Battery management device, power storage device, battery protection method, and battery protection program

Abstract

A monitoring data acquisition unit 141 acquires the voltage, current, and temperature of a storage battery 11 as monitoring data. When any of overdischarge, overcharging, overcurrent, and temperature abnormality of the storage battery 11 is detected on the basis of the acquired voltage, current, and temperature, a protection control unit 142 limits at least one of charging of the storage battery 11 and discharging from the storage battery 11. The protection control unit 142 prohibits discharge from the storage battery 11 if the acquired voltage is lower than or equal to an overdischarge threshold voltage for detecting overdischarge of the storage battery 11. When a forced discharge mode for preparing for discarding the storage battery 11 is set, the protection control unit 142 lowers the overdischarge threshold voltage to a forced discharge target voltage.

Description

Battery Management Device, Energy Storage Device, Battery Protection Method, Battery Protection Program

[0001] The present disclosure relates to a battery management device, an energy storage device, a battery protection method, and a battery protection program for managing a storage battery used for a backup power supply of a data center or the like.

[0002] In recent years, the demand for data centers has been expanding due to the spread of generative AI. In a data center, ensuring power supply is important, and in the event of a power outage, a power storage system using a battery pack is installed to ensure power supply until an emergency generator starts up. Since the storage battery deteriorates over time, it is necessary to discard and replace the deteriorated storage battery.

[0003] As a method for safely discharging a battery pack before discarding it, in Patent Document 1, a method of discharging the battery by immersing the battery in a conductive liquid has been proposed. In this method, in order to suppress the risk of ignition due to heat generation by large current discharge, it is necessary to use a special fluid with low conductivity. When the voltage of the battery pack decreases, the discharge current decreases, and it takes a long time until the discharge ends. Therefore, the amount of conductive substance added is increased to adjust the current value to increase, but it is difficult to reuse this liquid for discharging a high-voltage battery pack.

[0004] As another method for safely discharging a battery pack before discarding it, in Patent Document 2, a method of connecting a load device to the battery pack and performing discharge safely and quickly without altering the constituent materials of the battery when recycling the battery has been proposed. In a data center, the power storage system is removed from the rack, and the customer's user selects a load device and performs a discharge operation for disposal. The method disclosed in Patent Document 2 uses a special dedicated load device. When using this method, the degree of freedom of selecting a load device on the customer side decreases, and additional purchase costs are incurred.

[0005] Furthermore, while the energy storage system can be charged and discharged by supplying an external power source and activating it, the BMS (Battery Management System) monitors each battery parameter (voltage, current, temperature) in the same way as during normal operation. Therefore, if the voltage drops, the discharge is stopped due to over-discharge protection, preventing the battery from being discharged to a sufficient voltage. Performing battery replacement or disposal work before the voltage has dropped sufficiently carries the risk of smoke and fire due to short circuits during dismantling.

[0006] Furthermore, extreme over-discharge of a battery can cause the electrolyte to decompose and generate gas, or copper ions to leach from the copper foil of the negative electrode and precipitate into the electrolyte. There is also a risk of smoke and fire when recharging a battery after its materials have deteriorated due to extreme over-discharge.

[0007] International Publication No. 14 / 017085, Japanese Patent Publication No. 2019-029163

[0008] This disclosure is made in light of these circumstances, and its purpose is to provide a technology for safely discharging batteries for disposal.

[0009] To solve the above problems, a battery management device in one aspect of the present disclosure includes: an acquisition unit that acquires the voltage, current, and temperature of a storage battery as monitoring data; and a protection control unit that, based on the acquired voltage, current, and temperature, detects any of the following: over-discharge, overcharge, overcurrent, or temperature abnormality of the storage battery and restricts at least one of charging the storage battery or discharging the storage battery. The protection control unit prohibits discharging from the storage battery when the acquired voltage is below an over-discharge threshold voltage for detecting over-discharge of the storage battery, and when a forced discharge mode for preparing to discard the storage battery is set, the protection control unit lowers the over-discharge threshold voltage to a forced discharge target voltage.

[0010] Furthermore, any combination of the above components, as well as any conversion of the expressions of this disclosure between devices, systems, methods, computer programs, etc., are also valid forms of this disclosure.

[0011] According to this disclosure, it is possible to safely discharge batteries for disposal.

[0012] This diagram illustrates an example configuration of an energy storage system according to an embodiment. It shows a specific example configuration of the battery and control unit. It also shows the cell voltage and control for over-discharge protection in normal mode, the cell voltage and control for over-discharge protection in forced discharge mode, a table summarizing the relationship between protection thresholds in normal mode and forced discharge mode, definitions of each voltage range in normal mode and forced discharge mode, a table summarizing normal functional limitations according to the cell voltage level, a table summarizing additional functional limitations according to past maximum / minimum voltage levels in cases of forced discharge history, and a flowchart showing the operation flow in forced discharge mode in the energy storage device according to the embodiment.

[0013] Figure 1 is a diagram illustrating an example configuration of a power storage system 1 according to an embodiment. The power storage system 1 according to this embodiment is used as a backup power supply system for a data center. Load 3 is a collective term for a large number of servers and storage devices installed in the data center. Load 3 is connected to a DC bus 2. In this embodiment, a 48V DC bus 2 is assumed. An AC / DC converter 5 connected to a commercial power grid 4, an emergency generator 6, and the power storage system 1 are connected to the DC bus 2.

[0014] The AC / DC converter 5 converts the AC power supplied from the commercial power grid 4 into DC power while stepping it down, and outputs it to the DC bus 2. For example, it converts the 200-240V AC voltage supplied from the commercial power grid 4 into 48V DC power.

[0015] The emergency generator 6 is a generator that supplies power to the load 3 in the event of a power outage in the commercial power grid 4, and can be a diesel generator or a gas turbine generator, for example. It takes several tens of seconds to several minutes from the time a power outage in the commercial power grid 4 is detected until the emergency generator 6 starts up. The energy storage system 1 can continue to supply backup power to the load 3 during that time.

[0016] The energy storage system 1 includes a plurality of energy storage devices 10a-10c connected in parallel to the DC bus 2. Figure 1 shows an example of three parallel connections, but the number of parallel connections is arbitrary and may be two or more. Each energy storage device 10 is, for example, a BBU (Battery Backup Unit).

[0017] The energy storage device 10 comprises a battery 11, a discharge DC / DC converter 12, a charge DC / DC converter 13, a switch S1, and a control unit 14. The discharge DC / DC converter 12 and the charge DC / DC converter 13 are connected between the battery 11 and the DC bus 2. The discharge DC / DC converter 12 may be configured by connecting multiple DC / DC converters in parallel. In that case, the number of parallel connections is determined according to the output power required by each energy storage device 10 during a power outage. Alternatively, a single discharge DC / DC converter with high current withstand capability may be used. The charge DC / DC converter 13 does not need to have high current withstand capability because it only needs to charge the battery 11 at a low rate from the commercial power grid 4.

[0018] Switching-type DC / DC converters are used for the discharge DC / DC converter 12 and the charge DC / DC converter 13. They may be isolated or non-isolated.

[0019] A switch S1 is connected between the connection point N1 between the input terminal of the discharge DC / DC converter 12 and the output terminal of the charge DC / DC converter 13, and the storage battery 11. A semiconductor switch (for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor)) or a mechanical relay can be used for the switch S1.

[0020] Each control unit 14a-14c of the multiple energy storage devices 10a-10c is connected to the controller 20 via a serial communication line (e.g., a CAN (Controller Area Network) bus). The controller 20 may be a dedicated controller for the energy storage system 1, or it may be a general-purpose information terminal (e.g., a PC or tablet terminal).

[0021] Figure 2 shows a specific example of the configuration of the storage battery 11 and the control unit 14. The storage battery 11 is composed of a battery pack including a plurality of cells E1-En connected in series. Lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, etc., can be used for the cells. Hereinafter, this specification assumes the use of lithium-ion battery cells (nominal voltage: 3.6-3.7V). In addition, multiple cells may be connected in parallel in the series stage of each cell in order to increase the capacity.

[0022] A measurement unit 14m is provided on the same board as the control unit 14 or on a separate board. The measurement unit 14m is composed of, for example, an AFE (Analog Front End) IC or an ASIC (Application Specific Integrated Circuit). The measurement unit 14m is connected to each node of a plurality of series-connected cells E1-En by a plurality of voltage measurement lines, and measures the voltage of each cell E1-En by measuring the voltage between two adjacent voltage measurement lines.

[0023] The measurement unit 14m includes a multiplexer and an A / D converter. The multiplexer outputs the measured voltages of multiple cells E1-En in a predetermined order to the A / D converter. The A / D converter converts the analog measured voltages input from the multiplexer into digital values. The measurement unit 14m transmits the voltage values ​​of each cell E1-En, which have been converted into digital values, to the control unit 14 via a serial communication interface.

[0024] The measurement unit 14m can measure the current flowing through the battery 11. A shunt resistor Rs is connected to the power line between the battery 11 and connection point N1. A differential amplifier (not shown) amplifies the voltage across the shunt resistor Rs and outputs it to the A / D converter in the measurement unit 14m. The A / D converter converts the analog voltage indicating the current flowing through the battery 11, which is input from the differential amplifier, into a digital value. The measurement unit 14m transmits the digitally converted current value to the control unit 14 via a serial communication interface. A Hall element may be used instead of the shunt resistor Rs.

[0025] A thermistor T1 is installed on the surface of the battery 11. The thermistor T1 is a temperature-sensing element whose resistance changes according to temperature. The voltage divided by the thermistor T1 and a voltage divider resistor (not shown) is output to the A / D converter in the measurement unit 14m. The A / D converter converts the input analog voltage, which represents the surface temperature of the battery 11, into a digital value. The measurement unit 14m transmits the converted digital temperature value to the control unit 14 via a serial communication interface.

[0026] The control unit 14 includes a monitoring data acquisition unit 141, a protection control unit 142, a communication unit 143, and a storage unit 144. The control unit 14 is composed of, for example, a microcontroller on which a firmware program for realizing the battery protection function according to this embodiment is installed.

[0027] The monitoring data acquisition unit 141 acquires the voltage, current, and temperature of the storage battery 11 as monitoring data. The monitoring data acquisition unit 141 may acquire the voltage of all cells E1-En included in the storage battery 11 as the voltage of the storage battery 11, or it may acquire only the minimum voltage and maximum voltage of all cells E1-En.

[0028] The battery state estimation unit (not shown) estimates the State of Charge (SOC) by combining the Open Circuit Voltage (OCV) method and the current integration method. The OCV method estimates the SOC based on the measured OCV of the cell and the cell's SOC-OCV curve. The cell's SOC-OCV curve is created in advance based on characteristic tests conducted by the battery manufacturer and registered in the microcontroller at the time of shipment.

[0029] The current integration method is a method for estimating the State of Charge (SOC) based on the OCV at the start of charging and discharging of the cell and the integrated value of the measured current. In the current integration method, measurement errors in the current accumulate as the charging and discharging time increases. Therefore, it is preferable to use a weighted average of the SOC estimated by the current integration method and the SOC estimated by the OCV method.

[0030] Based on the voltage, current, and temperature of the battery 11 obtained from the measurement unit 14m, the protection control unit 142 detects over-discharge, overcharge, overcurrent, or temperature abnormality of the battery 11 and restricts or prohibits at least one of the charging of the battery 11 or the discharging of the battery 11. Details of the protection control will be described later.

[0031] The communication unit 143 can perform predetermined serial communication with the controller 20 or other energy storage device 10. The communication unit 143 receives a signal to switch the operating mode based on a command operation from the controller 20. In this embodiment, the operating mode of the energy storage device 10 is set to a forced discharge mode (also called a disposal mode) for preparing to discard the battery 11.

[0032] The memory unit 144 is a non-volatile memory for storing a history of specific events. When the protection control unit 142 performs a forced discharge mode on the battery 11, it stores the history of the forced discharge mode in the memory unit 144. The memory unit 144 can store the maximum and minimum voltages of the cells since the start of use of the battery 11. The protection control unit 142 compares the cell voltage when overcharging is detected with the past maximum voltage stored in the memory unit 144, and if the cell voltage detected this time is higher, it updates the maximum voltage stored in the memory unit 144 to the cell voltage detected this time. Similarly, the protection control unit 142 compares the cell voltage when over-discharge is detected with the past minimum voltage stored in the memory unit 144, and if the cell voltage detected this time is lower, it updates the minimum voltage stored in the memory unit 144 to the cell voltage detected this time.

[0033] When the communication unit 143 receives a switching signal to the forced discharge mode from the controller 20, the protection control unit 142 switches the operating mode of the energy storage device 10 from normal mode to forced discharge mode. In normal mode, the protection control unit 142 performs a protection operation (also called a fail-safe operation) that prohibits discharge from the battery 11 if the voltage of the storage battery 11 obtained from the measurement unit 14m is below the over-discharge threshold voltage for detecting over-discharge of the storage battery 11. Specifically, the protection control unit 142 may send a cutoff signal for switch S1 to the measurement unit 14m to turn off switch S1, or it may send a stop signal to the discharge DC / DC converter 12 to stop the operation of the discharge DC / DC converter 12. Also, if a discharge switch is set before or after the discharge DC / DC converter 12, the protection control unit 142 may turn off the discharge switch.

[0034] In forced discharge mode, the protection control unit 142 reduces the over-discharge threshold voltage (e.g., 2.5V) to the forced discharge target voltage (e.g., 1.7V). The forced discharge target voltage is set to a voltage that can prevent deterioration of the battery material 11. Switching to forced discharge mode can be performed from the controller 20, which can be operated not only by the battery manufacturer's service personnel but also by users (e.g., data center employees). A user with limited knowledge of batteries may execute forced discharge mode, forcibly discharge the battery 11, and then recharge the battery 11 without discarding it. As mentioned above, charging the battery 11 after its material has deteriorated carries the risk of smoke and fire.

[0035] Therefore, in this embodiment, the forced discharge target voltage is set to the lowest possible voltage that can prevent deterioration of the battery material 11. The voltage that can prevent deterioration of the battery material 11 is set according to the type of battery 11, based on the results of the designer's experiments or simulations.

[0036] Figure 3 shows the cell voltage and control for over-discharge protection in normal mode. After discharge begins, when the cell voltage drops to the over-discharge threshold voltage, the over-discharge abnormality flag becomes significant, and the protection control unit 142 prohibits discharge from the battery 11. If the battery 11 is discarded in this state, the remaining energy in the battery 11 poses a risk of smoke and fire due to a short circuit during dismantling.

[0037] Figure 4 shows the cell voltage and control for over-discharge protection in forced discharge mode. In forced discharge mode, the over-discharge threshold voltage drops to the forced discharge target voltage. After discharge begins, when the cell voltage drops to the forced discharge target voltage (over-discharge threshold voltage in forced discharge mode), the over-discharge abnormality flag becomes significant, and the protection control unit 142 prohibits discharge from the battery 11. If the battery 11 is to be disposed of in this state, it can be safely disposed of because there is little energy remaining in the battery 11 and the constituent materials (positive electrode, negative electrode, electrolyte) have not deteriorated.

[0038] The only difference between normal mode and forced discharge mode is the over-discharge protection function; other protection functions (specifically, overcharge protection, overcurrent protection, high temperature protection, and low temperature protection) are the same.

[0039] Figure 5 is a table summarizing the relationship between protection thresholds in normal mode and forced discharge mode. In normal mode, the protection control unit 142 activates protection when the cell voltage is above the overcharge threshold A [V]. The protection control unit 142 activates protection when the cell voltage is below the over-discharge threshold B [V]. The protection control unit 142 activates protection when the current flowing through the battery 11 during charging is above the overcurrent threshold C [A] for charging. The protection control unit 142 activates protection when the current flowing through the battery 11 during discharge is below the overcurrent threshold D [A] for discharge. The protection control unit 142 activates protection when the temperature of the battery 11 is above the high-temperature abnormal threshold E [°C]. Note that the value of the high-temperature abnormal threshold E [°C] may differ between charging and discharging. The protection control unit 142 activates protection when the temperature of the battery 11 is below the low-temperature abnormal threshold F [°C]. Furthermore, the low-temperature abnormality threshold F [°C] may differ between charging and discharging.

[0040] Incidentally, the protection control unit 142 may also activate the protection operation when the SOC of the storage battery 11 is equal to or higher than the high SOC abnormal threshold value [%]. The protection control unit 142 may also activate the protection operation when the SOC of the storage battery 11 is equal to or lower than the low SOC abnormal threshold value [%].

[0041] Even in the forced discharge mode, the values of the overcharge threshold A [V], the overcurrent threshold C [A] for charging, the overcurrent threshold D [A] for discharging, the high-temperature abnormal threshold E [°C], and the low-temperature abnormal threshold F [°C] are the same as those in the normal mode. In the forced discharge mode, the overdischarge threshold B [V] is changed to a lower overdischarge threshold X [V].

[0042] As a basic protection operation, the protection control unit 142 turns off the switch S1 to stop charging and discharging. In the case of overcharge, discharging may be permitted and only charging may be prohibited. In the case of overdischarge, charging may be permitted and only discharging may be prohibited.

[0043] When a fan for cooling the storage battery 11 is installed near the storage battery 11, the protection control unit 142 may operate the cooling fan as a protection operation when detecting a high-temperature abnormality, overcharge, or overcurrent. When a heater for warming the storage battery 11 is installed near the storage battery 11, the protection control unit 明显错误,应改为142 may operate the warming heater as a protection operation when detecting a low-temperature abnormality.

[0044] When an LED lamp for warning is installed in the power storage device 10, the protection control unit 142 may turn on the LED lamp for warning as a protection operation when detecting an abnormality in the power storage system 1. Further, when detecting an abnormality in the power storage system 1, the protection control unit 142 may transmit a notification of the occurrence of the abnormality to the controller 20 via CAN communication.

[0045] Hereinafter, the control for dividing the overcharge region into a normal overcharge region and an extreme overcharge region, and dividing the overdischarge region into a normal overdischarge region and an extreme overdischarge region will be described.

[0046] FIG. 6 is a diagram showing the definition of each voltage region in the normal mode and the forced discharge mode. The voltage range of the cell in the normal mode is classified into an extreme overcharge region, a normal overcharge region, a normal region, a normal overdischarge region, and an extreme overdischarge region. A voltage region between a first overcharge threshold voltage (e.g., 4.1 V) and a second overcharge threshold voltage higher than the first overcharge threshold voltage (e.g., 4.3 V) is set as the normal overcharge region, and a voltage region higher than the second overcharge threshold voltage is set as the extreme overcharge region. A voltage region between a first overdischarge threshold voltage and a second overdischarge threshold voltage lower than the first overdischarge threshold voltage is set as the normal overdischarge region, and a voltage region lower than the second overdischarge threshold voltage is set as the extreme overdischarge region.

[0047] The voltage range of the cell in the forced discharge mode is classified into an extreme overcharge region, a normal overcharge region, a normal region, a normal overdischarge region, a forced mode overdischarge region, and an extreme overcharge region. The above-described forced discharge target voltage (e.g., 1.7 V) is set to a voltage lower than the second overdischarge threshold voltage (e.g., 2.0 V). In the forced discharge mode, a voltage region between the second overdischarge threshold voltage and the forced discharge target voltage is set as the forced mode overdischarge region, and a voltage region lower than the forced discharge target voltage is set as the extreme overdischarge region.

[0048] FIG. 7 is a diagram showing a table summarizing normal function limitations according to the voltage level of the cell. When the measured cell voltage is in the extreme overcharge region, the protection control unit 142 prohibits charging and discharging. Subsequent restart is also prohibited. That is, the use of the storage battery 11 is completely prohibited. When the cell voltage is in the normal overcharge region, the protection control unit 142 prohibits charging. Normal discharge and forced discharge are permitted. When the cell voltage is in the normal region, no function limitation occurs.

[0049] When the cell voltage is in the normal overdischarge region, the protection control unit 142 prohibits normal discharge and permits charging and forced discharge. When the cell voltage is in the extreme overdischarge region, the protection control unit 142 prohibits charging and discharging. Forced discharge is also prohibited, and subsequent restart is also prohibited. That is, the use of the storage battery 11 is completely prohibited.

[0050] Figure 8 is a table summarizing additional functional limitations based on past maximum / minimum voltage levels in the case of a forced discharge history. If the past maximum voltage in the case of a forced discharge history is in the extreme overcharge region or the normal overcharge region, the normal functional limitations apply and no additional functional limitations occur. If the past maximum and minimum voltages in the case of a forced discharge history are in the normal region, no functional limitations occur. If the past minimum voltage in the case of a forced discharge history is in the normal over-discharge region, the normal functional limitations apply and no additional functional limitations occur.

[0051] If there is a history of forced discharge, and the past minimum voltage is in the forced mode over-discharge region, the protection control unit 142 prohibits charging and normal discharging, but allows forced discharge up to the forced discharge target voltage. If there is a history of forced discharge, and the past minimum voltage is in the extreme over-discharge region, the protection control unit 142 prohibits charging and discharging. Forced discharge is also prohibited, and subsequent restart is also prohibited. In other words, the use of the storage battery 11 is completely prohibited.

[0052] Figure 9 is a flowchart showing the operation flow in the forced discharge mode of the energy storage device 10 according to the embodiment. When the controller 20 receives a command to switch to the forced discharge mode (Y in S10), the protection control unit 142 of the energy storage device 10 determines whether it is possible to switch to the forced discharge mode based on the state of the energy storage device 10, the forced discharge history, and the past minimum voltage (S11). If it is possible to switch (Y in S11), it changes the over-discharge threshold voltage to the forced discharge target voltage (S12). The monitoring data acquisition unit 141 acquires the voltage, current, and temperature of the battery 11 from the measurement unit 14m as monitoring data (S13).

[0053] The protection control unit 142 detects an abnormality in the energy storage system 1 based on the acquired voltage, current, and temperature of the battery 11 (Y in S14), and terminates the forced discharge. If the voltage of the battery 11 drops to the forced discharge target voltage (Y in S15) while no abnormality is detected (N in S14), the forced discharge is terminated. As long as the voltage of the battery 11 is higher than the forced discharge target voltage (N in S15), the process transitions to step S13 and continues from step S13 to step S15.

[0054] As described above, according to this embodiment, in the forced discharge mode, the over-discharge threshold voltage is reduced to the forced discharge target voltage, allowing the battery 11 to be discharged to a voltage level suitable for disposal, thus enabling safe battery disposal. During forced discharge, normal protection operations are performed, so even if an overcurrent or temperature abnormality occurs, the protection operation is activated, ensuring safety.

[0055] Furthermore, by preventing over-discharging to a voltage lower than the voltage required to prevent deterioration of the battery material, safety can be ensured in the event that the user accidentally recharges the battery after forced discharge for disposal. Additionally, by discharging to the lowest possible voltage while ensuring safety in case of accidental recharging, the amount of remaining energy is reduced as much as possible, enhancing safety during dismantling. Moreover, by retaining the history of forced discharge mode execution and the minimum voltage history in cases of extreme over-discharge, the acceptable range for normal discharge can be set to an optimal range, achieving a balance between safety and convenience.

[0056] The present disclosure has been described above based on embodiments. The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in combinations of their components and processing processes, and that such modifications are also within the scope of the present disclosure.

[0057] In the embodiments described above, an example was explained in which the forced discharge mode is used as preparation for disposing of a storage battery 11 used as a backup power supply system for a data center. In this regard, the forced discharge mode according to this disclosure can also be used for disposing of storage batteries used for purposes other than backup power supply systems for data centers (for example, in-vehicle applications, consumer electronics (notebook PCs, smartphones, etc.) applications).

[0058] The embodiments may be specified by the following items.

[0059] [Item 1] Battery management device (14) comprising: an acquisition unit (141) that acquires the voltage, current, and temperature of a storage battery (11) as monitoring data; and a protection control unit (142) that, based on the acquired voltage, current, and temperature, detects over-discharge, overcharge, overcurrent, or temperature abnormality of the storage battery (11) and restricts at least one of charging the storage battery (11) or discharging from the storage battery (11); wherein the protection control unit (142) prohibits discharging from the storage battery (11) when the acquired voltage is below the over-discharge threshold voltage for detecting over-discharge of the storage battery (11); and when a forced discharge mode for preparing to dispose of the storage battery (11) is set, the protection control unit (142) lowers the over-discharge threshold voltage to the forced discharge target voltage. [Item 2] The battery management device (14) according to Item 1, characterized in that the forced discharge target voltage is set to a voltage that can prevent deterioration of the material of the storage battery (11). This ensures safety when the battery is recharged after forced discharge for disposal. [Item 3] The battery management device (14) according to Item 1, characterized in that the over-discharge threshold voltage is set to a first over-discharge threshold voltage, a second over-discharge threshold voltage lower than the first over-discharge threshold voltage is set, the forced discharge target voltage is set to a voltage lower than the second over-discharge threshold voltage, and the protection control unit (142) allows charging of the storage battery (11), prohibits normal discharge from the storage battery (11), allows forced discharge up to the forced discharge target voltage when the acquired voltage is between the first over-discharge threshold voltage and the second over-discharge threshold voltage, and prohibits the use of the storage battery (11) when the acquired voltage is less than or equal to the second over-discharge threshold voltage. According to this, safety can be enhanced by prohibiting the use of the battery (11) when it is extremely discharged.[Item 4] The battery management device (14) according to Item 1, further comprising a storage unit (144) that holds the execution history of the forced discharge mode of the storage battery (11) and the history of the past minimum voltage of the storage battery (11), wherein the over-discharge threshold voltage is set to a first over-discharge threshold voltage, a second over-discharge threshold voltage lower than the first over-discharge threshold voltage is set, the forced discharge target voltage is set to a voltage lower than the second over-discharge threshold voltage, and the protection control unit (142) prohibits charging of the storage battery (11), prohibits normal discharge from the storage battery (11), and allows forced discharge up to the forced discharge target voltage when there is an execution history of the forced discharge mode and the past minimum voltage of the storage battery (11) is less than or equal to the forced discharge target voltage, and prohibits the use of the storage battery (11), including forced discharge. According to this, by providing an over-discharge region that prohibits normal discharge while allowing forced discharge, a balance can be struck between safety and convenience for disposal. [Item 5] A battery storage device (10) characterized by comprising a battery (11) and a battery management device (14) described in any one of items 1 to 4. According to this, the battery (11) can be discharged to a voltage level appropriate for disposal, and battery disposal can be carried out safely. [Item 6] A battery protection method comprising the steps of: acquiring the voltage, current, and temperature of a storage battery (11) as monitoring data; and, based on the acquired voltage, current, and temperature, if any of the following is detected in the storage battery (11): over-discharge, overcharge, overcurrent, or temperature abnormality, the method restricts at least one of charging the storage battery (11) or discharging from the storage battery (11); wherein, in the restricting step, if the acquired voltage is less than or equal to the over-discharge threshold voltage for detecting over-discharge of the storage battery (11), the method prohibits discharging from the storage battery (11); and, if a forced discharge mode for preparing to discard the storage battery (11) is set, the method restricts the over-discharge threshold voltage to the forced discharge target voltage.According to this, the battery (11) can be discharged to a voltage level appropriate for disposal, and battery disposal can be carried out safely. [Item 7] A battery protection program characterized in that a computer is made to perform the following: a process of acquiring the voltage, current, and temperature of the battery (11) as monitoring data; and a process of restricting at least one of charging the battery (11) or discharging from the battery (11) when any of the following is detected based on the acquired voltage, current, and temperature of the battery (11): in the restricting process, if the acquired voltage is below the over-discharge threshold voltage for detecting over-discharge of the battery (11), discharging from the battery (11) is prohibited; and when a forced discharge mode for preparing to dispose of the battery (11) is set, the restricting process reduces the over-discharge threshold voltage to the forced discharge target voltage. According to this, the storage battery (11) can be discharged to a voltage level suitable for disposal, and battery disposal can be carried out safely.

[0060] This disclosure can be used in preparing for the disposal of storage batteries.

[0061] 1 Energy storage system, 2 DC bus, 3 Load, 4 Commercial power grid, 5 AC / DC converter, 10 Energy storage device, 11 Battery, E1-En cell, 12 DC / DC converter for discharge, 13 DC / DC converter for charging, 14 Control unit, 141 Monitoring data acquisition unit, 142 Protection control unit, 143 Communication unit, 144 Memory unit, 14m Measurement unit, 20 Controller, Rs Shunt resistor, T1 Thermistor, S1 Switch.

Claims

1. A battery management device comprising: an acquisition unit that acquires the voltage, current, and temperature of a storage battery as monitoring data; and a protection control unit that, based on the acquired voltage, current, and temperature, detects over-discharge, overcharge, overcurrent, or temperature abnormality of the storage battery and restricts at least one of charging the storage battery or discharging the storage battery, wherein the protection control unit prohibits discharging from the storage battery when the acquired voltage is below an over-discharge threshold voltage for detecting over-discharge of the storage battery, and when a forced discharge mode for preparing to discard the storage battery is set, the protection control unit lowers the over-discharge threshold voltage to a forced discharge target voltage.

2. The battery management device according to claim 1, characterized in that the forced discharge target voltage is set to a voltage that can prevent deterioration of the battery material.

3. The battery management device according to claim 1, characterized in that the over-discharge threshold voltage is set as the first over-discharge threshold voltage, a second over-discharge threshold voltage lower than the first over-discharge threshold voltage is set, the forced discharge target voltage is set to a voltage lower than the second over-discharge threshold voltage, and the protection control unit allows charging of the battery, prohibits normal discharge from the battery, and allows forced discharge up to the forced discharge target voltage when the acquired voltage is between the first over-discharge threshold voltage and the second over-discharge threshold voltage, and prohibits the use of the battery when the acquired voltage is less than or equal to the second over-discharge threshold voltage.

4. The battery management device according to claim 1, further comprising a storage unit that holds the execution history of the forced discharge mode of the battery and the history of the battery's past minimum voltage, wherein the over-discharge threshold voltage is set as a first over-discharge threshold voltage, a second over-discharge threshold voltage lower than the first over-discharge threshold voltage is set, the forced discharge target voltage is set to a voltage lower than the second over-discharge threshold voltage, and the protection control unit, when there is an execution history of the forced discharge mode, prohibits charging the battery, prohibits normal discharge from the battery, and allows forced discharge up to the forced discharge target voltage, and when there is an execution history of the forced discharge mode, prohibits the use of the battery, including forced discharge, when the battery's past minimum voltage is less than or equal to the forced discharge target voltage.

5. A power storage device comprising a storage battery and a battery management device according to any one of claims 1 to 4.

6. A battery protection method comprising the steps of: acquiring the voltage, current, and temperature of a storage battery as monitoring data; and, based on the acquired voltage, current, and temperature, if any of the following is detected, the charging of the storage battery or the discharging from the storage battery is restricted, wherein in the restricting step, if the acquired voltage is below the over-discharge threshold voltage for detecting over-discharge of the storage battery, the discharging from the storage battery is prohibited; and if a forced discharge mode for preparing the storage battery for disposal is set, in the restricting step, the over-discharge threshold voltage is reduced to the forced discharge target voltage.

7. A battery protection program characterized by causing a computer to perform the following: a process of acquiring the voltage, current, and temperature of a storage battery as monitoring data; a process of restricting at least one of charging the storage battery or discharging the storage battery when over-discharge, overcharge, overcurrent, or temperature abnormality of the storage battery is detected based on the acquired voltage, current, and temperature; in the restricting process, if the acquired voltage is below the over-discharge threshold voltage for detecting over-discharge of the storage battery, discharging from the storage battery is prohibited; and if a forced discharge mode for preparing to discard the storage battery is set, in the restricting process, the over-discharge threshold voltage is reduced to the forced discharge target voltage.

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