JP2012253975A - Charging/discharging control method for alkali storage battery, and charging/discharging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging/discharging method and a charging/discharging system that can efficiently utilize the available capacity of an alkali storage battery, and suppress a memory effect.SOLUTION: A charging/discharging control method for an alkali storage battery contains a step(a) of setting a temporary charging upper limit voltage or a temporary discharging lower limit voltage of an alkali storage battery on the basis of a standing time from the end of previous charging or discharging, the battery temperature at the time when the alkali storage battery is left as it stands and the charging state (SOC) when the alkali storage battery is started to be left before charging or discharging of the alkali storage battery is started, and a step(b) of stopping charging or discharging with the temporary charging upper limit voltage or the temporary discharging lower limit voltage for at least a fixed period from the start of the charging or discharging of the alkali storage battery.

Description

 The present invention relates to a charge / discharge control method and a charge / discharge system for an alkaline storage battery.

 Demand for alkaline storage batteries such as nickel metal hydride storage batteries is expanding mainly in industrial applications such as hybrid vehicles (hereinafter referred to as HEV) and emergency power supplies. In particular, in HEV, an alkaline storage battery as a main power source needs to perform both motor drive (discharge) and storage (charge) of regenerative power from a generator. Therefore, it is necessary to always monitor the state of charge (SOC) of the alkaline storage battery and control charging and discharging according to the SOC.

 In an alkaline storage battery using nickel hydroxide as the positive electrode active material, a memory effect occurs when a cycle in which complete discharge (SOC is almost 0%) or complete charge (SOC is almost 100%) is not repeated. That is, the electromotive force value with respect to the remaining capacity of the storage battery is lowered, and the capacity is apparently reduced. In order to suppress the occurrence of the memory effect, it is desirable to perform charge / discharge in a wide SOC region in an alkaline storage battery.

 However, in applications such as HEV, charging / discharging with a large current is performed continuously and instantaneously. Therefore, when a plurality of alkaline storage batteries each having a capacity difference are connected, it is necessary to avoid that the storage battery having the smallest capacity is overcharged or overdischarged. Therefore, an upper limit SOC (charge upper limit voltage) for prohibiting charging and a lower limit SOC (discharge lower limit voltage) for prohibiting discharge are provided so that complete discharge and full charge are not performed, and between the upper limit voltage and the lower limit voltage. The method of controlling charging / discharging is employed.

 In order to reduce the memory effect, various techniques have been conventionally proposed. For example, Patent Document 1 obtains an estimated battery voltage from an integrated value of the discharge current of a battery, and corrects the discharge lower limit voltage based on this to widen the width of the charge / discharge region even when the memory effect occurs. A method is disclosed.

JP 2001-186682 A

 However, if the alkaline storage battery that has been charged or discharged is left unattended, the self-decomposition reaction of nickel hydroxide, which is the positive electrode active material, is promoted, and the remaining capacity decreases according to the amount of the self-decomposition reaction. Further, since the reactivity of nickel hydroxide is reduced due to the self-decomposition reaction, the polarization at the start of the next charge or discharge increases. For this reason, when the charge upper limit voltage or the discharge lower limit voltage is set based only on the estimated battery voltage, a sufficient amount of electricity is not charged / discharged, and the usable capacity of the battery is reduced.

 The amount of self-decomposition reaction of nickel hydroxide, which is the positive electrode active material of alkaline storage battery, is considered to change depending on the standing time since the last charging and discharging, the ambient temperature at the time of leaving, and the state of charge at the start of leaving. .

 Therefore, one aspect of the present invention is based on the leaving time from the end of the previous charging or discharging, the battery temperature at the time of leaving, and the state of charge at the start of leaving before starting the charging or discharging of the alkaline storage battery. A step of setting a provisional upper limit charge voltage or provisional discharge lower limit voltage of the alkaline storage battery, and starting the charge or discharge of the alkaline storage battery, at least for a certain period of time, the set provisional charge upper limit voltage or And a step of stopping charging or discharging at a provisional discharge lower limit voltage.

 Another aspect of the present invention is an alkaline storage battery, a voltage detection unit that detects a voltage of the alkaline storage battery, a temperature detection unit that detects a temperature of the alkaline storage battery, and a standing time after charging or discharging ends. Based on the time detection unit that counts the battery, and before the charging or discharging of the alkaline storage battery starts, the leaving time since the last charging or discharging ends, the battery temperature at the time of leaving, and the state of charge at the start of leaving A calculation unit for setting a provisional upper limit voltage or a provisional discharge lower limit voltage of the alkaline storage battery, a storage unit for storing a provisional charge upper limit voltage or a provisional discharge lower limit voltage set by the calculation unit, and the alkali For a certain period after charging or discharging of the storage battery is started, the alkaline power storage is performed based on the stored temporary charging upper limit voltage or temporary discharging lower limit voltage. Of the charge and discharge control unit for controlling the charging and discharging or discharging comprises a relates to charge and discharge system.

 According to the charge / discharge control method and the charge / discharge system, the charge upper limit voltage or the discharge lower limit voltage of the alkaline storage battery can be set according to the degree of polarization of the battery, so that the usable capacity of the battery is efficiently used. it can. In addition, since insufficient charging / discharging due to polarization is suppressed, generation of the memory effect can be suppressed.

 In the charge / discharge control method and the charge / discharge system, after the predetermined period (provisional period), the standard charge upper limit voltage or standard discharge lower limit voltage is different from the provisional charge upper limit voltage or the provisional discharge lower limit voltage. The charging or discharging of the alkaline storage battery may be stopped.

 When the influence of polarization is reduced after the provisional period has elapsed, by controlling charging / discharging with the standard charge upper limit voltage or standard discharge lower limit voltage, for example, in HEV applications, a plurality of alkaline storage batteries having individual capacity differences Even when is connected, it is possible to avoid that the storage battery with the smallest capacity is overcharged or overdischarged.

 According to the present invention, the usable capacity of the alkaline storage battery can be efficiently used, and the memory effect can be suppressed.

It is a block diagram which shows the structure of an example of the charging / discharging system 1 of this invention. It is a graph which shows the relationship between charging / discharging electric current, provisional charge upper limit voltage, and discharge lower limit voltage. It is a flowchart of an example of the process which determines a temporary charging upper limit voltage or a temporary discharge lower limit voltage. It is a flowchart of an example of the process of the charging / discharging control of the battery by provisional mode.

 The degree of polarization at the start of charging or discharging of the alkaline storage battery varies depending on the leaving time after the end of the previous charging and discharging, the battery temperature at the time of leaving, and the state of charge at the start of leaving. Therefore, if the charge upper limit voltage or the discharge lower limit voltage of the alkaline storage battery is fixed without being fluctuated, if the polarization is large, the actual charge amount or discharge amount is charged even if the charge is charged to the charge upper limit voltage and discharged to the discharge lower limit voltage. Is less than the original usable capacity. Furthermore, if such charge / discharge is repeated, the charge or discharge is repeatedly stopped before reaching the planned charge state, and the memory effect is likely to occur.

 Therefore, in the charge / discharge control method and charge / discharge control system of the present invention, before starting the charging or discharging of the alkaline storage battery, the leaving time after the last charging or discharging ends, the battery temperature at the time of leaving, and the leaving Based on the charge state (SOC) at the start, a provisional upper limit voltage or a provisional discharge lower limit voltage of the alkaline storage battery is set. As a result, the usable capacity of the battery can be used effectively, and the occurrence of the memory effect is also suppressed.

 However, when a certain period of time has elapsed since the start of charging or discharging of the alkaline storage battery, the polarization of the battery is eliminated to some extent. The provisional discharge lower limit voltage is switched to the standard charge upper limit voltage or the standard discharge lower limit voltage.

 Here, the standard charge upper limit voltage or the standard discharge lower limit voltage is, for example, a charge upper limit voltage or a discharge lower limit voltage that is recommended when it is not necessary to consider the influence of battery leaving or battery deterioration on polarization. is there. Such a standard upper limit or lower limit voltage, for example, in HEV applications, can prevent the storage battery having the smallest capacity from being overcharged or overdischarged when a plurality of alkaline storage batteries having different capacity differences are connected. Is set as follows. The standard charge upper limit voltage or the standard discharge lower limit voltage may be a fixed value, or may be changed according to the deterioration state of the battery in long-term use or the like. The provisional upper limit charge voltage or the provisional discharge lower limit voltage is higher or lower than the standard charge upper limit voltage or the standard discharge lower limit voltage.

 Here, it is desirable to accurately measure the standing time after the end of the previous charging or discharging, but it is not necessary to be exact. The time taken into consideration only needs to reflect the actual neglected time. As the standing time is longer, the self-decomposition reaction of nickel hydroxide proceeds and the reactivity of nickel hydroxide decreases, so that the polarization at the start of the next charge or discharge tends to increase. Therefore, the longer the standing time, the higher the temporary charging upper limit voltage than the standard charging upper limit voltage when performing charging, and the lower the temporary discharging lower limit voltage than the standard discharging lower limit voltage when discharging, Can be set. Thereby, the usable capacity of the battery can be effectively utilized.

 The battery temperature at the time of leaving may be measured at least once during the battery leaving period. For example, the temperature may be periodically measured after the end of the previous use, and the average temperature of a plurality of measured values may be considered. The higher the temperature at the time of standing, the more the self-decomposition reaction of nickel hydroxide proceeds, and the reactivity of nickel hydroxide decreases, so the polarization at the start of the next charge or discharge tends to increase. is there. Therefore, when the battery temperature is high, when charging, the provisional upper limit voltage is higher than the standard upper limit voltage, and when discharging, the provisional lower discharge limit voltage is higher than the standard discharge lower limit voltage. Low and can be set.

 If the standing time is relatively long, the ambient temperature around the battery may be measured instead of the battery temperature. However, since the battery temperature may be higher than the environmental temperature when the standing time is relatively short, it is desirable to directly measure the battery temperature. On the other hand, when the leaving time is relatively long, the battery temperature can be regarded as the environmental temperature. In addition, when the leaving time is relatively short, the battery temperature is a function of the leaving time, so it is not necessary to place importance on the battery temperature or the environmental temperature. What is necessary is just to set a discharge minimum voltage.

 The state of charge (SOC) at the start of leaving can be obtained by various methods. For example, since the state of charge and the battery voltage have a corresponding relationship, the state of charge of the battery can be estimated from the measured value of the battery voltage. In addition, when a calibration curve showing the relationship between the SOC and the voltage-current characteristic (IV value) is created in advance, the SOC can be monitored by measuring the IV value as appropriate and comparing it with the calibration curve. .

 However, when the memory effect has already occurred in the alkaline storage battery, the measured value of the battery voltage may not reflect the actual state of charge. This is because the battery in which the memory effect is generated has a voltage that rapidly drops during discharge even if it has a sufficient remaining capacity. Therefore, the state of charge (SOC) at the start of leaving is preferably obtained from the integrated current value of the previous charge or discharge. Accumulated current value of charging or discharging accurately reflects the charging capacity or discharging capacity, so if the charging state at the start of the previous charging or discharging is accurate, the charging state at the start of leaving is accurately grasped Because it can be done. Moreover, you may correct | amend SOC obtained by collation with a calibration curve by SOC calculated from an electric current integrated value. As described above, it is possible to set a more appropriate provisional charge upper limit voltage or provisional discharge lower limit voltage.

It is considered that the higher the state of charge (SOC) at the start of the standing, the easier the nickel hydroxide self-decomposition reaction proceeds, and the lower the state of charge, the less likely the autodecomposition reaction proceeds.
Even when the SOC is the same, when the start of standing corresponds to the end of charging, the self-decomposition reaction of nickel hydroxide proceeds more easily, and when the start of standing corresponds to the end of discharge, Nickel hydroxide self-decomposition tends to be slower. Therefore, in addition to the standing time since the end of the previous charging or discharging, the battery temperature at the time of leaving and the charging state at the start of leaving, the provisional time is considered whether the charging start or discharge ends. A charge upper limit voltage or a provisional discharge lower limit voltage may be set.

 In a preferred embodiment of the present invention, a provisional charge upper limit voltage or a provisional discharge lower limit voltage is further set in consideration of the charge current or the discharge current. This is because the degree of polarization of the battery changes depending on the magnitude of the charging current or discharging current, and the closed circuit voltage tends to fluctuate. In general, the greater the current value, the greater the degree of polarization. Therefore, by considering the magnitude of the charging current or the discharging current, it is possible to set a more appropriate provisional charging upper limit voltage or provisional discharging lower limit voltage.

 In a preferred embodiment of the present invention, a temporary charge upper limit voltage or a temporary discharge lower limit voltage is set in consideration of the total charge / discharge capacity of the alkaline storage battery. Here, the total charge / discharge capacity is the sum of current accumulated values of all charges and discharges performed from the beginning of use of the battery to the present time (that is, when charging or discharging is started). The total charge / discharge capacity corresponds to the number of repetitions (cycles) of charge / discharge of the battery, and is an index of the degree of deterioration of the battery. Depending on the degree of deterioration of the battery, the degree of polarization of the battery may change. Therefore, by considering the total charge / discharge capacity, the degree of polarization of the battery can be grasped more accurately, and a more appropriate provisional charge upper limit voltage or provisional discharge lower limit voltage can be set. The total charge / discharge capacity is desirably measured as accurately as possible. However, the total charge / discharge capacity does not have to be exact, and may reflect the number of times the battery has been charged / discharged to some extent.

 The indicator of the degree of battery deterioration is not limited to the total charge / discharge capacity, and the total of the battery leaving periods over a long period of time or the average value of the temperature at the time of leaving the battery may be used. This is because the standing time and the standing temperature have a large influence on the self-discharge and the memory effect in the short term, but are considered to affect the deterioration of the battery in the long term.

Next, a charge / discharge system that performs the charge / discharge control will be described.
FIG. 1 is a block diagram showing the structure of an example of the charge / discharge system 1 of the present invention.
The charging / discharging system 1 includes an alkaline storage battery group 10, an end voltage setting circuit 20 that sets a charging upper limit voltage or a discharge lower limit voltage of the alkaline storage battery group 10, and charging / discharging of the alkaline storage battery group 10 based on the set upper limit or lower limit voltage. And a charge / discharge control unit 30 for controlling discharge. The charge / discharge system 1 is used in various power supply systems such as a backup power supply device, an electronic device, an electric vehicle, and an HEV.

 The end voltage setting circuit 20 is configured as an ECU (Electric Control Unit), for example. The end voltage setting circuit 20 includes a current detection unit 201 that detects the charge / discharge current of the battery group 10, a voltage detection unit 202 that detects the voltage of the battery group 10, and a temperature detection unit 203 that detects the temperature of the battery group 10. A timer 204 that counts (measures) a standing time from the end of charging or discharging to the start of the next charging or discharging; a current integrating unit 205 that integrates the current detected by the current detecting unit 201; And a central control unit 240.

 The central control unit 240 sets a provisional charge upper limit voltage or a provisional discharge lower limit voltage based on the information output from the various detection units, the timer 204, and the current integration unit 205, and sets the provisional discharge upper limit voltage to the charge / discharge control unit 30. The upper limit or lower limit voltage set for the output is output.

 A power generation device 100 and a load device 200 are connected to the charge / discharge control unit 30. Charging of the battery group 10 is mainly performed by the power generation device 100. The power generation apparatus 100 is, for example, a generator driven by the power of an HEV engine or the like, and generally uses an inverter that can convert kinetic energy of the internal combustion engine and frictional energy at the time of stoppage into electric energy. The load device 200 is, for example, a HEV motor. A similar inverter is also used when converting electrical energy into kinetic energy during discharge.

 The charge / discharge control unit 30 may be connected to a commercial power supply instead of the power generation device 100. The charge / discharge control unit 30 controls the battery group 10 to be charged with surplus power from the power generation device 100 and regenerative power generated in the load device 200. In addition, when the current consumption of the load device 200 suddenly increases or the required power of the load device 200 exceeds the output of the power generation device 100, the charge / discharge control unit 30 generates insufficient power from the battery group 10. To supply.

 The battery group 10 is composed of a plurality of alkaline storage batteries connected in series. As the alkaline storage battery, a nickel hydrogen battery, a nickel cadmium storage battery, or the like can be used. In addition, the number of alkaline storage batteries is not specifically limited, One may be sufficient and multiple may be sufficient. In the case of a plurality, the way of connecting the batteries is not limited to the series as shown in FIG. 1 but may be connected in parallel, or a combination of series and parallel may be used.

 Nickel metal hydride storage batteries and nickel cadmium batteries are secondary batteries including a positive electrode, a negative electrode, a separator, and an alkaline electrolyte (such as an aqueous potassium hydroxide solution) containing a nickel compound. The positive electrode includes a positive electrode active material (nickel compound) as an essential component, and includes a conductive material and other additives as optional components. As the nickel compound, nickel hydroxide is used. The memory effect and polarization of alkaline storage batteries are considered to be related to the self-decomposition reaction of nickel hydroxide. The negative electrode contains a negative electrode active material as an essential component and an additive as an optional component. A hydrogen storage alloy is used for the negative electrode active material of the nickel hydride storage battery, and a cadmium compound is used for the negative electrode active material of the nickel cadmium storage battery. The shape of the alkaline storage battery is not particularly limited, and examples thereof include a cylindrical battery and a rectangular battery.

 In the vicinity of the battery group 10, a temperature sensor 101 that measures the temperature of the battery group 10 or the ambient temperature around the battery group 10 and a current sensor 102 that detects charge / discharge current of the battery group 10 are installed. .

 For example, a thermocouple, a thermistor, or the like is used as the temperature sensor 101, and information corresponding to the battery temperature or the environmental temperature (T) is output to the temperature detection unit 203. The temperature output to the temperature detection unit 203 is sent to the central control unit 240 at a predetermined cycle.

 The current sensor 102 includes, for example, a resistance element or a current transformer connected in series with the battery group 10, and outputs information corresponding to the current (I) flowing through the battery group 10 to the current detection unit 201. The current value output to the current detection unit 201 is sent to the central control unit 240 and the current integration unit 205 at a predetermined cycle.

 The voltage detection unit 202 is configured using, for example, an analog-digital converter, and measures the voltage (V) between terminals of the battery group 10. For example, the voltage detection unit 202 converts the measured inter-terminal voltage into a digital value at a preset cycle and outputs the digital value to the central control unit 240. As shown in FIG. 1, the voltage detector 202 may measure the inter-terminal voltage of the battery group 10 together, but measures the inter-terminal voltage for each battery or for each of a plurality of batteries connected in parallel. These may be summed up.

 The timer 204 is connected to the current sensor 102, for example, and can receive analog information sent from the current sensor 102 when the battery group 10 is charged and discharged. When charging or discharging of the battery group 10 is finished and the battery group 10 is left as it is, the analog information from the current sensor 102 is not received for a certain period of time. Then, integration of the standing time (t) is started. It should be noted that the start timing of the neglect may be detected by any method, and need not be performed based on information from the current sensor. For example, the integration of the standing time by the timer 204 may be started after the HEV driver stops the HEV engine.

 The central control unit 240 is, for example, a CPU (Central Processing Unit), a predetermined control program, a standard charge upper limit voltage, a standard discharge lower limit voltage, and other nonvolatile ROM (Read Only) in which previously acquired information is stored. Memory), standing time, battery temperature, battery charge state, RAM (Random Access Memory) that temporarily stores a set upper limit charge voltage or lower discharge limit voltage, and other peripheral circuits. The central control unit 240 functions as an SOC detection unit 241 and a calculation unit 242 that executes calculation processing necessary for setting the temporary charge upper limit voltage or the temporary discharge lower limit voltage by executing a control program stored in the ROM. To do. The ROM and RAM function as the storage unit 243.

 The current integration unit 205 multiplies the detected current value by the minute time Δt and integrates it to obtain the amount of electricity (Q) charged / discharged by the battery group 10. When current accumulation is performed with the charge current as a positive current and the discharge current as a negative current, the accumulated amount of electricity (Q1) reflects the state of charge (SOC) of the battery group. The quantity of electricity (Q1) is output to the central controller 240 as information for calculating the SOC. Further, if integration based on the absolute value of the current is performed without considering the sign of the charging current and the discharging current, an electric quantity (Q2) corresponding to the total charge / discharge capacity can be obtained. The amount of electricity (Q2) is output to the central control unit 240 as information for determining the deterioration state of the battery group 10.

 The SOC detection unit 241 can obtain the SOC of the battery group 10 by calculating the ratio of the accumulated amount of electricity (Q1) to the amount of electricity in the fully charged state. Alternatively, when a calibration curve indicating the relationship between the SOC and the voltage-current characteristic (IV value) is stored in the ROM in advance, the SOC detection unit 241 calculates the IV value as appropriate, and the calibration curve. The SOC is obtained by checking the above. At that time, a correction coefficient corresponding to the temperature may be stored in the ROM, and the SOC may be corrected according to the battery temperature. In addition, a calibration curve indicating the relationship between the SOC and the voltage-current characteristics (IV value) is obtained for each battery temperature range, and an appropriate calibration curve may be referred to as appropriate according to the battery temperature. Good. The obtained SOC is stored in the RAM. Note that the SOCs of a plurality of batteries may be obtained separately for each of the batteries.

 The calculation unit 242 is a RAM of the storage unit 243 that is output from the current detection unit 201, the voltage detection unit 202, the temperature detection unit 203, the timer 204, and the current integration unit 205 before starting to charge or discharge the battery group 10. Using the parameters temporarily stored in the battery, the leaving time (t, x1) from the end of the previous charging or discharging, the battery temperature (T, x2) at the time of leaving, and the state of charge at the start of leaving (( SOC, x3) is determined, and based on these, a calculation process for setting the provisional charge upper limit voltage or the provisional discharge lower limit voltage of the battery group 10 is performed.

 For example, the ROM of the storage unit 243 stores a plurality of candidate charge upper limit voltages or candidate discharge lower limit voltages. Specifically, the candidate charge upper limit voltage or the candidate discharge lower limit voltage (Y) is set according to the variable X, and for example, a function having a relationship of Y = f (X) is stored in the ROM. The variable X includes at least the leaving time x1, the battery temperature x2 at the time of leaving, and the charge state x3 at the start of the leaving, and has a relationship of Y = f (x1, x2, x3). Such a relationship is data acquired in advance by various experiments and simulations, and one candidate charge upper limit voltage or candidate discharge lower limit voltage corresponds to one combination of x1, x2, and x3. ing. When the combination of the variables X is determined, the calculation unit 242 refers to a function indicating the relationship between the candidate charge upper limit voltage or the candidate discharge lower limit voltage and the variable X, selects an appropriate upper / lower limit voltage, and performs the charge / discharge control unit 30. Output to.

 It is desirable to correct the relationship between the parameters as described above and the candidate charge upper limit voltage or the candidate discharge lower limit voltage by the charge or discharge current value (x4) to be started. In this case, the relationship of Y = f (X) can be expressed by Y = f (x1, x2, x3, x4). Further, when considering the deterioration of the battery, it is desirable to further correct the above relationship by the total charge / discharge capacity (x5) of the battery group 10 obtained by the current integrating unit 205. In this case, the relationship of Y = f (X) can be expressed by Y = f (x1, x2, x3, x4, x5).

 When charging or discharging is started, the voltage detection detection unit 202 monitors the voltage between the terminals of the battery group 10 at a predetermined period and outputs it to the central control unit 240. When it is detected that the closed circuit voltage of the battery group 10 has reached the set provisional charge upper limit voltage or provisional discharge lower limit voltage, the information is output to the charge / discharge control unit 30, and charging or discharging is stopped.

 Here, charging or discharging may be performed in two stages. That is, until the voltage detection unit 202 detects that the provisional charge upper limit voltage or provisional discharge lower limit voltage at which the closed circuit voltage of the battery group 10 has been set has been reached, the battery with the first charge current or the first discharge current. The group 10 is first charged or discharged. When the voltage detecting means 202 detects that the provisional charge upper limit voltage or provisional discharge lower limit voltage at which the closed circuit voltage of the battery group 10 has been set has been reached, the first charge or the first discharge is stopped, The battery group 10 is subjected to the second charging or the second discharging with the second charging current or the second discharging current smaller than the one charging current or the first discharging current. By performing the two-stage charging or discharging as described above, the effect of suppressing the memory effect is remarkably enhanced, and the usable capacity can be used more effectively.

 FIG. 2 is a graph showing the relationship between the charge / discharge current and the set provisional charge upper limit voltage and discharge lower limit voltage. In FIG. 2, the charge upper limit voltage is a voltage equivalent to SOC 80%, and the discharge lower limit voltage is a voltage equivalent to SOC 20%.

 First, charging is performed at a relatively large first charging current I3 (for example, a current value of 0.1 to 0.3 hour rate (C)) until the voltage of the alkaline storage battery reaches the charging upper limit voltage (first charging). . The current value of the X time rate is a current value at which the SOC becomes 0% to 100% (or 100% to 0%) in X time. When the voltage of the alkaline storage battery reaches the charge upper limit voltage, the first charge is stopped. At this time, if the SOC of the battery does not actually reach 80% due to polarization, the voltage decreases. Thereafter, charging is performed with a second charging current I4 smaller than the first charging current I3 (second charging). By performing the second charging, the polarization is reduced, and charging up to SOC 80% becomes possible.

 Next, discharge is performed at a relatively large first discharge current I1 (for example, a current value of 0.03 to 0.3 hour rate (C)) until the voltage of the alkaline storage battery reaches the discharge lower limit voltage (first discharge). ). When the voltage of the alkaline storage battery reaches the discharge lower limit voltage, the first discharge is stopped. At this time, if the SOC of the battery does not actually reach 20% due to polarization, the voltage increases. Thereafter, discharge is performed with a second discharge current I2 smaller than the first discharge current I1 (second discharge). By performing the second discharge, the polarization becomes small, and discharge up to SOC 20% becomes possible.

The second charge is preferably stopped before the voltage of the alkaline storage battery reaches the charge upper limit voltage again or before reaching the charge upper limit voltage. When the second charging is stopped before reaching the charging upper limit voltage V ₁ , the voltage v ₁ for stopping the second charging is, for example, 95% of the charging upper limit voltage V ₁ from the viewpoint of efficiently using the usable capacity. may be set to more than _{(0.95 × V 1 ≦ v 1} ).

Similarly, the second discharge is preferably stopped before the voltage of the alkaline storage battery reaches the discharge lower limit voltage again or reaches the discharge lower limit voltage. When the second discharge is stopped before reaching the discharge lower limit voltage V ₂ , the voltage v ₂ for stopping the second discharge is, for example, 105% of the discharge lower limit voltage V ₂ from the viewpoint of efficiently using the usable capacity. The following may be set (v ₂ ≦ 1.05 × V ₂ ).

 The time for performing the second charge is not particularly limited as long as the voltage of the alkaline storage battery reaches a predetermined voltage, and the time for performing the second charge may be several seconds. The time for performing the second charging is, for example, 1 to 20 seconds. Similarly, the time for performing the second discharge is not particularly limited as long as the voltage of the alkaline storage battery reaches the predetermined voltage, and the time for performing the second discharge may be several seconds. The time for performing the second discharge is, for example, 1 to 20 seconds.

 The second charge or the second discharge may not be performed every charge / discharge cycle. For example, even when the second charge or the second discharge is performed every several tens of cycles in the charge / discharge cycle of the alkaline storage battery, it is effective in reducing the memory effect. For example, the second charge or the second discharge may be performed every 5 to 50 cycles.

 The second charging current may be any value as long as it is smaller than the first charging current, and can be arbitrarily changed by changing the end voltage as the cycle proceeds. Especially, it is preferable that a 2nd charging current is a value of 1/10 to 1/5 of a 1st charging current. Similarly, the second discharge current may be any value as long as it is smaller than the first discharge current, and the value can be arbitrarily changed by changing the end voltage with the progress of the cycle. Especially, it is preferable that a 2nd discharge current is a value of 1/10 to 1/5 of a 1st discharge current.

 The two-stage charging or discharging as described above can be similarly applied to the case where the charging / discharging of the battery is controlled based on the standard charging upper limit voltage or the standard discharging lower limit voltage.

 The charging or discharging is stopped at the set temporary charging upper limit voltage or the temporary discharging lower limit voltage for a certain period (provisional period tx) after starting the charging or discharging of the alkaline storage battery. Then, after the provisional period tx has elapsed, charging or discharging is stopped at the standard charge end voltage or standard discharge end voltage. Here, the provisional period may be a period until the polarization of the battery is eliminated to some extent. This period can be estimated from, for example, the difference (ΔV1) between the temporary charge upper limit voltage and the standard charge upper limit voltage or the difference (ΔV2) between the temporary discharge lower limit voltage and the standard discharge lower limit voltage. As ΔV1 or ΔV2 is larger, it is considered that the influence of leaving the battery is larger, and therefore the period for controlling charging / discharging with the temporary charging upper limit voltage or the temporary discharging lower limit voltage becomes longer.

 The relationship between ΔV1 or ΔV2 and the period during which charging / discharging is controlled with the temporary charging upper limit voltage or the temporary discharging lower limit voltage may be obtained in advance by experiments or simulations and stored in the ROM of the storage unit 243. When the provisional charging upper limit voltage or provisional discharge lower limit voltage is determined, the period for controlling charging / discharging at the end voltage is also determined at the same time. It can output to the charge / discharge control unit 30. The time from the start of charging or discharging based on the temporary charging upper limit voltage or the temporary discharging lower limit voltage (charging / discharging in the temporary mode) can be measured by the timer 204, for example, and output to the central control unit 240. It is output to the charge / discharge control unit 30.

 In applications such as HEV, the standard discharge lower limit voltage is preferably a voltage corresponding to a state of charge (SOC) of 15 to 30%. The memory effect can be effectively suppressed by setting the discharge lower limit voltage to a voltage corresponding to SOC 15 to 30%. On the other hand, the standard charge upper limit voltage is preferably a voltage corresponding to SOC 70 to 85%. By setting the charging upper limit voltage to a voltage corresponding to SOC 70 to 85%, the memory effect can be effectively suppressed. In addition, by setting the charging upper limit voltage to a voltage corresponding to SOC 85% or less, oxygen generation from the positive electrode can be sufficiently suppressed.

Next, an example of a process for determining the temporary charge upper limit voltage or the temporary discharge lower limit voltage will be described with reference to FIG.
First, the central control unit 240 detects that the use of the battery has ended and that the battery has been left unattended. Such detection may be performed based on information from the current sensor 102 as described above, and is detected by turning off a main switch provided in the power generation device 100, the load device 200, the end voltage setting circuit 20, or the like. Alternatively, the user of the charge / discharge system may manually perform an input operation to the central control unit 240.

 When the central control unit 240 detects that the battery has been left unattended, the SOC detection unit 241 obtains the state of charge (SOC) at the start of the battery leaving by a predetermined method and stores it in the RAM of the storage unit 243 ( S1). The method for obtaining the SOC is not particularly limited. For example, as described above, it can be calculated from the integrated value (Q1) of the previous charge or discharge.

 In addition, the central control unit 240 starts counting the time by the timer 204 from the start of the leaving of the battery (S2), continues to accumulate time until the next charging or discharging is started, and accumulates periodically. Store time in RAM. At that time, the previous information may be always rewritten with the latest accumulated time.

 Further, the central control unit 240 periodically acquires the battery temperature from the temperature detection unit 203 (S3), calculates an average value based on all the temperatures acquired so far, and periodically stores it in the RAM. . At that time, the previous information may always be rewritten at the latest average temperature. The acquisition of the battery temperature, the calculation of the average value, and the storage in the RAM are repeated until the end of the leaving of the battery (S4) is detected.

 The end of the leaving of the battery may be detected by any method. For example, it can be detected by turning on a main switch provided in the power generation apparatus 100, the load device 200, the end voltage setting circuit 20, or the like. .

 When the end of the leaving of the battery is detected, the central control unit 240 determines the latest accumulated time stored in the RAM as the leaving time ta of the battery, and the latest average temperature is the temperature during the leaving of the battery. T is determined (S5).

 Next, the temporary charging upper limit voltage or the temporary discharging lower limit voltage is determined by the calculation unit 242 based on the SOC of the battery stored in the storage unit 243, the battery temperature T when left, and the leaving time ta ( S6). For example, in the ROM of the storage unit 243, the preliminarily acquired storage time (x1), battery temperature (x2) and battery SOC (x3), and the provisional charging upper limit voltage (y1) or provisional Function data indicating the relationship with the discharge lower limit voltage (y2) is stored. This function data is called, and by substituting the information stored in the RAM as x1 = ta, x2 = T and x3 = SOC, the provisional charge upper limit voltage (y1) or the provisional discharge lower limit voltage (y2) Is determined. At the same time, the provisional period tx is determined from the difference ΔV between the provisional upper limit charge voltage or provisional discharge lower limit voltage and the standard charge upper limit voltage or standard discharge lower limit voltage.

 If the total charge / discharge capacity (Q2) can be acquired by the current integrating unit 205, Q2 is periodically output to the central control unit 240, and Q2 is stored in the RAM of the storage unit 243. I can keep it. In such a case, since Q2 is an indicator of battery deterioration, the provisional charge upper limit voltage or the provisional discharge lower limit voltage may be corrected in consideration of Q2. The function data necessary for such correction may be acquired in advance and stored in the ROM of the storage unit 243.

Next, an example of a process of battery charge / discharge control (provisional mode) using the provisional upper limit charge voltage or provisional discharge lower limit voltage will be described with reference to FIG.
First, in order to detect the provisional period tx, the timer 204 starts counting time simultaneously with the start of charging / discharging of the battery (S7). For example, the central control unit 240 includes a determination circuit that determines whether or not the time counted by the timer 204 has reached the provisional period tx, and the battery voltage is provisional charge upper limit voltage or provisional discharge lower limit. When the voltage is reached, the determination result is output (S14).

 In the charging / discharging of the battery, as described with reference to FIG. 2, the first charging or the first discharging is initially performed with a relatively large first current (S8). After the start of the first charge or the first discharge, the temporary charge upper limit voltage or the temporary discharge lower limit voltage may be corrected based on the current value detected by the current detection unit 201 (S9). The function data necessary for such correction may be acquired in advance and stored in the ROM of the storage unit 243.

 When the first charge or the first discharge is started, the voltage detection unit 202 periodically acquires the battery voltage and stores it in the RAM of the storage unit 243. For example, the central control unit 240 has a built-in determination circuit that determines whether or not the battery voltage has reached a provisional charge upper limit voltage or a provisional discharge lower limit voltage, and outputs a determination result (S10). The output information is sequentially sent to the charge / discharge control unit 30. When it is determined that the battery voltage has reached the temporary charge upper limit voltage (Vc) or the temporary discharge lower limit voltage (Vd), the second charge or the second discharge is performed with a second current smaller than the first current. (S11).

 Thereafter, when it is determined again by the determination circuit that the battery voltage has reached the provisional upper limit voltage (Vc) or the provisional discharge lower limit voltage (Vd) (S12), charging or discharging is stopped (S13). . Alternatively, the stop of the second charging or the second discharging may be uniformly set to a short time of about 1 to 20 seconds, for example.

 Thereafter, when the battery voltage is the charging upper limit voltage, the battery shifts to discharging by the first current, and when the battery voltage is the discharging lower limit voltage, the battery shifts to charging by the first current. However, if the time counted by the timer 204 has reached the provisional period tx (YES in S14), the provisional mode is terminated, and thereafter, charging is performed with the standard charge upper limit voltage and the standard discharge lower limit voltage. Discharge is controlled.

 The charge / discharge control method and charge / discharge system of the present invention are advantageous for effective use of the usable capacity of an alkaline storage battery and suppression of the memory effect, and various applications such as a backup power supply device, an electronic device, an electric vehicle, and an HEV. Suitable for

 DESCRIPTION OF SYMBOLS 1 ... Charge / discharge system, 10 ... Alkaline storage battery group, 20 ... Final voltage setting circuit, 30 ... Charge / discharge control part, 100 ... Power generation device, 101 ... Temperature sensor, 102. ..Current sensor 200 ... Load device 201 ... Current detection unit 202 ... Voltage detection unit 203 ... Temperature detection unit 204 ... Timer 205 ... Current integration unit 240 ... Central control unit, 241 ... SOC detection unit, 242 ... Calculation unit, 243 ... Storage unit

Claims (19)

Before starting the charging or discharging of the alkaline storage battery, the temporary storage of the alkaline storage battery is based on the leaving time since the end of the previous charging or discharging, the battery temperature at the time of leaving and the state of charge (SOC) at the start of leaving. A step (a) of setting a charging upper limit voltage or a provisional discharge lower limit voltage;
A step (b) of stopping charging or discharging at the set provisional charge upper limit voltage or provisional discharge lower limit voltage for at least a certain period after the start of charging or discharging of the alkaline storage battery, Storage battery charge / discharge control method.   A step of stopping charging or discharging of the alkaline storage battery at a standard charge upper limit voltage or standard discharge lower limit voltage different from the provisional charge upper limit voltage or provisional discharge lower limit voltage after the predetermined period has elapsed (c) The charging / discharging control method of the alkaline storage battery of Claim 1 containing this.   The charge / discharge control method for an alkaline storage battery according to claim 1, wherein the state of charge at the start of the leaving is determined from a current integrated value of the previous charge or discharge.   The charge / discharge control method for an alkaline storage battery according to any one of claims 1 to 3, wherein the provisional charge upper limit voltage or the provisional discharge lower limit voltage is set in consideration of a current value of charge or discharge. .   Furthermore, the charging / discharging of the alkaline storage battery according to any one of claims 1 to 4, wherein the temporary charging upper limit voltage or the temporary discharging lower limit voltage is set in consideration of the total charging / discharging capacity of the alkaline storage battery. Control method.   The first charge or the first discharge is performed with the first charge current or the first discharge current up to the temporary charge upper limit voltage or the provisional discharge lower limit voltage, and then the first charge current or the first discharge current is exceeded. The charge / discharge control method of an alkaline storage battery according to any one of claims 1 to 5, wherein the second charge or the second discharge is performed with a small second charge current or a second discharge current.   In the second charging or the second discharging, the voltage of the alkaline storage battery reaches the temporary charging upper limit voltage or the temporary discharging lower limit voltage again, or the temporary charging upper limit voltage or the temporary discharging lower limit voltage. The charge / discharge control method for an alkaline storage battery according to claim 6, wherein the charge / discharge control method is stopped before reaching.   The charge / discharge control method for an alkaline storage battery according to any one of claims 1 to 7, wherein the standard charge upper limit voltage is a voltage corresponding to a state of charge (SOC) of 70 to 85%.   The charge / discharge control method for an alkaline storage battery according to any one of claims 1 to 8, wherein the standard discharge lower limit voltage is a voltage corresponding to a state of charge (SOC) of 15 to 30%.   10. The method according to claim 6, wherein the second charging current or the second discharging current is a value that is 1/10 to 1/5 of the first charging current or the first discharging current. The charge / discharge control method of the alkaline storage battery of description. The first charging current is a current value of 0.1 to 0.3C,
The charge / discharge control method for an alkaline storage battery according to any one of claims 6 to 10, wherein the first discharge current has a current value of 0.03 to 0.3C.   The charge / discharge control method for an alkaline storage battery according to any one of claims 6 to 11, wherein a time for performing the second charge or the second discharge is 1 to 20 seconds. Alkaline storage battery,
A voltage detector for detecting the voltage of the alkaline storage battery;
A temperature detector for detecting the temperature of the alkaline storage battery;
A time detector that counts the amount of time left after charging or discharging ends,
Before starting the charging or discharging of the alkaline storage battery, the temporary charging of the alkaline storage battery based on the standing time since the end of the previous charging or discharging, the battery temperature at the time of leaving, and the charging state at the start of leaving. An arithmetic unit for setting an upper limit voltage or a provisional discharge lower limit voltage;
A storage unit for storing a temporary charge upper limit voltage or a temporary discharge lower limit voltage set by the arithmetic unit;
Charge / discharge control for controlling charging or discharging of the alkaline storage battery based on the stored provisional charging upper limit voltage or provisional discharging lower limit voltage for at least a certain period after the charging or discharging of the alkaline storage battery is started. A charge / discharge system.   After the predetermined period, the charging / discharging or discharging of the alkaline storage battery is controlled based on a standard charge upper limit voltage or standard discharge lower limit voltage different from the provisional charge upper limit voltage or provisional discharge lower limit voltage. The charge / discharge system according to claim 13. Furthermore, it has a current integration unit that integrates the charge and discharge current of the alkaline storage battery,
The charging / discharging system according to claim 13 or 14, wherein the calculation unit obtains a state of charge at the start of the leaving from a current integrated value of the previous charging or discharging of the alkaline storage battery obtained by the current integrating unit. Furthermore, it has a current detection unit for detecting the charging current or discharging current,
The charge according to any one of claims 13 to 15, wherein the calculation unit sets the provisional charge upper limit voltage or the provisional discharge lower limit voltage in consideration of a current value obtained by the current detection unit. Discharge system.   The calculation unit sets the temporary charge upper limit voltage or the temporary discharge lower limit voltage in consideration of the total charge / discharge capacity of the alkaline storage battery obtained by the current integrating unit. The charge / discharge system according to item 1. The storage unit stores a plurality of candidate charge upper limit voltages or a plurality of candidate discharge lower limit voltages, and the plurality of candidate charge upper limit voltages or candidate discharge lower limit voltages are respectively set according to a variable X, The variable X includes the leaving time, the ambient temperature at the time of leaving, and the state of charge at the start of leaving,
18. The calculation unit according to claim 13, wherein the arithmetic unit selects the provisional charge upper limit voltage or the provisional discharge lower limit voltage from the plurality of candidate charge upper limit voltages or candidate discharge lower limit voltages according to a variable X. The charge / discharge system according to item. The charge / discharge control unit
Until the voltage detection unit detects that the closed circuit voltage of the alkaline storage battery has reached the provisional upper limit voltage or the provisional discharge lower limit voltage, the alkaline storage battery is configured with the first charging current or the first discharging current. First charge or first discharge,
When the voltage detection unit detects that the closing voltage of the alkaline storage battery has reached the provisional upper limit voltage or the provisional discharge lower limit voltage, it stops the first charge or the first discharge, and The charge / discharge system according to any one of claims 13 to 18, wherein the second charge or the second discharge current is smaller than the first charge current or the second discharge current smaller than the first discharge current.

Images