Power supply device

Abstract

To continue power supply to a load and a storage battery even when a circuit fails that performs discharge operation of the storage battery according to monitoring results.SOLUTION: Even when a monitoring circuit that monitors a state of a storage battery fails, a power supply device continues to charge the storage battery with power from a power converter and to output power from the power converter to a load.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The disclosed technology relates to a power supply device. [Background technology]

[0002] A known uninterruptible power supply includes a converter that converts AC power to DC power, a storage battery that is charged with DC power from the converter, and an inverter that converts DC power from the storage battery into AC power during a power outage (see Patent Document 1). In this uninterruptible power supply, a control switch is provided in a charging path from the converter to the storage battery, and a circuit breaker is provided in a discharging path from the storage battery to the inverter that is different from the charging path. A battery state detection circuit is provided that detects the state of the storage battery, and when the battery state detection circuit detects that the voltage value of the storage battery exceeds a predetermined value, the control switch is opened, and when an abnormality in the storage battery is detected, a trip signal is output to the circuit breaker to cause the circuit breaker to perform a tripping operation. The circuit breaker is provided on the storage battery side of the control switch and on a path that shares the charging path and the discharging path, and the battery state detection circuit outputs the trip signal even when an abnormality occurs in the charging of the storage battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5990878 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above Patent Document 1 does not describe the continuity of power supply to the load and the storage battery in the event of a failure, and there is room for improvement in the continuity of power supply to the load and the storage battery in the event of a failure.

[0005] The disclosed technology has been developed in consideration of the above points, and aims to provide a power supply device that can continue to supply power to a load and a storage battery even if a circuit that performs charging and discharging operations of the storage battery according to the monitoring results fails. [Means for solving the problem]

[0006] A first aspect of the present disclosure is a power supply device that continues charging the storage battery with power from a power converter and outputting power from the power converter to a load even if a monitoring circuit that monitors the state of the storage battery fails.

[0007] A second aspect of the present disclosure is a power supply device according to the first aspect, further including a control circuit that controls conversion by the power converter so that, when a failure of the monitoring circuit is detected, the upper limit voltage during charging of the storage battery is reduced below the upper limit voltage when a failure of the monitoring circuit is not detected.

[0008] A third aspect of the present disclosure is the power supply device of the first aspect, further including a control circuit that stops conversion by the power converter after a certain period of time has elapsed if a failure in the monitoring circuit is detected.

[0009] A fourth aspect of the present disclosure is a power supply device according to the first aspect, wherein when a failure of the monitoring circuit is detected, the control circuit controls the conversion by the power converter so that the upper limit voltage during charging of the storage battery is lowered below the upper limit voltage when a failure of the monitoring circuit is not detected.

[0010] A fifth aspect of the present disclosure is a power supply device according to the third aspect, wherein, when a failure of the monitoring circuit is detected, the control circuit controls the conversion by the power converter so as to lower the upper limit voltage of the storage battery during charging below the upper limit voltage when no failure of the monitoring circuit is detected, the storage battery being a plurality of storage battery cells connected in series, and the certain period is calculated based on the charge rate from the highest voltage of the storage battery cells when the voltages are lowered to an overcharge voltage, the capacity of the storage battery cells, and the difference between the floating charge amount and the self-discharge amount of the storage battery cells.

[0011] A sixth aspect of the present disclosure is the power supply device of the third aspect, wherein, when a failure of the monitoring circuit is detected, the control circuit controls the conversion by the power converter so as to lower the upper limit voltage during charging of the storage battery below the upper limit voltage when a failure of the monitoring circuit is not detected, the storage battery being a plurality of storage battery cells connected in series, and the certain period is calculated based on the charge rate from the lowest voltage of the storage battery cells when the voltages are lowered to an over-discharge voltage, the capacity of the storage battery cells, and the difference between the float charge amount and the self-discharge amount of the storage battery cells.

[0012] A seventh aspect of the present disclosure is a power supply device according to any one of the second to sixth aspects, further including a circuit breaker for disconnecting AC power from the power converter, wherein the control circuit controls the circuit breaker to disconnect the power when a failure in the monitoring circuit is detected and a power outage is detected.

[0013] An eighth aspect of the present disclosure is the power supply device of the first aspect, wherein the storage battery is a lithium ion storage battery. [Effects of the Invention]

[0014] According to the disclosed technology, even if a circuit that performs charging and discharging operations of the storage battery according to the monitoring results fails, it is possible to continue supplying power to the load and the storage battery. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram showing the configuration of a DC power supply device according to a first embodiment. [Figure 2] FIG. 10 is a diagram for explaining cell balancing control in a storage battery unit. [Figure 3] 10A and 10B are diagrams for explaining charging and discharging of each storage battery cell with and without cell balancing control. [Figure 4]10 is a diagram for explaining that the battery cell with the smallest amount of self-discharge is charged due to the difference between the floating charge amount and the self-discharge amount of each battery cell. [Figure 5] 10 is a diagram for explaining the number of days until a storage battery cell is overcharged when the upper limit voltage during charging of the storage battery unit is reduced. FIG. [Figure 6] 10 is a diagram for explaining a method for calculating the number of days from when a failure in the monitoring circuit occurs until over-discharge of a storage battery cell occurs. FIG. [Figure 7] FIG. 10 is a block diagram showing the configuration of an AC power supply device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] An example of an embodiment of the disclosed technology will be described below with reference to the drawings. Note that the same or equivalent components and parts in each drawing are given the same reference numerals. Also, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0017] <Outline of this embodiment> In a conventional power supply device equipped with a storage battery, if the battery monitoring circuit fails, the connection to the AC power source is cut off, charging of the storage battery is stopped, and power supply to the load is switched to discharging from the storage battery. As a result, even if the AC power source from the grid is available, power supply to the load ends prematurely.

[0018] Therefore, in this embodiment, even if the battery monitoring circuit fails, the storage battery continues to be charged, ensuring time to replace the battery monitoring circuit. Also, although there is a possibility that the storage battery cells may be overcharged after a failure of the battery monitoring circuit occurs, the charging voltage is lowered to prevent overcharging for a certain period of time.

[0019] [First embodiment] <Configuration of DC power supply device according to first embodiment> 1 is a diagram showing the configuration of a DC power supply device 10 as a power supply device in this embodiment. The DC power supply device 10 has an input terminal 12 connected to a commercial power source and an output terminal 22 connected to an external device, and normally supplies DC power to a load which is an external device while storing a portion of the power supplied from the commercial power source in a storage battery unit 28, and in the event of a commercial power outage, supplies DC power to the external device using the power stored in the storage battery unit 28.

[0020] In the DC power supply device 10, a rectifier 14 and a breaker 18 are connected in series via wiring 16 between an input terminal 12 and an output terminal 22. The rectifier 14 is located closer to the input terminal 12 than the breaker 18, and converts AC power supplied from a commercial power source into DC power. The rectifier 14 is an example of a power converter.

[0021] The breaker 18 cuts off the current for each component to prevent thermal runaway when an overload current occurs. A breaker 18 is provided for each load.

[0022] A plurality of storage battery units 28 are connected to the wiring 16 between the rectifier 14 and the breaker 18 via wiring 26 .

[0023] A plurality of series circuits, each having a breaker 24 and a storage battery unit 28 connected in series, are connected in parallel to the wiring 26. The breaker 24 is arranged closer to the wiring 16 than the storage battery unit 28, and when the storage battery unit 28 is discharging, a current flows from the storage battery unit 28 to the wiring 16 in the wiring 26, and when the storage battery unit 28 is charging, a current flows from the wiring 16 to the storage battery unit 28.

[0024] 2, the storage battery unit 28 includes a plurality of storage battery cells 28A connected in series, and a switching element SW1 is connected in parallel to each of the storage battery cells 28A. A resistance component exists between the storage battery cell 28A and the switching element SW1.

[0025] The storage battery cell 28A is charged with DC power from the rectifier 14, and discharges the DC power during a power outage. The storage battery cell 28A is, for example, a lithium ion storage battery.

[0026] The monitoring circuit 36 ​​performs cell balancing control to control the on / off of the switching element SW1 according to individual differences between the storage battery cells 28A. Specifically, the monitoring circuit 36 ​​measures the voltage of each storage battery cell 28A, and periodically controls the switching element SW1 to be on for a longer time to perform a discharging operation as the difference in voltage between the storage battery cells 28A increases (see FIG. 2).

[0027] The monitoring circuit 36 ​​also monitors the status of each storage battery unit 28, and if an abnormality is detected, controls the breaker 24 corresponding to that storage battery unit 28 to perform a cutoff operation. The monitoring circuit 36 ​​also detects a failure of the monitoring circuit 36 ​​itself, and if a failure of the monitoring circuit 36 ​​is detected, outputs a signal indicating the failure of the monitoring circuit 36 ​​to the control circuit 44.

[0028] The wiring 26 is connected to a monitoring circuit 36 ​​via a wiring 48. A converter 38 is connected in parallel to the wiring 48. DC power from the rectifier 14 is supplied to the monitoring circuit 36 ​​via the converter 38. The converter 38 is a DC-DC converter.

[0029] When a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 continues charging of the storage battery unit 28 with DC power from the rectifier 14 and output of DC power to each load from the rectifier 14. Furthermore, when a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 controls conversion by the rectifier 14 so as to lower the upper limit voltage during charging of the storage battery unit 28 below the upper limit voltage when a failure of the monitoring circuit 36 ​​is not detected.

[0030] Furthermore, if a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 stops the conversion by the rectifier 14 after a certain period of time has elapsed. This certain period of time is calculated based on the charging rate from the voltage of the storage battery cell 28A to the overcharge voltage when the upper limit voltage during charging of the storage battery unit 28 is lowered, or the charging rate from the voltage of the storage battery cell 28A to the overdischarge voltage when the upper limit voltage during charging of the storage battery unit 28 is lowered, the capacity of the storage battery cell 28A, and the difference between the float charge amount and the self-discharge amount of the storage battery cell 28A.

[0031] The principle of calculating this fixed period will be explained below.

[0032] First, as shown in FIG. 3, charging and discharging of each storage battery cell 28A with and without cell balancing control will be described.

[0033] If the monitoring circuit 36 ​​fails and cell balancing control is not performed, the battery cells 28A will self-discharge while differences in the self-discharge amounts remain. At this time, the battery cell 28A with the smallest self-discharge amount will be charged because its self-discharge amount is smaller than the float charge amount, and the battery cell 28A with the largest self-discharge amount will be discharged because its self-discharge amount is greater than the float charge amount (see the left side of Figure 3).

[0034] On the other hand, when cell balancing control is performed by the monitoring circuit 36, as shown on the right side of Figure 3, in order to make up for the difference in the self-discharge amount of each storage battery cell 28A, the discharge amount due to cell balancing is added to the storage battery cell 28A with a small self-discharge amount.

[0035] The difference in the amount of self-discharge among the cells is eliminated by discharging the battery with a discharge current amount achieved by cell balancing.

[0036] Here, if the self-discharge rate of storage battery cell 28A with the smallest self-discharge rate is 0 Ah / day and the self-discharge rates of the other storage battery cells 28A are 0.23 Ah / day, the float charge rate of storage battery cell 28A will be close to 0.23 Ah / day. In this case, the difference between the float charge rate and the self-discharge rate of storage battery cell 28A with the smallest self-discharge rate is 0.23 Ah / day. Since storage battery cell 28A with the smallest self-discharge rate is charged by the difference between the float charge rate and the self-discharge rate (0.23 Ah / day), the cell voltage rises as shown in Figure 4. In this case, the number of days from when monitoring circuit 36 ​​fails until overcharging of a storage battery cell occurs is calculated as follows:

[0037] Number of days until battery cell is overcharged = SOC of single cell overcharge from highest battery cell voltage when upper limit voltage during charging is lowered × LiB capacity × maintenance rate / difference between floating charge amount and self-discharge amount of battery cell =SOC8%×42Ah×0.8 / 0.23Ah / day=12 days

[0038] Here, the SOC for battery cell overcharge based on the battery cell voltage variation warning voltage is set to 8% (=100% - 92%), the capacity of battery cell 28A is set to 42 Ah, and the maintenance factor is set to 0.8. Here, as an example, from the perspective of more reliably preventing the battery cells from being overcharged, the number of days until the battery cell voltage becomes overcharged is adjusted by multiplying it by the maintenance factor to provide a margin. The maintenance factor may be 0.5 or more and 1.0 or less.

[0039] In this example calculation, the number of days until the battery cell becomes overcharged is 12. The longer the number of days until the battery cell becomes overcharged, the better, in order to allow time to repair a faulty monitoring circuit 36.

[0040] Next, the number of days until the storage battery cells are overcharged when the control circuit 44 reduces the upper limit voltage during charging of the storage battery unit 28 will be described.

[0041] Here, as shown in Figure 5, the floating charge voltage is set to 80% SOC, while the upper limit voltage during charging of the storage battery unit 28 is reduced by 30% SOC, and the reduced voltage charge voltage is set to 50% SOC. This reduces the discharge time during a power outage to 5 / 8.

[0042] In this case, the number of days from when the monitoring circuit 36 ​​fails until the battery cell overcharge occurs is calculated as follows.

[0043] Number of days until battery cell is overcharged = SOC × LiB capacity × maintenance rate / difference in cell self-discharge rate from the highest battery cell voltage when the upper limit voltage during charging is lowered to the voltage discharged at 30% of SOC until the battery cell is overcharged =SOC38%×42Ah×0.8 / 0.23Ah / day=56 days

[0044] Here, the SOC from the voltage discharged to 30% SOC from the highest battery cell voltage to the battery cell overcharge is set to 38% (=100%-62%).

[0045] In this calculation example, the number of days until the battery cell becomes overcharged when using reduced voltage charging is 56 days. In this way, by using reduced voltage charging, the number of days until the battery cell becomes overcharged can be increased to a maximum of 56 days.

[0046] Next, the number of days until the storage battery cells are over-discharged when the control circuit 44 reduces the upper limit voltage during charging of the storage battery unit 28 will be described.

[0047] Here, if the self-discharge rate of storage battery cell 28A with the largest self-discharge rate is 0.23 Ah and the self-discharge rates of the other storage battery cells 28A are 0 Ah / day, the float charge rate of storage battery cell 28A approaches 0 Ah / day. In this case, the difference between the float charge rate and the self-discharge rate of storage battery cell 28A with the largest self-discharge rate is 0.23 Ah / day, and storage battery cell 28A with the largest self-discharge rate discharges by the difference between the float charge rate and the self-discharge rate (0.23 Ah / day).

[0048] The number of days from when the monitoring circuit 36 ​​fails until the battery cell over-discharge occurs is calculated as follows (see FIG. 6).

[0049] Number of days until battery cell is over-discharged = SOC × LiB capacity × maintenance rate / difference in cell self-discharge rate from the lowest battery cell voltage when the upper limit voltage during charging is lowered to the voltage discharged at 30% SOC to the battery cell over-discharge =SOC38%×42Ah×0.8 / 0.23Ah / day=56 days

[0050] In this calculation example, the number of days until the battery cell becomes over-discharged when charging at reduced voltage is 56. The above example was explained using an example where the difference between the float charge amount and the self-discharge amount is 0.23 Ah / day, but this is not limited to this.

[0051] When a failure of the monitoring circuit 36 ​​is detected and a power outage is also detected, the control circuit 44 controls the circuit breaker 13 to perform a cutoff. As a result, even when the power is restored from the power outage and the power supply from the commercial power source is resumed, charging of the storage battery unit 28 is not resumed.

[0052] <Control of DC power supply> Next, each process of the DC power supply device 10 will be described.

[0053] <Charging control> When the DC power supply device 10 is started up, DC power is supplied to each load via the wiring 16, while DC power is supplied to the storage battery unit 28 via the wiring 26, and each storage battery cell 28A is charged.

[0054] At this time, the monitoring circuit 36 ​​performs cell balancing control to control the on / off of the switching element SW1 in accordance with the individual differences of the storage battery cells 28A.

[0055] <Discharge control> When the power supply from the commercial power source is stopped (power outage), the DC power stored in the storage battery unit 28 is used to supply power to each load, allowing the loads to continue operating despite the power outage. When the power outage is restored and the power supply from the commercial power source is resumed, the DC power from the rectifier 14 continues to operate each load, and charging of the storage battery unit 28 resumes.

[0056] <Control in case of an abnormality> When a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 continues charging of the storage battery unit 28 with DC power from the rectifier 14 and output of DC power from the rectifier 14 to each load. When a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 controls the conversion by the rectifier 14 so as to lower the upper limit voltage during charging of the storage battery unit 28 below the upper limit voltage when no failure of the monitoring circuit 36 ​​is detected. When a certain period of time has elapsed since the failure of the monitoring circuit 36 ​​was detected, the control circuit 44 stops the conversion by the rectifier 14.

[0057] When a failure of the monitoring circuit 36 ​​is detected and a power outage is also detected, the control circuit 44 controls the circuit breaker 13 to perform a cutoff. As a result, even when the power is restored from the power outage and the power supply from the commercial power source is resumed, charging of the storage battery unit 28 is not resumed, and therefore the storage battery unit 28 can be protected.

[0058] As described above, the DC power supply device according to the first embodiment continues charging the storage battery with power from the rectifier and outputting power from the rectifier to the load even if the monitoring circuit that monitors the state of the storage battery fails. This makes it possible to continue supplying power to the load and the storage battery even if the monitoring circuit that discharges the storage battery according to the monitoring results fails.

[0059] Furthermore, although overcharging and over-discharging of the storage battery may occur after a failure of the monitoring circuit occurs, lowering the charging voltage prevents overcharging and over-discharging for a certain period of time. This allows time to be secured for replacing the monitoring circuit. It also makes it possible to ensure power supply functionality from the detection of a monitoring circuit failure until the replacement of the monitoring circuit.

[0060] [Second embodiment] An AC power supply device according to a second embodiment will be described below. Note that parts having the same configuration as those in the first embodiment will be given the same reference numerals and descriptions thereof will be omitted.

[0061] <Configuration of AC power supply device according to second embodiment> 7 is a diagram showing the configuration of an AC power supply device 210 as a power supply device in this embodiment. The AC power supply device 210 has an input terminal 12 connected to a commercial power source and an output terminal 22 connected to an external device, and normally supplies AC power to a load which is an external device while storing a portion of the power supplied from the commercial power source in a storage battery unit 28, and in the event of a commercial power outage, supplies AC power to the external device using the power stored in the storage battery unit 28.

[0062] In AC power supply device 210, rectifier 14, inverter 212, and breaker 18 are connected in series via wiring 16 between input terminal 12 and output terminal 22. Rectifier 14 is located closer to input terminal 12 than inverter 212 and breaker 18, and converts AC power supplied from a commercial power source into DC power. Rectifier 14 is an example of a power converter.

[0063] In addition, in the AC power supply device 210 , a breaker 218 is connected between the input terminal 12 and the output terminal 22 via a wiring 216 .

[0064] The breaker 218 cuts off the current for each component to prevent thermal runaway when an overload current occurs. A breaker 218 is provided for each load.

[0065] When a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 continues charging of the storage battery unit 28 with DC power from the rectifier 14 and output of AC power to each load from the inverter 212. Furthermore, when a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 controls conversion by the rectifier 14 so as to lower the upper limit voltage during charging of the storage battery unit 28 below the upper limit voltage when a failure of the monitoring circuit 36 ​​is not detected.

[0066] Furthermore, if a failure in the monitoring circuit 36 ​​is detected, the control circuit 44 stops the conversion by the rectifier 14 after a certain period of time has elapsed.

[0067] When a failure of the monitoring circuit 36 ​​is detected and a power outage is also detected, the control circuit 44 controls the circuit breaker 13 to perform a break.

[0068] <AC power supply control> Next, each process of the AC power supply device 210 will be described.

[0069] <Charging control> When AC power supply device 210 is started up, AC power is supplied to each load via wiring 16, 216, while DC power is supplied to storage battery unit 28 via wiring 26, charging each storage battery cell 28A.

[0070] At this time, the monitoring circuit 36 ​​performs cell balancing control to control the on / off of the switching element SW1 in accordance with the individual differences of the storage battery cells 28A.

[0071] <Discharge control> When the power supply from the commercial power source is stopped (power outage), AC power is supplied to each load via inverter 212 using the DC power stored in storage battery 32, allowing the loads to continue operating despite the power outage. When the power outage is restored and the power supply from the commercial power source is resumed, the operation of each load continues using AC power via wiring 216, and charging of storage battery unit 28 resumes.

[0072] <Control in case of an abnormality> When a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 continues charging the storage battery unit 28 with DC power from the rectifier 14 and outputting AC power to each load via the inverter 212. When a failure of the monitoring circuit 36 ​​is detected, the control circuit 44 controls the conversion by the rectifier 14 so as to lower the upper limit voltage during charging of the storage battery unit 28 below the upper limit voltage when no failure of the monitoring circuit 36 ​​is detected. When a certain period of time has elapsed since the failure of the monitoring circuit 36 ​​was detected, the control circuit 44 stops the conversion by the rectifier 14.

[0073] When a failure of the monitoring circuit 36 ​​is detected and a power outage is also detected, the control circuit 44 controls the circuit breaker 13 to perform a cutoff. As a result, even when the power is restored from the power outage and the power supply from the commercial power source is resumed, charging of the storage battery unit 28 is not resumed, and therefore the storage battery unit 28 can be protected.

[0074] As described above, the AC power supply device according to the second embodiment continues charging the storage battery with power from the rectifier and outputting power from the rectifier and inverter to the load even if the monitoring circuit that monitors the state of the storage battery fails. This allows power supply to the load and the storage battery to continue even if the circuit that discharges the storage battery according to the monitoring results fails.

[0075] <Modification> The present invention is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the spirit and scope of the present invention.

[0076] For example, although the storage battery is a lithium ion storage battery in the above description, the present invention is not limited to this, and a storage battery other than a lithium ion battery may also be used. [Explanation of symbols]

[0077] 10 DC power supply 13 Circuit Breaker 14 Rectifier 28 Battery Unit 28A battery cell 36 Monitoring circuit 44 Control circuit 210 AC power supply 212 Inverter

Claims

1. Even if a monitoring circuit that monitors the state of the storage battery fails, the storage battery continues to be charged with power from the power converter, and the power converter continues to output power to the load. power supply.

2. 2. The power supply device according to claim 1, further comprising a control circuit that controls conversion by the power converter so that, when a failure of the monitoring circuit is detected, an upper limit voltage during charging of the storage battery is reduced below an upper limit voltage when no failure of the monitoring circuit is detected.

3. 2. The power supply device according to claim 1, further comprising a control circuit that stops conversion by said power converter after a certain period of time has elapsed if a failure of said monitoring circuit is detected.

4. 4. The power supply device according to claim 3, wherein the control circuit controls conversion by the power converter so that, when a failure of the monitoring circuit is detected, an upper limit voltage during charging of the storage battery is lowered below an upper limit voltage when no failure of the monitoring circuit is detected.

5. when a failure of the monitoring circuit is detected, the control circuit controls conversion by the power converter so as to reduce an upper limit voltage during charging of the storage battery below an upper limit voltage when a failure of the monitoring circuit is not detected; The storage battery is a plurality of storage battery cells connected in series, 4. The power supply device according to claim 3, wherein the certain period is calculated based on a charging rate from the highest voltage among the voltages of the storage battery cells when the voltages are reduced to an overcharge voltage, a capacity of the storage battery cells, and a difference between a floating charge amount and a self-discharge amount of the storage battery cells.

6. when a failure of the monitoring circuit is detected, the control circuit controls conversion by the power converter so as to reduce an upper limit voltage during charging of the storage battery below an upper limit voltage when a failure of the monitoring circuit is not detected; The storage battery is a plurality of storage battery cells connected in series, 4. The power supply device according to claim 3, wherein the certain period is calculated based on a charge rate from the lowest voltage among the voltages of the storage battery cells when the voltages are reduced to an over-discharge voltage, a capacity of the storage battery cells, and a difference between a floating charge amount and a self-discharge amount of the storage battery cells.

7. further comprising a circuit breaker for disconnecting AC power from the power converter; The power supply device according to any one of claims 2 to 6, wherein the control circuit controls the circuit breaker to perform a shutdown when a failure of the monitoring circuit is detected and a power outage is detected.

8. 2. The power supply device according to claim 1, wherein the storage battery is a lithium ion storage battery.

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