open circuit voltage corresponding to a charging rate of 100[%] in the information indicating the correspondence relationship between the open circuit voltage and the charging rate of the second battery B2.

[0091] 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.

[0092] <Modification> In the above first and second embodiments, the control unit Cntc1 mainly controls the operation of the first power converter Cnv1 and the second power converter Cnv2 to estimate the full charge capacity of the first battery B1, but the control unit Cntc2 may mainly control the operation of the first power converter Cnv1 and the second power converter Cnv2 to estimate the full charge capacity of the first battery B1. [Explanation of symbols]

[0093] Chg charging device St1 First power storage device St2 2nd power storage device Cnv1 First power converter Cnv2 Second power converter Cntc1, Cntc2 control section P lineage

Claims

1. a first power converter connected between the grid and the first power storage device; a second power converter connected between the first power converter and a second power storage device; A control unit that controls operations of the first and second power converters; Equipped with When estimating a full charge capacity of a first battery included in the first power storage device, the control unit: executing a first charging process in which power is supplied from the grid to the first power storage device via the first power converter and power is supplied from the second power storage device to the first power storage device via the second power converter until the first battery is fully charged; executing an estimation process for supplying power from at least the first power storage device to the second power storage device via the second power converter until the first battery reaches a completely discharged state, and estimating, as a full charge capacity of the first battery, an integrated value of a current output from the first power storage device during a period when the first power storage device goes from a fully charged state to a completely discharged state; A second charging process is executed to supply electric power from the second power storage device to the first power storage device via the second power converter and recharge the first battery. A charging device characterized by:

2. The charging device according to claim 1, When the first charging process is performed, if the power supply and demand of the grid is tight, the control unit reduces the power supplied from the grid to the first power storage device and increases the power supplied from the second power storage device to the first power storage device, compared to when the power supply and demand of the grid is not tight. A charging device characterized by:

3. The charging device according to claim 1 or 2, When the remaining capacity of the first battery is greater than the available capacity of a second battery provided in the second power storage device during execution of the estimation process, the control unit controls the first power storage device to supply power to the second power storage device via the second power converter until the second battery is in a fully charged state, and then controls the first power storage device to supply power to the grid via the first power converter until the first battery is in a completely discharged state. A charging device characterized by:

4. The charging device according to any one of claims 1 to 3, After the second charging process is performed, the control unit resets the charging rate of the second battery by charging the second battery included in the second power storage device until the second battery is fully charged. A charging device characterized by:

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