Maintenance charging control method and power storage system

Abstract

Provided are a control method for maintenance charging and a power storage system which can suppress the occurrence of overcharging or undercharging during recovery charging. As the maintenance charging of a storage battery, constant voltage charging is performed after constant current charging, and in the constant voltage charging, a charging rate calculated from the total charge amount and total discharge amount of the storage battery calculated from current values of the storage battery is used along with a threshold value to determine whether to continue or end the constant voltage charging on the basis of the temperature of the storage battery.

Description

[Technical Field]

[0001] The present invention relates to a method for controlling maintenance charging such as equalization charging and recovery charging, and to an electricity storage system. [Background technology]

[0002] As shown in Figure 1, lead-acid batteries are operated in a partial state of charge (PSOC) state, where the remaining capacity of the battery is kept between 30% and 90% to prevent overcharging and discharging. Lead-acid batteries are more resistant to overcharging than other batteries, but overcharging causes corrosion of the positive electrode grid, which leads to deterioration due to increased internal resistance and breakage. Such lead-acid batteries are subjected to maintenance charging such as equalization charging and recovery charging. Equalization charging is performed at specified intervals with the aim of equalizing the voltage variations between cells of a lead-acid battery, since any voltage variations (potential differences) that occur between cells of the lead-acid battery can have a negative impact on the battery. Recovery charging is performed each time a discharged storage battery is charged to full capacity as quickly as possible, with the aim of quickly charging a storage battery that has discharged and lost capacity in preparation for the next discharge.

[0003] The maintenance charging method for such lead-acid batteries is to perform constant current charging (CC charging) and then constant voltage charging (CV charging) for a specified time once a certain voltage has been reached, as shown in Figure 2. In this case, the condition where the ratio of the total charge amount to the total discharge amount (charge rate) reaches a certain value is used as an indicator of the completion of maintenance charging. Furthermore, for example, Patent Document 1 discloses a method for terminating CV charging in maintenance charging of a lithium ion battery when the current value during CV charging converges to a constant value as a termination condition for CV charging. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-292534 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with conventional maintenance charging as shown in Figure 2, the internal resistance changes depending on the temperature conditions, and the charge acceptance also changes. As a result, conventional maintenance charging can result in overcharging or undercharging depending on the temperature conditions, which can lead to accelerated deterioration. Furthermore, even with the method described in the cited document 1, the magnitude of the charging current during CV charging is affected by internal resistance, so there is a possibility that insufficient charging may occur depending on the temperature conditions.

[0006] Therefore, the present invention has been made with a focus on the above-mentioned problems, and aims to provide a maintenance charging control method and a storage system that can suppress the occurrence of overcharging and undercharging during maintenance charging such as equalization charging and recovery charging. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a control method for maintenance charging of a storage battery, in which constant current charging is followed by constant voltage charging, and in the constant voltage charging, a charge rate calculated from the total charge amount and total discharge amount of the storage battery calculated from the current value of the storage battery, and a threshold value are used to determine whether to continue or terminate the constant voltage charging based on the temperature of the storage battery.

[0008] According to one aspect of the present invention, there is provided a power storage system comprising a plurality of storage batteries, a temperature sensor that measures the temperature of the storage batteries, a host system that performs energy management of the plurality of storage batteries, a battery pack sensor that measures the charge / discharge current and total voltage of the plurality of storage batteries, and a battery monitoring device that determines the state of the plurality of storage batteries and controls charge / discharge processes including maintenance charging, wherein the maintenance charging is performed by constant current charging followed by constant voltage charging, and during the constant voltage charging, a determination is made as to whether to continue or terminate the constant voltage charging based on the temperature of the storage batteries using a charging rate calculated from the total charge amount and total discharge amount of the storage batteries calculated from the current value of the storage batteries and a threshold value. [Effects of the Invention]

[0009] (1) According to one aspect of the present invention, there is provided a method for controlling maintenance charging of a storage battery, in which constant current charging is followed by constant voltage charging, and in the constant voltage charging, a charge rate calculated from the total charge amount and total discharge amount of the storage battery calculated from the current value of the storage battery, and a threshold value are used to determine whether to continue or terminate the constant voltage charging based on the temperature of the storage battery. According to the configuration (1) above, the decision to continue or terminate constant voltage charging using the charging rate and threshold value is made based on the temperature of the storage battery, thereby making it possible to prevent overcharging and undercharging from occurring during maintenance charging.

[0010] (2) In the configuration of (1) above, when performing charging and discharging processes for the storage battery, including maintenance charging, the temperature and current of the storage battery are measured, the measured current value is corrected based on the measured temperature, and the corrected current value is integrated to calculate the total charge amount and total discharge amount of the storage battery.In the constant voltage charging, if a first charging rate calculated from the total charge amount and total discharge amount of the storage battery is less than a first threshold, the constant voltage charging is continued, and if the first charging rate is equal to or greater than the first threshold, the constant voltage charging is terminated. According to the above configuration (2), the current value measured is corrected depending on the temperature conditions, which makes it possible to respond to changes in charge acceptance due to temperature changes, thereby reducing overcharging and undercharging.

[0011] (3) In the configuration of (2) above, when correcting the current value, a value obtained by multiplying the current value by a temperature correction coefficient set in accordance with the temperature of the storage battery is used. (4) In the configuration of (1) above, in the constant voltage charging, if a second charging rate calculated from the total charge amount and total discharge amount of the storage battery is less than a second threshold value according to the temperature of the storage battery, the constant voltage charging is continued, and if the second charging rate is equal to or greater than the second threshold value, the constant voltage charging is terminated. According to the above configuration (4), the charging rate at which constant voltage charging is terminated is changed depending on the temperature condition, which makes it possible to respond to changes in charge acceptance due to temperature changes, thereby reducing overcharging and undercharging.

[0012] (5) In the configuration of (4) above, the second threshold value is a value obtained by multiplying a set value, which is a predetermined charging rate, by a temperature correction coefficient. (6) In any one of the configurations (1) to (5) above, the storage battery is a bipolar lead storage battery.

[0013] (7) According to one aspect of the present invention, there is provided a power storage system comprising a plurality of storage batteries, a temperature sensor that measures the temperature of the storage batteries, a host system that performs energy management of the plurality of storage batteries, a battery pack sensor that measures the charge / discharge current and total voltage of the plurality of storage batteries, and a battery monitoring device that determines the state of the plurality of storage batteries and controls charge / discharge processes including maintenance charging, wherein the maintenance charging is performed by constant current charging followed by constant voltage charging, and during the constant voltage charging, a determination is made as to whether to continue or terminate the constant voltage charging based on the temperature of the storage batteries using a charging rate calculated from the total charge amount and total discharge amount of the storage batteries calculated from the current value of the storage batteries and a threshold value. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram showing an operation image of a lead-acid battery. [Figure 2] FIG. 10 is an explanatory diagram showing maintenance charging. [Figure 3] 1 is a configuration diagram showing a power storage system according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a diagram illustrating a system configuration of a battery monitoring device. [Figure 5] FIG. 2 is an explanatory diagram showing a cycle of charge and discharge treatment. [Figure 6] FIG. 3 is a flowchart showing a method of charge / discharge processing in the first embodiment. [Figure 7] FIG. 10 is a flowchart showing a method of charge / discharge processing in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described. Note that the embodiment described below is merely an example of the present invention. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0016] First Embodiment 3, the power storage system 1 according to the first embodiment of the present invention includes a battery monitoring unit (BMU) 2, an upper level system (EMS) 3, an AC / DC converter (PCS) 4, an assembled battery sensor 5, a plurality of storage batteries 6, and a plurality of temperature sensors 7. As will be described later, the power storage system 1 is a system that performs charge and discharge processing including maintenance charging of the plurality of storage batteries 6.

[0017] The battery monitoring device 2 is a device that determines the state of the battery based on measurement information from the battery pack sensor 5 and multiple temperature sensors 7. As shown in FIG. 4 , the battery monitoring device 2 has a system configuration including a setting unit 20 that sets various settings such as determination thresholds, a measurement unit 21 that collects measurement information from sensors such as the battery pack sensor 5 and the temperature sensor 7, a recording unit 22 that stores setting conditions, measurement results, and state determination results, a state determination unit 23 that determines the state of the battery 6 using information from the measurement results, and a communication unit 24 that communicates with the higher-level system 3 to transmit the state determination results, etc. The battery monitoring device 2 also controls charging and discharging processes including maintenance charging.

[0018] The upper system 3 is a system that performs energy management including PCS control. The battery pack sensor 5 is a sensor that measures the charge / discharge current and total voltage of the storage battery 6. The storage battery 6 is a bipolar lead storage battery. In this embodiment, as an example, a battery pack is used in which four storage batteries 6 are connected in series and three are connected in parallel. The plurality of temperature sensors 7 are installed in the plurality of storage batteries 6 and measure the temperature of each storage battery 6. Here, the temperature sensor 7 is not limited to this example, and may be installed in, for example, a representative storage battery among the plurality of storage batteries 6, or may measure the ambient temperature around the storage battery 6. In the first embodiment, the host system 3, the assembled battery sensor 5, the temperature sensor 7, and the like constitute a storage battery monitoring system.

[0019] In such a power storage system 1, after a predetermined number of discharges and charges have been repeated, a maintenance charge, for example, an equalized charge, is performed, as shown in Fig. 5. Switching between charge and discharge is performed when the remaining capacity of the storage battery 6 reaches the upper or lower limit of a preset PSOC range. In the example shown in Fig. 5, equalized charge is performed after five discharges and four charges. The charging and discharging process of the storage battery 6, including equalization charging, is performed according to the processing flow shown in Fig. 6. The processing shown in Fig. 6 is a processing section in which charging and discharging are performed from the state in which equalization charging is completed as shown in Fig. 5, and until equalization charging is performed again. Although not shown in Fig. 6, switching between charging and discharging and performing equalization charging are performed by the storage battery monitoring device 2 according to the remaining capacity of the storage battery 6 and the number of times it has been charged and discharged.

[0020] 6, when the charge / discharge process is started, first, the battery pack sensor 5 measures the current, and the temperature sensor 7 measures the temperature of the storage battery 6 (S100). The measurement information of the current and temperature is collected by the measurement unit 21 and stored in the recording unit 22. Next, the state determination unit 23 of the storage battery monitoring device 2 determines whether or not the storage battery 6 is being charged (S102).

[0021] If it is determined in step S102 that the storage battery 6 is not being charged, i.e., that the storage battery 6 is being discharged, the measurement unit 21 of the battery monitoring device 2 performs temperature correction on the current value (discharge current value) measured in step S100 (S104). In step S104, the measured current value is multiplied by a correction temperature coefficient (discharge current value × current correction coefficient). As described above, the internal resistance of the storage battery 6 is temperature-dependent. The current correction coefficient is a coefficient corresponding to this temperature dependency and is set based on the temperature dependency and the temperature of the storage battery 6 measured by the temperature sensor 7. The current correction coefficient is set, for example, as a function of the temperature of the storage battery 6, and is calculated by substituting the measured temperature into this function. This function can be set appropriately depending on the temperature dependency of the estimated charge acceptance or on changes in charge acceptance measured by actually changing the temperature. The temperature used to calculate the current correction coefficient can be the average temperature, minimum temperature, or maximum temperature measured during the charge / discharge process. From the viewpoint of further suppressing overcharging, it is preferable to use the minimum temperature measured during the charge / discharge process. The temperature used to calculate the current correction coefficient is the same whether measuring the representative battery or the temperature of the atmosphere in which the battery 6 is placed. By correcting with the current correction coefficient, the actual current value flowing inside the battery 6 can be obtained.

[0022] After step S104, the battery monitoring device 2 updates the accumulated value of the discharged amount (total discharged amount) (S106). The accumulated value of the discharged amount is the accumulated value of the current since the charge / discharge process was performed. As will be described later, while the charge / discharge process is being performed, the current value is repeatedly measured and the measured current values ​​are accumulated to determine the total discharged amount, and ultimately the accumulated value for the processing interval shown in FIG. 5 is determined. In other words, the total discharged amount is updated by adding the current value measured in the immediately preceding step S100 and corrected in step S104 to the total discharged amount up to that point.

[0023] If it is determined in step S102 that the storage battery 6 is being charged, the measurement unit 21 of the storage battery monitoring device 2 performs temperature correction on the current value (charging current value) measured in step S100 (S108). In step S108, similar to the correction in step S104, correction is performed by multiplying the measured current value by a current correction coefficient (charging current value × current correction coefficient). The current correction coefficient may be the same value used to correct the discharging current value, or a value different from that used to correct the discharging current value may be used.

[0024] After step S108, the battery monitoring device 2 updates the integrated value of the charge amount (total charge amount) (S110). The integrated value of the charge amount is the integrated value of the current since the charge / discharge process was performed. As will be described later, while the charge / discharge process is being performed, the current value is repeatedly measured and the measured current values ​​are integrated to determine the total charge amount, and ultimately the integrated value for the processing section shown in FIG. 5 is determined. In other words, the total charge amount is updated by adding the current value measured in the immediately preceding step S100 and corrected in step S108 to the total charge amount up to that point.

[0025] After step S110, the state determination unit 23 of the battery monitoring device 2 determines whether CV charging of equalized charging is being performed (S112). In the control method for equalized charging according to the first embodiment, as shown in FIG. 2, CC charging is performed followed by CV charging. In CC charging, charging is performed at a constant current until the voltage reaches a predetermined value. In CV charging, charging is performed at a constant voltage until a termination condition, which will be described later, is met. Then, when the termination condition is met, charging is stopped.

[0026] If it is determined in step S112 that CV charging is being performed, the state determination unit 23 of the battery monitoring device 2 calculates the actual charging rate and determines whether the calculated charging rate is equal to or greater than a threshold (S114). The charging rate is the ratio of the total charging amount to the total discharging amount (total charging amount / total discharging amount) and is calculated from the updated total charging amount and the total charging amount. The threshold is a predetermined charging rate that is set in advance, and may be set as the charging rate when optimal equalized charging is performed. The charging rate in the first embodiment is also referred to as a first charging rate, and the threshold in the first embodiment is also referred to as a first threshold.

[0027] If the charging rate is equal to or greater than the threshold in step S114, the battery monitoring device 2 ends the equalized charging (S116). At this time, the total charged amount and the total discharged amount are reset to 0. Completion of step S114 marks the end of one charge / discharge process including equalized charging. In the energy storage system 1, the charge / discharge process including equalized charging is repeatedly performed by repeating the process flow shown in FIG. 6. After step S106, if it is determined in step S112 that CV charging is not being performed, or if the state of charge is less than the threshold in step S114, the processing from step S100 onwards is repeated. In this way, in the processing section shown in Fig. 5, the accumulation of the charge amount and discharge amount, and the determination of the end of equalized charging according to the temperature conditions are repeatedly performed. In other words, if the state of charge is less than the threshold in step S114, equalized charging continues.

[0028] In the maintenance charge control method according to the first embodiment, when performing charge / discharge processing of the storage battery 6, including maintenance charging, the temperature and current of the storage battery 6 are measured, the current is corrected based on the measured temperature, and the corrected current is integrated to calculate the total charge amount and total discharge amount of the storage battery. Furthermore, during maintenance charging, if the charge rate calculated from the total charge amount and total discharge amount is below a threshold, constant voltage charging is continued, and if the charge rate is equal to or greater than the threshold, constant voltage charging is terminated. This configuration corrects the current value according to temperature conditions, making it possible to respond to changes in charge acceptance due to temperature changes. This reduces overcharging and undercharging of the storage battery 6. Furthermore, by correcting the current temperature each time a measurement is performed, it becomes easier to follow temperature changes, enabling highly accurate determinations.

[0029] Although the first embodiment has been described with reference to the case of equalization charging, the present invention is not limited to this example and can be applied to the case of maintenance charging, such as recovery charging, in the same manner as in this embodiment. In the first embodiment, the storage battery 6 is a bipolar lead-acid battery, but the present invention is not limited to this example. The present invention can be applied to storage batteries 6 such as other general lead-acid batteries in the same manner as the present embodiment. However, the present invention is extremely effective when used with a bipolar lead-acid battery such as the first embodiment. In the first embodiment, a function of temperature is used as the temperature correction coefficient, but the present invention is not limited to this example. The temperature correction coefficient may be set according to the temperature of the storage battery 6. For example, the temperature correction coefficient may be set in stages for each temperature range of the storage battery 6, and the temperature correction coefficient may be set from the measured temperature.

[0030] (11) According to a first embodiment of the present invention, there is provided a control method for maintenance charging, which, when performing charge / discharge processing of a storage battery including maintenance charging, measures the temperature and current of the storage battery, corrects the measured current value based on the measured temperature, and calculates the total charge amount and total discharge amount of the storage battery by integrating the corrected current value, and in the maintenance charging, performs constant current charging followed by constant voltage charging, and in the constant voltage charging, if the charging rate calculated from the total charge amount and the total discharge amount is less than a threshold, continues the constant voltage charging, and if the charging rate is equal to or greater than the threshold, terminates the constant voltage charging.

[0031] According to the configuration of (11), the current value measured is corrected according to the temperature conditions, which makes it possible to respond to changes in charge acceptance due to temperature changes, thereby reducing overcharging and undercharging. (12) In the configuration of (11) above, when correcting the current, a value obtained by multiplying the current by a temperature correction coefficient set according to the temperature of the storage battery is used. (13) In the configuration of (11) or (12), the storage battery is a bipolar lead-acid battery.

[0032] (14) According to a first embodiment of the present invention, there is provided a power storage system comprising: a plurality of storage batteries; a temperature sensor that measures the temperature of the storage batteries; an upper system that performs energy management of the plurality of storage batteries; an assembled battery sensor that measures charge / discharge currents and total voltages of the plurality of storage batteries; and a storage battery monitoring device that determines the state of the plurality of storage batteries and controls charge / discharge processes including maintenance charging, wherein the storage battery monitoring device corrects a measured current value based on the measured temperature and calculates a total charge amount and a total discharge amount of the storage batteries by integrating the corrected current value, and constant-voltage charging is performed as the maintenance charging, and during the constant-voltage charging, if a charging rate calculated from the total charge amount and the total discharge amount is less than a threshold value, the constant-voltage charging is continued, and if the charging rate is equal to or greater than the threshold value, the constant-voltage charging is terminated.

[0033] Second Embodiment Next, a second embodiment of the present invention will be described. As in the first embodiment, the power storage system 1 according to the second embodiment includes a battery monitoring unit (BMU) 2, an upper level system (EMS) 3, an AC / DC converter (PCS) 4, an assembled battery sensor 5, a plurality of storage batteries 6, and a plurality of temperature sensors 7, as shown in Fig. 3. Note that, in the following, a description of the same configuration as in the first embodiment may be omitted, and the description will focus on the configuration that differs from the first embodiment.

[0034] Similar to the first embodiment, the battery monitoring device 2 is a device that determines the state of the battery based on measurement information from the battery pack sensor 5 and the plurality of temperature sensors 7, and as a system configuration, as shown in Fig. 4, has a setting unit 20, a measurement unit 21, a recording unit 22, a state determination unit 23, and a communication unit 24. The host system 3, the battery pack sensor 5, the battery 6, and the plurality of temperature sensors 7 are also configured in the same manner as in the first embodiment. Also in the second embodiment, the host system 3, the battery pack sensor 5, the temperature sensor 7, etc. form a battery monitoring system.

[0035] In this energy storage system 1, as in the first embodiment, after a predetermined number of discharges and charges are repeated, maintenance charging, for example, equalization charging, is performed as shown in Fig. 5. Switching between charging and discharging is performed when the remaining capacity of the storage battery 6 reaches the upper or lower limit of a preset PSOC range. In the example shown in Fig. 5, equalization charging is performed after five discharges and four charges.

[0036] The charging and discharging process of the storage battery 6, including equalization charging, is performed according to the processing flow shown in Fig. 7. The processing shown in Fig. 7 is a processing section in which charging and discharging are performed from the state in which equalization charging is completed as shown in Fig. 5, and until equalization charging is performed again. Although not explained in Fig. 7, switching between charging and discharging and performing equalization charging are performed by the storage battery monitoring device 2 according to the remaining capacity of the storage battery 6 and the number of times it has been charged and discharged.

[0037] 7, when the charge / discharge process is started, first, the battery pack sensor 5 measures the current, and the temperature sensor 7 measures the temperature of the storage battery 6 (S200). The measurement information of the current and temperature is collected by the measurement unit 21 and stored in the recording unit 22. Next, the state determination unit 23 of the battery monitoring device 2 determines whether or not the battery 6 is being charged (S202).

[0038] If it is determined in step S202 that the storage battery 6 is not being charged, i.e., that the storage battery 6 is being discharged, the battery monitoring device 2 updates the accumulated value of the discharge amount (total discharge amount) (S204). The accumulated value of the discharge amount is the accumulated value of the current since the charge / discharge process was performed. As will be described later, while the charge / discharge process is being performed, the current value is repeatedly measured and the measured current values ​​are accumulated to determine the total discharge amount, and ultimately the accumulated value for the processing interval shown in FIG. 5 is determined. In other words, the total discharge amount is updated by accumulating the current value measured in the immediately preceding step S200 with the total discharge amount up to that point.

[0039] On the other hand, if it is determined in step S202 that the storage battery 6 is being charged, the storage battery monitoring device 2 updates the integrated value of the charge amount (total charge amount) (S206). The integrated value of the charge amount is the integrated value of the current since the charge / discharge process was performed. The integrated value of the charge amount is the same as the total discharge amount, and the total charge amount is updated by adding the current value measured in the immediately preceding step S200 to the total charge amount up to that point.

[0040] After step S206, the state determination unit 23 of the battery monitoring device 2 determines whether CV charging of equalized charging is being performed (S208). In the control method for equalized charging according to this embodiment, as shown in FIG. 2, CC charging is performed followed by CV charging. In CC charging, charging is performed at a constant current until the voltage reaches a predetermined value. In CV charging, charging is performed at a constant voltage until a termination condition, which will be described later, is met. Then, when the termination condition is met, charging is stopped.

[0041] If it is determined in step S208 that CV charging is being performed, the setting unit 20 of the battery monitoring device 2 calculates a threshold value for the charging rate (S210). The threshold value for the charging rate is a value obtained by multiplying the set value by a temperature correction coefficient (set value × temperature correction coefficient). The set value is a predetermined charging rate, and may be set, for example, as a charging rate at which optimal equalized charging is performed at a predetermined temperature. The temperature correction coefficient is set based on the temperature dependence of the internal resistance of the storage battery 6, i.e., the temperature dependence of the charge acceptance, and the temperature of the storage battery 6 measured by the temperature sensor 7. The temperature dependence of the charge acceptance is set, for example, as a function of the temperature of the storage battery 6. This function is set appropriately based on the estimated temperature dependence of the charge acceptance or on changes in the charge acceptance measured by actually changing the temperature. The temperature used to calculate the temperature correction coefficient can be the average temperature, minimum temperature, or maximum temperature measured during the charge / discharge process. Note that, from the perspective of further suppressing overcharging, it is preferable to use the minimum temperature measured during the charge / discharge process. The temperature used to calculate the temperature correction coefficient is the same whether measuring the representative storage battery or measuring the temperature of the atmosphere in which the storage battery 6 is placed. The threshold value in the second embodiment is also referred to as the second threshold value.

[0042] After step S210, the state determination unit 23 of the battery monitoring device 2 calculates the actual charging rate and determines whether the calculated charging rate is equal to or greater than the threshold calculated in step S210 (S212). The charging rate is the ratio of the total charging amount to the total discharging amount (total charging amount / total discharging amount), and is calculated from the updated total charging amount and the total charging amount. If the charging rate is equal to or greater than the threshold in step S212, the battery monitoring device 2 ends the equalized charging (S214). At this time, the total charging amount and the total discharging amount are reset to 0. Completion of step S214 marks the end of one charge / discharge process including equalized charging. The battery monitoring system 1 repeats the process flow shown in FIG. 7 to repeatedly perform charge / discharge processes including equalized charging. The charging rate in the second embodiment is also referred to as the second charging rate.

[0043] After step S204, if it is determined in step S208 that CV charging is not being performed, or if the state of charge is less than the threshold in step S212, the processing from step S200 onwards is repeated. In this way, in the processing section shown in Fig. 5, the integration of the charge amount and discharge amount, and the determination of the end of equalized charging according to the temperature conditions are repeatedly performed. In other words, if the state of charge is less than the threshold in step S214, equalized charging continues.

[0044] In the equalization charge control method according to the second embodiment, CV charging is performed after CC charging as equalization charging of the storage battery 6. In CV charging, CV charging continues when the charging rate is below a threshold value according to the temperature of the storage battery 6, and ends when the charging rate is equal to or greater than the threshold value. The threshold value is a value obtained by multiplying a set value, which is a predetermined charging rate, by a temperature correction coefficient. This configuration changes the charging rate at which equalization charging ends depending on the temperature conditions. This makes it possible to respond to changes in charge acceptance due to temperature changes, thereby reducing overcharging and undercharging.

[0045] Although the second embodiment has been described with reference to the case of equalization charging, the present invention is not limited to this example. The present embodiment can also be applied to the case of maintenance charging, such as recovery charging. In the second embodiment, the storage battery 6 is a bipolar lead-acid battery, but the present invention is not limited to this example. The present invention can be applied to storage batteries 6 such as other general lead-acid batteries in the same manner as the present embodiment. However, the present invention is extremely effective when used with a bipolar lead-acid battery such as the second embodiment.

[0046] (15) According to a second embodiment of the present invention, there is provided a control method for maintenance charging of a storage battery, in which constant current charging is followed by constant voltage charging, and in the constant voltage charging, if a charging rate calculated from a total charge amount and a total discharge amount of the storage battery is less than a threshold value according to the temperature of the storage battery, the constant voltage charging is continued, and if the charging rate is equal to or greater than the threshold value, the constant voltage charging is terminated.

[0047] According to the configuration of (15), the charging rate at which the recovery charge is terminated is changed depending on the temperature condition. This makes it possible to respond to changes in charge acceptance due to temperature changes, thereby reducing overcharging and undercharging. (16) In the configuration of (15) above, the threshold value may be a value obtained by multiplying a set value, which is a predetermined charging rate, by a temperature correction coefficient. (17) In the configuration of (15) or (16) above, the storage battery may be a bipolar lead-acid battery.

[0048] (18) According to a second embodiment of the present invention, there is provided a power storage system including a plurality of storage batteries, a temperature sensor that measures the temperature of the storage batteries, a host system that performs energy management of the plurality of storage batteries, a battery pack sensor that measures the charge / discharge current and total voltage of the plurality of storage batteries, and a battery monitoring device that determines the state of the plurality of storage batteries and controls charge / discharge processes including maintenance charging, wherein the maintenance charging is performed by constant current charging followed by constant voltage charging, and during the constant voltage charging, if a charging rate calculated from the total charge amount and total discharge amount of the storage batteries is less than a threshold value corresponding to the temperature of the storage batteries, the constant voltage charging is continued, and if the charging rate is equal to or greater than the threshold value, the constant voltage charging is terminated.

[0049] In addition, a maintenance charging control method according to one aspect of the present invention performs constant current charging followed by constant voltage charging as maintenance charging of the storage battery 6, and in the constant voltage charging, a charge rate (first charge rate in the first embodiment, or second charge rate in the second embodiment) calculated from the total charge amount and total discharge amount of the storage battery calculated from the current value of the storage battery 6 and a threshold value (first threshold value in the first embodiment, or second threshold value in the second embodiment) are used to determine whether to continue or terminate the constant voltage charging based on the temperature of the storage battery.

[0050] According to another aspect of the present invention, there is provided a power storage system 1 including a plurality of storage batteries 6, a temperature sensor 7 that measures the temperature of the storage batteries 6, a host system 3 that performs energy management of the plurality of storage batteries 6, a battery pack sensor 5 that measures the charge / discharge current and total voltage of the plurality of storage batteries 6, and a battery monitoring device 2 that determines the state of the plurality of storage batteries 6 and controls charge / discharge processes including maintenance charging, wherein constant current charging is performed followed by constant voltage charging as maintenance charging, and in the constant voltage charging, a determination is made as to whether to continue or end the constant voltage charging based on the temperature of the storage batteries using a charging rate (first charging rate in the first embodiment, or second charging rate in the second embodiment) calculated from the total charge amount and total discharge amount of the storage batteries calculated from the current value of the storage batteries 6, and a threshold value (first threshold value in the first embodiment, or second threshold value in the second embodiment). [Explanation of symbols]

[0051] 1. Energy storage system 2 Battery monitoring device 20 Setting section 21 Measurement section 22 Recording section 23 Status determination unit 24 Communications Department 3. Upper system 4 AC / DC converter 5 Battery pack sensor 6. Storage battery 7 Temperature Sensor

Claims

1. As a maintenance charge for the storage battery, a constant current charge is followed by a constant voltage charge. In the constant voltage charging, a determination is made as to whether to continue or terminate the constant voltage charging based on a temperature of the storage battery using a first charging rate calculated from a total charge amount and a total discharge amount of the storage battery calculated from a current value of the storage battery and a first threshold value; When performing battery charging and discharging, including maintenance charging, measuring the temperature and current of the battery; correcting the measured current value based on the measured temperature; calculating a total charge amount and a total discharge amount of the storage battery by integrating the corrected current value; A control method for maintenance charging, wherein, in the constant voltage charging, when the first charging rate is less than the first threshold, the constant voltage charging is continued, and when the first charging rate is equal to or greater than the first threshold, the constant voltage charging is terminated.

2. 2. The method for controlling maintenance charging according to claim 1, wherein when correcting the current value, a value obtained by multiplying the current value by a temperature correction coefficient set in accordance with the temperature of the storage battery is used.

3. As a maintenance charge for a storage battery, a constant current charge is followed by a constant voltage charge, In the constant voltage charging, a determination is made as to whether to continue or terminate the constant voltage charging based on a temperature of the storage battery using a second charging rate calculated from a total charge amount and a total discharge amount of the storage battery calculated from a current value of the storage battery, and a second threshold value; A control method for maintenance charging, wherein, in the constant voltage charging, if the second charging rate is less than the second threshold value corresponding to the temperature of the storage battery, the constant voltage charging is continued, and if the second charging rate is equal to or greater than the second threshold value, the constant voltage charging is terminated.

4. 4. The method for controlling maintenance charging according to claim 3, wherein the second threshold value is a value obtained by multiplying a set value that is a predetermined charging rate by a temperature correction coefficient.

5. The method for controlling maintenance charging according to any one of claims 1 to 4, wherein the storage battery is a bipolar lead-acid battery.

6. A plurality of batteries; a temperature sensor for measuring the temperature of the storage battery; a host system that performs energy management of the plurality of storage batteries; an assembled battery sensor that measures charge / discharge currents and total voltages of the plurality of storage batteries; a battery monitoring device that determines the states of the plurality of batteries and controls charging and discharging processes including maintenance charging; Equipped with As the maintenance charge, a constant current charge is followed by a constant voltage charge, When performing battery charging and discharging, including maintenance charging, measuring the temperature and current of the battery; correcting the measured current value based on the measured temperature; calculating a total charge amount and a total discharge amount of the storage battery by integrating the corrected current value; In the constant voltage charging, a first charging rate is calculated from the total charge amount and total discharge amount of the storage battery calculated from the current value of the storage battery, and a first threshold is used to determine whether to continue or terminate the constant voltage charging based on the temperature of the storage battery, and when the first charging rate is less than the first threshold, the constant voltage charging is continued, and when the first charging rate is equal to or greater than the first threshold, the constant voltage charging is terminated.

7. A plurality of storage batteries; a temperature sensor for measuring the temperature of the storage battery; a host system that performs energy management of the plurality of storage batteries; an assembled battery sensor that measures charge / discharge currents and total voltages of the plurality of storage batteries; a battery monitoring device that determines the states of the plurality of batteries and controls charging and discharging processes including maintenance charging; Equipped with As the maintenance charge, a constant current charge is followed by a constant voltage charge, In the constant voltage charging, a second charging rate calculated from the total charge amount and total discharge amount of the storage battery calculated from the current value of the storage battery and a second threshold are used to determine whether to continue or terminate the constant voltage charging based on the temperature of the storage battery, and the constant voltage charging is continued when the second charging rate is less than the second threshold based on the temperature of the storage battery, and the constant voltage charging is terminated when the second charging rate is equal to or greater than the second threshold.

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