Battery deterioration determination device, battery deterioration determination method, battery system, and battery monitoring device

Abstract

Provided are a deterioration determination device for a storage battery system, a deterioration determination method for a storage battery system, a storage battery system, and a storage battery monitoring device, which have improved accuracy in determining deterioration of the storage battery system. [Solution] A deterioration determination device for a battery system in which multiple battery strings, each consisting of multiple batteries connected in series, are connected in parallel, wherein the multiple battery strings are connected in parallel with each other at the batteries located at the ends of the battery strings and the batteries located midway through the battery strings, thereby dividing the battery system into multiple battery string blocks, and the deterioration determination device for a battery system includes: a current sensor that measures the circulating current generated between the battery strings in each of the battery string blocks when charging or discharging of the batteries stops; a measurement control unit that collects the circulating current values ​​measured by the current sensor; and a battery state determination unit that determines whether or not deterioration has occurred in the batteries in the battery string blocks from the collected circulating current values.

Description

[Technical field]

[0001] The present invention relates to a deterioration determination device for a storage battery system, a deterioration determination method for a storage battery system, a storage battery system, and a storage battery monitoring device, and in particular to a deterioration determination device for a storage battery system, a deterioration determination method for a storage battery system, a storage battery system, and a storage battery monitoring device that determine deterioration of a storage battery system by measuring a circulating current generated when charging and discharging are stopped. [Background technology]

[0002] When using a storage battery, in order to obtain a desired voltage or capacity, the storage batteries are sometimes connected in series to form a storage battery string, and the storage battery strings are sometimes connected in parallel to form a battery pack. When an abnormality such as an internal short circuit or an internal liquid short occurs in some of the storage batteries in the storage battery system, the internal resistance of the storage battery string including the abnormal storage battery increases or decreases more than that of the other storage battery strings, and the storage battery string may enter an over-discharged state or an over-charged state, and deterioration may be accelerated. In particular, when the storage battery is a bipolar lead-acid battery, the temperature of the center part is likely to rise due to the structure in which the electrodes are stacked, and since the temperature differs from battery to battery, the progress of deterioration also differs from battery to battery, and there is a risk that temperature deterioration, internal short circuit, internal liquid short circuit, etc. due to deterioration progression may occur, accelerating deterioration. Therefore, when a bipolar lead-acid battery is used as a storage battery system, it is necessary to determine whether the storage batteries constituting the storage battery system have deteriorated, and to replace the deteriorated storage batteries in advance before an abnormality occurs.

[0003] It has therefore been proposed to measure the charging current (Ic) of each battery string and determine deterioration, such as internal short circuits or internal liquid shorts, of a specific battery string based on a relative comparison of the measured charging current (Ic) of each battery string, or the difference between the charging current (Ic) at the beginning of use and the charging current (Ic) after some use (Patent Document 1).

[0004] However, when there is a temperature distribution in the battery pack, a temperature difference may occur in each battery string. The charging characteristics of the battery vary depending on the temperature state during charging, and a battery charged under high temperature conditions tends to have better charging characteristics than a battery charged under low temperature conditions. Therefore, in Patent Document 1, when there is a temperature distribution in the battery pack, the charging current value (Icc) of the battery string charged under relatively high temperature conditions is larger than the charging current value (Icc) of the battery string charged under relatively low temperature conditions, which may lead to an erroneous judgment when judging the deterioration of the battery string.

[0005] The above problems of the conventional deterioration determination device for a battery system will be described in detail with reference to the drawings. Fig. 8 is a schematic diagram of the conventional deterioration determination device for a battery system. Fig. 9 is a schematic diagram of the conventional deterioration determination device for a battery system in which two battery strings are installed on the same battery rack. Fig. 10 is a graph showing the change over time in charging current (Ic) when two battery strings in the conventional deterioration determination device for a battery system are installed on the same battery rack and the batteries are charged.

[0006] As shown in Fig. 8, in the deterioration determination device 110 of the conventional battery system, a plurality of batteries 100 (eight batteries in Fig. 8) are connected in series to form a battery string 200, and a plurality of battery strings 200 (four in Fig. 8: a first battery string 200-1, a second battery string 200-2, a third battery string 200-3, and a fourth battery string 200-4) are connected in parallel to form a battery pack 600. The battery pack 600 is connected to a power conditioning system (PCS) 500. In each battery string 200, a current sensor 400 that measures charge / discharge current is installed between the battery string 200 and the power conditioning system 500, and measurement information of the current sensor 400 is input to a battery monitoring device (BMU: Battery Management Unit) 300. When the AC / DC converter 500 starts charging the battery pack 600, the battery monitoring device 300 determines the degree of variation in the charging current (Ic) between the battery strings 200 from the charging current (Ic) values ​​input from the current sensors 400 installed in each battery string 200, and compares the charging current (Ic) of each battery string 200 at the beginning of installation of the battery system with the charging current (Ic) of each battery string 200 after use, and determines from the difference whether the batteries 100 in each battery string 200 have deteriorated, which may lead to abnormalities such as an internal short circuit or an internal liquid short circuit. Therefore, the deterioration determination device 110 of the conventional battery system determines whether the batteries 100 have deteriorated, which may lead to abnormalities such as an internal short circuit or an internal liquid short circuit, when the battery pack 600 is being charged.

[0007] 9, for example, when the first battery row 200-1 and the second battery row 200-2 are installed in the same battery rack 700 with the first battery row 200-1 on the lower level and the second battery row 200-2 on the upper level, a temperature distribution occurs in the battery rack 700 that is mainly due to charging of the battery pack 600. That is, the batteries 100 of the second battery row 200-2 installed on the upper level of the battery rack 700 tend to have a higher temperature than the batteries 100 of the first battery row 200-1 installed on the lower level of the battery rack 700. Therefore, when the batteries 100 are charged, the charging current (Ic) of the second battery row 200-2 tends to be larger than that of the first battery row 200-1.

[0008] Fig. 10 is a graph showing the change over time in the charging current (Ic) of the first storage battery row 200-1 and the charging current (Ic) of the second storage battery row 200-2 when the first storage battery row 200-1 and the second storage battery row 200-2 are arranged in the same battery rack 700 as shown in Fig. 9, i.e., with the first storage battery row 200-1 on the lower level and the second storage battery row 200-2 on the upper level, and the storage battery 100 is charged. Note that the average temperature during charging of the storage battery 100 was about 2°C higher in the second storage battery row 200-2 than in the first storage battery row 200-1.

[0009] 10, in region A immediately after charging of the storage battery 100 begins and in region B before charging ends, the charging current (Ic) of the second storage battery string 200-2 is greater than the charging current (Ic) of the first storage battery string 200-1. On the other hand, in region C immediately before charging of the storage battery 100 ends, the charging current (Ic) of the first storage battery string 200-1 is greater than the charging current (Ic) of the second storage battery string 200-2. In this way, when a temperature distribution occurs among the battery strings 200 of the storage battery system that constitutes the assembled battery 600, if the presence or absence of deterioration of the batteries 100 of the storage battery system is determined from the charging current (Ic), there are cases where it is erroneously determined that deterioration has occurred in the batteries 100 of the storage battery system that constitutes the assembled battery 600, even though there is no deterioration that could lead to abnormalities such as an internal short circuit or an internal liquid short in the batteries 100 of the storage battery system that constitutes the assembled battery 600, and there are cases where it is erroneously determined that there is no deterioration in the batteries 100 of the storage battery system that constitutes the assembled battery 600, even though there is deterioration that could lead to abnormalities such as an internal short circuit or an internal liquid short in the batteries 100 of the storage battery system that constitutes the assembled battery 600.

[0010] In addition, when the number of series connections of the storage batteries 100 in the storage battery string 200 is large, the internal resistance of the storage battery string 200 becomes large in the first place, and it may be difficult to determine that the storage battery 100 has deteriorated in a manner that could lead to the above-mentioned abnormality, such as an internal short circuit or an internal liquid short, before the abnormality occurs in the storage battery 100. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2012-88097 A Summary of the Invention [Problem to be solved by the invention]

[0012] In view of the above circumstances, an object of the present invention is to provide a deterioration determination device for a storage battery system, a deterioration determination method for a storage battery system, a storage battery system, and a storage battery monitoring device, which have improved accuracy in determining the deterioration of a storage battery system. [Means for solving the problem]

[0013] In this invention, a battery string consisting of a number of batteries connected in series is divided into a number of battery string blocks, and the presence or absence of deterioration of the battery system is determined by measuring the circulating current generated between the battery strings for each battery string block when charging or discharging of the batteries constituting the battery system is stopped. The circulating current generated between the battery strings is generated by voltage differences caused by differences in the charging characteristics of each battery string.

[0014] The gist of the configuration of the present invention is as follows. [1] A deterioration determination device for a storage battery system in which a plurality of storage batteries are connected in series and connected in parallel in multiple rows, the plurality of battery strings are connected in parallel to each other at the ends of the battery strings and the intermediate batteries of the battery strings, thereby dividing the battery system into a plurality of battery string blocks; a measurement control unit that collects values ​​of the circulating current measured by the current sensor; and a battery state determination unit that determines whether or not the batteries in the battery string block have deteriorated from the collected values ​​of the circulating current. [2] The deterioration determination device for a battery system according to [1], wherein the battery string block is connected in series to another battery string block via a single connection part. [3] The deterioration determination device for a battery system described in [1] or [2], wherein a plurality of the current sensors are provided in each battery string block. [4] The deterioration determination device for a battery system described in [3], wherein the current sensor is provided between each of the adjacent battery strings in the battery string block. [5] The deterioration determination device for a battery system described in [1] or [2], wherein the current sensor is provided for each battery string block. [6] A deterioration determination device for a storage battery system described in any one of [1] to [5], wherein a switch means is provided between the AC / DC conversion device and the storage battery system, the switch means disconnecting the AC / DC conversion device from the storage battery system when charging or discharging of the storage battery is stopped. [7] A method for determining deterioration of a storage battery system in which a plurality of storage batteries are connected in parallel in a plurality of series-connected storage battery strings, the plurality of battery strings are connected in parallel to each other at the ends of the battery strings and the intermediate batteries of the battery strings, thereby dividing the battery system into a plurality of battery string blocks; measuring a circulating current occurring between the battery strings in each of the battery string blocks when charging or discharging of the battery is stopped; collecting measured values ​​of the circulating current; and determining whether or not deterioration has occurred in the batteries in the battery string block from the collected circulating current values.

[0015] [8] A deterioration determination device for determining deterioration of a storage battery in a storage battery system having a plurality of assembled batteries connected in series, each assembled battery being configured to have a plurality of storage battery blocks connected in parallel in a plurality of battery strings each including a plurality of storage batteries connected in series, the plurality of assembled batteries being connected in parallel, a measurement control unit that is provided for each of the assembled batteries and connected in parallel, and that collects values ​​of circulating currents measured by current sensors that measure circulating currents generated between the assembled batteries when charging or discharging of the storage battery is stopped; a battery state determination unit that determines deterioration of the battery from the collected value of the circulating current; A deterioration determination device for a storage battery system comprising: [9] The deterioration determination device for a battery system described in [8], wherein the battery state determination unit determines that the battery is deteriorated when the sum of the circulating currents measured by the current sensor is less than or equal to a predetermined first threshold and when the absolute values ​​of each of the circulating currents measured by the current sensors are greater than or equal to a predetermined second threshold.

[10] A battery monitoring device that monitors a battery system in which a plurality of assembled batteries are connected in parallel, the assembled batteries being each configured to have a plurality of battery blocks connected in series, the battery blocks being each configured to have a plurality of battery rows connected in parallel, the apparatus comprising: a measurement control unit that is provided for each of the assembled batteries and connected in parallel, and that collects values ​​of circulating currents measured by current sensors that measure circulating currents generated between the assembled batteries when charging or discharging of the storage battery is stopped; a battery state determination unit that determines deterioration of the battery from the collected value of the circulating current; A battery monitoring device comprising:

[11] The battery monitoring device described in

[10] , wherein the battery state determination unit determines that the battery is deteriorated when the sum of the circulating currents measured by the current sensors is less than or equal to a predetermined first threshold and when the absolute values ​​of each of the circulating currents measured by the current sensors are greater than or equal to a predetermined second threshold.

[12] A deterioration determination device for a storage battery system according to [8] or [9], or a storage battery monitoring device according to

[10] or

[11] ; A battery string in which a plurality of batteries are connected in series; A storage battery system having A plurality of the assembled batteries are connected in parallel, a current sensor for measuring a circulating current generated between the battery packs when charging or discharging of the storage battery is stopped is provided for each battery pack and connected in parallel; Battery storage system.

[13] A deterioration determination method for a storage battery system having a plurality of assembled batteries connected in series, each of which has a plurality of storage battery blocks connected in parallel in a plurality of battery strings, each of which has a plurality of storage batteries connected in series, and determining deterioration of the storage batteries in the storage battery system in which the assembled batteries are connected in parallel, a step of collecting values ​​of circulating currents measured by current sensors provided for each of the assembled batteries and connected in parallel, the current sensors measuring circulating currents generated between the assembled batteries when charging or discharging of the storage battery is stopped; determining deterioration of the storage battery from the collected value of the circulating current; A method for determining deterioration of a storage battery system comprising: Effect of the Invention

[0016] According to an aspect of the present invention, since the circulating current generated by the voltage difference between the battery strings is measured when charging or discharging of the batteries is stopped, the battery system can be prevented from being affected by temperature distribution, and the accuracy of determining deterioration of the battery system is improved. Also, according to an aspect of the present invention, since a battery string in which a plurality of batteries are connected in series is divided into a plurality of battery string blocks, an increase in the internal resistance of the battery string can be prevented, making it easier for the circulating current to flow, improving the accuracy of measuring the circulating current, and improving the accuracy of determining that the battery has deteriorated before an abnormality such as an internal short circuit or an internal liquid short occurs in the battery.

[0017] According to an embodiment of the present invention, since the battery string blocks are connected in series to other battery string blocks via a single connection, the circulating current generated in each battery string block can be measured with high accuracy, thereby further improving the accuracy of determining the deterioration of the battery system.

[0018] According to this aspect of the present invention, a current sensor is provided between each of the adjacent battery strings in a battery string block, making it possible to accurately determine the deterioration of each battery string in the battery string block.

[0019] According to an embodiment of the present invention, by providing each battery string block with one current sensor, it is possible to determine the deterioration of the battery system for each battery string block. Therefore, when replacing batteries for each battery string block, the accuracy of determining the deterioration of the battery system is improved with a simple structure.

[0020] According to an aspect of the present invention, a switch means is provided between the AC / DC conversion device and the battery system, which disconnects the AC / DC conversion device and the battery system when charging or discharging of the battery is stopped.This makes it possible to measure the circulating current while preventing the influence of the AC / DC conversion device, thereby further improving the accuracy of determining the deterioration of the battery system. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a deterioration determination device for a battery system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a configuration diagram of functional blocks of a battery monitoring device provided in a deterioration determination device for a battery system according to a first embodiment of the present invention. [Diagram 3] FIG. 3 is a flowchart showing the deterioration determination process performed by the deterioration determination device for a battery system according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the relationship between the circulating current occurring between battery strings and the degree of deterioration of the battery string blocks. [Diagram 5] FIG. 5 is a schematic diagram of a deterioration determination device for a battery system according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a schematic diagram of a deterioration determination device for a battery system according to a third embodiment of the present invention. [Figure 7] FIG. 7 is a schematic diagram of a deterioration determination device for a battery system according to a fourth embodiment of the present invention. [Figure 8] FIG. 8 is a schematic diagram of a conventional deterioration determination device for a storage battery system. [Figure 9] FIG. 9 is a schematic diagram of a conventional deterioration determination device for a storage battery system in which two rows of storage batteries are installed on one battery rack. [Figure 10] FIG. 10 is a graph showing the change over time in charging current when two battery strings in a conventional deterioration determination device for a storage battery system are installed in one battery rack and the storage batteries are charged. [Figure 11] FIG. 11 is a schematic diagram of a deterioration determination device for a battery system according to a fifth embodiment of the present invention. [Figure 12] FIG. 12 is a flowchart showing the deterioration determination process performed by the deterioration determination device for a battery system according to the fifth embodiment of the present invention. [Figure 13] FIG. 13 is a schematic diagram of a deterioration determination device for a battery system according to a fifth embodiment of the present invention. [Figure 14] FIG. 14 is a schematic diagram showing a modified example of the fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <First Example> A deterioration determination device 1 for a battery system according to a first embodiment of the present invention will now be described. FIG. 1 is a schematic configuration diagram of the deterioration determination device for a battery system according to the first embodiment of the present invention. FIG. 2 is a configuration diagram of functional blocks of a battery monitoring device provided in the deterioration determination device for a battery system according to the first embodiment of the present invention. FIG. 3 is a flowchart of deterioration determination in the deterioration determination device for a battery system according to the first embodiment of the present invention. FIG. 4 is a graph showing the relationship between circulating current generated between battery strings and the degree of deterioration of a battery string block.

[0023] As shown in Fig. 1, the deterioration determination device 1 for a storage battery system according to the first embodiment is a device for determining deterioration of a storage battery system 11, which is an assembled battery in which a storage battery string 20 in which a plurality of storage batteries 10, 10, 10, ... are connected in series and connected in parallel in multiple strings. For ease of explanation, in Fig. 1, eight storage batteries 10 are connected in series to form one storage battery string 20. Also, in the deterioration determination device 1 for a storage battery system, for ease of explanation, four storage battery strings 20 are connected in parallel in the storage battery system 11, in the order of a first storage battery string 20-1, a second storage battery string 20-2, a third storage battery string 20-3, and a fourth storage battery string 20-4.

[0024] The storage battery system 11 is also connected to a power conversion system (PCS) 50. The storage battery system 11 is connected via the power conversion system (PCS) 50 to an external power system (not shown).

[0025] In the deterioration determination device 1 for a storage battery system, a storage battery system 11 is divided into a plurality of storage battery string blocks 12 by connecting a plurality of storage battery strings 20 in parallel with each other at a storage battery 10 (10A) located at an end of the storage battery string 20 and a storage battery 10 (10B) located midway through the storage battery string 20. For convenience of explanation, FIG. 1 illustrates a configuration in which the plurality of storage battery strings 20 are connected in parallel with each other between the fourth storage battery 10 (10B) and the fifth storage battery 10 (10B) from the AC / DC converter (PCS) 50 side. Also, the storage battery 10 (10B) located midway through the storage battery string 20 is connected in parallel with each other by a conductive bar 70, which is a connection cable. In the deterioration determination device 1 for a battery system, for each battery string 20, the multiple battery strings 20, 20, 20... are connected in parallel to each other at a predetermined battery 10 (10B) among the multiple batteries 10 (10B) located along the battery string 20. Therefore, the battery system 11 is divided by a single conductive bar 70 into two blocks, a battery string block 12A and a battery string block 12B.

[0026] Furthermore, the multiple battery strings 20, 20, 20... located in battery string block 12A, i.e., the first battery string 20-1, the second battery string 20-2, the third battery string 20-3, and the fourth battery string 20-4, are connected to the multiple battery strings 20, 20, 20... located in battery string block 12B, i.e., the first battery string 20-1, the second battery string 20-2, the third battery string 20-3, and the fourth battery string 20-4, by the above-mentioned single conduction bar 70. In other words, battery string block 12A and battery string block 12B share the single conduction bar 70.

[0027] The deterioration determination device 1 for a battery system is also provided with current sensors 40 and 80. The current sensors 40 and 80 are sensors that measure a current value and a direction of current flow. The current sensor 40 is connected between the battery string 20 and the power conversion system (PCS) 50. For each battery string 20, the current sensor 40 is connected to the battery 10 (10A) located at the end of the battery string 20 on the power conversion system (PCS) 50 side. Thus, the current sensor 40 is provided between the first battery string 20-1 and the second battery string 20-2, between the second battery string 20-2 and the third battery string 20-3, and between the third battery string 20-3 and the fourth battery string 20-4. From the above, in the deterioration determination device 1 for a battery system, a plurality of current sensors 40 (four in FIG. 1) are provided in the battery string block 12A.

[0028] As shown in Fig. 1, for example, if deterioration progresses in the storage battery 10 of the first storage battery string 20-1 located in the storage battery string block 12A, the voltage of the first storage battery string 20-1 when charging / discharging of the storage battery 10 is stopped is lower than the voltages of the second storage battery string 20-2, the third storage battery string 20-3, and the fourth storage battery string 20-4 located in the storage battery string block 12A. This causes a circulating current (hereinafter, the circulating current may also be referred to as Ic) which is a charging current Ic from the second storage battery string 20-2, the third storage battery string 20-3, and the fourth storage battery string 20-4 to the first storage battery string 20-1. In other words, when charging / discharging of the storage battery 10 is stopped, a circulating current Ic is generated from a storage battery string 20 that does not have a deteriorated storage battery 10 to a storage battery string 20 that has a deteriorated storage battery 10. The current sensor 40 measures the circulating current Ic and its direction generated among the first battery row 20-1, the second battery row 20-2, the third battery row 20-3, and the fourth battery row 20-4 located in the battery row block 12A when charging or discharging of the battery 10 is stopped.

[0029] The current sensor 80 is provided on the conduction bar 70. Specifically, one current sensor 80 is provided each between the first battery row 20-1 and the second battery row 20-2 located in the battery row block 12B, between the second battery row 20-2 and the third battery row 20-3, and between the third battery row 20-3 and the fourth battery row 20-4. As described above, a plurality of current sensors 80 (three in FIG. 1 ) are provided in the battery row block 12B.

[0030] For example, if deterioration progresses in the storage battery 10 of the first storage battery row 20-1 located in the storage battery row block 12B, the voltage of the first storage battery row 20-1 when charging / discharging of the storage battery 10 is stopped will be lower than the voltages of the second storage battery row 20-2, the third storage battery row 20-3, and the fourth storage battery row 20-4 located in the storage battery row block 12B. This causes a circulating current (not shown) to be generated from the second storage battery row 20-2, the third storage battery row 20-3, and the fourth storage battery row 20-4 to the first storage battery row 20-1. The current sensor 80 measures the circulating current and its direction generated between the first storage battery row 20-1, the second storage battery row 20-2, the third storage battery row 20-3, and the fourth storage battery row 20-4 located in the storage battery row block 12B when charging or discharging of the storage battery 10 is stopped.

[0031] 1, a battery management unit (BMU) 30 is connected to each of the current sensors 40, 80. Measurement information of the circulating current measured by each of the current sensors 40, 80 is input to the battery monitoring unit 30.

[0032] The battery monitoring device 30 is also connected to the AC / DC converter 50. When charging from the AC / DC converter 50 to the battery system 11 is stopped or discharging from the battery system 11 to an external power system is stopped, the battery monitoring device 30 analyzes the degree of variation in the charging current Ic between the first battery string 20-1, the second battery string 20-2, the third battery string 20-3, and the fourth battery string 20-4 and compares the charging current values ​​(Icc) based on information on the charging current value (Icc) and the direction of the charging current (Ic) from the current sensors 40 and 80. Based on the results of the above analysis, the battery monitoring device 30 determines whether or not the batteries 10 in the first battery string 20-1, the second battery string 20-2, the third battery string 20-3, and the fourth battery string 20-4 have deteriorated, which may lead to abnormalities such as an internal short circuit or an internal liquid short circuit.

[0033] As shown in Figure 2, the battery monitoring device 30 is composed of a setting unit 31 that sets the deterioration judgment conditions of the battery 10, a measurement control unit 32 that collects measurement information of the circulating current from the current sensors 40, 80, a battery state judgment unit 33 that judges the state of the battery 10 based on the measurement information collected by the measurement control unit 32, a memory unit 34 that stores the above-mentioned measurement information, setting information and judgment information, and a communication unit 35 that displays the judgment information on a higher-level system or on a screen.

[0034] The battery state determination unit 33 determines whether or not degradation has occurred in the batteries 10 in the first battery row 20-1, the second battery row 20-2, the third battery row 20-3, and the fourth battery row 20-4 located in the battery row block 12A, based on measurement information of the circulating current (Ic) collected from the current sensor 40. The battery state determination unit 33 also determines whether or not degradation has occurred in the batteries 10 in the first battery row 20-1, the second battery row 20-2, the third battery row 20-3, and the fourth battery row 20-4 located in the battery row block 12B, based on measurement information of the circulating current collected from the current sensor 80.

[0035] Next, the operation of the deterioration determination device 1 of the battery system, which is an embodiment of the deterioration determination method of the battery system according to the present invention, will be described with reference to a flowchart 60 in FIG. 3. The deterioration determination process of the battery system 11 is started at a timing set by the setting unit 31 of the battery monitoring unit (BMU) 30 for determining whether or not the battery system 11 has deteriorated by repeatedly charging the battery system 11 from an external power system and discharging the battery system 11 to a load for a predetermined period of time (step 61). Next, the battery monitoring unit 30 determines whether or not the charging and discharging of the battery system 11 has been stopped based on information from the current sensor 40 or the AC / DC converter (PCS) 50 (step 62). When the battery monitoring unit 30 determines that the charging and discharging of the battery system 11 has been stopped, the measurement control unit 32 of the battery monitoring unit 30 measures the circulating current value (Icc) and the direction of the circulating current (Ic) from the current sensors 40 and 80, and collects measurement information (step 63).

[0036] Next, the battery state determination unit 33 determines whether the circulating current value (Icc) is equal to or greater than the threshold value a (step 64). The threshold value a of the circulating current value (Icc) is set in the setting unit 31 in advance.

[0037] Next, when the battery state determination unit 33 determines that the circulating current value (Icc) is equal to or greater than the threshold value a, the battery state determination unit 33 determines that deterioration has occurred in any of the batteries 10 in the battery system 11 (step 65). Furthermore, the battery monitoring device 30 displays the occurrence of deterioration on a control screen, which is a higher-level system or the communication unit 35 of the battery monitoring device (BMU) 30, as necessary. Next, the battery state determination unit 33 determines the battery string block 12 and the battery string 20 having the deteriorated battery 10 based on the measurement information of the circulating current (Ic) from the current sensors 40 and 80 (step 66). Next, the battery state determination unit 33 determines the degree of deterioration (SOH: State Of Health) of the battery string 20 having the deteriorated battery 10 from the value of the circulating current value Icc (step 67).

[0038] As shown in Fig. 4, the state of health (SOH) of the battery string 20 is determined, for example, by calculating it from a linear function of the circulating current value (Icc) and the state of health (SOH). In Fig. 4, a smaller SOH indicates a greater degree of degradation, and a larger SOH indicates a smaller degree of degradation. If necessary, the temperature of each battery string block 12 may be measured when measuring the circulating current Ic, and the state of health (SOH) may be corrected according to the temperature distribution.

[0039] On the other hand, if the battery monitoring device 30 determines in step 62 that the charging and discharging of the storage battery system 11 has not been stopped, it again determines whether or not the charging and discharging of the storage battery system 11 has been stopped (step 62). If the battery state determination unit 33 determines in step 64 that the circulating current value (Icc) is less than the threshold value a, the process returns to step 62, and the battery monitoring device 30 determines whether or not the charging and discharging of the storage battery system 11 has been stopped.

[0040] The storage battery 10 may be, for example, a bipolar lead-acid battery. In a bipolar lead-acid battery, a plurality of cell members with electrolytic layers interposed therebetween and resin substrates are alternately stacked between a positive electrode and a negative electrode, and a resin frame-shaped frame that surrounds the cells is disposed between the opposing substrates, and the cell members are electrically connected in series. The positive electrode has a positive electrode lead layer made of lead or a lead alloy, and a positive electrode active material layer containing an active material provided on the positive electrode lead layer. The negative electrode has a negative electrode lead layer made of lead or a lead alloy, and a negative electrode active material layer containing an active material provided on the negative electrode lead layer. The electric field layer interposed between the positive electrode and the negative electrode is, for example, a glass fiber mat impregnated with an electrolyte such as sulfuric acid. The resin substrate is a frame plate made of a sulfuric acid-resistant thermoplastic resin (e.g., polyethylene, polypropylene, polystyrene, polyvinyl chloride, polymethyl methacrylate (acrylic resin), acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (nylon), polycarbonate, etc.) formed into a rectangular flat plate shape. The current sensors 40, 80 measure the charge / discharge current flowing through each storage battery string 20 and determine the state of charge (SOC) of the storage battery 10, so a highly accurate current sensor with excellent temperature characteristics and little measurement error is preferred.

[0041] In this way, in the deterioration determination device 1 for a storage battery system, the circulating current Ic generated by the voltage difference between the storage battery strings 20 or the like is measured when charging or discharging of the storage batteries 10 is stopped, so that the storage battery system 11 can be prevented from being affected by temperature distribution, and the accuracy of deterioration determination of the storage battery system 11 is improved. In addition, in the deterioration determination device 1 for a storage battery system, the circulating current Ic is measured when charging or discharging of the storage batteries 10 is stopped, so that the measurement of the current value of the circulating current Ic itself is facilitated and highly accurate, and the accuracy of deterioration determination of the storage battery system 11 is improved. In addition, in the deterioration determination device 1 for a storage battery system, the storage battery string 20 in which a plurality of storage batteries 10 are connected in series is divided into a plurality of storage battery string blocks 12, so that an increase in the internal resistance of the storage battery string 20 can be prevented, so that the circulating current Ic flows more easily, the measurement accuracy of the circulating current Ic is improved, and the accuracy of determining that the storage battery 10 has deteriorated before an abnormality such as an internal short circuit or an internal liquid short occurs in the storage battery 10 is improved.

[0042] In addition, in the deterioration determination device 1 for the battery system, current sensors 40, 80 are provided between adjacent battery strings 20 in the battery string block 12, so that deterioration determination can be performed accurately for each battery string 20 in the battery string block 12.

[0043] <Second Example> Next, a deterioration determination device for a battery system according to a second embodiment of the present invention will be described. Note that the deterioration determination device for a battery system according to the second embodiment has major components in common with the deterioration determination device for a battery system according to the first embodiment, and therefore the same components as those in the first embodiment will be described using the same reference numerals. Fig. 5 is a schematic diagram of a deterioration determination device 2 for a battery system according to the second embodiment of the present invention.

[0044] In the device 1 for determining deterioration of a battery system, the battery system 11 is divided into two blocks, a battery string block 12A and a battery string block 12B, by a single conduction bar 70. Instead, as shown in Fig. 5, in the device 2 for determining deterioration of a battery system, the first battery string 20-1, the second battery string 20-2, the third battery string 20-3, and the fourth battery string 20-4 located in the battery string block 12A are connected in parallel by the first conduction bar 70-1, and the first battery string 20-1, the second battery string 20-2, the third battery string 20-3, and the fourth battery string 20-4 located in the battery string block 12B are connected in parallel by a second conduction bar 70-2 that is different from the first conduction bar 70-1. In the deterioration determination device 2 for a storage battery system, a storage battery system 11 is divided by different conduction bars 70 into two blocks, a storage battery string block 12A and a storage battery string block 12B.

[0045] The first conductive bar 70-1 and the second conductive bar 70-2 are connected by a single battery string block connection bar 90. Therefore, the battery string block 12A and the battery string block 12B are connected in series by a single connection portion (the battery string block connection bar 90).

[0046] In the deterioration determination device 2 for the battery system, a current sensor 40 for measuring a circulating current Ic occurring between the battery strings 20 located in the battery string block 12A is connected to a battery 10 (10A) located at an end of the battery string 20 on the side of the AC / DC converter (PCS) 50 for each battery string 20. A current sensor 80 for measuring a circulating current Ic occurring between the battery strings 20 located in the battery string block 12B is provided between the first battery string 20-1 and the second battery string 20-2, between the second battery string 20-2 and the third battery string 20-3, and between the third battery string 20-3 and the fourth battery string 20-4, one each. The current sensor 80 is provided in the second conduction bar 70-2.

[0047] In the battery system deterioration determination device 2, the battery string block 12A is connected in series with the battery string block 12B via a single connection, so that the circulating current Ic generated in each battery string block 12 can be accurately measured for each battery string block 12, further improving the accuracy of deterioration determination for the battery system 11. That is, in the battery system deterioration determination device 2, for example, if the battery 10 located in the battery string block 12A is deteriorated and the battery 10 located in the battery string block 12B is not deteriorated, the circulating current Ic will more easily flow only through the battery string block 12A, and the circulating current Ic originating from the battery string block 12A will more unlikely to flow through the battery string block 12B.

[0048] <Third Example> Next, a deterioration determination device for a battery system according to a third embodiment of the present invention will be described. Note that the deterioration determination device for a battery system according to the third embodiment has major components in common with the deterioration determination devices for a battery system according to the first and second embodiments, so the same components as those in the first and second embodiments will be described using the same reference numerals. Fig. 6 is a schematic diagram of a deterioration determination device 2 for a battery system according to the third embodiment of the present invention.

[0049] In the deterioration determination device 2 for a battery system according to the second embodiment, the current sensors 40 for measuring the circulating current Ic occurring between the battery strings 20 located in the battery string block 12A are connected to each of the battery strings 20, and the current sensors 80 for measuring the circulating current Ic occurring between the battery strings 20 located in the battery string block 12B are provided between the first battery string 20-1 and the second battery string 20-2, between the second battery string 20-2 and the third battery string 20-3, and between the third battery string 20-3 and the fourth battery string 20-4. Instead, as shown in FIG. 6, in the deterioration determination device 3 for a battery system, each of the battery string blocks 12 is provided with one current sensor.

[0050] As shown in FIG. 6, one current sensor 40 is provided between the multiple battery strings 20, 20, 20... connected in parallel at the position of the battery string block 12A, and one current sensor 80 is provided between the multiple battery strings 20, 20, 20... connected in parallel at the position of the battery string block 12B. As described above, in the deterioration determination device 3 for a battery system, one current sensor 40, 80 measures the circulating current of the multiple battery strings 20. In addition, in the deterioration determination device 3 for a battery system, one current sensor 40 and one current sensor 80 are each provided between the third battery string 20-3 and the fourth battery string 20-4. In addition, in the deterioration determination device 3 for a battery system, a current sensor 41 is provided between the battery string block 12A and the AC / DC converter (PCS) 50 to measure the charge / discharge current between the battery system 11 and the AC / DC converter (PCS) 50.

[0051] In the battery system deterioration determination device 3, each battery string block 12 is provided with one current sensor, so that the deterioration of the battery system 11 can be determined for each battery string block 12. Therefore, when replacing the batteries 10 for each battery string block 12, the accuracy of determining the deterioration of the battery system 11 is improved with a simple structure.

[0052] <Fourth Example> Next, a deterioration determination device for a storage battery system according to a fourth embodiment of the present invention will be described. Note that the deterioration determination device for a storage battery system according to the fourth embodiment has major components in common with the deterioration determination devices for storage battery systems according to the first to third embodiments, and therefore the same components as those in the first to third embodiments will be described using the same reference numerals. Fig. 7 is a schematic diagram of the deterioration determination device for a storage battery system according to the fourth embodiment of the present invention.

[0053] As shown in Fig. 7, in the deterioration determination device 4 for a storage battery system of the fourth embodiment, a switch means 42 is provided between the AC / DC converter (PCS) 50 and the current sensor 41 of the deterioration determination device 3 for a storage battery system, for disconnecting the AC / DC converter (PCS) 50 and the storage battery system 11 when charging or discharging of the storage battery 10 is stopped. By turning on and off the switch means 42, the AC / DC converter (PCS) 50 and the storage battery system 11 can be electrically connected or disconnected. In Fig. 7, the AC / DC converter (PCS) 50 and the storage battery system 11 are electrically disconnected by the switch means 42.

[0054] By providing the switch means 42 between the power conversion system (PCS) 50 and the battery system 11, the power conversion system (PCS) 50 and the battery system 11 can be separated from each other when determining the deterioration of the battery system 11 when charging or discharging of the battery 10 is stopped. Therefore, the circulating current can be measured without being affected by the power conversion system (PCS) 50, which further improves the accuracy of determining the deterioration of the battery system 11.

[0055] Next, other embodiments of the deterioration determination device for a battery system of the present invention will be described. In each of the above-mentioned embodiments, the battery string has eight batteries connected in series, but depending on the usage conditions of the battery system, the battery string may have nine or more batteries connected in series, or may have seven or less batteries connected in series. In each of the above-mentioned embodiments, the battery system is divided into two battery string blocks, but instead, the battery system may be divided into three or four or more battery string blocks.

[0056] <Fifth Example> Next, a deterioration determination device for a storage battery system according to a fifth embodiment of the present invention will be described. Note that the deterioration determination device for a storage battery system according to the fifth embodiment has major components in common with the deterioration determination devices for storage battery systems according to the first to fourth embodiments, and therefore the same components as those in the first to fourth embodiments will be described using the same reference numerals.

[0057] Fig. 11 is a schematic diagram of a deterioration determination device for a storage battery system according to a fifth embodiment of the present invention. As shown in Fig. 11, a storage battery system 11 of the deterioration determination device 5 for a storage battery system according to the fifth embodiment has a plurality of storage batteries 10. A plurality of storage batteries 10 are connected in series to form storage battery strings L11-L14 and L21-L24. Fig. 11 shows an example in which four storage batteries 10 are connected in series as an example of the storage battery strings L11-L14 and L21-L24, but the number of storage batteries 10 forming one storage battery string is not limited to four and may be two or more.

[0058] The battery rows L11 to L14 and L21 to L24 are connected in parallel to form battery blocks B11, B12, B21, and B22. Specifically, adjacent battery rows L11 and L12 are connected in parallel to form battery block B11, and adjacent battery rows L13 and L14 are connected in parallel to form battery block B12. Adjacent battery rows L21 and L22 are connected in parallel to form battery block B21, and adjacent battery rows L23 and L24 are connected in parallel to form battery block B22. In FIG. 11, an example in which two battery rows are connected in parallel is shown as an example of battery blocks B11, B12, B21, and B22, but the number of battery rows forming one battery block is not limited to two and may be three or more.

[0059] The storage battery blocks B11, B12, B21, and B22 are connected in series to form the assembled batteries BP1 and BP2. Specifically, the storage battery block B11 and the storage battery block B21 are connected in series to form the assembled battery BP1, and the storage battery block B12 and the storage battery block B22 are connected in series to form the assembled battery BP2. In FIG. 11, an example of an assembled battery is shown in which two storage battery blocks are connected in series, but the number of storage battery blocks forming one assembled battery is not limited to two, and three or more storage battery blocks may be connected in series to form one assembled battery. In the storage battery system 11, the number of assembled batteries is not limited to two, and may be three or more.

[0060] A current sensor 40 is connected in series to each of the assembled batteries BP1 and BP2. The current sensor 40 connected in series to the assembled battery BP1 and the current sensor 40 connected in series to the assembled battery BP2 are connected in parallel, and the connection point of the two current sensors 40 is connected to the AC / DC converter 50. In addition, the current sensor 40 connected in series to the assembled battery BP1 and the current sensor 40 connected in series to the assembled battery BP2 are each connected to the battery monitoring device 30.

[0061] 11, if deterioration of the storage battery 10 progresses, a circulating current is generated when charging and discharging are stopped in the storage battery system 11. The deterioration determination device 5 of the storage battery system measures this circulating current and determines the deterioration of the storage battery 10 based on the measurement result.

[0062] Fig. 12 is a flowchart showing the flow of a process for determining the deterioration of the storage battery 10 in the fifth embodiment. Fig. 13 is a diagram showing an example of the flow of circulating current when there is a deteriorated storage battery 10 in the battery pack BP1, and the deteriorated storage battery 10 is indicated by hatching. The operation of determining the deterioration of the storage battery 10 in the fifth embodiment will be described with reference to Figs. 12 and 13.

[0063] When the battery monitoring device 30 has operated the battery system 11 by repeatedly charging the battery system 11 from an external power system and discharging the battery system 11 to a load for a predetermined period of time, and it becomes time to determine whether or not the battery system 11 has deteriorated as set in the setting unit 31, the battery monitoring device 30 starts the deterioration determination process for the battery system 11 shown in Figure 12.

[0064] First, the battery monitoring device 30 determines whether or not charging and discharging of the battery system 11 has been stopped based on information from the current sensor 40 or the AC / DC converter 50 (step S101). If the battery monitoring device 30 determines that charging and discharging have not been stopped (NO in step S101), it repeats the process of step S101. If the battery monitoring device 30 determines that charging and discharging of the battery system 11 have been stopped (YES in step S101), it acquires the circulating current value and the direction of the circulating current measured by the current sensor 40 in the measurement control unit 32 (step S102).

[0065] For example, as shown in Fig. 13, if deterioration of the hatched storage battery 10 in the battery pack BP1 progresses, a current distribution occurs in the battery system 11 during charging and discharging, and as a result, when charging and discharging are stopped, a voltage difference occurs between the battery strings L11 and L12 in the battery block B11 of the battery pack BP1 that includes the deteriorated storage battery 10. To eliminate this voltage difference, a circulating current i11 occurs in the battery block B11 in the direction of the arrow from the battery string L12 to the battery string L11 shown in Fig. 12.

[0066] Furthermore, when a circulating current occurs in the storage battery block B11, a voltage difference occurs between the battery packs BP1 and BP2. To eliminate this voltage difference between the battery packs BP1 and BP2, a circulating current flows from the battery pack BP1 to the battery pack BP2 in the storage battery system 11. The current sensor 40 connected to the battery pack BP1 measures the circulating current i1 flowing from the battery pack BP2 to the battery pack BP1, and the current sensor 40 connected to the battery pack BP2 measures the circulating current i2 flowing from the battery pack BP2 to the battery pack BP1, i.e., the sum of the circulating current i21 flowing from the battery pack L13 and the circulating current i22 flowing from the battery pack L14.

[0067] The battery monitoring device 30 acquires the current value and direction of the circulating current i1 measured by the current sensor 40 connected to the assembled battery BP1, and the current value and direction of the circulating current i2 measured by the current sensor 40 connected to the assembled battery BP2 using the measurement control unit 32 (step S102).

[0068] Next, the battery monitoring device 30 determines the deterioration of the battery 10 in the battery state determination unit 33 based on the current value and direction of the acquired circulating current i1 and the current value and direction of the acquired circulating current i2. Specifically, the battery monitoring device 30 first determines whether the sum of the current value of the circulating current i1 and the current value of the circulating current i2 is equal to or less than a predetermined first threshold value (step S103). The first threshold value is set in advance by the setting unit 31.

[0069] When the storage battery 10 has deteriorated and a circulating current is occurring between the assembled batteries BP1 and BP2, the circulating currents i1 and i2 have equal values ​​but opposite polarities, so the sum of the circulating currents i1 and i2 is 0, and the battery monitoring device 30 determines that the circulating currents are equal to or less than the first threshold (YES in step S103). If the battery monitoring device 30 determines NO in step S103, it returns the process to step S101.

[0070] When the sum of the current value of the circulating current i1 and the current value of the circulating current i2 is equal to or less than a first threshold value, the battery monitoring device 30 determines the deterioration of the battery 10 based on the absolute value of the current value of the circulating current i1 and the absolute value of the current value of the circulating current i2 (step S104). Specifically, the battery monitoring device 30 determines whether the absolute value of the current value of the circulating current i1 and the absolute value of the current value of the circulating current i2 are both equal to or more than a second threshold value determined in advance. The second threshold value is set in advance by the setting unit 31. When the absolute value of the current value of the circulating current i1 and the absolute value of the current value of the circulating current i2 are both equal to or more than a second threshold value determined in advance (YES in step S104), the battery monitoring device 30 determines that the battery 10 is deteriorated (step S105). When the battery monitoring device 30 determines NO in step S104, the process flow returns to step S101.

[0071] According to this embodiment, the occurrence of deterioration of the storage battery 10 can be detected without providing a current sensor 40 in each of the series-connected storage battery strings L11 to L14 and L21 to L24.

[0072] In the fifth embodiment, as shown in Fig. 14, a switch means 42 may be provided between the power conversion system (PCS) 50 and the current sensor 40, for disconnecting the power conversion system (PCS) 50 from the battery system 11 when charging or discharging of the battery 10 is stopped. By turning on and off the switch means 42, the power conversion system (PCS) 50 and the battery system 11 can be electrically connected or disconnected. In Fig. 14, the power conversion system (PCS) 50 and the battery system 11 are electrically disconnected from each other by the switch means 42.

[0073] By providing the switch means 42 between the AC / DC converter (PCS) 50 and the storage battery system 11, the AC / DC converter (PCS) 50 and the storage battery system 11 can be separated from each other when determining deterioration of the storage battery system 11 when charging or discharging of the storage battery 10 is stopped. Therefore, the circulating current can be measured without being affected by the AC / DC converter (PCS) 50, further improving the accuracy of determining deterioration of the storage battery system 11. The switch means 42 may be a mechanical switch or a semiconductor switch. [Industrial Applicability]

[0074] The present invention can be used to determine the deterioration of a storage battery. [Explanation of symbols]

[0075] 1, 2, 3, 4 Battery system deterioration determination device 10. Storage battery 11 Battery storage system 12 Battery String Block 20 Battery Array 30 Battery monitoring device 32 Measurement control section 33 Battery state determination unit 40 Current Sensor 80 Current Sensor

Claims

1. A deterioration determination device for a storage battery system in which a plurality of storage batteries are connected in series and a plurality of battery strings are connected in parallel, the plurality of battery strings are connected in parallel to each other at the ends of the battery strings and the intermediate batteries of the battery strings, thereby dividing the battery system into a plurality of battery string blocks; a measurement control unit that collects values ​​of the circulating current measured by the current sensor; and a battery state determination unit that determines whether or not the batteries in the battery string block have deteriorated from the collected values ​​of the circulating current.

2. The deterioration determination device for a battery system according to claim 1 , wherein the battery string block is connected in series to another battery string block via a single connection part.

3. The deterioration determination device for a battery system according to claim 1 , wherein each battery string block is provided with a plurality of the current sensors.

4. The deterioration determination device for a battery system according to claim 3 , wherein the current sensor is provided between each of the adjacent battery strings in the battery string block.

5. The deterioration determination device for a battery system according to claim 1 , wherein the current sensor is provided for each of the battery string blocks.

6. A deterioration determination device for a storage battery system as described in any one of claims 1 to 5, wherein a switch means is provided between the AC / DC conversion device and the storage battery system, for disconnecting the AC / DC conversion device and the storage battery system when charging or discharging of the storage battery is stopped.

7. A method for determining deterioration of a battery system in which a plurality of battery strings, each of which is connected in parallel, is formed by connecting a plurality of storage batteries in series, the plurality of battery strings are connected in parallel to each other at the ends of the battery strings and the intermediate batteries of the battery strings, thereby dividing the battery system into a plurality of battery string blocks; measuring a circulating current occurring between the battery strings in each of the battery string blocks when charging or discharging of the battery is stopped; collecting measured values ​​of the circulating current; and determining whether or not deterioration has occurred in the batteries in the battery string block from the collected circulating current values.

8. A deterioration determination device for determining deterioration of a storage battery in a storage battery system in which a plurality of assembled batteries are connected in parallel, the assembled batteries being each configured to have a plurality of storage battery blocks connected in parallel in a plurality of battery strings each including a plurality of storage batteries connected in series, the deterioration determination device comprising: a measurement control unit that is provided for each of the assembled batteries and connected in parallel, and that collects values ​​of circulating currents measured by current sensors that measure circulating currents generated between the assembled batteries when charging or discharging of the storage battery is stopped; a battery state determination unit that determines deterioration of the battery from the collected value of the circulating current; A deterioration determination device for a storage battery system comprising:

9. The storage battery state determination unit determines that the storage battery is degraded when a sum of the circulating currents measured by the current sensors is equal to or less than a predetermined first threshold value and an absolute value of each of the circulating currents measured by the current sensors is equal to or greater than a predetermined second threshold value. The deterioration determination device for a storage battery system according to claim 8.

10. A battery monitoring device includes a plurality of assembled batteries, each of which is configured by connecting a plurality of battery blocks in series, each of which is configured by connecting a plurality of batteries in parallel in a plurality of battery strings, and monitors a battery system in which the assembled batteries are connected in parallel, a measurement control unit that is provided for each of the assembled batteries and connected in parallel, and that collects values ​​of circulating currents measured by current sensors that measure circulating currents generated between the assembled batteries when charging or discharging of the storage battery is stopped; a battery state determination unit that determines deterioration of the battery from the collected value of the circulating current; A battery monitoring device comprising:

11. The storage battery state determination unit determines that the storage battery is degraded when a sum of the circulating currents measured by the current sensors is equal to or less than a predetermined first threshold value and an absolute value of each of the circulating currents measured by the current sensors is equal to or greater than a predetermined second threshold value. The battery monitoring device according to claim 10.

12. A deterioration determination device for a storage battery system according to claim 8 or claim 9, or a storage battery monitoring device according to claim 10 or claim 11; A battery string in which a plurality of batteries are connected in series; A storage battery system having A plurality of the assembled batteries are connected in parallel, a current sensor for measuring a circulating current generated between the battery packs when charging or discharging of the storage battery is stopped is provided for each battery pack and connected in parallel; Battery storage system.

13. A deterioration determination method for a storage battery system, comprising: a plurality of assembled batteries each including a plurality of battery blocks connected in series, each battery block including a plurality of battery strings each including a plurality of batteries connected in parallel, the plurality of assembled batteries being connected in parallel, the method determining deterioration of the storage batteries in the storage battery system, the plurality of assembled batteries being connected in parallel, a step of collecting values ​​of circulating currents measured by current sensors provided for each of the assembled batteries and connected in parallel, the current sensors measuring circulating currents generated between the assembled batteries when charging or discharging of the storage battery is stopped; determining deterioration of the storage battery from the collected value of the circulating current; A method for determining deterioration of a storage battery system comprising:

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