Management device and power storage system

The present invention relates to a management device and a power storage system for performing a control for equalizing a plurality of power storage blocks configuring a power storage module.

In a battery module in which battery blocks in which a plurality of battery cells is connected in parallel are connected in series, a fuse that is connected in series to each of the battery cells and that is used for breaking an over current blows when an excessive current flows, and blocks a path. In each of the battery blocks, when many fuses blow, amounts of currents flowing into others of the battery cells in which no fuse is blown increase, and the increased amounts of currents burden the others of the battery cells. A system for detecting a blown fuse is therefore required.

For example, a possible idea is to detect a voltage at both ends of a fuse to detect whether the fuse is blown. However, when many battery cells are used, increases in a number of wires used, a circuit area, and a cost become significant. Another possible idea is to detect whether a fuse is blown based on a relationship between an amount of change in a State Of Charge (SOC) in a battery block and an assumed amount of change in an SOC when no fuse is blown (for example, see PTL 1). However, when obtaining an SOC through a current integration method, a method for detecting whether a fuse is blown based on an amount of change in SOC could be affected by an error when measuring a current.

Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 2013-160539

The present invention is developed for the purpose of solving such requirements. One non-limiting and explanatory embodiment provides a technology for precisely detecting at a lower cost whether a fuse connected to a cell is blown.

To solve the above-mentioned requirements, a management device according to an aspect of the present invention is a management device for managing a power storage device in which a plurality of power storage blocks in which a plurality of series circuits of fuses and power storage cells is connected in parallel is connected in series, and includes an equalization controller for performing, when a voltage difference among the power storage blocks exceeds a set voltage difference, a control for equalizing the power storage blocks, and a blowout determination unit for determining, based on a frequency of equalization performed by the equalization controller, whether one of the fuses is blown.

Any desired combinations of the above described components and converted expressions of the present invention in methods, devices, systems, and other similar entities are still effective as aspects of the present invention.

According to the present invention, whether a fuse connected to a cell is blown can precisely be detected at a lower cost.

FIG. 1 is a view illustrating an example of a power storage module according to an exemplary embodiment of the present invention.

FIG. 2 is a view for describing a power storage system according to the exemplary embodiment of the present invention.

FIG. 3 is a view illustrating voltages of a first battery block to a third battery block according to the exemplary embodiment of the present invention, after the first battery block to the third battery block have been charged or discharged from a state where voltages are even.

FIG. 4 is a flowchart illustrating an example of a process for determining whether a fuse is blown, according to a practical example 1.

FIG. 5 is a flowchart illustrating an example of a process for determining whether a fuse is blown, according to a practical example 2.

FIG. 6 is a view illustrating an example of integral times of equalization of the battery blocks after charging and integral times of equalization of the battery blocks after discharging.

An exemplary embodiment of the present invention relates to a battery management device for managing a power storage module. Power storage modules that this exemplary embodiment encompasses are power storage modules in which a plurality of battery blocks in which a plurality of series circuits of fuses and battery cells is connected in parallel is connected in series. Available battery cells include lithium ion battery cells, nickel hydride battery cells, and lead battery cells. A voltage of a power storage module can be increased by connecting in series many battery cells, while a capacity of a power storage module can be increased by connecting in parallel many battery cells.

FIG. 1 is a view illustrating an example of power storage module 20 according to the exemplary embodiment of the present invention. In the example shown in FIG. 1 , three battery blocks (first battery block B 1 , second battery block B 2 , and third battery block B 3 ) are connected in series to form power storage module 20 . In first battery block B 1 , positive electrodes of 20 battery cells S 11 to S 120 are respectively connected with fuses F 11 to F 120 , and 20 battery cells S 11 to S 120 connected with the fuses are connected in parallel. The example shown in FIG. 1 renders cylindrical lithium ion batteries connected in parallel to form a battery block. Also in second battery block B 2 , similar to first battery block B 1 , positive electrodes of 20 battery cells S 21 to S 220 are respectively connected with fuses F 21 to F 220 , and 20 battery cells S 21 to S 220 connected with the fuses are connected in parallel. Similarly, in third battery block B 3 , positive electrodes of 20 battery cells S 31 to S 320 are respectively connected with fuses F 31 to F 320 , and 20 battery cells S 31 to S 320 connected with the fuses are connected in parallel.

First equalizing circuit 21 is connected in parallel to first battery block B 1 , second equalizing circuit 22 is connected in parallel to second battery block B 2 , and third equalizing circuit 23 is connected in parallel to third battery block B 3 . The example of FIG. 1 renders a series circuit of first discharge switch SW 1 and first resistor R 1 configuring first equalizing circuit 21 . Second equalizing circuit 22 and third equalizing circuit 23 are configured in a similar manner. A configuration of this type is to equalize voltages of first battery block B 1 to third battery block B 3 through discharging. In first battery block B 1 to third battery block B 3 , when one of the battery blocks has a least voltage, voltages of others of the battery blocks are leveled to the least voltage to achieve equalization. As an example, the discharge switches of the others of the battery blocks are controlled and turned on to cause the others of the battery blocks to discharge electricity so that the voltages of the others of the battery blocks lower to the least voltage of the one of the battery blocks.

Power storage module 20 is connected to load 2 . For example, in an on-vehicle application, load 2 is a motor. In this case, between power storage module 20 and load 2 , an inverter circuit (not shown) is connected. At a time of power running, DC power discharged from power storage module 20 is converted into AC power by the inverter circuit and supplied to the motor. At a time of regeneration, AC power generated by the motor is converted into DC power by the inverter circuit and used for charging power storage module 20 . A chargeable configuration through a plug-in manner from an external battery charger may be applied.

When power storage module 20 is used for a stationary peak shaving/back up application, load 2 is a load of a system or a general/special purpose. Also in this case, between power storage module 20 and load 2 , an inverter circuit (not shown) is connected. When charging power storage module 20 , AC power supplied from the system is converted into DC power by the inverter circuit and used for charging power storage module 20 . When discharging power storage module 20 , DC power discharged from power storage module 20 is converted into AC power by the inverter circuit and allowed to flow back to the system, or supplied to a load of the general/special purpose. No inverter circuit is required when a charging power supply is a DC power supply such as a solar power generation system, and load 2 is a DC load. A DC/DC converter may be connected as required.

FIG. 2 is a view for describing power storage system 1 according to the exemplary embodiment of the present invention. Power storage system 1 includes power storage module 20 and battery management device 10 . Hereinafter, an assumed example uses power storage module 20 shown in FIG. 1 as power storage module 20 .

Battery management device 10 includes first voltage detector 11 , second voltage detector 12 , third voltage detector 13 , and controller 14 . First voltage detector 11 detects a voltage at both ends of first battery block B 1 , second voltage detector 12 detects a voltage at both ends of second battery block B 2 , and third voltage detector 13 detects a voltage at both ends of third battery block B 3 . Differential amplifier circuits using operational amplifiers may be used, for example, to configure first voltage detector 11 to third voltage detector 13 .

Controller 14 includes equalization controller 15 , equalization implementation information acquisition unit 16 , equalization implementation information storage unit 17 , and fuse blowout determination unit 18 . A configuration of controller 14 can be achieved through a hardware resource and a software resource co-operating each other, or by a hardware resource only. Available hardware resources include microcomputers, DSPs, ROMs, RAMs, FPGAs, and other LSIs. Available software resources include programs such as firmware.

Equalization controller 15 performs, based on voltages of first battery block B 1 to third battery block B 3 entered from first voltage detector 11 to third voltage detector 13 , when a voltage difference among the battery blocks exceeds a set voltage difference, a control for equalizing the battery blocks. In this exemplary embodiment, while power storage module 20 is neither charged nor discharged, a control for equalizing first battery block B 1 to third battery block B 3 is performed. In an on-vehicle application, a control for equalization is performed during an ignition off period. For example, when a difference in voltages (Open Circuit Voltage: OCV) among first battery block B 1 to third battery block B 3 exceeds 1% in terms of an SOC conversion, equalization controller 15 performs a control for equalization. For example, a control may be performed, so that, when a battery block has a least voltage, and a voltage difference between the least voltage and a voltage of another battery block is equal to or above a predetermined value set beforehand, a discharge switch of the other battery block is turned on to level or to almost level both the voltages. Another control may be performed, so that, when a battery block has a least voltage, a discharge switch of another battery block is turned on to level or to almost level a voltage of the other battery block to the least voltage.

Equalization implementation information acquisition unit 16 acquires information on implementation of equalization performed by equalization controller 15 , and records the information in equalization implementation information storage unit 17 . In this exemplary embodiment, information on implementation of equalization refers to information on discharging for equalizing battery blocks. Information on discharging includes a discharging time during which a discharge current flows. Equalization implementation information storage unit 17 is a non-volatile storage area for retaining information on implementation of equalization of battery blocks. Information on implementation of equalization exceeding a retention period is deleted. Fuse blowout determination unit 18 reads the information on implementation of equalization performed in a certain period, which is stored in equalization implementation information storage unit 17 , calculates a frequency of equalization, and determines, based on the calculated frequency of equalization, whether a fuse is blown.

In this exemplary embodiment, a frequency of equalization is defined to a number of discharging for equalizing battery blocks performed in a certain period, or an accumulated time of discharging for equalizing battery blocks performed in a certain period. A single equalization control, for example, discharging of first battery block B 1 and second battery block B 2 , increments a number of discharging of first battery block B 1 and a number of discharging of second battery block B 2 . Each discharge time taken for this equalization is also added to each accumulated time of discharging. A specific example for determining whether a fuse is blown based on a frequency of equalization will be described later.

Even when none of fuses F 11 to F 320 is blown, voltages of first battery block B 1 to third battery block B 3 might become uneven. For example, power storage module 20 self-discharges when left behind, but an amount of self-discharging differs depending on a temperature. For example, when self-discharging occurs while a temperature of first battery block B 1 is higher than a temperature of second battery block B 2 , first battery block B 1 self-discharges greater in amount. Consumption power of peripheral circuits also leads to unevenness in an amount of self-discharging. For example, when power to first voltage detector 11 to third voltage detector 13 is respectively supplied from first battery block B 1 to third battery block B 3 , due to unevenness in consumption power in first voltage detector 11 to third voltage detector 13 , a difference should occur in voltages of first battery block B 1 to third battery block B 3 .

A capacity of a battery block in which at least one fuse is blown becomes smaller than a capacity of another battery block in which no fuse is blown. The capacity of the battery block in which the fuse is blown therefore fluctuates greater than the capacity of the other battery block in which no fuse is blown, and thus a voltage difference should occur between the battery blocks. As described above, when a voltage difference among battery blocks reaches a certain value or greater, a control for equalization is performed. In this exemplary embodiment, whether a frequency of controls for equalization actually performed is greater than an assumed frequency is determined, and, when it is determined that a frequency exceeds the assumed frequency, it is assumed that a fuse is blown. In an assumed example state described below, as shown in FIG. 1 , two fuses F 319 , F 320 included in third battery block B 3 are blown.

FIG. 3 is a view illustrating voltages of first battery block B 1 to third battery block B 3 according to the exemplary embodiment of the present invention, after first battery block B 1 to third battery block B 3 have been charged or discharged from a state where voltages are even. Part (a) of FIG. 3 shows voltages after charging, while part (b) of FIG. 3 shows voltages after discharging. As described above, since, in third battery block B 3 , two fuses F 319 , F 320 are blown, two battery cells S 319 , S 320 are disconnected. A capacity of third battery block B 3 accordingly is smaller than capacities of first battery block B 1 and second battery block B 2 . In this state, since, after power storage module 20 is charged, an SOC of third battery block B 3 relatively increases, a voltage of third battery block B 3 accordingly becomes greater than voltages of first battery block B 1 and second battery block B 2 . On the other hand, since, from this state, when power storage module 20 is discharged, an SOC of third battery block B 3 relatively reduces, a voltage of third battery block B 3 accordingly becomes smaller than voltages of first battery block B 1 and second battery block B 2 .

Practical Example 1

Next, a practical example 1 when determining whether a fuse is blown based on a frequency of equalization will now be described herein. In the practical example 1, a total value of a number of discharging of all battery blocks is used. Fuse blowout determination unit 18 compares the total value and a threshold value to determine whether a fuse is blown. Alternatively, a total value of an accumulated time of discharging of all the battery blocks is used, and the total value and a threshold value are compared to determine whether a fuse is blown.

FIG. 4 is a flowchart illustrating an example of a process for determining whether a fuse is blown, according to the practical example 1. While power storage module 20 is stopped, when a voltage difference among battery blocks exceeds a set voltage difference, equalization controller 15 performs a control for equalization (S 10 ). Equalization implementation information acquisition unit 16 acquires information on implementation of equalization from equalization controller 15 , and records the information in equalization implementation information storage unit 17 (S 11 ).

When a time for determining whether a fuse is blown comes (Y in S 12 ), fuse blowout determination unit 18 reads, from equalization implementation information storage unit 17 , the information on implementation of equalization performed in a certain period to calculate a frequency of equalization (S 13 ). The time for determination comes each time a certain period passes. A certain period refers to a period for collecting data in a process for determining whether a fuse is blown, and is set by a designer. A frequency of equalization differs depending on whether a fuse is blown. However, a tendency of separation in such differences increases remarkably as a period extends longer. Accordingly, the longer a certain period, the higher precision in determining whether a fuse is blown. However, a period from when a fuse is blown to when the blown fuse is recognized would likely extend longer. The designer should take into account this trade-off relationship to determine a value of a certain period.

Fuse blowout determination unit 18 compares the calculated frequency of equalization and the threshold value (S 14 ), and determines that, when the frequency of equalization is greater than the threshold value (Y in S 14 ), a fuse is blown (S 15 ). When the frequency of equalization is equal to or smaller than the threshold value (N in S 14 ), fuse blowout determination unit 18 determines that no fuse is blown.

For the threshold value, an assumed value of a frequency of equalization to be performed in the above described certain period during which no fuse is blown is set. A frequency of equalization differs depending on a specification of a battery cell, a State Of Health (SOH), an application of power storage module 20 , a temperature in an installation location, and other factors. The designer should set the above described threshold value based on data obtained through experiments and simulations. For example, for power storage module 20 for which three controls for equalization are performed in a week, an assumed number of discharging in a week is six. To this number, a margin of two is added to set a threshold value of eight. In this example, when a number of discharging in a week, which is calculated based on collected data, exceeds eight, it is determined that a fuse is blown. A similar idea is used when a discharge time is used to set a threshold value.

A different threshold value in accordance with an SOH may be used. An SOH refers to a ratio between an initial full charge capacity and a present full charge capacity. Since a storage battery degrades through frequent use, a full charge capacity also lowers. When a full charge capacity lowers, a voltage difference would likely easily occur among battery blocks even though no fuse is blown. Accordingly, as an SOH lowers, the above described threshold value should accordingly be set to a greater value. Fuse blowout determination unit 18 retains a map of threshold values described by SOH ranges. Negative effects due to a lowered SOH can be eliminated, and thus precision in determining whether a fuse is blown can be kept in a certain range.

Practical Example 2

Next, a practical example 2 when determining whether a fuse is blown based on a frequency of equalization will now be described herein. In the practical example 2, when equalization implementation information acquisition unit 16 collects, by battery block, information on implementation of equalization, charge/discharge information indicating that whether a last (latest) charging/discharging operation performed before equalization is performed is a charging or discharging operation is also collected. Equalization implementation information acquisition unit 16 classifies information on implementation of equalization by battery block into whether the equalization has been performed after charging or discharging, and records the classified information. When power storage module 20 is used for an on-vehicle application, equalization implementation information acquisition unit 16 acquires charge/discharge information from, for example, an ECU. When power storage module 20 is used for a stationary peak shaving/back up application, equalization implementation information acquisition unit 16 acquires charge/discharge information from, for example, a power conditioner.

FIG. 5 is a flowchart illustrating an example of a process for determining whether a fuse is blown, according to the practical example 2. While power storage module 20 is stopped, when a voltage difference among battery blocks exceeds a set voltage difference, equalization controller 15 performs a control for equalization (S 20 ). Equalization implementation information acquisition unit 16 acquires charge/discharge information before the control for equalization is performed (S 21 ). Equalization implementation information acquisition unit 16 acquires from equalization controller 15 information on implementation of equalization (S 22 ). Equalization implementation information acquisition unit 16 separates the acquired information on implementation of equalization by battery block, and by after charging/discharging, and records the separated information in equalization implementation information storage unit 17 (S 23 ).

When a time for determining whether a fuse is blown comes (Y in S 24 ), fuse blowout determination unit 18 reads, from equalization implementation information storage unit 17 , the information on implementation of equalization performed in a certain period to calculate, by battery block, and by after charging/discharging, an integral time of equalization (S 25 ). In this example, as an integral time of equalization, an accumulated time of discharging is used. An initial value of “1” is set to parameter n (S 26 ).

Fuse blowout determination unit 18 determines whether an integral time of equalization after battery block (n) is charged is greater by first set value α or more than an average of integral times of equalization after another battery block (other than n) is charged, and an integral time of equalization after battery block (n) is discharged is smaller by second set value β or more than an average of integral times of equalization after another battery block (other than n) is discharged (S 27 ). When the above two conditions are satisfied (Y in S 27 ), fuse blowout determination unit 18 determines that a fuse included in battery block (n) is blown (S 28 ). When at least either of the above two conditions is not satisfied (N in S 27 ), fuse blowout determination unit 18 determines that no fuse included in battery block (n) is blown. After that, parameter n is incremented (S 29 ). While parameter n falls within a number of battery blocks included in power storage module 20 (N in S 30 ), step S 27 begins, and steps S 27 to S 29 are repeatedly processed. When parameter n exceeds the number of battery blocks included in power storage module 20 (Y in S 30 ), the process for determining whether a fuse is blown ends.

FIG. 6 is a view illustrating an example of integral times of equalization of the battery blocks after charging and integral times of equalization of the battery blocks after discharging. Part (a) of FIG. 6 shows integral times of equalization after charging, while part (b) of FIG. 6 shows integral times of equalization after discharging. As described above, since, in third battery block B 3 , two fuses F 319 , F 320 are blown, a capacity of third battery block B 3 is smaller than capacities of first battery block B 1 and second battery block B 2 .

As shown in part (a) of FIG. 3 and described above, since, after charging, an SOC of third battery block B 3 relatively increases, a voltage of third battery block B 3 accordingly becomes greater than voltages of first battery block B 1 and second battery block B 2 . Therefore, since, after charging, a control for equalization is performed to cause third battery block B 3 to discharge electricity, an integral time of equalization of third battery block B 3 after charging becomes largest. On the other hand, as shown in part (b) of FIG. 3 and described above, since, after discharging, an SOC of third battery block B 3 relatively reduces, a voltage of third battery block B 3 accordingly becomes smaller than voltages of first battery block B 1 and second battery block B 2 . Therefore, since, after discharging, a control for equalization is performed to cause first battery block B 1 and second battery block B 2 to discharge electricity, an integral time of equalization of third battery block B 3 after discharging becomes smallest.

Determination conditions used in step S 27 shown in FIG. 5 can be defined by Equations (1), (2) shown below.

Integral time of equalization after battery block ( n ) is charged>Average integral time of equalization after battery block (other than n ) is charged+α  Equation (1)

Integral time of equalization after battery block ( n ) is discharged<Average integral time of equalization after battery block (other than n ) is discharged−β  Equation (2)

Symbols α, β represent margins for preventing erroneous determinations, and are calculated beforehand based on differences in a standard integral time of equalization of battery blocks.

The example shown in part (a) of FIG. 6 satisfies a relationship of Integral time of equalization after third battery block B 3 is charged>Average integral time of equalization after first battery block B 1 and second battery block B 2 are charged+α. The example shown in part (b) of FIG. 6 satisfies a relationship of Integral time of equalization after third battery block B 3 is discharged<Average integral time of equalization after first battery block B 1 and second battery block B 2 are discharged−β. Therefore, it is determined that a fuse included in third battery block B 3 is blown. The examples shown in FIGS. 5, 6 have exemplified that, as a frequency of equalization, an integral time of equalization (accumulated time of discharging for equalization) is used. However, an integral number of equalization (accumulated number of discharge for equalization) may be used.

As described above, according to this exemplary embodiment, by comparing a frequency of equalization performed in a certain period and an assumed frequency of equalization, whether a fuse connected to a cell is blown can precisely be detected at a lower cost. Since no voltage detection line is required for fuses, increases in both cost and circuit area can be suppressed. Since no current integration value is used for determination, higher determination precision can be achieved. When a current integration value is used, errors in offset/gain in a current sensor (for example, hole element) and a current detection circuit (for example, operational amplifier) are integrated, and thus a total error would increase. On the other hand, in this exemplary embodiment, since a voltage value (OCV) is used, no error is integrated, and thus erroneous determinations can be suppressed.

According to the practical example 2, a battery block in which a fuse is blown can be identified. On the other hand, a method based on a current integration value faces difficulty in identifying a battery block in which a fuse is blown. According to the practical example 2, since a difference in voltage behavior in the battery blocks between a case when a fuse is blown and a case when no fuse is blown can be identified quicker than the practical example 1, the certain time described above can be set shorter than the certain time used in the practical example 1. Therefore, while precision in determination is kept maintained, a blown fuse can promptly be found.

The above explanation is made based on the exemplary embodiment of the present invention. The person of the ordinary skill in the art can understand that the exemplary embodiment is illustrated, and these constitution elements and these combined processes can be modified, and such modified examples are covered by the scope of the present invention.

In the above exemplary embodiment, as a control for equalization, a control for causing, when a battery block has a least voltage, another battery block to discharge electricity to level or to almost level at least a voltage of the other battery block to the least voltage has been described. For this point, a control may be performed, such that, when a battery block has a highest voltage, an auxiliary power supply is used to charge another battery block to level or to almost level at least a voltage of the other battery block to the highest voltage. In this case, the relationships of charging and discharging shown in FIGS. 3, 6 become opposite, as well as the inequality signs of Equations (1), (2) described above become opposite.

In the above exemplary embodiment, the examples where a period for determining whether a fuse is blown is set to a certain time have been described. For this point, whether a fuse is blown may be determined each time equalization is performed. In this case, when data is acquired from equalization implementation information storage unit 17 , data for a specified past period (the period should advantageously include a past period before previous equalization is performed) should be acquired to calculate a frequency.

In the above described exemplary embodiment, the examples using, as a power storage device, a storage battery have been assumed. However, a capacitor (for example, electric double layer capacitor) may be used. Since a control for equalization can be performed for a capacitor, similar or identical to a storage battery, a consideration similar or identical to a storage battery can be applied to a capacitor.

The exemplary embodiment may be identified with items described below.

[Item 1]

Management device ( 10 ) for managing power storage device ( 20 ) in which a plurality of power storage blocks (B 1 to B 3 ) in which a plurality of series circuits of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) and power storage cells (S 11 to S 120 , S 21 to S 220 , S 31 to S 320 ) is connected in parallel is connected in series, management device ( 10 ) including equalization controller ( 15 ) for performing, when a voltage difference among power storage blocks (B 1 to B 3 ) exceeds a set voltage difference, a control for equalizing power storage blocks (B 1 to B 3 ), and blowout determination unit ( 18 ) for determining, based on a frequency of equalization performed by equalization controller ( 15 ), whether one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) is blown.

Therefore, whether one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) connected to power storage cells (S 11 to S 120 , S 21 to S 220 , S 31 to S 320 ) is blown can precisely be detected at a lower cost.

[Item 2]

Management device ( 10 ) according to item 1, further including voltage detectors ( 11 to 13 ) for detecting voltages of power storage blocks (B 1 to B 3 ), where blowout determination unit ( 18 ) determines that, when the frequency of equalization is higher than a set frequency, one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) is blown.

Therefore, based on a difference in a frequency of equalization between a case when one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) is blown and a case when no fuse is blown, whether one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) is blown can be determined.

[Item 3]

Management device ( 10 ) according to item 2, where, for the set frequency, a different value in accordance with a State Of Health (SOH) is used.

Therefore, in a process for determining whether one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) is blown, negative effects due to a change in an SOH can be eliminated.

[Item 4]

Management device ( 10 ) according to item 1, where equalization controller ( 15 ) performs, in a period during which power storage device ( 20 ) is neither charged nor discharged, a control for equalizing power storage blocks (B 1 to B 3 ), management device ( 10 ) further includes equalization implementation information acquisition unit ( 16 ) for acquiring information on implementation of a control for equalizing the power storage blocks, and information indicating that a state before the control for equalization is performed is either of a charging state and a discharging state, and blowout determination unit ( 18 ) determines, based on a frequency of equalization of power storage blocks (B 1 to B 3 ) performed after charging and a frequency of equalization of power storage blocks (B 1 to B 3 ) performed after discharging, whether one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) included in power storage blocks (B 1 to B 3 ) is blown.

Therefore, a process for further precisely determining whether a fuse is blown can be achieved.

[Item 5]

Management device ( 10 ) according to item 4, where equalization controller ( 15 ) causes, when, among the plurality of power storage blocks (B 1 to B 3 ) included in power storage device ( 20 ), one of power storage blocks (B 3 ) has a least voltage, at least another one of power storage blocks (B 1 , B 2 ) to discharge electricity so that a voltage of the other one of power storage blocks (B 1 , B 2 ) lowers closer to the least voltage, and blowout determination unit ( 18 ) determines that, when an integral time of equalization performed, for a certain period, after one of power storage blocks (Bn) is charged is greater by first set value (α) or more than an average integral time of equalization performed, for a certain period, after another one of power storage blocks (other than Bn) is charged, and when an integral time of equalization performed, for a certain period, after the one of power storage blocks (Bn) is discharged is smaller by second set value (β) or more than an average integral time of equalization performed, for a certain period, after the other one of power storage blocks (other than Bn) is discharged, one of fuses (Sn 1 to Sn 20 ) included in the one of power storage blocks (Bn) is blown.

Therefore, one of battery blocks (Bn) in which one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) is blown can be identified.

[Item 6]

Power storage system ( 1 ) including power storage device ( 20 ), and management device ( 10 ) for managing power storage device ( 20 ), according to any one of items 1 to 5.

Therefore, whether one of fuses (F 11 to F 120 , F 21 to F 220 , F 31 to F 320 ) connected to power storage cells (S 11 to S 120 , S 21 to S 220 , S 31 to S 320 ) is blown can precisely be detected at a lower cost.