Energy storage system

Abstract

To accurately estimate remaining discharge time even during high-rate discharge. [Solution] The power storage system 1 includes a chargeable and dischargeable battery 10, and a battery monitoring system 30 that generates battery information that is to be notified to a control system 90 and indicates the state of the battery 10. When supplying power to a load 91 by discharging from the battery 10, the battery monitoring system 30 estimates the amount of voltage drop Vdrop due to the internal resistance of the battery 10 based on the internal resistance value DCIR of the battery 10 and the discharge current I from the battery 10, estimates the dischargeable capacity of the battery 10 based on the estimated amount of voltage drop Vdrop, and notifies the control system 90 of information associated with the estimated dischargeable capacity as battery information.

Description

[Technical Field]

[0001] The present disclosure relates to a power storage system. [Background technology]

[0002] Patent Document 1 discloses a method for calculating the remaining discharge time (remaining discharge time) of a battery, which is corrected according to the temperature and discharge current of the storage battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-083222 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the output of battery-powered electrical loads has been increasing. Accordingly, when supplying power to a load by discharging from a battery, a larger discharge power may be required. However, the above-mentioned methods do not sufficiently consider high-rate discharge, which involves a large amount of discharge power (Wh) or discharge charge (Ah).

[0005] An object of the present disclosure is to provide an electricity storage system that can accurately estimate how much a battery can discharge even during high-rate discharge. [Means for solving the problem]

[0006] One aspect of the present disclosure provides an energy storage system that includes a rechargeable battery and a battery monitoring system that generates battery information, which is information to be notified to an external or higher-level control system and indicates the state of the battery; when supplying power to a load by discharging from the battery, the battery monitoring system estimates the amount of voltage drop due to the internal resistance of the battery based on the internal resistance value of the battery and the value of the current discharged from the battery, estimates the dischargeable capacity of the battery based on the estimated amount of voltage drop, and notifies the control system of information associated with the estimated dischargeable capacity as the battery information. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an electricity storage system that can accurately estimate how much a battery can discharge even during high-rate discharge. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a power storage system according to an embodiment. [Figure 2] FIG. 2 is a block diagram of the power storage system showing the power storage device of FIG. 1 in more detail. [Figure 3] 1 is a graph showing voltage versus discharge capacity. [Figure 4] 3 is a flowchart showing a process for estimating a dischargeable capacity and a remaining discharge time, which is executed by the power storage device of FIG. 2; [Figure 5A] 3 is a diagram showing an example of an initial value calculation table constituting the internal resistance calculation table of FIG. 2; FIG. [Figure 5B] 3 is a diagram showing an example of a coefficient calculation table constituting the internal resistance calculation table of FIG. 2; FIG. [Figure 6A] FIG. 10 is a diagram showing an example of a process for estimating a charge reference capacity (dischargeable capacity based on the charge amount) taking into account the amount of voltage drop. [Figure 6B] FIG. 10 is a diagram showing another example of the process of estimating the charge reference capacity (dischargeable capacity based on the charge amount) taking into account the amount of voltage drop. [Figure 7] FIG. 10 is an explanatory diagram of a dischargeable capacity calculation voltage. DETAILED DESCRIPTION OF THE INVENTION

[0009] In one embodiment, the energy storage system comprises a rechargeable battery and a battery control device that generates battery information, which is information to be notified to an external or higher-level control system and indicates the state of the battery. When power is supplied to a load by discharging from the battery, the battery monitoring system estimates the amount of voltage drop due to the internal resistance of the battery based on the internal resistance value of the battery and the value of the current discharged from the battery, estimates the dischargeable capacity of the battery based on the estimated amount of voltage drop, and notifies the control system of information associated with the estimated dischargeable capacity as the battery information.

[0010] According to the above configuration, the amount of voltage drop due to internal resistance is estimated based on the current value discharged from the battery, and the dischargeable capacity of the battery is estimated taking this voltage drop into consideration. Therefore, even when the amount of voltage drop is large due to so-called high-rate discharge, the dischargeable capacity can be estimated with high accuracy. Therefore, the reliability of battery information associated with the dischargeable capacity, such as the remaining discharge time, is improved, and reliable battery information can be reported to an external or higher-level control system.

[0011] In another embodiment, the battery monitoring system may estimate the internal resistance value based on at least one of the temperature, duration of use, voltage, and SOC of the battery, and estimate the amount of voltage drop based on the estimated internal resistance value.

[0012] According to the above configuration, the internal resistance value is estimated depending on the situation, so that the accuracy of estimating the internal resistance value, the amount of voltage drop, and the dischargeable capacity is improved, and the reliability of the battery information is improved.

[0013] In another embodiment, the dischargeable capacity includes a charge reference capacity, which is a dischargeable capacity based on the amount of charge, and the battery monitoring system may correct the charge reference capacity based on the amount of voltage drop.

[0014] According to the above configuration, the charge reference capacity, which is the dischargeable capacity based on the amount of charge, is estimated taking into account the voltage drop due to internal resistance, thereby improving the accuracy of estimating the dischargeable capacity and the reliability of the battery information.

[0015] In another embodiment, when the open circuit voltage of the battery can be acquired, the battery monitoring system may estimate the reference capacity of charge based on the acquired open circuit voltage and the amount of voltage drop.

[0016] According to the above configuration, the charge reference capacity can be estimated with high accuracy using the SOC-OCV characteristics.

[0017] In another embodiment, when the open circuit voltage of the battery cannot be obtained, the battery monitoring system may estimate the charge reference capacity based on the rate of voltage change caused by the voltage drop due to the internal resistance.

[0018] According to the above configuration, the charge reference capacity can be estimated even if the open circuit voltage cannot be obtained.

[0019] In another embodiment, the dischargeable capacity further includes a power reference capacity, which is a dischargeable capacity based on the amount of electricity, and the battery monitoring system may calculate the power reference capacity by multiplying the charge reference capacity by a predetermined voltage value for capacity calculation.

[0020] According to the above configuration, the charge reference capacity is estimated taking into account the voltage drop due to internal resistance, and the power reference capacity based on the amount of electric energy is estimated based on this charge reference capacity. That is, the power reference capacity is also estimated taking into account the voltage drop due to internal resistance. This improves the accuracy of estimating the dischargeable capacity and the reliability of the battery information.

[0021] In another embodiment, the battery monitoring system may correct the predetermined voltage value based on the amount of voltage drop.

[0022] According to the above configuration, when the power reference capacity is calculated as the product of the charge reference capacity and the predetermined voltage value, the voltage drop amount is taken into account not only in the charge reference capacity but also in the predetermined voltage value, thereby further improving the estimation accuracy of the power reference capacity.

[0023] In another embodiment, the battery monitoring system may estimate the remaining discharge time of the battery based on the estimated dischargeable capacity, and notify the control system of the estimated remaining discharge time as the battery information.

[0024] According to the above configuration, the remaining discharge time is notified with high accuracy, thereby improving convenience for the user.

[0025] Hereinafter, embodiments will be described with reference to the drawings. Note that identical or corresponding elements are designated by the same reference numerals throughout the drawings, and detailed descriptions will be omitted. In this specification, terms indicating specific directions or positions (e.g., "upper," "lower," etc.) are used as necessary. However, these terms are intended to facilitate understanding of the present disclosure based on the drawings, and the use of such terms does not limit the technical scope of the present disclosure. The embodiments described below are specific examples based on the technical ideas of the present disclosure and are not intended to limit the scope of the present disclosure. Furthermore, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the described components are merely examples and do not limit the scope of the present disclosure. The configurations, actions, effects, etc. of one embodiment or example may also be applied to other embodiments or examples. Note that the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0026] 1 and 2, a power storage system 1 according to an embodiment can be used as an emergency power supply device installed in a data center, for example. In this case, the user of the power storage system 1 can be the operator of the data center.

[0027] The data center may be an external system or a higher-level system for the power storage system 1. Such an external or higher-level system includes a control system 90 that can communicate with the power storage system 1, a load 91 that normally operates on commercial power, and a power supply unit 92 that supplies power to the power storage system 1.

[0028] The power storage system 1 includes a plurality of power storage devices 2 (only one of which is shown in FIG. 1). Each power storage device 2 includes a battery 10, a peripheral circuit 20, and a battery monitoring system 30. The power storage device 2 has an exterior case (not shown) that houses these elements.

[0029] Battery 10 is a secondary battery that can be repeatedly charged and discharged. Battery 10 has multiple battery cells connected to each other. For example, the battery cells are non-aqueous electrolyte secondary batteries such as lithium-ion batteries. However, battery 10 may also be a battery other than a lithium-ion battery, such as an all-solid-state battery. The multiple battery cells include multiple parallel units, each consisting of two or more battery cells connected in parallel to each other. The multiple parallel units are sequentially connected in series. The battery cells are connected to each other by wiring components made of conductive materials, such as bus bars and lead plates.

[0030] The battery 10 is selectively connected to a load 91 or a power supply unit 92 of a higher-level system via a peripheral circuit 20. The peripheral circuit 20 may include a step-down circuit or a voltage conversion circuit, such as a DC-DC converter or an AC-DC converter, that operates when charging or discharging the battery 10. However, this is just one example, and the peripheral circuit 20 may include a circuit with a different function in addition to or instead of the step-down circuit or voltage conversion circuit. The battery 10 is charged with power supplied from the power supply unit 92. In an emergency such as a power outage, the battery 10 discharges and functions as a power source for the load 91.

[0031] The battery 10 includes internal resistance that resists the flow of current. Examples of internal resistance include ohmic resistance, contact resistance, and electrochemical resistance. Ohmic resistance is resistance caused by the material properties of the components of the battery cell, such as the electrolyte and electrodes. Ohmic resistance can include resistance caused by the material properties, shape, or size of the wiring components connecting the battery cells. Contact resistance is resistance that occurs at the interface between the terminals of the battery cell and the wiring components. Electrochemical resistance is resistance that occurs during the electrochemical reaction of the battery cell (for example, at the interface between the electrode and electrolyte).

[0032] The battery monitoring system 30 includes a plurality of sensors 31, 32, ... and a battery control device 40. The plurality of sensors 31, 32, ... include, for example, a current sensor that detects the discharge current discharged from the battery 10, a voltage sensor that measures the open circuit voltage of the battery 10 in an unloaded state, and a temperature sensor that detects the temperature of the battery 10.

[0033] The battery control device 40 is a computer that serves as the subject of the device, system, or method according to this embodiment. By executing a program on this computer, the subject function of the device, system, or method according to this disclosure is realized. The computer has a processor that operates according to a program as its main hardware component. The processor may be of any type, as long as it can realize the function by executing the program. The processor is composed of one or more electronic circuits, including a semiconductor integrated circuit (IC) or large-scale integration (LSI). While ICs and LSIs are used here, the names may vary depending on the degree of integration, and may be referred to as system LSIs, very large-scale integration (VLSIs), or ultra large-scale integration (ULSIs). Field-programmable gate arrays (FPGAs), which are programmed after LSI fabrication, or reconfigurable logic devices that can reconfigure the connections within an LSI or set up circuit partitions within an LSI, can also be used for the same purpose. Multiple electronic circuits may be integrated on a single chip or provided on multiple chips. Multiple chips may be integrated into a single device or provided on multiple devices. The computer may also include storage devices such as RAM (random access memory), ROM (read only memory), and EEPROM (electrically erasable programmable read only memory) as hardware components. The program is recorded on a non-transitory recording medium such as a computer-readable ROM, an optical disk, or a hard disk drive. The program may be pre-stored on the recording medium or may be supplied to the recording medium via a wide area communication network including the Internet.

[0034] The battery control device 40 includes a storage unit 41 , a processing unit 42 , and a communication unit 43 .

[0035] The storage unit 41 is realized by the above-mentioned storage device. The storage unit 41 may store a program for estimating the dischargeable capacity and remaining discharge time of the battery 10, and may also temporarily or permanently store information necessary for executing this program.

[0036] The processing unit 42 is realized by the above-mentioned processor. The processing unit 42 executes processing for estimating the dischargeable capacity and remaining discharge time of the battery 10 according to the procedure instructed by the program.

[0037] The communication unit 43 is connected to be able to communicate with a communication unit 90a of an external or higher-level control system 90. The communication unit 43 notifies the control system 90 of battery information, which is information indicating information about the battery 10. The communication unit 43 can also acquire information about the output power W (W) from the control system 90, for example. In addition, the communication unit 43 can also acquire information about the ambient temperature, the system operating status, etc. from the control system 90.

[0038] 3, as the discharge capacity increases (i.e., as the dischargeable capacity decreases, or as the remaining battery power decreases), the voltage of battery 10 decreases. In the case of a lithium-ion battery, the voltage of battery 10 drops sharply during a first period T1 immediately after the start of discharge, then continues to drop gradually during a second period T2, and then drops sharply again toward the discharge cut-off voltage during a third period T3 when only a small amount of power remains. The sudden drop during the first period T1 is thought to be caused by a voltage drop due to internal resistance.

[0039] The dashed line in Figure 3 shows the graph for a normal discharge rate (so-called C rate). In this case, the amount of current or charge during discharge is normal, and the voltage drop is not very large. When the discharge capacity reaches the full charge capacity, the voltage of the battery 10 reaches the discharge end voltage. In other words, at a normal discharge rate, the dischargeable capacity is roughly equal to the full charge capacity.

[0040] The solid line in Figure 3 shows the graph for high-rate discharge, which is performed at a high discharge rate. During high-rate discharge, the discharge current is large, which increases the voltage drop due to internal resistance, resulting in a larger, more rapid drop in the voltage of battery 10 during the first period T1. As a result, the voltage of battery 10 reaches the discharge cut-off voltage before the discharge capacity reaches the full charge capacity. In other words, during high-rate discharge, the dischargeable capacity is smaller than when the discharge rate is normal due to the voltage drop. Therefore, during high-rate discharge, the remaining discharge time is shorter than when the discharge rate is normal, due not only to the large amount of charge but also to the voltage drop.

[0041] Therefore, the battery control device 40 according to this embodiment accurately estimates the remaining discharge time even during high-rate discharge. The estimation process for this purpose will be described below. FIG. 4 is a flowchart showing this estimation process. Note that the flow of FIG. 4 is not limited to when the battery 10 of the power storage device 2 is being discharged and power is being supplied from the power storage device 2 to the load 91, such as in an emergency, but is always executed while the battery control device 40 is running.

[0042] 4, first, the battery control device 40 determines whether or not the open circuit voltage can be acquired (step S1). If the open circuit voltage can be acquired (S1: YES), the battery control device 40 acquires the open circuit voltage by measurement (step S2) and proceeds to step S3. If the open circuit voltage cannot be acquired (S1: NO), the battery control device 40 proceeds directly to step S3.

[0043] In step S3, the battery control device 40 estimates the amount of voltage drop Vdrop (V) due to the internal resistance of the battery 10. The process of estimating the amount of voltage drop Vdrop (step S3) includes a process of acquiring the amount of current during discharge (hereinafter referred to as the discharge current I (A)) (step S31), a process of estimating the resistance value of the internal resistance of the battery 10 (hereinafter referred to as the internal resistance value DCIR (Ω)) (step S32), and a process of calculating the amount of voltage drop Vdrop based on the discharge current I and the internal resistance value DCIR (step S33).

[0044] In step S31, the battery control device 40 may acquire the discharge current I detected by the current sensor. Alternatively, a value learned from the history of past discharges may be used as the discharge current I. In this case, the storage unit 41 may store in advance time-series data of the current amount during past discharges or a learned value obtained based on the time-series data. In particular, it may be necessary to estimate the initial value of the discharge current I before the start of discharge, such as immediately after the start of control. Even in such a case, the initial value can be estimated by referring to the past learned value. In this way, when no discharge is being performed, a value predetermined in the energy storage system 1 may be used as the discharge current I.

[0045] In step S32, the battery control device 40 may estimate the internal resistance DCIR according to the state of the battery 10. In this case, the battery control device 40 acquires information indicating the state of the battery 10 related to the internal resistance DCIR. Examples of such information include temperature information indicating the battery temperature, the number of years of use of the battery 10, the number of charge / discharge cycles, the voltage, and the SOC. When the internal resistance DCIR is estimated using the number of years of use or the number of charge / discharge cycles, the battery control device 40 updates and stores such parameters in the memory unit 41 as appropriate.

[0046] There are no particular limitations on the estimation method according to the state of the battery 10. As an example, the storage unit 41 may previously store an internal resistance calculation table 51 that defines the correspondence between the state of the battery 10 and the internal resistance value DCIR. Then, the processing unit 42 may refer to the internal resistance calculation table 51 and derive the internal resistance value DCIR based on the state of the battery 10.

[0047] For example, the storage unit 41 may store, as the internal resistance calculation table 51, a temperature table 51a (see FIG. 5A) that defines the correspondence relationship between the battery temperature and the initial internal resistance R0, and a coefficient table 51b (see FIG. 5B) that defines the correspondence relationship between the age Ty of the battery 10 and the deterioration coefficient K. In this case, the processing unit 42 derives the initial internal resistance R0 based on the battery temperature T B by referring to the temperature table 51a, derives the deterioration coefficient K based on the age Ty by referring to the coefficient table 51b, and calculates the internal resistance value DCIR by multiplying the initial internal resistance R0 by the deterioration coefficient K (DCIR = R0 * K). Note that the temperature table 51a defines the correspondence relationship between the initial internal resistance R0 and the battery temperature T B such that the initial internal resistance R0 decreases as the age Ty increases. The coefficient table 51b defines the correspondence relationship between the initial internal resistance R0 and the battery temperature T B such that the deterioration coefficient K increases as the age Ty increases.

[0048] However, this is just one example. Instead of the internal resistance calculation table 51, the storage unit 41 may store an arithmetic expression for deriving the internal resistance value DCIR by substituting parameters such as the battery temperature and the number of years of use.

[0049] In step S32, the battery control device 40 may also calculate the internal resistance value DCIR from the current and voltage during charging and discharging. If this method is used during charging and discharging in which the influence of measurement errors is small, for example, during charging and discharging at a slow rate, high estimation accuracy can be achieved.

[0050] In step S33, the battery control device 40 calculates the voltage drop amount Vdrop by multiplying the discharge current I acquired in step S31 by the internal resistance value DCIR estimated in step S32.

[0051] Next, the battery control device 40 estimates the dischargeable capacity of the battery 10 based on the voltage drop Vdrop estimated in step S3 (step S4). In the process of estimating the dischargeable capacity (step S4), the battery control device 40 first estimates the dischargeable capacity based on the amount of charge (hereinafter referred to as the charge reference capacity RCeff (Ah)) (step S41), and then calculates the dischargeable capacity based on the amount of power (hereinafter referred to as the power reference capacity RCeffv (Wh)) (step S43). The power reference capacity RCeffv is calculated as the product of the charge reference capacity RCeff and a predetermined voltage value Vrdt. Therefore, prior to step S43, the predetermined voltage value Vrdt is calculated (step S42).

[0052] The charge reference capacitance RCeff is estimated taking into account the voltage drop Vdrop. The predetermined voltage value Vrdt is also estimated taking into account the voltage drop Vdrop. Therefore, the power reference capacitance RCeffv is also calculated as a value taking into account the voltage drop Vdrop.

[0053] In step S41, different estimation methods may be applied when the open circuit voltage is measured in step S2 and when it is determined in step S1 that the open circuit voltage cannot be measured.

[0054] 6A, in a case where the open circuit voltage has been measured, in step S41, the battery control device 40 calculates the net voltage OCVβ (V) of the battery 10 by subtracting the voltage drop Vdrop from the measured open circuit voltage value OCVα (OCVβ=OCVα-Vdrop). Next, the battery control device 40 references the SOC-OCV curve 52 pre-stored in the memory unit 41 to derive the SOC value corresponding to the net voltage OCVβ. Next, the battery control device 40 estimates the net reference charge capacity RCeff by multiplying the derived SOC value by the full charge capacity.

[0055] If the voltage drop Vdrop is not taken into consideration, the charge reference capacity RCα corresponding to the measured open-circuit voltage OCVα is estimated. According to the above method, the net charge reference capacity RCeff is corrected downward relative to the charge reference capacity RCα corresponding to the measured open-circuit voltage OCVα in accordance with the voltage drop Vdrop. Therefore, the charge reference capacity RCeff is estimated accurately by taking the voltage drop into consideration. Because the SOC-OCV curve 52 tends to monotonically increase (the slope of the tangent line is always positive), the larger the voltage drop Vdrop, the larger the correction amount, and the greater the improvement in estimation accuracy. In other words, the estimation accuracy of the net charge reference capacity RCeff is improved even during high-rate discharge.

[0056] The reference charge capacity RCeff may be estimated by referring to a curve (RC-OCV curve) in which the horizontal axis represents remaining capacity RC (Ah) instead of the curve in which the horizontal axis represents SOC.

[0057] Next, referring to FIG. 6B, when the open circuit voltage cannot be measured, it is difficult to estimate the net voltage, and therefore it is difficult to adopt the method of estimating the net charge reference capacity RCeff from the net voltage by referring to the SOC-OCV curve 52.

[0058] Therefore, the battery control device 40 calculates the voltage change rate rV due to the voltage drop. The voltage change rate rV corresponds to the value obtained by subtracting the voltage drop amount Vdrop (see Veff in FIG. 7) from the total cell voltage value Vttl (see Vttl in FIG. 7) and dividing the result by the total cell voltage value Vttl (rV=Veff / Vttl). Next, the battery control device calculates the remaining capacity RC corresponding to the total cell voltage value Vttl with reference to the SOC-OCV curve 52. Next, the battery control device estimates the reference charge capacity RCeff that takes the voltage drop into consideration by multiplying the remaining capacity RC by the voltage change rate rV (RCeff=RC×Veff / Vttl).

[0059] When the SOC-OCV curve 52 is linear in the range between the total cell voltage Vttl and the subtraction value Veff (the dashed-dotted ellipse in Figure 6B represents a region exhibiting strong linearity), the ratio of two values ​​on the vertical axis is equal to the ratio of two corresponding values ​​on the horizontal axis (RCeff / RC = Veff / Vttl). Therefore, by correcting the remaining capacity RC using the voltage change rate rV, the remaining capacity corresponding to the subtraction value Veff (i.e., the charge-based capacity RCeff) can be accurately estimated. Note that ternary batteries that use ternary positive electrode materials (electrode materials primarily composed of nickel, manganese, and cobalt) in the positive electrode have the characteristic of having a linear SOC-OCV curve 52. For this reason, employing this estimation method for ternary batteries is particularly beneficial.

[0060] Next, regarding step S42, the power reference capacity RCeffv can generally be calculated as the product of the charge reference capacity RCeff and the nominal voltage Vn. However, the nominal voltage Vn is an average voltage value within the voltage range output by the battery 10 under standard discharge conditions. Therefore, in step S43, the battery control device 40 derives the predetermined voltage value Vrdt by correcting the nominal voltage Vn.

[0061] Here, the nominal voltage Vn can be defined as the average value of the upper limit voltage Vmax and the lower limit voltage Vmin of the voltage range output under standard discharge conditions. When calculating the predetermined voltage value Vrdt, the upper limit voltage Vmax is corrected by decreasing it by the voltage drop amount Vdrop. The average value of the corrected upper limit voltage and lower limit voltage Vmin is calculated as the predetermined voltage value Vrdt. In other words, the predetermined voltage value Vrdt is calculated as the nominal voltage Vn minus half the voltage drop amount Vdrop.

[0062] Next, in step S43, as described above, the battery control device 40 calculates the reference power capacity RCeffv by multiplying the reference charge capacity RCeff by the predetermined voltage value Vrdt.

[0063] Next, the battery control device 40 estimates the remaining discharge time RDT of the battery 10 based on the chargeable capacity (reference power capacity RCeffv) estimated in step S3 (step S5). As an example, the battery control device 40 calculates the remaining discharge time RDT by multiplying the reference power capacity RCeffv (Wh) by the output power W (W) of the battery 10. When calculating the remaining discharge time RDT in units other than hours (for example, minutes or seconds), the battery control device 40 may further multiply the multiplied value by a conversion coefficient Kt for unit conversion. The output power W may be obtained from an external or higher-level control system 90, or may be obtained by measurement.

[0064] Next, the battery control device 40 generates battery information to be notified to the external or higher-level control system 90 (step S6). The battery information generated here is information associated with the estimated dischargeable capacity. "Information associated with the dischargeable capacity" includes remaining discharge time information indicating the remaining discharge time RDT, which is correlated with the dischargeable capacity. In addition, "information associated with the dischargeable capacity" may include dischargeable capacity information indicating the dischargeable capacity itself. The dischargeable capacity information may be charge reference capacity information indicating the charge reference capacity RCeff, or may be power reference capacity information indicating the power reference capacity RCeffv.

[0065] Next, the communication unit of the battery control device 40 notifies the generated battery information to an external or higher-level control system 90 (step S7). Because the battery information includes remaining discharge time information, users of the power storage system 1 and / or users or operators of the control system 90 can easily ascertain the remaining discharge time RDT by referring to the notified battery information. Compared to when only the dischargeable capacity is notified, this can support smooth operation of the system (especially operation during an emergency).

[0066] The flow ends here. The battery control device 40 repeats the flow shown in Fig. 4 at a predetermined control cycle of several milliseconds to several tens of milliseconds.

[0067] If the battery temperature changes during discharge, the estimated results of the dischargeable capacity and remaining discharge time RDT are corrected in real time in response to the change (see step S3). Furthermore, for example, when discharging at a constant power output, the battery voltage decreases as the battery is discharged, while the discharge current I increases accordingly. In response to such changes in the voltage and current during discharge, the estimated results of the dischargeable capacity and remaining discharge time RDT are corrected in real time (see steps S3 and S4). The battery information notified to the control system 90 changes from moment to moment as the discharge time elapses and in response to changes in the state of the battery 10. By referring to the notified battery information, the user of the power storage system 1 and / or the user or operator of the control system can always ascertain the dischargeable capacity or remaining discharge time RDT at that time.

[0068] As described above, in the energy storage system 1 according to this embodiment, the battery control device 40 estimates the voltage drop Vdrop due to the internal resistance of the battery 10 based on the internal resistance value DCIR of the battery 10 and the value of the current discharged from the battery 10, estimates the dischargeable capacity of the battery 10 based on the estimated voltage drop Vdrop, and notifies the control system 90 of information associated with the estimated dischargeable capacity as battery information.

[0069] Therefore, even if the voltage drop is large due to so-called high-rate discharge, the dischargeable capacity can be estimated with high accuracy. Therefore, the reliability of battery information associated with the dischargeable capacity, such as the remaining discharge time RDT, is improved, and the control system 90 can be notified of highly reliable battery information.

[0070] Although the embodiments have been described above, the above configurations can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0071] 1. Energy storage system 2. Energy storage device 10 batteries 20 Peripheral circuits 30 Battery Monitoring System 31,32 Sensors 40 Battery control device 41 Storage section 42 Processing section 43 Communications Department 51 Internal resistance calculation table 51a Temperature Table 51b Coefficient Table 52 SOC-OCV curve 90 Control System 90a Communications Department 91 Load 92 Power supply unit DCIR internal resistance value I discharge current K Degradation factor Kt conversion factor OCVα measurement value OCVβ Net voltage R0 Initial internal resistance RC remaining capacity RCeff Charge reference capacitance RCeffv Power Reference Capacity RDT remaining discharge time T1 1st period

Claims

1. A rechargeable battery; a battery monitoring system that generates battery information that is to be notified to an external or higher-level control system and indicates the state of the battery; Equipped with When power is supplied to a load by discharging the battery, the battery monitoring system estimating a voltage drop due to the internal resistance of the battery based on an internal resistance value of the battery and a current value discharged from the battery; estimating a dischargeable capacity of the battery based on the estimated voltage drop amount; notifying the control system of information associated with the estimated dischargeable capacity as the battery information; The dischargeable capacity includes a charge-based capacity, which is a dischargeable capacity based on the amount of charge; The battery monitoring system includes: correcting the charge reference capacitance based on the amount of voltage drop; determining whether an open circuit voltage of the battery can be obtained; When the open circuit voltage of the battery can be acquired, the charge reference capacity is estimated based on the acquired open circuit voltage and the voltage drop amount. Energy storage system.

2. The battery monitoring system includes: The internal resistance value is estimated according to at least one of a temperature, a period of use, a voltage, and an SOC of the battery; estimating the voltage drop amount based on the estimated internal resistance value; The power storage system according to claim 1 .

3. When the open circuit voltage of the battery cannot be obtained, the battery monitoring system estimates the charge reference capacity based on a rate of voltage change caused by a voltage drop due to the internal resistance. The power storage system according to claim 1 .

4. The dischargeable capacity further includes a power reference capacity, which is a dischargeable capacity based on an amount of power, The battery monitoring system calculates the power reference capacity by multiplying the charge reference capacity by a predetermined voltage value for capacity calculation. The power storage system according to claim 1 .

5. A rechargeable battery; a battery monitoring system that generates battery information that is to be notified to an external or higher-level control system and indicates the state of the battery; Equipped with When power is supplied to a load by discharging the battery, the battery monitoring system estimating a voltage drop due to the internal resistance of the battery based on an internal resistance value of the battery and a current value discharged from the battery; estimating a dischargeable capacity of the battery based on the estimated voltage drop amount; notifying the control system of information associated with the estimated dischargeable capacity as the battery information; The dischargeable capacity includes a charge-based capacity, which is a dischargeable capacity based on the amount of charge; The battery monitoring system includes: correcting the charge reference capacitance based on the amount of voltage drop; When the open circuit voltage of the battery cannot be obtained, the charge-based capacity is estimated based on a rate of voltage change caused by a voltage drop due to the internal resistance. Energy storage system.

6. The dischargeable capacity further includes a power reference capacity, which is a dischargeable capacity based on an amount of power, The battery monitoring system calculates the power reference capacity by multiplying the charge reference capacity by a predetermined voltage value for capacity calculation. The power storage system according to claim 5 .

7. A rechargeable battery; a battery monitoring system that generates battery information that is to be notified to an external or higher-level control system and indicates the state of the battery; Equipped with When power is supplied to a load by discharging the battery, the battery monitoring system estimating a voltage drop due to the internal resistance of the battery based on an internal resistance value of the battery and a current value discharged from the battery; estimating a dischargeable capacity of the battery based on the estimated voltage drop amount; notifying the control system of information associated with the estimated dischargeable capacity as the battery information; The dischargeable capacity includes a charge reference capacity, which is a dischargeable capacity based on the amount of charge, and a power reference capacity, which is a dischargeable capacity based on the amount of power, The battery monitoring system includes: correcting the charge reference capacitance based on the amount of voltage drop; correcting a predetermined voltage value for calculating a capacitance based on the amount of voltage drop; calculating the power reference capacity by multiplying the charge reference capacity by the predetermined voltage value; Energy storage system.

8. The battery monitoring system includes: estimating a remaining discharge time of the battery based on the estimated dischargeable capacity; notifying the control system of the estimated remaining discharge time as the battery information; The power storage system according to any one of claims 1 to 7.

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