Charge / discharge inspection system for secondary battery

Abstract

To provide a charge / discharge inspection system for cells that eliminates requirements for inverters and matching circuits during discharge regeneration, thereby reducing costs and easily increasing regeneration efficiency with a simple configuration.SOLUTION: A system includes: an AC / DC power supply circuit that is connected to an AC system and outputs DC power via a DC bus; a plurality of charging / discharging units connected in parallel to the DC bus to perform charge / discharge on each cell; and a surplus power regeneration circuit that consists of a capacitor and a switch and is connected to the DC bus, wherein the cells are charged via the charging / discharging units by the DC power from the AC / DC power supply circuit in a charging cycle, and the cells are discharged via the charging / discharging units and the switch is turned on to charge the capacitor by a discharge current in a discharging cycle.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a charge / discharge inspection system for secondary batteries (cells) such as lithium-ion batteries and lithium iron phosphate batteries (LiFePO4), and in particular to a charge / discharge inspection system for secondary batteries that can significantly reduce power consumption by efficiently performing cell charge / discharge inspections through the optimization of a DC (direct current) regenerative charge / discharge power supply and inspection sequence.

[0002] In the charge / discharge inspection process for secondary batteries (hereinafter referred to as "cells") such as lithium-ion batteries, cells are repeatedly charged and discharged in various patterns depending on the inspection item, but to improve productivity, it is common to inspect multiple cells at once.The mechanism for setting multiple cells in the inspection unit and inspecting them simultaneously is called a "magazine," and the same inspection is performed on multiple cells housed in the magazine at the same time, and the inspection system as a whole is capable of inspecting multiple magazines simultaneously.

[0003] In the actual process, produced cells are placed in magazines and transported to the inspection location (inspection unit) on a conveyor or other device, resulting in an inspection sequence in which multiple magazines are inspected in parallel with a time lag. Depending on the inspection sequence, magazines may be operating differently (charging or discharging) at the same time, such as one magazine discharging while another is charging. By actively utilizing this, we can design an inspection sequence that minimizes the differences in magazine operation, and under these conditions, we can design an efficient inspection system that inputs the discharge current of a magazine being discharged into a magazine being charged. This is the gist of this invention, and we propose a system design for achieving this. [Background technology]

[0004] Charging and discharging tests are performed as a step or final step in battery production to automatically inspect the quality and characteristics of cells or cells housed in a magazine. Only cells with good quality and appropriate characteristics are shipped as products. Figure 1 shows a schematic diagram of a conventional charging and discharging test. Magazines MG1-MG3 are connected to a charging and discharging power supply 10 controlled by a control system 20, which is connected to an AC (alternating current) system. As shown in Figure 2, constant current (CC) / constant voltage (CV) chargers 12-1-12-3 are connected to magazines MG1-MG3 via a regenerative AC / DC power supply circuit 11 of the charging and discharging power supply 10. The CC / CV chargers 12-1-12-3, controlled by the control system 20, switch between charging and discharging to inspect the cells. In this example, three cells (C1-C3) are housed in a magazine, but any number of cells can be used.

[0005] Although three magazines MG1 to MG3 are shown in Fig. 1, the number of magazines may be any appropriate number. CC / CV chargers 12-1 to 12-3 shown in Fig. 2 may be provided inside or outside the magazines MG1 to MG3.

[0006] In this configuration, an example of the operation of the charge / discharge inspection will be described with reference to the flowchart of FIG.

[0007] First, in a charging cycle, control system 20 instructs CC / CV chargers 12-1 to 12-3 to output a constant current, which causes charge / discharge power supply 10 to obtain DC from the AC system using regenerative AC / DC power supply circuit 11, and charges cells C1 to C3 in magazines MG1 to MG3 with this DC current (step S1). During the charging period, control system 20 measures the terminal voltage of the magazine (cell) using a voltmeter and measures the charging current value via charge / discharge power supply 10 (step S2). Control system 20 continues the charging until the rated voltage is measured by the voltmeter (step S3), and stops charging when the measured voltage reaches the rated voltage (step S4).

[0008] Next, the control system 20 moves to the discharge cycle, in which it instructs the CC / CV chargers 12-1 to 12-3 to output a constant current, and discharges each of the cells C1 to C3 in the magazines MG1 to MG3 according to the flow of the dashed lines as shown in Fig. 5 (step S5). During the discharge period, the control system 20 measures the terminal voltage of the magazine (cell) using a voltage meter and measures the discharge current value via the charge / discharge power supply 10 (step S6). The control system 20 continues the discharge until the cut-off voltage is measured by the voltage meter (step S7), and stops the discharge when the measured terminal voltage reaches the cut-off voltage (step S8).

[0009] The cells (C1 to C3) housed in the magazine are inspected through such charge and discharge cycles. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] WO2012 / 093652 [Patent Document 2] Patent No. 6850935 [Patent Document 3] Japanese Patent Publication No. 2022-53841 Summary of the Invention [Problem to be solved by the invention]

[0011] In the conventional charge / discharge test described above, during the charge cycle, current flows as shown by the dashed lines in Figure 4 to charge each cell C1 to C3, and charging is stopped when the rated voltage is reached. However, since the entire charging current during the charge cycle is supplied from the AC system, the power consumption of the entire system is large.

[0012] During the discharge cycle, a discharge current flows as shown by the dashed lines in Figure 5, discharging each cell C1-C3. When the voltage of each cell C1-C3 drops to a specified level, the CC / CV chargers 12-1-12-3 stop discharging. The discharge current returned to the AC / DC power supply circuit 11 is then returned to the AC system (AC regeneration). However, if the power consumption of an external device connected to the AC system is low, the discharge current with nowhere to go can raise the AC system voltage, potentially resulting in overvoltage and malfunction. Additionally, AC regeneration requires an inverter to convert the DC discharge current to AC and a matching circuit to match the phase and voltage and reverse the current back to the AC system. This requires costs for the inverter and matching circuit, and power losses in the inverter and matching circuit reduce regeneration efficiency. Another issue is that multi-channel AC / DC power supply circuits with regeneration functionality are expensive compared to conventional AC / DC power supply circuits.

[0013] The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a secondary battery charge / discharge inspection system that eliminates the need for an inverter or matching circuit during discharge regeneration, thereby reducing costs and easily improving regeneration efficiency and power saving effects with a simple configuration. [Means for solving the problem]

[0014] The present invention relates to a system that inspects the charging and discharging of a plurality of secondary batteries stored in a magazine in accordance with an inspection sequence, and the above-mentioned object of the present invention is achieved by comprising: an AC / DC power supply circuit connected to an AC system and outputting DC power via a DC bus; a plurality of chargers and dischargers composed of chargers and dischargers for charging and discharging the secondary batteries, connected in parallel to the DC bus; and a surplus power regeneration circuit composed of a capacitor and switch means and connected to the DC bus, wherein in the charge cycle of the inspection sequence, the secondary batteries are charged via the charger and discharger with the DC power from the AC / DC power supply circuit, and in the discharge cycle of the inspection sequence, the secondary batteries are discharged via the charger and discharger, and the switch means is turned ON to charge the capacitor with the discharge current from the secondary batteries. [Effects of the Invention]

[0015] The charge / discharge inspection system of the present invention replaces the conventional AC regeneration function with a DC regeneration function, eliminating the need for an inverter or matching circuit, significantly reducing overall system costs and simplifying the configuration. Furthermore, the discharge current of the cells during the discharge cycle is used to charge the cells during the charge cycle, and the excess discharge current is stored in a capacitor and used as charging current for the cells during the charging operation, or regenerated to the AC grid as needed. This reduces power consumption by up to 70% compared to conventional systems. This reduction in power consumption reduces CO2 emissions and contributes to national policies aimed at achieving carbon neutrality.

[0016] For example, in a cell manufacturing process with a production capacity of 10,000 cells per day, the actual daily power loss consumed in charge / discharge testing is approximately 4 kWh / day. If the electricity rate per kWh is assumed to be 25 yen, the electricity bill would be 4,000 x 25 yen = 100,000 yen. If operated 365 days a year, this would amount to 36,500,000 yen, and over 10 years it would be 365,000,000 yen. If we could reduce this by 70%, it would result in a savings of 255,500,000 yen. From the perspective of the SDGs (Sustainable Development Goals), these reductions would also significantly reduce CO2 emissions. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of a conventional charge / discharge inspection system. [Figure 2] 10 is a flowchart showing an example of the operation of a conventional charge / discharge inspection process. [Figure 3] FIG. 1 is a block diagram showing an example of the configuration of a conventional charge / discharge inspection system. [Figure 4] FIG. 10 is a block diagram showing an example of operation (charging) of a conventional charge / discharge inspection system. [Figure 5] FIG. 10 is a block diagram showing an example of operation (discharging) of a conventional charge / discharge inspection system. [Figure 6] 1 is a schematic diagram showing an example of the overall configuration of the present invention; [Figure 7] 1 is a block diagram showing an example of the configuration of a magazine according to the present invention; [Figure 8] FIG. 2 is a block diagram showing a configuration example of a charger / discharger. [Figure 9] FIG. 10 is a wiring diagram showing an example of connection of a plurality of magazines. [Figure 10] 4 is a flowchart showing an example of the operation of the present invention and the surplus power regeneration circuit. [Figure 11] FIG. 10 is a wiring diagram showing another example of the configuration of the surplus power regeneration circuit (dissipation type). [Figure 12] FIG. 10 is a wiring diagram showing another example of the configuration of the surplus power regeneration circuit (regeneration type). [Figure 13] 10 is a time chart showing an example of an optimum sequence. [Figure 14] FIG. 2 is a path diagram illustrating a charging cycle of the present invention. [Figure 15] FIG. 2 is a path diagram illustrating a discharge cycle of the present invention. [Figure 16] FIG. 2 is a path diagram illustrating a charging cycle of the present invention. [Figure 17] FIG. 10 is a block diagram showing an example of a system configuration for making the number of magazines for the charge cycle and the number of magazines for the discharge cycle equal to each other. [Figure 18] FIG. 1 is a characteristic diagram showing power losses in conventional AC regeneration and DC regeneration according to the present invention. [Figure 19] FIG. 10 is a characteristic diagram showing power losses in DC regeneration and AC regeneration in the case of optimization. DETAILED DESCRIPTION OF THE INVENTION

[0018] This invention is a cell charge / discharge inspection system for inspecting the quality and characteristics of secondary batteries (cells) such as lithium-ion batteries and lithium iron phosphate batteries (LiFePO4). It does not require an inverter or matching circuit during regeneration, and by optimizing the circuit configuration and inspection sequence of a DC regenerative charge / discharge power supply, it efficiently and economically inspects cells (including cells in magazines), enabling a significant reduction in power consumption. Because the AC regeneration function is replaced with a DC regeneration function, there is no need for an inverter or matching circuit, which has the advantages of a simple configuration and reduced equipment and inspection costs.

[0019] Although cell discharge results in DC power, the present invention allows the cell discharge power to be regenerated as DC. As mentioned above, conventional systems use an AC regeneration method in which all DC discharge power is converted to AC by an inverter and then regenerated into the AC system after matching the phase, etc., resulting in many problems. In contrast, the DC regeneration method of the present invention solves all of these problems, enabling inspection with a simple configuration and significantly reduced power consumption. Furthermore, by optimizing the inspection sequence, more effective operation can be achieved.

[0020] To prevent the waste of regenerative power, power is regenerated from the AC / DC power supply circuit to the AC system only when the charging capacitor is fully charged.In addition, sequence control is also performed to determine the order in which magazines are transported and inserted, so that the number of magazines in the charging cycle in the inspection section matches the number of magazines in the discharging cycle, and inspections can be carried out effectively while saving energy.

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] Figure 6 shows a schematic overview of the present invention in correspondence with Figure 1, and the entire system is controlled by a control system 110 configured with a computer or the like, and magazines MG1 to MG3 are connected to a charge / discharge power supply 100 connected to an AC system, and a surplus power regeneration circuit 120 is also connected to it. In this example, for convenience, three magazines MG1 to MG3 are shown, but the number of magazines is arbitrary.

[0023] The internal configuration of a magazine of the present invention, for example magazine MG1, is as shown in Figure 7, but in an actual system, the AC / DC power supply circuit 101 and surplus power regeneration circuit 120 may be installed outside the magazine as shown in Figure 6, but for convenience, we will explain here the case where they are installed inside the magazine. Also, magazines MG1 to MG3 have the same configuration, but the number of cells they accommodate may differ from magazine to magazine.

[0024] The cells C1 to C3 to be inspected are housed in a magazine, and chargers / dischargers 111 to 113 are connected to the cells C1 to C3, respectively. The chargers / dischargers 111 to 113 are connected in parallel via a DC bus (+) and a DC bus (-) to an AC / DC power supply circuit 101 that converts AC power into DC power and supplies the DC power. The chargers / dischargers 111 to 113 all have the same configuration, and each has the function of charging or discharging the cells C1 to C3 under the control of a control system 110. The chargers / dischargers 111 to 113 all have the same configuration, and an example configuration of the charger / discharger 111 is shown in FIG. 8. That is, a changeover switch SW111-1 having contacts a11 and b11, a charger 111-2, and a changeover switch SW111-2 having contacts a12 and b12 are connected in series to the DC bus (+). In addition, a booster 111-3 and a discharger 111-4 are connected in series between a contact b11 of the changeover switch SW111-1 and a contact b12 of the changeover switch SW111-2. The contacts a11 and b11 of the changeover switch SW111-1 and the contacts a12 and b12 of the changeover switch SW111-2 are both switched by the control system 110.

[0025] In addition, a surplus power regeneration circuit 120 is connected between the DC bus (+) and the DC bus (-). As shown in FIG. 7, the surplus power regeneration circuit 120 is composed of two ON / OFF switches SW1 and SW2 connected in parallel to the DC bus (+), a large-capacity capacitor C connected between the ON / OFF switch SW1 and the DC bus (-), and a booster 121 connected between the ON / OFF switches SW1, SW2 and the DC bus (-).

[0026] As shown in FIG. 9, other magazines may be connected to the DC bus (+) and DC bus (-), and each magazine is configured to receive AC power from a common AC system. Any number of magazines may be connected. Discharge current is exchanged between magazines via the DC bus (+) and DC bus (-). That is, the discharge current flows from a magazine in a discharge cycle to a magazine in a charge cycle via the DC bus.

[0027] In this configuration, if the first step in the magazine inspection sequence is a charge cycle, the contact of the changeover switch SW111-1 of the charger / dischargers 111-113 is connected to "a11," and the contact of the changeover switch SW111-2 is connected to "a12," and cell C1 is charged by the output of the AC / DC power supply circuit 101 and the charger 111-2, and the charging characteristics at that time are inspected. Similar charging inspections are also performed on cells C2 and C3 by the charger / dischargers 112 and 113.

[0028] If the next test sequence is a magazine discharge cycle, the contact of the changeover switch SW111-1 is switched to contact b11 and the contact of the changeover switch SW111-2 is switched to contact b12, and cell C1 is discharged via the booster 111-3 and the discharger 111-4, and the discharge characteristics at that time are inspected. Similar discharge inspections are performed on cells C2 and C3 by the charger / dischargers 112 and 113.

[0029] During discharge, the destination of the discharge current is another external magazine, via the commonly connected DC bus (+) and DC bus (-). As shown in FIG. 9, all magazines are connected by two DC buses, and the discharge current flows via the DC buses from a magazine in a discharge cycle to another magazine in a charge cycle, where it is consumed (regenerated). In the present invention, a circuit configuration is used to charge a cell by giving priority to the cell's discharge current over the output of the AC / DC power supply circuit 101, and charging is performed using the output of the AC / DC power supply circuit 101 only when the cell's discharge current is insufficient. This makes it possible to reduce the power consumption of the AC / DC power supply circuit 101.

[0030] The ideal test sequence for performing DC regeneration according to the present invention is to have half of all magazines in the discharge cycle and the other half in the charge cycle at the same time. In other words, ideally, the number of magazines in the discharge cycle (hereinafter simply referred to as the "number of discharging magazines") should be the same as the number of magazines in the charge cycle (hereinafter simply referred to as the "number of charging magazines"). In this case, power can be effectively regenerated by charging the discharged power of all discharging magazines (cells) to other charging magazines (cells), so no special mechanism or circuit is required other than the common DC bus. This mechanism will be described later.

[0031] However, in reality, various conditions are involved in the inspection sequence, and situations may arise in which the number of discharging magazines exceeds the number of charging magazines, or in which the number of charging magazines exceeds the number of discharging magazines. When the number of charging magazines exceeds the number of discharging magazines, the total power required for charging cannot be covered by the discharge power from the other discharging magazines alone, so the shortfall is made up by the output of the AC / DC power supply circuit 101. On the other hand, when the number of discharging magazines exceeds the number of charging magazines, the discharge power of the discharging magazine in question exceeds the total power required for charging by the other charging magazines. Therefore, if the surplus discharge power is not consumed, the discharge current that has nowhere to go will raise the voltage on the DC bus, which could lead to malfunctions or failures due to overvoltage.

[0032] For this reason, the present invention provides a surplus power regeneration circuit 120 as shown in Fig. 7. The ON / OFF switches SW1 and SW2 of the surplus power regeneration circuit 120 may be relays or FETs (Field Effect Transistors), and the capacitor C may be any large-capacity capacitor, such as a LIC (Lithium Ion Capacitor) or an EDLC (Electric Double-Layer Capacitor).

[0033] An example of the operation of the present invention, including an example of the operation of the surplus power regeneration circuit 120, will be described with reference to the flowchart of FIG.

[0034] First, the control system 110 determines whether the number of discharging magazines is the same as the number of charging magazines (step S10). If they are the same, the ON / OFF switches SW1 and SW2 of the surplus power regeneration circuit 120 are both turned OFF, and the discharging and charging described above are carried out efficiently (step S11). In other words, the discharging current from each cell in the discharging magazine is transmitted through each cell in the charging magazine. At this time, there is no output from the AC / DC power supply circuit 101.

[0035] If it is determined in step S10 that the numbers are not the same, it is then determined whether the number of discharging magazines is greater than the number of charging magazines (step S20), and if the number of discharging magazines is greater than the number of charging magazines, ON / OFF switch SW1 is turned ON and ON / OFF switch SW2 is turned OFF (step S21), and the surplus power is charged to capacitor C of surplus power regeneration circuit 120 (step S22). This charging continues until it is determined that the number of charging magazines is the same as or greater than the number of discharging magazines (step S23).

[0036] On the other hand, if it is determined in step S23 that the number of magazines being charged is equal to or greater than the number of magazines being discharged, it is then determined whether the number of magazines being charged is equal to the number of magazines being discharged (step S24). If they are equal, the process skips to step S11. If they are not equal, that is, if the number of magazines being charged is greater than the number of magazines being discharged, the ON / OFF switch SW1 is turned OFF and the ON / OFF switch SW2 is turned ON (step S30), and the power stored in capacitor C is discharged to the DC bus (step S31). As the discharge progresses, the voltage of capacitor C decreases. Therefore, in order to use up the power stored in capacitor C, a booster 121 is connected to capacitor C, and the stored power is discharged to the DC bus via the booster 121. The voltage of booster 121 is set slightly higher than the output voltage of AC / DC power supply circuit 101, and when charging the cells, the discharge output of surplus power regeneration circuit 120 is used via booster 121 preferentially over the output of AC / DC power supply circuit 101 (step S32) to charge the cells (step S33). Only when the discharge output of surplus power regeneration circuit 120 is insufficient (step S34), is the output of AC / DC power supply circuit 101 used (step S35), and the cells are charged by the output of AC / DC power supply circuit 101 (step S36).

[0037] In this way, the surplus power regeneration circuit 120 is a circuit that suppresses voltage increases on the DC bus, charges (stores) surplus discharge power in capacitor C, and reuses (regenerates) the charged power. Therefore, if it is sufficient to simply suppress voltage increases on the DC bus and there is no need to reuse surplus discharge power, a consumption-type circuit as shown in FIG. 11 can be used, with the ON / OFF switch SW2 and booster 121 removed from the configuration of FIG. 7 and capacitor C replaced with resistor R. The operation of this surplus power regeneration circuit 120A is simple; when the number of discharging magazines exceeds the number of charging magazines, the ON / OFF switch SW1 is turned ON and the surplus power is simply consumed as heat by resistor R.

[0038] The resistor R can be any element that can convert electricity into other energy such as heat, light, or motion.

[0039] In the consumption-type system shown in FIG. 11, excess power is simply consumed, resulting in wasted energy. Therefore, a regeneration-type system as shown in FIG. 12 may also be used. In this example, instead of immediately regenerating power when the number of discharging magazines exceeds the number of charging magazines, charging of capacitor C begins as described above when the number of discharging magazines exceeds the number of charging magazines. A full-charge detection unit 122 is provided to detect when the capacitor C is fully charged. When the full-charge detection unit 122 detects that capacitor C is fully charged, a full-charge detection signal FC is output. The full-charge detection signal FC is input to the control system 110 and the AC / DC power supply circuit 101. When the full-charge detection signal FC is input to the control system 110, the control system 110 turns off the ON / OFF switch SW1, and the AC / DC power supply circuit 101 converts excess DC power to AC and regenerates it into the AC system, thereby reducing unnecessary power consumption.

[0040] In this example, an inverter and a matching circuit are required to regenerate surplus power to the AC system, but the benefit of the power saving effect achieved by power regeneration is greater than wasting the surplus power.

[0041] Next, an example of an inspection sequence optimized for the DC regeneration method of the present invention will be described with reference to FIG. 13. For ease of explanation, the inspection process for one magazine is considered to be one set of "charge → discharge." When inspection of one magazine is completed, the next magazine is immediately set on the same line, and inspection is carried out continuously without interruption. For each of magazines MG1 to MG3, the order of magazines arriving on the same line is indicated by diagonal lines or the like. To optimize the inspection sequence, inspection of magazine MG1 starts (time T1), while inspection of magazine MG2 starts at time T2 and inspection of magazine MG3 starts at time T3. The charging and discharging operations at each of times T1 to T7 are as follows:

[0042] At time T1, magazine MG1 is charged by AC / DC power supply circuit 101. At time T2, magazine MG2 is charged with the discharge power of magazine MG1. At time T3, there are two charging magazines and one discharging magazine, so there is insufficient discharge power, and the shortage is made up for by the output of AC / DC power supply circuit 101. At time T4, there is one charging magazine and two discharging magazines, so there is surplus discharge power, and the surplus is charged to capacitor C. At time T5, there are two charging magazines and one discharging magazine, so there is insufficient discharge power, and the surplus is charged to capacitor C. At time T6, there is one charging magazine and two discharging magazines, so there is surplus discharge power, and the surplus is charged to capacitor C. At time T7, there are two charging magazines and one discharging magazine, so there is insufficient discharge power, and the surplus is charged to capacitor C. As a result, power saving effects are achieved at times T2, T3, T5, and T7. The actual sequence will be more complicated than the example in Figure 12, but in either case, the test sequence will be optimized by combining the operation order of each magazine so as to minimize the number of times the cells are charged by the AC / DC power supply circuit 101.

[0043] During the first charging cycle of the test sequence, as shown in FIG. 14, the selector switches SW of the chargers 111-113 are all connected to the upper contacts a11 and a12, contacts a21 and a22, and contacts a31 and a32, and each charger is activated. Charging current flows from the AC / DC power supply circuit 101 as shown by the dashed lines in FIG. 13, and each cell C1-C3 is CC / DC charged. When each cell reaches its rated voltage, each charger stops charging. At this time, all charging current is supplied from the AC system via the AC / DC power supply circuit 101, so power consumption is equivalent to that of the AC regeneration system. However, with the DC regeneration system of the present invention, the power supply line is shared with multiple magazines as shown in FIG. 9, so the AC / DC power supply circuit 101 only needs a single output (1 channel), which has the advantage of reducing costs.

[0044] Next, referring to FIG. 15, the discharge cycle will be described. In this discharge cycle, all of the switches SW are connected to the lower contacts b11 and b12, contacts b21 and b22, and contacts b31 and b32, and the dischargers and boosters in each charger / discharger are activated. Discharge current flows from each cell C1 to C3 as indicated by the dashed lines in FIG. 15, and each cell C1 to C3 is discharged via CC / CV. Because the cell voltage is generally lower than the DC bus voltage, the discharger output voltage must be increased using a booster. To prioritize the use of the booster output over the AC / DC power supply circuit 101, the booster output voltage is set slightly higher than the output voltage of the AC / DC power supply circuit 101. When each cell voltage drops to a specified voltage, each discharger stops discharging. However, if the lower limit of the booster's input voltage range is higher than the cell's specified discharge voltage, the discharge current may stop before the cell voltage drops to the specified voltage. In this case, the discharger consumes the remaining power in the cell.

[0045] The DC bus is connected to the DC bus of other external magazines, and if there are other magazines in the charging cycle at the same time, the discharge current flows through the DC bus into those magazines as charging current and is regenerated there. If there are no magazines in the charging cycle at the same time, or if there are only a few magazines being charged, the discharge current will have nowhere to go, and the voltage on the DC bus will rise. In that case, as mentioned above, the surplus power is charged to capacitor C in the surplus power regeneration circuit 120.

[0046] The charging cycle (all of the selector switches SW are set to their upper contacts a11, a12, a12, a22, a31, and a32a) performed in the subsequent test sequence will be described with reference to FIG. 16. The charging current to cells C1 to C3 flows as indicated by the dashed lines in FIG. 16, and cells C1 to C3 are CC / CV charged. When each cell C1 to C3 reaches a specified voltage, the charger stops charging. Because the output voltage of the surplus power regeneration circuit 120 is set slightly higher than the voltage of the AC / DC power supply circuit 101, the discharge output of the surplus power regeneration circuit 120 is used preferentially as the charging current to the cells. The output of the AC / DC power supply circuit 101 is used only when the discharge output of the surplus power regeneration circuit 120 is insufficient. This reduces the power consumption of the AC system. Furthermore, because there is no need to return the regenerative current to the AC system, there is no risk of the voltage of the AC system rising, and power loss in the system interconnection circuit can be avoided.

[0047] As mentioned above, if the number of discharging magazines is the same as the number of charging magazines, all of the discharging current can be used extremely efficiently as charging current, so it is desirable to control the transport and insertion of magazines to the inspection unit to the same number. An example of such a system configuration is shown and explained in Figure 17.

[0048] The magazines MG1-MGn notify the control system 110 of a charge / discharge signal CD via a wired or wireless connection. That is, the magazines MG1-MGn notify the control system 110 by the charge / discharge signal CD whether they are discharge-cycle magazines or charge-cycle magazines. Based on the charge / discharge signal CD, the control system 110 selects magazines so that the number of discharge-cycle magazines in the inspection unit 140 is the same as the number of charge-cycle magazines, and sends a transport control signal CS to the transport means 130. The transport means 130 transports and inserts the magazines specified by the transport control signal CS into the inspection unit 140. Magazines that have completed inspection in the inspection unit 140 are transported separately in sequence, and the control system 110 selects the next magazine, transports it to the inspection unit 140, and inserts it there, controlling the inspection unit 140 so that the number of discharge-cycle magazines in the normal operation is the same as the number of charge-cycle magazines. This allows for efficient inspection with a significant power-saving effect.

[0049] The lower the power loss, the better, indicating higher regeneration efficiency. The power loss shown in Figure 18 is the characteristic obtained as a result of a general test sequence that is not optimized for the DC regeneration system, while the power loss shown in Figure 19 is the characteristic obtained as a result of a test sequence that is optimized for the DC regeneration system. When tested with a non-optimized test sequence, DC regeneration is slightly better than AC regeneration in terms of power loss, but the difference is not significant. On the other hand, when tested with an optimized test sequence, DC regeneration is far better than AC regeneration in terms of power loss. This comparison shows that to achieve significant power savings with the DC regeneration system, circuit configuration alone is not enough; optimal combination of the charging / discharging timing of each magazine is also important.

[0050] Although the above example describes a case where a surplus power regeneration circuit is provided for each magazine, it is also possible to provide one surplus power regeneration circuit for multiple magazines. Also, although the number of cells accommodated in the magazine is described as three, the number of cells that can be accommodated may be any appropriate number. [Explanation of symbols]

[0051] 10, 100 charge / discharge power supply 11 AC / DC power supply circuit with regenerative function 12-1~12-3 CC / CV charger / discharger 20, 110 Control System 101 AC / DC power circuit 111~113 Charger / discharger 111-2 Charger 111-3 Booster 111-4 Discharger 120, 120A, 120B Surplus power regeneration circuit 121 Booster 122 Full charge detection unit 130 Transportation 140 Inspection Department

Claims

1. A system that inspects the charging and discharging of a plurality of secondary batteries housed in a magazine according to an inspection sequence, an AC / DC power supply circuit connected to an AC system and outputting DC power via a DC bus; a plurality of chargers and dischargers connected in parallel to the DC bus for charging and discharging the secondary batteries; a surplus power regeneration circuit connected to the DC bus, the surplus power regeneration circuit comprising a capacitor and a switch means; and in a charging cycle of the inspection sequence, the secondary battery is charged via the charger / discharger with the DC power from the AC / DC power supply circuit, and in a discharging cycle of the inspection sequence, the secondary battery is discharged via the charger / discharger and the switch is turned ON to charge the capacitor with the discharge current from the secondary battery.

2. 2. The secondary battery charge / discharge inspection system according to claim 1, wherein the AC / DC power supply circuit, the plurality of chargers / dischargers, and the surplus power regeneration circuit are housed in the magazine.

3. 2. The secondary battery charge / discharge inspection system according to claim 1, wherein at least one of the AC / DC power supply circuit, the plurality of chargers / dischargers, and the surplus power regeneration circuit is installed outside the magazine.

4. 2. The secondary battery charge / discharge inspection system according to claim 1, wherein there are a plurality of magazines, the DC power is supplied from the AC / DC power supply circuit to the plurality of magazines, and the DC bus is connected in common to the plurality of magazines.

5. 5. The secondary battery charge / discharge inspection system according to claim 4, wherein the inspection sequence operates the plurality of magazines as magazines for charge cycles and magazines for discharge cycles, and discharge current is exchanged between the magazines via the DC bus.

6. 6. The secondary battery charge / discharge inspection system according to claim 5, wherein the discharge current flows from the magazine for the discharge cycle to the magazine for the charge cycle via the DC bus.

7. 7. The secondary battery charge / discharge inspection system according to claim 6, wherein the inspection sequence is such that the number of magazines for the discharge cycle is the same as the number of magazines for the charge cycle.

8. 7. The secondary battery charge / discharge inspection system according to claim 6, wherein when the number of magazines for the discharge cycle is greater than the number of magazines for the charge cycle, the switch is turned on to charge the capacitor with the discharge current.

9. 7. The secondary battery charge / discharge inspection system of claim 6, wherein when the number of magazines for the charge cycle is greater than the number of magazines for the discharge cycle, the switch is turned OFF and the power charged in the capacitor is used as the power for the charge cycle.

10. 10. The secondary battery charge / discharge inspection system according to claim 9, wherein a booster is connected to the capacitor, and when the power of the capacitor is insufficient, the DC power is output from the AC / DC power supply circuit.

11. 2. The secondary battery charge / discharge inspection system according to claim 1, wherein surplus power generated when the capacitor is fully charged is regenerated from the AC / DC power supply circuit to the AC system.

12. 6. The secondary battery charge / discharge inspection system according to claim 5, wherein sequence control is performed to determine the order in which magazines are inserted so that the number of magazines for the charge cycle matches the number of magazines for the discharge cycle.

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