JP2023117796A - Control method and control device for nickel-metal hydride storage battery - Google Patents

Abstract

To suppress a decrease in the capacity of a nickel-metal hydride storage battery.SOLUTION: A nickel-metal hydride storage battery is charged and discharged with SOC 100 [%] as the upper limit SOC, and is performed within a charge and discharge range that includes this upper limit SOC (S5). During charging, Ni(OH)2, which is a positive electrode active material, changes to nickel oxyhydroxide (NiOOH), but to avoid variations at this time, charge at a slow charging rate of 1/3C or less (S7) is performed. By slowly charging at such a low rate, the positive electrode active material can be uniformly charged while suppressing the occurrence of local overcharging within the positive electrode. As a result, the nickel-metal hydride storage battery can be refreshed.SELECTED DRAWING: Figure 6

Description

The present invention relates to a nickel-metal hydride storage battery control method and control device, and more particularly to a nickel-metal hydride storage battery control method and control device capable of suppressing errors in SOC estimation.

In recent years, nickel-metal hydride storage batteries are safe and capable of inputting and outputting a large amount of current, so they are also used for electric vehicles, notebook PCs, etc., and for storing late-night power and solar power in homes and factories. .

Such nickel-metal hydride storage batteries are used in various ways. In this case, depending on the charging and discharging conditions, electrochemically inactive nickel oxide (Ni ₂ O ₃ H) may be generated by repeated charging and discharging, which may cause an increase in battery resistance and a decrease in battery capacity. There is Therefore, in the invention disclosed in Patent Document 1, the state of charge (SOC) at a current density of 100 A/m ² (hereinafter sometimes simply abbreviated as “SOC”) is within the range of 20 to 80 [%]. A battery has been proposed in which the amount of Ni ₂ O ₃ H is less than or equal to a specified amount when the battery is charged and discharged with a total amount of electricity of 10 kAh.

JP 2011-233423 A

However, it is necessary to accurately estimate the SOC for such control.
FIG. 1 is an OCV-SOC curve showing the relationship between the open-circuit battery voltage OCV (hereinafter sometimes abbreviated simply as "OCV") and the SOC of a nickel-metal hydride storage battery with no capacity deterioration. As shown in FIG. 1, the SOC can be estimated from the OCV by acquiring the relationship between the OCV and SOC of the target nickel-metal hydride storage battery as an OCV-SOC curve. In FIG. 1, OCV [V] at SOC 100 [%] indicates V ₁₀₀ [V]. Also, when the OCV is V ₈₀ [V], it can be estimated that the SOC is 80 [%].

FIG. 2 is an OCV-SOC curve showing the relationship between the OCV and SOC of a nickel-metal hydride storage battery with reduced capacity. In a nickel-metal hydride storage battery or the like, the battery capacity may decrease due to repeated partial charge/discharge in the middle SOC region such as the SOC range of 20 to 80[%] as described above. When the battery capacity decreases, even with the same OCV, the SOC may actually be higher than the initial OCV-SOC curve, as shown in FIG. In FIG. 1, the OCV [V] when the SOC is 80 [%] is OCV= _V80 . However, when the capacity of the nickel-metal hydride storage battery decreases, as shown in the OCV-SOC curve shown in FIG. 2, when OCV=V ₈₀ [V], the SOC actually exceeds 80 [%]. It's becoming

Therefore, when OCV = V80 [V], if the SOC at that time is estimated to be 80 [%], the nickel-metal hydride storage battery is actually controlled at an SOC [%] higher than SOC = 80 [%]. It will be. If an error occurs in the estimation of the SOC in this way, the SOC will be used in a high SOC region exceeding 80 [%], and in some cases, overcharging will occur, and furthermore, it will be a factor in the production of Ni ₂ O ₃ H. may be lost. In such a case, if even a small amount of Ni ₂ O ₃ H is produced, the capacity of the battery will decrease, so if the specified capacity (Ah) is assumed to be used continuously, the SOC estimation error will substantially increase. and lead to the formation of more Ni ₂ O ₃ H. As a result, repeated use of the battery may even become impossible. In order to accurately estimate the SOC in this way, it is necessary to suppress a decrease in the capacity of the nickel-metal hydride storage battery.

The problem to be solved by the nickel-metal hydride storage battery control method and control device of the present invention is to suppress the decrease in the capacity of the nickel-metal hydride storage battery.

In order to solve the above problems, in the nickel-metal hydride storage battery control method of the present invention, the nickel-metal hydride storage battery is charged in advance, and when the state where uncharged nickel hydroxide is gone is defined as SOC 100 [%], the nickel-metal hydride storage battery Charging and discharging are performed in a charging and discharging range including the upper limit SOC with SOC 100 [%] as the upper limit.

When the nickel-metal hydride storage battery is pre-discharged and the state in which the charged nickel hydroxide is exhausted is defined as SOC 0 [%], the charging and discharging of the nickel-metal hydride storage battery is set to exceed SOC 0 [%] as the lower limit. You may make it charge/discharge in the charge/discharge range used as SOC.

The lower limit SOC may be set to 20 to 40[%].
The charging and discharging of the nickel-metal hydride storage battery is performed in a charging and discharging range of the battery voltage OCV including the upper limit voltage UL [V], which is the battery voltage OCV at SOC 100 [%], and including the upper limit voltage UL [V]. It can be carried out.

Charging and discharging of the nickel-metal hydride storage battery may be performed in a charging and discharging range of battery voltage OCV whose lower limit is a lower limit voltage LL [V], which is a battery voltage set to exceed SOC 0 [%]. .

It is preferable that the charging/discharging rate is limited to 1/3C or less. Moreover, it is also preferable that the discharge rate of the charging and discharging is limited to 1C or less.
controlled to be switchable between normal mode and refresh mode,
In the normal mode, a reference SOC of less than 100 [%] is set, and charging and discharging are performed within a charging and discharging range with the reference SOC as the upper limit. It is also preferable to perform charge/discharge in a charge/discharge range including V].

It is controlled to be switchable between a normal mode and a refresh mode, and in the normal mode, it has an OCV reference voltage RV [V] of less than SOC 100 [%], and a charge/discharge range with the reference voltage RV [V] as an upper limit. , and in the refresh mode, charging and discharging can be performed in a charging and discharging range that includes the upper limit voltage UL [V] with the upper limit voltage UL [V] as the upper limit.

It is also possible to set the charging width in the normal mode, and execute the refresh mode when the number of charging times equal to or greater than the set charging width reaches a preset number of times or more.

A control device for a nickel-metal hydride storage battery according to the present invention is a control device for a nickel-metal hydride storage battery that controls a charging/discharging device that charges and discharges a nickel-metal hydride storage battery, wherein the upper limit voltage is the battery voltage at an SOC of 100 [%] of the nickel-metal hydride storage battery. UL [V] can be stored, and charging and discharging can be performed in a charging and discharging range whose upper limit is the upper limit voltage UL [V] and always includes the upper limit voltage UL [V].

A lower limit voltage LL [V], which is a battery voltage set to exceed the SOC0 [%] of the nickel-metal hydride storage battery, is stored, and in the charging and discharging range of the battery voltage OCV with the lower limit voltage LL [V] as the lower limit, Charging and discharging can be performed.

According to the nickel-metal hydride storage battery control method and control device of the present invention, it is possible to suppress a decrease in the capacity of the nickel-metal hydride storage battery.

4 is an OCV-SOC curve showing the relationship between the open-circuit battery voltage OCV and SOC of a nickel-metal hydride storage battery with no capacity deterioration. 4 is an OCV-SOC curve showing the relationship between the open-circuit battery voltage OCV and the SOC of a nickel-metal hydride storage battery with reduced capacity. 4 is an OCV-SOC curve showing the relationship between the open-circuit battery voltage OCV and the SOC showing the control method of the nickel-metal hydride storage battery of the present embodiment. 4 is an OCV-SOC curve showing the relationship between open-circuit battery voltage OCV and SOC during charging and discharging. 1 is a block diagram of a control device 1 for a nickel-metal hydride storage battery; FIG. 4 is a flow chart showing the control procedure of the nickel-metal hydride storage battery 10 of the present embodiment. 5 is a graph showing the relationship between the total amount of discharged electricity [Ah] and the chargeable battery capacity [Ah] of the nickel-metal hydride storage battery at that point in Experimental Examples 1 to 7 when the charging/discharging SOC conditions are changed. 9 is a flow chart showing procedures of a main routine of a method for controlling a nickel-metal hydride storage battery according to a second embodiment; 4 is a flow chart showing a procedure of a subroutine for controlling a nickel-metal hydride storage battery in normal mode; 4 is a graph showing changes in OCV [V] over time of a nickel-metal hydride storage battery in normal mode. 4 is a flow chart showing a procedure of a subroutine for controlling a nickel-metal hydride storage battery in refresh mode; Graph showing the relationship between the total amount of discharged electricity [Ah] in Experimental Examples 1, 8, and 9 when the charging/discharging SOC conditions are changed, and the rechargeable battery capacity [Ah] of the nickel-metal hydride storage battery at that time. be.

A method and apparatus for controlling a nickel-metal hydride storage battery according to the present invention will be described below with reference to FIGS.
(First embodiment)
<Technical background of the present embodiment>
As described in the prior art, when Ni ₂ O ₃ H is generated, the battery capacity of the nickel-metal hydride storage battery 10 decreases. A battery has been proposed in which the amount of Ni ₂ O ₃ H is less than a specified amount when charging/discharging with a total amount of electricity of 10 kAh within the range of 20 to 80 [%].

The inventors of the present invention also confirmed by experiments that when the battery is charged in a high SOC state such as overcharge, oxygen is generated at the positive electrode, and Ni ₂ O ₃ H is generated due to the generation of this oxygen.
<Memory effect and conventional refresh method>
However, even if the nickel-metal hydride storage battery 10 is repeatedly partially charged and discharged in an intermediate SOC region such as the SOC 20 to 80 [%] as described above, the battery will be affected by factors other than the generation of Ni ₂ O ₃ H at a high SOC. Capacity may decrease. One of the causes of this is the so-called memory effect of the nickel-hydrogen storage battery 10 .

One of the causes of the memory effect is considered to be variation in charging of nickel hydroxide, which is a positive electrode active material. In such a case, the so-called battery refresh that eliminates the memory effect conventionally involves completely discharging the battery to an SOC of 0 [%] and removing the charged nickel hydroxide. It was common general knowledge for those skilled in the art to eliminate the memory effect by charging the nickel hydroxide at a low rate so as not to cause variations in charging of the nickel hydroxide from that state.

However, according to the analysis of the present inventors, by completely discharging such SOC 0 [%] once, the charged nickel hydroxide is eliminated, and then charging at a low rate. However, it was found that the capacity of the nickel-metal hydride storage battery decreased.

<Method of Refreshing Nickel Metal Hydride Storage Battery of the Present Embodiment>
Therefore, in view of such a background, the present inventors have found a new method of controlling a nickel-metal hydride storage battery in which the capacity of the nickel-metal hydride storage battery is less likely to decrease. This method suppresses a decrease in the capacity of the nickel-metal hydride storage battery. The SOC can be accurately estimated while the capacity of the nickel-metal hydride storage battery is constant. As a result, appropriate control can be performed according to the accurate SOC at that time.

In the control method of the nickel-metal hydride battery 10 of the present embodiment, the nickel-metal hydride battery 10 is completely discharged in advance, and then charged at a low rate. Then, charging and discharging of the nickel-metal hydride storage battery 10 is performed in a charging and discharging range including the upper limit SOC, with SOC 100 [%] as the upper limit. However, charging exceeding SOC 100 [%] is not performed.

Ni(OH) ₂ , which is the positive electrode active material, is changed to nickel oxyhydroxide (NiOOH) by charging. At this time, the charging is performed slowly at a low rate of 1 C or less, for example, so that there is no variation. Furthermore, it is more preferable that it is 1/3C or less. By slowly charging at such a low rate, the positive electrode active material is uniformly charged while suppressing the occurrence of local overcharge in the positive electrode.

The state in which uncharged nickel hydroxide is removed from the positive electrode after such charging is defined as "SOC 100 [%]". That is, charging is completed at this point. If the battery is charged further than this, the battery is overcharged and oxygen (O ₂ ) is likely to be generated at the positive electrode. When oxygen (O ₂ ) is easily generated, Ni ₂ O ₃ H is easily generated. Therefore, it is necessary to accurately grasp the time point of this SOC 100[%].

<Estimation of SOC>
For exact measurement of SOC [%], X-ray photoelectron spectroscopy (XPS) or the like is used to determine the chemical bonding state of nickel hydroxide, which is the positive electrode active material present on the surface of the positive electrode plate (at a depth of several nm). By clarifying, it is possible to estimate. However, it cannot be analyzed easily because it requires a dedicated measuring device or a destructive inspection.

As a simple method, there is a method of estimating by integrating the battery current [Ah], or a method of analyzing a change in OCV [V]. These methods enable non-destructive inspection by measuring current and voltage. In particular, in estimating the SOC from the battery voltage OCV, the SOC can be easily estimated using the above-described OCV-SOC curve.

<Two-step charging reaction of nickel-metal hydride storage battery>
Here, charging of the nickel-metal hydride storage battery will be described with reference to FIG. As shown in FIG. 1, the OCV-SOC curve generally consists of regions St1 to St4.

In the region St1, the uncharged nickel hydroxide is gradually charged at a low SOC, the capacity increases, and the OCV [V] also increases. Here, since there is a large amount of uncharged nickel hydroxide, the OCV rises quickly at the start of charging. After that, the rate of increase in OCV gradually slows down.

In the region St2, the potential is most easily changed from nickel hydroxide (Ni(OH) ₂ ) to nickel oxyhydroxide (NiOOH). Therefore, the electric energy for charging is consumed for the energy for chemical change, so the battery capacity [Ah] increases, but the OCV [V] hardly increases, and the graph becomes almost horizontal.

In region St3, the amount of uncharged nickel hydroxide decreases, and the battery voltage OCV increases as the capacity increases. At this time, the battery voltage OCV when the SOC is 80 [%] indicates V ₈₀ [V]. Moreover, the right end of the region St3 is just SOC 100[%], and at this time there is no uncharged nickel hydroxide. The battery voltage OCV [V] at this time indicates V ₁₀₀ [V].

In region St4, an overcharge state occurs, and the charging current is not used for charging nickel hydroxide, but serves as energy for generating oxygen. Therefore, the battery voltage OCV does not rise even after charging, and the graph becomes horizontal again.

If the battery capacity of the nickel-metal hydride storage battery does not decrease, the OCV-SOC curve as shown in FIG. 1 can be obtained, so the SOC [%] can be easily estimated by measuring the OCV [V].

<Generation of Ni ₂ O ₃ H at low SOC>
<Condition 1 for Ni ₂ O ₃ H formation>
Here, FIG. 4 is an OCV-SOC curve showing the relationship between the open-circuit battery voltage OCV and SOC during charging and discharging.

A first condition for the production of Ni ₂ O ₃ H is as follows. As shown in FIG. 4, memory effect occurs when the battery is repeatedly charged and discharged at a low SOC. As a result, the OCV-SOC curve Lc of the nickel-metal hydride storage battery during charging shifts to the noble side (higher potential), so that the system tends to generate oxygen O ₂ during charging.

On the other hand, since the OCV-SOC curve Ld during discharge shifts to the base side (lower potential), the system is used at a lower positive electrode potential during discharge. When oxygen is generated at the nickel hydroxide interface of the positive electrode, the oxygen locally causes a liquid dry state at the nickel hydroxide particle interface. When discharging is performed in a state in which this water is insufficient, the discharge voltage shifts to the base and stays at a lower positive electrode potential than usual, thereby approaching the Ni ₂ O ₃ H generation potential.

<Condition 2 for Ni ₂ O ₃ H formation>
A second condition for the formation of Ni ₂ O ₃ H is as follows. The generation of oxygen accelerates the reaction in which H ₂ O and Ni ₂ O ₃ H are simultaneously generated from βNiOOH in order to compensate for locally deficient water.

<Ni ₂ O ₃ H formation>
Conditions 1 and 2 above overlap, and Ni ₂ O ₃ H is produced at an accelerated rate. As a result, a decrease in capacity is caused.

<Control method of the present embodiment>
FIG. 2 is an OCV-SOC curve showing the relationship between the open-circuit battery voltage OCV and the SOC of a nickel-metal hydride storage battery whose capacity has decreased due to memory effect.

Therefore, based on the mechanism by which these Ni ₂ O ₃ H are generated at an accelerated rate, the initial partial charge/discharge is the main factor (starting point). Therefore, it is necessary to prevent this. Since there are almost no uncharged Ni(OH) ₂ particles in the charging voltage at the start of the two-step charging reaction (≈oxygen generation voltage), charging and discharging from this point will cause the memory effect. will no longer generate particles.

As a result, deviation of the initial OCV-SOC curve can be suppressed.
<Capacity recovery in conventional region St4>
It has been described that the range indicated by region St4 in FIG. 1 is overcharge. Conventionally, there has been a method of intentionally restoring the capacity of a nickel-metal hydride storage battery by overcharging it (for example, Japanese Patent Laid-Open No. 2018-4270).

The method of recovering the capacity is based on the premise that the hydrogen _H2 in the nickel-metal hydride storage battery leaks to the outside and the equilibrium of the hydrogen partial pressure in the battery case is lost.
In order to maintain this balance, hydrogen is released from the metal hydride (MH) of the negative electrode according to the amount of hydrogen leakage. When hydrogen is discharged to the outside of the battery module in this way, the discharge capacity is reduced because the discharge reserve of the negative electrode is reduced.

Therefore, in order to increase the discharge reserve, the battery module is overcharged. In overcharging, charging is continued even after the uncharged portion of the positive electrode is exhausted. Therefore, as shown in the following half-reaction formula (1), hydroxyl groups in the electrolyte are decomposed to generate oxygen. At the negative electrode, as shown in the following half-reaction formula (2), a reaction proceeds in which hydrogen is absorbed by the uncharged portion of the negative electrode active material, ie, the hydrogen absorbing alloy. In addition, as shown in the following semi-reaction formula (3), simultaneously with the reaction of absorbing hydrogen into the hydrogen-absorbing alloy, the metal hydride reacts with oxygen in the charged portion, that is, in the hydrogen-absorbing alloy that has absorbed hydrogen, A reaction occurs that produces water. At this time, the metal hydride (MH) returns to the hydrogen storage alloy (M). In other words, when the safety valve is not opened during overcharge, the reaction of charging the uncharged portion and the reaction of returning the charged portion to the uncharged portion occur simultaneously in the negative electrode.

(Positive electrode) OH ⁻ →1/4O ₂ +1/2H ₂ O+e ⁻ (1)
(Negative electrode) M+H ₂ O+e ⁻ →MH+OH ⁻ (2)
MH+1/4O ₂ →M+1/2H ₂ O (3)
On the other hand, oxygen is generated from the positive electrode, the internal pressure rises, and when the internal pressure exceeds the valve opening pressure, the safety valve opens and oxygen gas is discharged to the outside. When the oxygen gas is exhausted, the reaction represented by half-reaction formula (3), that is, the reaction in which the charged portion returns to the uncharged portion, is suppressed. Therefore, the hydrogen-absorbing alloy that has occluded hydrogen maintains the hydrogen-occluded state, and if there is an uncharged portion of the negative electrode, the reaction shown in the half-reaction formula (2) proceeds to ensure a discharge reserve. .

<Control in Region St4 in this Embodiment>
In this embodiment, there is no premise that the hydrogen _H2 in the nickel-metal hydride storage battery leaks to the outside and the balance of the hydrogen partial pressure in the battery case is lost.

For this reason, oxygen is generated from the positive electrode, the internal pressure rises, and when the internal pressure exceeds the valve opening pressure, the safety valve opens and oxygen gas is discharged to the outside. The demerits are also great, such as a decrease in the amount.

Furthermore, the present inventors have confirmed through experiments that oxygen O ₂ is generated at the positive electrode due to overcharge, and Ni ₂ O ₃ H is generated due to the generation of this oxygen.
For this reason, in the present embodiment, the nickel-metal hydride storage battery is not used in the region St4 where the SOC exceeds 100[%].

<Control Device 1 for Nickel Metal Hydride Storage Battery>
FIG. 5 is a block diagram of the control device 1 of the nickel-metal hydride storage battery 10. As shown in FIG. Solid lines shown in FIG. 5 indicate that they are electrically connected. Broken lines indicate connection of signals for control. The control device 1 of the nickel-metal hydride storage battery 10 of the present embodiment is a stationary battery for home use. I'm assuming something to supply.

Of course, the nickel-metal hydride storage battery of this embodiment can be used in vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). In addition, it can also be used in homes and factories that generate small-scale power generation such as solar power generation and wind power generation. Furthermore, its use is not limited. Here, a household stationary battery will be described as an example because the charging and discharging operation is simple and the description of the control method for the nickel-metal hydride storage battery of the present embodiment is easy to understand. Only the common basic configuration is shown here.

The control device 1 includes a charge/discharge control device 2 , a power supply device 3 , a voltage measurement device 4 , a current measurement device 5 , a switch 6 and a load 7 .
<Charge/discharge control device 2>
The charge/discharge control device 2 exchanges signals with the power source device 3, the voltage measurement device 4, the current measurement device 5, the switch 6, and the load 7. FIG. Data on the OCV [V] and the battery current [A] of the nickel-metal hydride storage battery 10 are received from the voltage measuring device 4 and the current measuring device 5 . Based on these, the amount of power supplied from the power supply device 3 and a control signal for supplying power to the load 7 are transmitted, thereby executing the control method of the nickel-metal hydride storage battery 10 of the present embodiment.

The charge/discharge control device 2 includes a CPU (Central Processing Unit) 21 , a RAM (Random Access Memory) 22 and a ROM (Read Only Memory) 23 . Furthermore, it is configured as a computer having a storage device 24 such as a PROM (Programmable ROM). The ROM 23 and storage device 24 store programs for controlling the nickel-metal hydride storage battery 10 of the present embodiment.

In addition, it has a well-known computer configuration such as a power supply, an interface, and a timer.
<Power supply device 3>
The power supply device 3 is a device capable of supplying electric power to the nickel-metal hydride storage battery 10 . In this embodiment, it corresponds to a late-night power supply device via a power line. In addition, for example, in an electric vehicle (EV), the supplied power is power supplied from a charger via a power line or regenerated power. In a hybrid vehicle (HV) or the like, electric power generated by a prime mover or regenerated electric power corresponds. Also, in homes and factories that use photovoltaic power generation, wind power generation, and small-scale hydroelectric power generation, electricity is generated by power generation facilities including solar panels.

The power supply device 3 has a switch, a voltage regulator, a current regulator, an inverter, and the like (not shown) for supplying proper power, and is controlled by the control device 1 .
<Voltage measuring device 4>
The voltage measuring device 4 measures OCV [V], which is the open-circuit battery voltage of the nickel-metal hydride storage battery 10 . Although the power supply device 3 and the load 7 are actually connected, the method is not limited as long as the OCV can be actually measured or estimated.

<Current measuring device 5>
The current measuring device 5 measures the battery current [A] of the nickel-hydrogen storage battery 10 . Although the power supply device 3 and the load 7 are actually connected, the method is not limited as long as the battery current [A] can be actually measured or estimated.

<Load 7>
The load 7 in the present embodiment corresponds to devices that consume power in the home, such as lighting, air conditioning, and household appliances. In the case of an electric vehicle or a hybrid vehicle, such equipment as a motor generator for driving or an air conditioner corresponds. In households and factories that use photovoltaic power generation, this also corresponds to power transmission by selling electricity. It also includes the adjustment of the SOC of the nickel-metal hydride storage battery 10 by simply discharging it.

In addition, the switch 6 provided in the load 7 is also not shown, but it includes not only switching means but also a switch, a voltage regulator, a current regulator, an inverter, etc., which are not shown so that the power to be supplied is appropriate. are controlled by the charge/discharge control device 2 .

<Procedure for controlling the nickel-metal hydride storage battery of the present embodiment>
FIG. 6 is a flow chart showing the procedure for controlling the nickel-metal hydride storage battery 10 of this embodiment.

As described above, the control device 1 of the nickel-metal hydride storage battery 10 of the present embodiment stores late-night power at home and consumes it during the day, for the sake of simplicity of explanation. Therefore, in practice, an exceptional charging/discharging procedure or the like may be performed, but the description is omitted in this flowchart. A control method for the nickel-metal hydride battery 10 of the present embodiment using the control device 1 for the nickel-metal hydride battery 10 of the present embodiment will be described below. In addition, the application is not limited to electric vehicles (EV), hybrid vehicles, and stationary use in homes and factories equipped with power generation equipment such as solar power generation and wind power generation. In addition, it goes without saying that the control procedure differs depending on the application, and the present embodiment is not limiting.

<Preparation stage>
When the use of the nickel-metal hydride storage battery 10 is started (start), first, an "OCV-SOC curve" is obtained (S1). Here, the charging/discharging control device 2 completely discharges the nickel-metal hydride storage battery 10 and records the relationship between the integrated value [Ah] of the charging current and the OCV while charging at a low charging rate of 1/3C.

Next, the OCV of SOC 100 [%] is set as the upper limit voltage UL [V] (S2). Here, the moment when the OCV-SOC curve becomes smaller than the set slope at the boundary between the area St3 and the area St4 shown in FIG. It is regarded as "upper limit voltage UL [V]" and stored in the storage device 24 . Note that "dQ/dV", which is the change dQ of the capacitance [Ah] with respect to the change dV of OCV [V], may be measured, and the "upper limit voltage UL [V]" may be obtained from the peak value. This completes the preparation stage.

<Start of control of nickel-metal hydride storage battery (S3)>
After the preparation stage is completed, the charge/discharge control device 2 starts controlling the nickel-metal hydride storage battery 10 . In the case of this embodiment, it is operated within the range of SOC 20 to 100 [%].

<Basic control>
In principle, the nickel-metal hydride storage battery 10 is controlled by, for example, late-night power from power lines, and the nickel-metal hydride storage battery 10 is charged to the upper limit voltage UL [V] so that the SOC is 100 [%]. . The charging rate in this case is 1/3C. Charging is stopped when the SOC of the nickel-hydrogen storage battery 10 reaches 100 [%]. During the daytime, the battery is discharged at a discharge rate of 1C as the upper limit until the lower limit voltage LL [V] is reached, depending on the magnitude of the load. Although the battery is always charged to the upper limit voltage UL [V], it is not always necessary to discharge to the lower limit voltage LL [V], and charging can be performed as appropriate.

<Exceptional control>
Note that, as an exceptional control, for example, in a home having a solar panel, there is charging with power generated by solar power generation. In such a case, high-rate charging may be permitted. Also, when the battery capacity drops due to the use of the air conditioner due to extreme heat, high-rate charging may be allowed in order to maintain the minimum capacity.

On the other hand, the discharge rate is basically limited to 1C or less. Further, in the present embodiment, discharge is restricted when the SOC becomes less than 20[%]. In this case, too, high-rate discharge is permitted when necessary due to the use of an air conditioner due to extreme heat.

Since these exceptional controls are not essential controls in this embodiment, detailed descriptions are omitted in this flowchart, but they are always performed. Moreover, if the purposes are different, it goes without saying that a person skilled in the art will appropriately perform the control according to the purpose and the usage environment.

<Acquisition of current voltage PV [V] (S4)>
The charge/discharge control device 2 acquires and monitors the voltage PV [V], which is the current OCV measured by the voltage measurement device 4 .

<Control of upper limit voltage UL [V]>
The charge/discharge control device 2 compares the obtained voltage PV [V] with the upper limit voltage UL [V]. Here, if "PV>upper limit voltage UL" does not hold, that is, if the voltage PV [V] is equal to or lower than the upper limit voltage UL [V] (S5: NO), charging at a charging rate of 1/3C is permitted (S7). In this case, that is, when the SOC [%] is 100 [%] or less.

On the other hand, charging is continued at 1/3C, and when "PV > upper limit voltage UL", that is, when the voltage PV [V] exceeds the upper limit voltage UL [V] (S5: NO), charging is terminated immediately. (S6). In this case, the SOC [%] exceeds 100 [%] and enters the overcharge region, so charging is immediately stopped.

In the flow chart of the present embodiment, once charging is finished (S6), the subsequent determination in S5 is not performed, and in principle charging is not performed thereafter. Basically, the refresh effect can be exhibited at the stage when this charging is completed.

<Control of Lower Limit Voltage LL [V]>
When charging is completed (S6), the charge/discharge control device 2 compares the obtained voltage PV [V] with the lower limit voltage LL [V]. If "PV<lower limit voltage LL" is not satisfied, that is, if the voltage PV [V] is equal to or higher than the lower limit voltage LL [V] (S8: NO), discharging at a charge rate of 1C or lower is permitted (S9). In this case, the SOC [%] is 20 [%] or more in the present embodiment.

On the other hand, if "PV<lower limit voltage LL", that is, if voltage PV [V] is lower than lower limit voltage LL [V] (S8: NO), discharge is limited (S10). In this case, that is, the SOC [%] falls below 20 [%], so the discharge is stopped. In addition to the procedure of "charging at 1/3 C or less" shown in S7, if charging not described in this flowchart is performed and "PV < lower limit voltage LL" is not satisfied, " Discharge is allowed at 1C or less (S10).

<End and continue control>
For example, when ending the control (S11: YES), the control is ended (terminated). In such a case, for example, when charging is performed again, the control returns to "Start" again. Otherwise (S11: NO), the process returns to obtaining the current voltage PV [V] (S4), and the steps S8 to S11 are repeated.

The above description is simplified for understanding of the present embodiment, and describes only main procedures. Descriptions of procedures for cases such as when there is an exceptionally large charge/discharge are omitted. As described above, it is needless to say that a person skilled in the art performs processes not described in this flowchart according to the purpose to which this embodiment is applied.

(Experimental example of the first embodiment)
FIG. 7 shows the relationship between the total amount of discharged electricity [Ah] and the chargeable battery capacity [Ah] of the nickel-metal hydride storage battery 10 at that time in Experimental Examples 1 to 7 when the charging/discharging SOC conditions are changed. It is a graph showing. In the experiment, charging/discharging was repeatedly performed at a charging/discharging rate of 1/3C within a specified SOC range.

<Experimental example 1>
Experimental Example 1 shown in FIG. 7 shows the relationship between the total amount of discharged electricity [Ah] and the battery capacity [Ah] in the present embodiment described above. As shown here, the charge/discharge SOC range was set to 100 to 20 [%], and the range was set to ΔSOC=80 [%]. Here, "ΔSOC" represents the difference between the maximum and minimum values of SOC [%]. Then, when charging, the battery was charged to the upper limit voltage UL [V], and the SOC was always set to 100 [%]. In this case, it was found that the battery capacity [Ah], which is about 5.2 [Ah] at the time of manufacture, does not decrease even if the total amount of discharged electricity [Ah] increases.

<Experimental example 2>
Next, in Experimental Example 2, the charge/discharge SOC range is set to 100 to 40 [%]. When the range is reduced to ΔSOC=60[%], similarly, the SOC is set to 100[%] during charging without fail. In such a case, it was found that the battery capacity [Ah], which is about 3.9 [Ah] at the time of manufacture, does not decrease even if the total amount of discharged electricity [Ah] increases.

<Experimental example 3>
Furthermore, in Experimental Example 3, the SOC range of charging and discharging is set to 100 to 60 [%], and ΔSOC is further reduced to 40 [%]. Even in such a case, if the SOC is always set to 100 [%] at the time of charging, the battery capacity of about 2.6 [Ah] at the beginning of manufacture will be reduced even if the total discharge electricity amount [Ah] increases. It was found that the capacity [Ah] did not decrease.

<Experimental example 4>
In Experimental Example 4, ΔSOC=80[%] as in Experimental Example 1, but SOC90[%] is set as the upper limit and SOC10[%] is set as the lower limit. Then, when charging, the battery was always charged so that the SOC was 90 [%]. In this case, the battery capacity [Ah] decreased from the initial battery capacity of about 5.2 [Ah] as the total discharged electricity [Ah] increased. As shown in FIG. 7, the charge capacity of the battery, which was initially about 5.2 [Ah], decreased to about 4.8 [Ah] when the total discharged electricity [Ah] reached 2000 [Ah]. Furthermore, when the total amount of discharged electricity [Ah] reached 4000 [Ah], it decreased to about 4.2 [Ah]. Furthermore, when the total amount of discharged electricity [Ah] reached 6000 [Ah], it decreased to about 3.5 [Ah]. Then, when the total amount of discharged electricity [Ah] reached 8000 [Ah], it decreased to about 3.2 [Ah]. From this, it was confirmed that the battery capacity [Ah] decreased as the battery was used in charging and discharging that does not include charging up to an SOC of 100 [%].

<Experimental example 5>
In Experimental Example 5, ΔSOC=80[%] as in Experimental Example 1, but SOC80[%] is set as the upper limit and SOC0[%] is set as the lower limit. Then, when charging, the battery was always charged so that the SOC was 80 [%]. In this case, the battery capacity [Ah] decreased from the initial battery capacity of about 5.2 [Ah] as the total discharged electricity [Ah] increased. As shown in FIG. 7, the charge capacity of the battery, which was initially about 5.2 [Ah], suddenly dropped to about 2.6 [Ah] when the total discharge electricity [Ah] reached 2000 [Ah]. . From this, it was confirmed that the battery capacity [Ah] decreased as the battery was used in charging and discharging that does not include charging up to an SOC of 100 [%]. In particular, even when compared with Experimental Example 4, the battery capacity was greatly reduced.

What the present inventors particularly focused on is that in Experimental Example 5, charging and discharging are performed in a range including SOC 0 [%]. Conventionally, it was thought that the nickel-metal hydride storage battery 10 could be refreshed by completely discharging it to an SOC of 0 [%] and then slowly charging it at a low charging rate.

However, as described above, the present inventors have found that the battery capacity is greatly reduced even through SOC 0 [%], which was considered to be effective in eliminating the memory effect by those skilled in the art, as shown in FIG. Found it.

<Experimental example 6>
In Experimental Example 6, ΔSOC=60[%] as in Experimental Example 2, but SOC70[%] was set as the upper limit and SOC10[%] was set as the lower limit. Then, when charging, the battery was always charged so that the SOC was 70 [%]. In this case, the battery capacity [Ah] decreased from the initial battery capacity of about 3.8 [Ah] as the total discharged electricity [Ah] increased. As shown in FIG. 7, the charge capacity of the battery, which was initially about 3.8 [Ah], decreased to about 4.8 [Ah] when the total discharged electricity [Ah] reached 2000 [Ah].

<Experimental example 7>
In Experimental Example 7, ΔSOC=40[%] as in Experimental Example 3, but SOC50[%] is set as the upper limit and SOC10[%] is set as the lower limit. Then, when charging, the battery was always charged so that the SOC was 50 [%]. In this case, the battery capacity [Ah] decreased from the initial battery capacity of about 2.6 [Ah] as the total discharged electricity [Ah] increased. As shown in FIG. 7, the charge capacity of the battery, which was initially about 2.6 [Ah], decreased to about 1.1 [Ah] when the total discharged electricity [Ah] reached 2000 [Ah].

<Summary of the experiment>
(a) As derived from Experimental Examples 1, 2, and 3, in the charge/discharge range with an upper limit of SOC 100 [%], when charging is always performed until the SOC reaches 100 [%] at the time of charging, ΔSOC, which is the charging range, It differs from 80 to 40 [%]. In spite of this, deterioration of the battery capacity [Ah] did not occur in any case. That is, at least the so-called memory effect does not occur. That is, a refreshing effect is recognized.

Also, it can be seen that Ni ₂ O ₃ H was not generated at the same time. That is, in this experiment, the charging is stopped and the discharging is started at the instant when the SOC becomes 100[%] during the charging. From this, it can be estimated that Ni ₂ O ₃ H was not generated by avoiding the overcharged state in which oxygen is likely to be generated.

(b) On the other hand, as derived from Experimental Examples 4, 6, and 7, in the charge/discharge range with the upper limit of SOC lower than SOC 100 [%], the battery capacity [Ah] deteriorates regardless of ΔSOC, which is the charge range. occurred.

In this case, the SOC does not exceed the SOC 100 [%] at which oxygen is generated.
Moreover, the charge/discharge rate is ⅓ C in both cases, and high rate charge/discharge is not performed at a low SOC of 10[%]. Therefore, _it is unlikely that the deterioration of the battery capacity [Ah] is caused by the formation of _Ni2O3H .

Therefore, it can be estimated that the refreshing effect by surely reaching SOC 100[%] during charging proposed by the present invention could not be exhibited.
(c) Furthermore, as derived from Experimental Example 5, at least under the conditions of this experiment, the battery capacity [ Ah] has deteriorated. That is, conventionally, the battery is completely discharged to SOC 0 [%], and the nickel hydroxide, which is the positive electrode active material, is completely uncharged, thereby eliminating the variation among the positive electrode active materials. After that, it was found that the common technical knowledge of those skilled in the art that the memory effect can be eliminated by charging at a low charging rate is not necessarily true, and epoch-making results were obtained. was made.

(Action of the first embodiment)
In the control method of the nickel-metal hydride battery 10 of the present embodiment, charging and discharging of the nickel-metal hydride battery 10 is performed within the range of SOC 100 [%] as the upper limit SOC and the lower limit SOC 20 [%], for example. Discharge. Ni(OH) ₂ which is a positive electrode active material is changed to nickel oxyhydroxide (NiOOH) by charging. At this time, charging is performed slowly at a low rate of, for example, 1/3 C or less so that there is no variation. By slowly charging to SOC 100[%] at such a low rate, the positive electrode active material is uniformly charged while suppressing the occurrence of local overcharge in the positive electrode. Charging is completed when the SOC reaches 100 [%].

If the battery is charged further than this, the battery is overcharged and oxygen (O ₂ ) is likely to be generated at the positive electrode. This is because when oxygen (O ₂ ) is easily generated, Ni ₂ O ₃ H is easily generated.
The control method for the nickel-metal hydride storage battery 10 of the present embodiment has the effect of suppressing the decrease in battery capacity by refreshing the decrease in battery capacity due to the memory effect.

Also, by not performing charging _in a range exceeding SOC 100[%], there is an effect of suppressing the generation of _Ni2O3H .
Also, since the battery capacity is not lowered, the OCV-SOC curve does not change. Therefore, based on the once obtained OCV-SOC curve, there is an effect that the SOC can be easily and accurately estimated from the OCV [V].

Furthermore, based on the SOC accurately estimated in this way, there is an effect that control corresponding to the SOC [%] at that time becomes possible. Therefore, there is an effect that the deterioration of the battery capacity can be further suppressed.

(Effect of the first embodiment)
(1-1) In the control method of the nickel-metal hydride battery 10 of the present embodiment, the charge/discharge of the nickel-metal hydride battery 10 is set to SOC 100 [%] as the upper limit SOC, and the charge/discharge range includes the upper limit SOC [%]. do in Therefore, capacity deterioration of the nickel-hydrogen storage battery 10 can be suppressed.

(1-2) In the nickel-hydrogen storage battery 10 to be controlled, since the state in which the nickel-hydrogen storage battery 10 to be controlled is actually charged in advance and the uncharged nickel hydroxide has disappeared is assumed to be SOC 100 [%], can be controlled.

(1-3) Assuming that the nickel-metal hydride storage battery 10 is discharged in advance and the state in which the charged nickel hydroxide is exhausted is defined as SOC 0 [%], charge and discharge the nickel-metal hydride storage battery 10 so as to exceed SOC 0 [%]. Charge/discharge is performed within a charge/discharge range with the set SOC as the lower limit SOC. Even in this range, refreshing can be performed by setting the SOC to 100[%]. Therefore, there is an effect that the nickel-hydrogen storage battery 10 is neither completely discharged nor over-discharged.

(1-4) In addition, since the nickel-metal hydride storage battery 10 is never completely discharged, there is an effect that a surplus power supply can always be left. In addition, overdischarge does not occur.
(1-5) Since the OCV-SOC curve is acquired in the present embodiment, the SOC [%] can be easily and accurately estimated from the OCV [V].

(1-6) In addition, since the control method of the nickel-metal hydride storage battery 10 of the present embodiment does not deteriorate the battery capacity, the SOC [%] can always be easily and accurately estimated from the OCV-SOC curve.

(1-7) Since the SOC [%] can always be accurately estimated, appropriate control according to the SOC [%] can further effectively suppress the deterioration of the nickel-metal hydride storage battery. .

(1-8) Since the charging rate is as low as 1/3C, the positive electrode active material can be uniformly charged so as not to locally overcharge the positive electrode.
(Second embodiment)
In the second embodiment of the present invention, charging is always performed up to SOC 100[%] in principle, except for the first embodiment. On the other hand, in the second embodiment, it is controlled so as to be switchable between the "normal mode" and the "refresh mode." In the "normal mode", it has an OCV reference voltage RV [V] corresponding to an SOC of less than 100 [%] (for example, SOC 80 [%]), and charging and discharging is performed within the charging and discharging range with the reference voltage RV [V] as the upper limit. conduct.

On the other hand, in the "refresh mode", the upper limit voltage UL [V] corresponding to the SOC 100 [%] is set as the upper limit at the set timing as in the first embodiment, and the charge/discharge range includes the upper limit voltage UL [V]. Then charge and discharge.

The set timing is, for example, a method of executing the refresh mode when the OCV reaches the reference voltage RV [V] the number of times set in the normal mode (for example, 5 times).

(Procedures of the control method of the nickel-metal hydride storage battery of the second embodiment)
FIG. 8 is a flow chart showing the procedure of the main routine of the control method for the nickel-metal hydride storage battery of the second embodiment.

First, steps S101 and S102, which are preparatory stages, are the same as steps S1 and S2 of the first embodiment shown in FIG. 6, so description thereof will be omitted.
<Start of control of nickel-metal hydride storage battery (S103)>
After the preparatory stages (S101, S102) are finished, the control of the nickel-metal hydride storage battery is started (S103). Here, as in the procedure S3 of the first embodiment, principle control of the nickel-metal hydride storage battery 10 and exceptional control of the nickel-metal hydride storage battery 10 are performed. These controls are always performed. A different point from the first embodiment is that, in principle, the control of the nickel-metal hydride storage battery 10 is characterized by switching between two modes of "normal mode" and "refresh mode".

<Normal Mode (S104)>
FIG. 9 is a flow chart showing the procedure of a subroutine for controlling the nickel-metal hydride storage battery 10 in the normal mode (S104).

When the normal mode (S104) is started (S1041), the following control is performed.
<Basic control>
In principle, the nickel-metal hydride storage battery 10 is charged with the reference voltage RV [V] as the upper limit, not only with late-night power but also with power from the outside generated by solar power generation during the daytime, for example. The charging rate in this case is 1C. This is because the normal mode is not intended to refresh the nickel-metal hydride storage battery 10 . Charging is stopped when the nickel-metal hydride storage battery 10 reaches the reference voltage RV [V]. Further, the discharge is performed with the lower limit voltage LL [V] as the lower limit and the discharge rate 1C as the upper limit. Repeat this randomly.

Note that unlike the first embodiment, it is not always necessary to charge to the reference voltage RV [V]. Also, it is not always necessary to discharge to the lower limit voltage LL [V].
That is, in the normal mode, charging/discharging is performed particularly according to the operation of the nickel-metal hydride storage battery 10 except that the reference voltage RV [V] is the upper limit and the lower limit voltage LL [V] is the lower limit. Unlike the refresh mode (S105), control to ensure the upper limit voltage UL [V] is not performed. Therefore, the nickel-metal hydride storage battery 10 can be used efficiently.

On the other hand, depending on the environment in which the nickel-metal hydride storage battery 10 is placed, it is assumed that the SOC [%] fluctuates randomly and violently. For example, high rate charging/discharging at low SOC [%] is allowed. As a result, the occurrence of memory effect and the formation of Ni ₂ O ₃ H are also feared.

Therefore, it is desirable to eliminate the memory effect at a constant rate in the refresh mode (S105).
<Exceptional control>
Exceptional control is performed in the same manner as in the first embodiment, but the description is omitted here.

<Transition to refresh mode>
As shown in FIG. 9, after the normal mode control (S1041) is started, it is determined whether or not charging has reached five times (S1402), and until charging reaches five times (S1042: NO ), normal mode control is performed. When the battery has been charged five times (S1042: YES), the normal mode control (S104) subroutine ends and the main routine shown in FIG. 8 returns to perform refresh mode control (S105).

FIG. 10 is a graph showing an example of changes in OCV [V] over time of the nickel-hydrogen storage battery 10 in the normal mode. In the normal mode, charging and discharging are performed with the reference voltage RV [V] as the upper limit and the lower limit voltage LL [V] as the lower limit. Here, charging/discharging is performed particularly according to the operation of the nickel-metal hydride storage battery 10 except that the reference voltage RV [V] is the upper limit and the lower limit voltage LL [V] is the lower limit. Unlike the refresh mode (S105), control is not performed to ensure that the voltage reaches the upper limit voltage UL [V].

Therefore, the following procedure is used as a trigger for ending the normal mode (104) and returning to the main routine shown in FIG.
As shown in FIG. 10, charging/discharging in the normal mode is discharged from the upper limit voltage UL [V] when the previous refresh mode ends, and charging/discharging is freely performed in the normal mode according to the operation of the nickel-metal hydride storage battery. . At this time, a predetermined charging width is set as a reference. The charge width may be a difference in OCV [V], but is preferably a difference in OCV [V] converted from a certain difference in SOC [%] (for example, 40 [%]).

Then, in the variation of OCV [V] shown in FIG. 10, when the previous refresh mode ends, discharging is performed first, and when the lower limit voltage LL [V] is reached, charging is performed up to the reference voltage RV [V]. . At this time, the lower limit voltage LL [V] corresponds to SOC 20 [%], and if the reference voltage RV [V] corresponds to SOC 80 [%], the charging range corresponds to 60 [%]. Therefore, since the SOC 40 [%], which is the set charge width, is exceeded, this charge is counted as "first charge".

Similarly, since the second and third charges also exceed the SOC 40[%], which is the charge range, these charges are also counted as "one charge".
On the other hand, in the next charging, if the charging width is approximately SOC 10 [%], this charging is not counted as "one charging" in the normal mode because it is smaller than the set charging width SOC 40 [%].

When charging is performed in this manner, the charging width is determined to determine whether or not to count "one charging" in the normal mode. The number of times “one charge” is counted in the normal mode is accumulated in the RAM 22 or storage device 24 of the charge/discharge control device 2 .

Since the last charge shown in FIG. 10 exceeds the set charge width of SOC 40[%], this charge is counted as "one charge" and the charge is judged as "fifth charge".
In the normal mode, the charging width is set, and when the number of charging times equal to or greater than the set charging width reaches a preset number of times (five times in this case) or more, the refresh mode is executed.

Therefore, as shown in FIG. 10, when it is determined that the charging has reached 5 times (FIG. 9: S1042: YES), the main routine shown in FIG. 8 is returned to and the control in the refresh mode (S105).

<Refresh Mode (S105)>
FIG. 11 is a flow chart showing the procedure of a subroutine for controlling the nickel-metal hydride storage battery 10 in the refresh mode.

The procedure of S1051 to S1059 for the control of the refresh mode is basically the same as the procedure of S3 to S11 in the flow chart for controlling the nickel-metal hydride storage battery of the first embodiment shown in FIG. The difference is that step S1059 of the refresh mode (S105) is not the end of the entire control, but the end of the subroutine, so the procedure returns to the main routine shown in FIG.

(Experimental example of the second embodiment)
FIG. 12 shows the total discharge amount of electricity [Ah] in Experimental Examples 1, 4, and 9 when the charging/discharging SOC conditions are changed, and the chargeable battery capacity [Ah] of the nickel-metal hydride storage battery 10 at that time. It is a graph showing the relationship.

<Experimental example 1>
Experimental Example 1 shown in FIG. 12 shows the relationship between the total amount of discharged electricity [Ah] and the battery capacity [Ah] in the present embodiment described above. As shown here, the charge/discharge SOC range was set to 100 to 20 [%], and the range was set to ΔSOC=80 [%]. Here, "ΔSOC" represents the difference between the maximum and minimum values of SOC [%]. Then, during charging, the battery was charged at a charging rate of 1/3 C up to the upper limit voltage UL [V], and the SOC was always set to 100 [%].

In this case, it was found that the battery capacity [Ah], which is about 5.2 [Ah] at the time of manufacture, does not decrease even if the total amount of discharged electricity [Ah] increases.
<Experimental example 4>
In Experimental Example 4, ΔSOC=80[%] as in Experimental Example 1, but SOC90[%] is set as the upper limit and SOC10[%] is set as the lower limit. Then, when charging, the battery was charged at a charging rate of 1/3C so that the SOC was always 90[%].

In this case, the battery capacity [Ah] decreased from the initial battery capacity of about 5.2 [Ah] as the total discharged electricity [Ah] increased. As shown in FIG. 7, the charge capacity of the battery, which was initially about 5.2 [Ah], decreased to about 4.8 [Ah] when the total discharged electricity [Ah] reached 2000 [Ah]. Furthermore, when the total amount of discharged electricity [Ah] reached 4000 [Ah], it decreased to about 4.2 [Ah]. Furthermore, when the total amount of discharged electricity [Ah] reached 6000 [Ah], it decreased to about 3.5 [Ah]. Then, when the total amount of discharged electricity [Ah] reached 8000 [Ah], it decreased to about 3.2 [Ah]. From this, it was confirmed that the battery capacity [Ah] decreased as the battery was used in charging and discharging that does not include charging up to an SOC of 100 [%].

<Experimental Example 8>
In Experimental Example 8, as shown in the second embodiment, the battery is charged at a charge rate of ⅓ C to an SOC of 80[%] in the normal mode, and discharged at a discharge rate of 1C to an SOC of 20[%]. After repeating this five times, the refresh mode was set to charge at a charging rate of ⅓ C until reaching the upper limit voltage UL [V], and the SOC was always set to 100 [%]. Then, the battery was discharged at a discharge rate of 1C to an SOC of 20%. This was repeated as one set.

In this case, the battery capacity [Ah] decreased from the initial battery capacity of about 5.2 [Ah] as the total discharged electricity [Ah] increased. As shown in FIG. 12, the charge capacity of the battery, which was initially about 5.2 [Ah], did not change when the total discharged quantity of electricity [Ah] was 2000 [Ah]. Furthermore, when the total amount of discharged electricity [Ah] reached 4000 [Ah], it decreased to about 5.0 [Ah]. Furthermore, when the total amount of discharged electricity [Ah] reached 6000 [Ah], it decreased to about 4.7 [Ah]. Then, when the total amount of discharged electricity [Ah] reached 8000 [Ah], it decreased to about 4.5 [Ah].

<Summary of the experiment>
In Experimental Example 8, charging and discharging are performed five times in the normal mode, and charging and discharging are performed once in the refresh mode. This is almost the same as that in Experimental Example 1, charging and discharging are performed only in the refresh mode of the second embodiment. Also, Experimental Example 4 is almost the same as performing charging and discharging only in the normal mode of the second embodiment. On the other hand, in Experimental Example 8, as shown in the second embodiment, it can be said that these conditions are mixed. Then, it can be expected that the deterioration in Experimental Example 8 will be about 5/6 of that in Experimental Example 4 because the refresh mode is performed only once out of six times. However, the deterioration in Experimental Example 8 is about 1/3 of the deterioration in Experimental Example 4.

It can be seen from this result that deterioration is suppressed by performing charging and discharging in the refresh mode.
(Action of Second Embodiment)
In the second embodiment, charging/discharging is performed five times in the normal mode, and charging/discharging is performed once in the refresh mode. Therefore, in the refresh mode, by slowly charging the battery up to SOC 100[%] at a charge rate of ⅓, the same refresh action as in the first embodiment can be achieved.

Further, there is an effect that deterioration in the normal mode is recovered in the refresh mode.
(Effect of Second Embodiment)
(2-1) Even if charging/discharging is performed without restriction in the normal mode and deterioration occurs, the deterioration of the nickel-metal hydride storage battery 10 can be recovered by performing charging/discharging in the refresh mode.

(2-2) Therefore, the degree of freedom of use of the nickel-metal hydride storage battery 10 is increased, the capacity of the battery can be fully used, and the decrease in the capacity of the nickel-metal hydride storage battery 10 can be suppressed.
(separate example)
The present invention is not limited to the embodiments and can be implemented as follows.

In the present embodiment, the stationary nickel-metal hydride storage battery 10 for use at home, which is charged at night with late-night power, was exemplified. In the present invention, the use of the nickel-metal hydride storage battery 10 is not limited. For example, it can be applied as a battery for driving vehicles such as an electric vehicle (EV), a plug-in hybrid (PHV), and a hybrid (HV). It can also be applied as a stationary battery for homes and factories equipped with solar power generation facilities, wind power generation facilities, and small-scale hydroelectric power generation facilities. Furthermore, it can also be carried out for the purpose of refreshing the nickel-metal hydride storage battery 10 in the power supply for computers and audio equipment.

○ The method of measuring and estimating the SOC [%] in charging and discharging is not limited to acquisition by the OCV-SOC curve, and any method may be used as long as the SOC [%] can be actually measured and estimated.
○ The OCV-SOC curves shown in FIGS. 1 to 4 and the graphs of capacity deterioration shown in FIGS.

○ The lower limit SOC [%], the lower limit voltage LL [V], the reference voltage RV [V], the charge rate [C], the discharge rate [C], etc. in the embodiment are examples, and are not limited to these numerical values. Those skilled in the art will optimize accordingly.

The block diagram shown in FIG. 5 is a diagram for explaining the present embodiment, and in order to control the nickel-metal hydride storage battery 10, the present invention can use a control device 1 having a different configuration.
The flowcharts shown in FIGS. 6, 8, 9, and 11 show an example of control procedures, and the procedures can be added, deleted, or changed for implementation.

○ In addition, it goes without saying that a person skilled in the art can add, delete, and change the configuration of the present invention without departing from the scope of the claims.

DESCRIPTION OF SYMBOLS 1... Control apparatus of a nickel metal hydride storage battery 2... Charge/discharge control apparatus 3... Power supply device 4... Voltage measurement apparatus 5... Current measurement apparatus 6... Switch 7... Load 10... Nickel metal hydride storage battery 21... CPU
22 RAM
23 ROM
24... Storage device OCV... Battery voltage UL... Upper limit voltage [V]
LL...Lower limit voltage [V]
RV … reference voltage [V]
PV...Current voltage [V]

Claims (12)

When a nickel-metal hydride storage battery is charged in advance and the state in which uncharged nickel hydroxide has disappeared is defined as SOC 100 [%],
A control method for a nickel-metal hydride storage battery in which charging and discharging of the nickel-metal hydride storage battery is performed in a charging/discharging range including the upper limit SOC with an upper limit SOC of 100%. When the nickel-hydrogen storage battery is discharged in advance and the state in which the charged nickel hydroxide is exhausted is defined as SOC 0 [%],
2. The method of controlling a nickel-metal hydride storage battery according to claim 1, wherein the charge-discharge of the nickel-metal hydride storage battery is performed within a charge-discharge range with an SOC set to exceed SOC 0[%] as a lower limit SOC. 3. The method of controlling a nickel-metal hydride storage battery according to claim 2, wherein said lower limit SOC is set to 20 to 40[%]. The charging and discharging of the nickel-metal hydride storage battery is performed within the charging and discharging range of the battery voltage OCV including the upper limit voltage UL [V], which is the battery voltage OCV at SOC 100 [%] as the upper limit. A control method for a nickel-metal hydride storage battery. 5. The charging and discharging of the nickel-metal hydride storage battery is performed in the charging and discharging range of the battery voltage OCV whose lower limit is the lower limit voltage LL [V], which is the battery voltage set to exceed SOC 0 [%]. A control method for a nickel-metal hydride storage battery. 6. The method of controlling a nickel-metal hydride storage battery according to claim 1, wherein the charging rate of said charging/discharging is limited to 1/3C or less. 7. The method of controlling a nickel-metal hydride storage battery according to claim 1, wherein the discharge rate of said charging and discharging is limited to 1C or less. controlled to be switchable between normal mode and refresh mode,
In the normal mode, a reference SOC of less than SOC 100 [%] is set, charging and discharging are performed in a charging and discharging range with the reference SOC as the upper limit,
3. The method of controlling a nickel-metal hydride storage battery according to claim 1, wherein in the refresh mode, charging and discharging are performed within a charging and discharging range including the upper limit SOC and an upper limit voltage UL [V]. . controlled to be switchable between normal mode and refresh mode,
In the normal mode, it has a reference voltage RV [V] of OCV of less than SOC 100 [%], performs charging and discharging in a charging and discharging range with the reference voltage RV [V] as an upper limit,
9. The nickel-metal hydride battery according to claim 8, wherein in the refresh mode, charging and discharging are performed in a charging and discharging range including the upper limit voltage UL [V] and including the upper limit voltage UL [V] at set timing. Control method of storage battery. 10. The method according to claim 9, wherein a charge width is set in the normal mode, and the refresh mode is performed when the number of times the battery is charged with the set charge width or more reaches a preset number of times or more. control method for nickel-metal hydride storage batteries. A control device for a nickel-metal hydride storage battery that controls a charging/discharging device that charges and discharges the nickel-metal hydride storage battery,
The upper limit voltage UL [V], which is the battery voltage at SOC 100 [%] of the nickel-metal hydride storage battery, is stored, and the charge/discharge range includes the upper limit voltage UL [V] as the upper limit and always includes the upper limit voltage UL [V]. A control device for nickel-metal hydride storage batteries that charges and discharges. A lower limit voltage LL [V], which is a battery voltage set to exceed the SOC0 [%] of the nickel-metal hydride storage battery, is stored, and in the charging and discharging range of the battery voltage OCV with the lower limit voltage LL [V] as the lower limit, 12. The nickel-metal hydride storage battery control device according to claim 11, wherein charging and discharging are performed.

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