JP2022151160A - Method of controlling alkaline secondary battery - Google Patents

Abstract

To provide a method of controlling an alkaline secondary battery, with which a valve is avoided from being opened, and thereby electrolyte depletion can be effectively suppressed.SOLUTION: A method of controlling an alkaline secondary battery includes the steps of: calculating an inner pressure drop rate (S6); calculating an inner pressure drop rate correction value from an estimated charge reserve amount and calculating a corrected inner pressure drop rate (S7); calculating an estimated inner pressure from the corrected inner pressure drop rate and an inner pressure increase rate calculated based on temperatures (S8); further estimating a negative electrode SOC (S9); calculating a hydrogen equilibrium pressure of a negative electrode from temperatures (S10); on the other hand, calculating a corrected negative electrode hydrogen equilibrium pressure from the relationship between the negative electrode SOC and the hydrogen equilibrium pressure of the negative electrode (S11); and, based on the negative electrode hydrogen equilibrium pressure, calculating a more accurate corrected estimated inner pressure (S12). Based on the corrected estimated inner pressure, a control part appropriately limits the SOC of a nickel metal hydride storage battery 1, as necessary, so that, even if a reserve balance changes, a valve is avoided from being opened and thereby electrolyte depletion can be effectively suppressed.SELECTED DRAWING: Figure 7

Description

The present invention relates to a control method for an alkaline secondary battery, and more particularly to a control method suitable for a vehicle alkaline secondary battery that effectively suppresses depletion of electrolyte.

2. Description of the Related Art An electric vehicle (including a hybrid vehicle, etc.) equipped with an electric motor drives the electric motor with electric power stored in a secondary battery. A characteristic function of such an electric vehicle is regenerative braking. Regenerative braking converts the kinetic energy of the vehicle into electrical energy by causing the electric motor to function as a generator when braking the vehicle. Also, the obtained electric energy is charged in a secondary battery and reused when accelerating or the like. Among such secondary batteries, alkaline secondary batteries such as nickel-metal hydride storage batteries are widely used for vehicles because they can charge and discharge large currents.

In the case of such a nickel-hydrogen storage battery, as the voltage rises during charging, gas is generated as a side reaction of charging, and the internal pressure of the secondary battery rises. Oxygen gas is generated mainly at the positive electrode, and the internal pressure may rise. When the generated gas increases the internal pressure, the exhaust valve may open to discharge the gas. When the gas discharge valve operates, the electrolyte is discharged out of the battery system together with the gas. As a result, the electrolyte in the separator is depleted (separator dryout), the internal resistance increases, and the capacity decreases. Therefore, in order to improve the battery life, it is necessary to avoid opening the valve and ensure sufficient electrolyte.

Therefore, conventionally, in the control of alkaline secondary batteries for vehicles, a control method has been proposed in which the valve opening is suppressed by estimating the internal pressure of the battery from the amount of gas generated by the side reaction.
In nickel-metal hydride storage batteries, oxygen gas is generated at the positive electrode, and the generated oxygen gas returns to water through a recombination reaction with hydrogen at the negative electrode, and the increased internal pressure of the secondary battery decreases. The gas absorption reaction such as the recombination reaction as described above depends on the temperature of the nickel-metal hydride storage battery, and the reaction slows down when the temperature of the battery is low. Therefore, it is possible to reduce the increased internal pressure of the battery by the method of controlling the charging power of the battery based on the estimated internal pressure of the battery.

However, it takes time for the internal pressure of the battery to recover once it has risen. Therefore, control is performed to limit the charging power of the secondary battery for a long period of time, and the recovery rate of electrical energy by regenerative braking may decrease.

Therefore, in Patent Document 1, the internal pressure is estimated by summing the amount of increase in internal pressure (gas generation) and the amount of decrease in internal pressure (gas absorption). In particular, a method of estimating the amount of internal pressure drop using the temperature dependence of a reaction (recombination reaction) in which oxygen generated in a side reaction is absorbed by the negative electrode alloy has been proposed. With such internal pressure estimation, it is possible to alleviate or suppress the increase in internal pressure.

JP 2011-239573 A

However, even when the control as in Patent Document 1 is performed, the internal pressure may become excessive and the valve may open depending on the history of use of the vehicle. By opening the valve, the alkaline electrolyte is consumed, and the so-called dry life has been reached, so that the battery cannot be protected in some cases. The problem to be solved by the control method of the alkaline secondary battery of the present invention is to effectively suppress depletion of the electrolytic solution by analyzing the case where the internal pressure becomes excessive and avoiding the valve opening. be.

In order to solve the above-mentioned problems, in the alkaline secondary battery control method of the present invention, in an alkaline secondary battery, an internal pressure decrease rate calculation step of calculating an internal pressure decrease rate based on a gas absorption rate of a negative electrode; a charge reserve amount estimation step of estimating; an internal pressure decrease rate correction value calculation step of calculating an internal pressure decrease rate correction value based on the charge reserve amount estimated by the charge reserve amount estimation step; and the internal pressure decrease rate. calculating a corrected internal pressure decrease speed by correcting the internal pressure decrease speed calculated in the calculation step based on the internal pressure decrease speed correction value calculated in the internal pressure decrease speed correction value calculation step; It is characterized by having

In the step of calculating the internal pressure decrease speed correction value, the internal pressure decrease speed correction value may be calculated based on a relational expression in which the internal pressure decrease speed decreases as the charge reserve amount decreases.
The step of calculating the correction value of the internal pressure drop rate is based on a map created in advance based on the actual measurement value of the internal pressure drop rate decreasing as the charge reserve amount decreases, which is obtained in the step of acquiring the relationship between the charge reserve and the gas absorption rate. Based on this, the internal pressure decrease speed correction value may be calculated.

In the step of calculating the corrected internal pressure drop speed, the corrected internal pressure drop speed may be calculated by: corrected internal pressure drop speed=internal pressure drop speed×internal pressure drop speed correction value.
The step of calculating the internal pressure decrease rate may calculate the internal pressure decrease rate based on the gas absorption rate of the negative electrode based on the battery temperature.

The step of estimating the reserve charge amount may estimate the reserve charge amount using at least one of voltage, current, and temperature of the battery.
From the step of calculating the internal pressure increase rate based on the step of measuring the corrected internal pressure decrease rate calculated in the step of calculating the corrected internal pressure decrease rate of the alkaline secondary battery and the voltage, current, and temperature of the alkaline secondary battery An estimated internal pressure calculation step of calculating an estimated internal pressure of the alkaline secondary battery from the calculated internal pressure increase rate may be provided.

A negative electrode SOC estimation step of estimating the negative electrode SOC from the relationship between the voltage of the alkaline secondary battery and the negative electrode SOC and the voltage with respect to the estimated internal pressure of the alkaline secondary battery calculated in the step of calculating the estimated internal pressure of the alkaline secondary battery. and a hydrogen equilibrium pressure calculation step of calculating the negative electrode hydrogen equilibrium pressure from the temperature;
calculating a corrected negative electrode hydrogen equilibrium pressure from the relationship between the negative electrode SOC and the negative electrode hydrogen equilibrium pressure, and calculating an estimated internal pressure of the alkaline secondary battery based on the negative electrode hydrogen equilibrium pressure. A step of calculating a corrected estimated internal pressure may be provided.

In the step of calculating the corrected negative electrode hydrogen equilibrium pressure, the hydrogen equilibrium pressure corresponding to the temperature and the negative electrode SOC may be calculated using a two-dimensional map based on the PCT curve.
By comparing the corrected estimated internal pressure with a preset internal pressure threshold value based on the corrected estimated internal pressure calculated in the step of calculating, the alkaline secondary pressure is determined based on the corrected estimated internal pressure. Control may be performed to limit the battery usage SOC.

When the corrected estimated internal pressure exceeds the internal pressure threshold as compared with the upper limit of the internal pressure threshold set in advance, the negative electrode SOC limit is controlled so as to limit the upper limit of the usable SOC of the alkaline secondary battery. A step may be provided.

When the corrected estimated internal pressure is less than the internal pressure threshold as compared with a preset lower limit of the internal pressure threshold, the negative electrode SOC is controlled to relax the upper limit of the use SOC of the alkaline secondary battery. A step of deregulation may be provided.

The alkaline secondary battery can be suitably implemented in a nickel-hydrogen storage battery.
The alkaline secondary battery can be suitably implemented as an in-vehicle battery for driving a vehicle.

According to the method for controlling an alkaline secondary battery of the present invention, it is possible to avoid opening the valve and effectively suppress depletion of the electrolytic solution even if the reserve balance changes.

FIG. 4 is a conceptual diagram showing the balance between the positive electrode capacity and the negative electrode capacity of a nickel-metal hydride storage battery, in which (a) shows a state of positive electrode regulation, and (b) shows a state of negative electrode regulation. FIG. 2 is a conceptual diagram showing the relationship between the charge capacities [Ah] of the positive electrode and the negative electrode in a nickel-metal hydride storage battery with positive electrode regulation in the initial state. (a) is region 1 where the SOC is less than 100%, (b) is region 2 where the SOC is 100% and the negative electrode SOC is less than 100%, and (c) is the region where the negative electrode SOC is less than 100%. Region 3 is shown with 100% or more. 4 is a graph showing the relationship between the charge capacity [Ah] and the amount of oxygen/hydrogen generated [ml] in the charge reserve in the initial state. FIG. 2 is a conceptual diagram showing the relationship between the charge capacities [Ah] of the positive electrode and the negative electrode in a nickel-metal hydride storage battery with negative electrode regulation in a negative state. (a) is a region 1 in which the SOC is less than 100%, (b) is a region 2 in which the SOC is 100% and the positive electrode SOC is less than 100%, and (c) is a region 2 in which the positive electrode SOC is Region 3 is shown with 100% or more. 4 is a graph showing the relationship between the charge capacity [Ah] and the amount of oxygen/hydrogen generated [ml] in the negative charge reserve. 4 is a graph showing the relationship between the charge reserve and the rate of internal pressure decrease. 4 is a flowchart showing a control method for the nickel-metal hydride storage battery of the present embodiment; FIG. 2 is a cross-sectional view of the nickel-metal hydride storage battery of the present embodiment; 1 is a block diagram of a control device for a nickel-metal hydride storage battery according to the present embodiment; FIG. PCT curve showing the relationship between negative electrode SOC [%] and hydrogen equilibrium pressure [MPa] at different temperatures. A two-dimensional map showing the relationship between temperature, negative electrode SOC [%], and hydrogen equilibrium pressure [MPa]. A conventional one-dimensional map showing the relationship between temperature and hydrogen equilibrium pressure [MPa].

A method for controlling an alkaline secondary battery according to the present invention will be described below using an embodiment of a method for controlling a nickel-metal hydride storage battery 1 with reference to FIGS. 1 to 11. FIG.
<Outline of this embodiment>
The problem to be solved by the control method of the nickel-metal hydride storage battery 1 of the present embodiment is to avoid the valve opening and effectively suppress the depletion of the electrolytic solution. Through analysis, the inventors have newly discovered that the cause of the excessive internal pressure causing the valve to open is that the balance of the charge reserve collapses from the initial state. The reason is as follows.

The charge reserve of the nickel-metal hydride storage battery 1 may decrease. In the state where the charge reserve is reduced, unlike the initial state in which the charge reserve is sufficient, the rate of gas absorption at the negative electrode decreases. Therefore, the conventional method of calculating the rate of decrease in internal pressure, which depends only on temperature, overestimates the rate of gas absorption when the charge reserve is decreasing. As a result, the internal pressure becomes excessive and the valve opens, consuming the alkaline electrolyte and reaching the so-called dry life, which may result in failure to protect the battery. In the present embodiment, by more accurately estimating the internal pressure of the nickel-metal hydride storage battery 1, opening of the valve is avoided and reduction of the alkaline electrolyte accompanying the opening of the valve is effectively suppressed.

<Main Reaction and Side Reaction of Nickel Metal Hydride Battery 1>
In general, the main reactions of the electrode active material of a nickel-metal hydride storage battery are represented by equations (1) and (2).

Positive electrode; Ni(OH) ₂ +OH ⁻ ⇔NiOOH+H ₂ O+e ⁻ …………(1)
Negative electrode; M+H ₂ O+e ⁻ ⇔ MH+OH ⁻ ……………………(2)
(M is a hydrogen storage alloy)
Further, when electrolysis of water occurs, the reaction of the following formula (3) occurs at the positive electrode to generate oxygen.

Positive electrode; OH ⁻ →1/4O ₂ +1/2H ₂ O+e ⁻ ……………………(3)
At the negative electrode, the reaction of the following formula (4) occurs to generate hydrogen.
Negative electrode; H ₂ O+e ⁻ →1/2H ₂ +OH ⁻ …………………(4)
It is also known that, at the end of charging, the reaction of formula (1) competes with the reaction of generating oxygen, which is a side reaction of formula (3) shown below, at the positive electrode.

Oxygen generated from the positive electrode during overcharge is smoothly absorbed by the negative electrode through the separator (recombination reaction) as shown in formula (5) below, maintaining a closed system.
Negative electrode; 2MH+1/ _2O2 →2M+ _H2O (5)
In this case, if the equations (3) and (5) are well balanced, O ₂ will not be generated.

These reactions are influenced by various factors such as battery temperature, SOC of positive and negative electrodes, hydrogen equilibrium pressure, charge reserve and discharge reserve, and the balance changes to determine the gas generated in the nickel-metal hydride storage battery.

<Regarding reserve balance>
Next, the reserve balance, which is the premise of this embodiment, will be described. The charge reserve of the negative electrode in the initial state is formed because the negative electrode capacity is set larger than the positive electrode capacity. That is, the positive electrode is regulated so that the battery capacity is regulated by the positive electrode so that the negative electrode is not overcharged.

After that, as the charge/discharge cycle progresses, the charge reserve decreases due to deterioration of the negative electrode. In the present application, the state in which the charge reserve decreases and disappears and the negative electrode capacity becomes smaller than the positive electrode capacity is referred to as a "minus state".

Furthermore, corrosion of alloys and oxidative decomposition of organic substances such as binders and separators occur, and a new discharge reserve is formed, increasing the total discharge reserve. If the amount of discharge reserve in the negative electrode increases, the charge reserve decreases, oxygen gas absorption at the end of charging does not proceed smoothly, and hydrogen is likely to be generated from the negative electrode as well. As a result, the internal pressure of the battery rises, the gas discharge valve operates, and the electrolyte is discharged to the outside of the battery system. As a result, the electrolyte in the separator is depleted (separator dryout), the internal resistance increases, and the capacity decreases.

FIG. 1 is a conceptual diagram showing the balance between the positive electrode capacity and the negative electrode capacity of a unit cell of a nickel-metal hydride storage battery. FIG. 1(a) is a diagram showing a state of positive electrode regulation in which a charge reserve exists in the initial state, and FIG. 1(b) is a diagram showing a state of negative electrode regulation in which the charge reserve is negative in a deteriorated state.

In the unit cell shown in FIG. 1A, the negative electrode capacity M21 is larger than the positive electrode capacity P21, and the positive electrode capacity is regulated by the positive electrode capacity P21. In the initial state at the time of shipment or the like, the negative electrode capacity M21 includes a charge reserve R2, which is the remaining charge capacity when the positive electrode is fully charged L1, and a capacity L0 when the SOC of the positive electrode reaches 0%. A discharge reserve R1, which is the remaining discharge capacity of the battery, is secured. In the initial state, the positive electrode capacity P21 and the negative electrode capacity M21 of each unit cell are well balanced. The term "fully charged" of the positive electrode used herein refers to a state in which there is no uncharged portion of the positive electrode active material in the cell (full charge L1). At this time, the SOC of the positive electrode is 100%. In addition, the state in which the SOC of the positive electrode reaches 0%, that is, the state in which there is no charged portion of the positive electrode active material (capacity L0) is defined as the state in which the SOC of the cell is 0%, and the SOC of the positive electrode reaches 100%. This state is defined as a state where the SOC of the cell is 100%. By providing the charge reserve R2 in the negative electrode capacity M21 in this manner, generation of hydrogen from the negative electrode during overcharge can be suppressed. Further, by providing the discharge reserve R1 in the negative electrode capacity M21, generation of oxygen from the negative electrode during overdischarge can be suppressed.

As shown in FIG. 1(b), in a unit cell that has deteriorated due to usage history, the charge reserve R2 of the negative electrode disappears in the relative relationship between the positive electrode capacity P21 and the negative electrode capacity M21. Along with this, the 100% of the negative electrode may fall below the full charge L1, which is the SOC of 100% of the positive electrode, by the value of the negative charge reserve R3. At this time, even if the SOC of the positive electrode is less than 100%, the cell cannot be charged when the SOC of the negative electrode reaches 100%, so charging is restricted to the negative electrode. Therefore, the charge capacity of the single cell is positive electrode regulation (capacity L0) in discharging and negative electrode regulation (full charge L1−negative charge reserve R3) in charging, which is smaller than in the case of positive electrode regulation. In this case, when the positive electrode SOC approaches 100%, it is difficult for the negative electrode to absorb oxygen. Furthermore, if the negative electrode is overcharged, hydrogen is generated. Note that when the negative electrode SOC increases, the hydrogen equilibrium pressure of the negative electrode also increases, and the reabsorption of generated hydrogen decreases.

At this time, the negative electrode is in a state in which the negative electrode capacity M21 is shifted to the discharging side, that is, the charging reserve R2 and the negative charging reserve R3, which have disappeared from the charging side, are increased in the discharging reserve R1.

<Relationship between the balance of charge reserve in the initial state and the amount of oxygen and hydrogen generated>
FIGS. 2(a) to 2(c) are conceptual diagrams showing the relationship between the charge capacities [Ah] of the positive electrode and the negative electrode in a nickel-metal hydride storage battery with positive electrode restriction in the initial state. (a) is region 1 where the positive electrode SOC is less than 100%, (b) is region 2 where the positive electrode SOC is 100% and the negative electrode SOC is less than 100%, and (c) is the negative electrode. Region 3 is shown when the SOC is 100% or higher.
FIG. 3 is a graph showing the relationship between the charge capacity [Ah] and the amount of oxygen/hydrogen generated [ml] in the charge reserve in the initial state.

In region 1 where the charge capacity [Ah] shown in FIG. 2A is less than 6.5 Ah (positive electrode SOC 100%), almost no O ₂ or H ₂ is generated as shown in region 1 in FIG. The H ₂ /O ₂ ratio (ratio of hydrogen evolution to oxygen evolution) is much less than two.

Charging progresses, and in region ₂ where the charge capacity ^[ Ah ^] shown in _FIG . reaction prevails. As shown in region 2 of FIG. 3, a large amount of O ₂ is gradually generated, and the H ₂ /O ₂ ratio becomes H ₂ /O ₂ <2.

Then, in region 3 where the charge capacity shown in FIG. 2C exceeds 10.0 [Ah], the H ₂ /O ₂ ratio converges to 2 near 13.0 [Ah] shown in region 3 in FIG. As a result, H ₂ /O ₂ ≈2, which is approximately 1.78.

In other words, in the nickel-metal hydride storage battery in the initial state, oxygen is predominantly generated and oxygen is absorbed by the negative electrode, so the internal pressure is less likely to increase.
<Relationship between the negative charge reserve balance and the amount of oxygen and hydrogen generated>
FIGS. 4A to 4C are conceptual diagrams showing the relationship between the charge capacity [Ah] of the positive electrode and the negative electrode in a nickel-metal hydride storage battery with negative electrode regulation in a negative state. (a) is region 1 where the negative electrode SOC is less than 100%, (b) is region 2 where the negative electrode SOC is 100% and the positive electrode SOC is less than 100%, and (c) is the positive electrode. Region 3 is shown when the SOC is 100% or higher.
FIG. 5 is a graph showing the relationship between the charge capacity [Ah] and the amount of oxygen/hydrogen generated [ml] in the negative charge reserve.

As shown in FIG. 4(a), in the case of area 1 where the charge reserve decreases due to use and becomes negative, as shown in area 1 in FIG. Less than 0 Ah (negative electrode SOC 100%), almost neither O ₂ nor H ₂ is generated. The H ₂ /O ₂ ratio (ratio of hydrogen evolution to oxygen evolution) is much less than two.

Charging progresses, and the charge capacity [Ah] shown in FIG. The reaction ₂ →2M+H ₂ O predominates. As shown in region 2 in FIG. 5, H ₂ is gradually generated and the H ₂ /O ₂ ratio becomes H ₂ /O ₂ >2.

Then, in region 3 where the charge capacity shown in FIG. 4C exceeds 13.0 [Ah], the H ₂ /O ₂ ratio converges to 2 near 13.0 [Ah] shown in region 3 in FIG. As a result, H ₂ /O ₂ ≈2, which is approximately 2.11.

That is, in a nickel-metal hydride storage battery with a negative charge reserve, hydrogen is predominantly generated, and hydrogen is not absorbed by the negative electrode, so the internal pressure tends to increase.
<Relationship between reserve balance and internal pressure drop rate>
FIG. 6 is a graph showing the relationship between the charge reserve and the rate of internal pressure decrease. As shown in FIG. 6, if the ratio of the internal pressure decrease rate is 1 when the charge reserve of the nickel-hydrogen storage battery 1 is about 20%, it drops to nearly 0.85 when the charge reserve is about -5%. Also, when the charge reserve is approximately -20%, it falls below 0.8. Furthermore, when the charge reserve is approximately -30%, it drops to nearly 0.6.

Through such experiments, the inventors have confirmed that the decrease in the charge reserve has a great effect on the decrease in the rate of decrease in internal pressure.
<Estimation of Internal Pressure of Nickel Metal Hydride Battery 1>
Thus, when the reserve balance changes, the oxygen absorption rate of the negative electrode also changes. Conventionally, when estimating the internal pressure of the nickel-metal hydride storage battery 1, the influence of such a reserve balance change has not been taken into consideration.

In the present embodiment, not only the temperature but also various factors such as the decrease in the charge reserve that affects the internal pressure of the nickel-metal hydride storage battery 1 as described above are considered to estimate the internal pressure more accurately.
<Outline of control method of the present embodiment>
Therefore, in the present embodiment, based on the knowledge as described above, control is performed by the following method in order to solve the problem of effectively suppressing depletion of the electrolytic solution even if the reserve balance changes.

FIG. 7 is a flow chart showing the control method of the nickel-metal hydride storage battery of this embodiment. Hereinafter, the outline of the control method of the nickel-hydrogen storage battery 1 in this embodiment will be described with reference to FIG. First, the control device 10 (see FIG. 9) measures the voltage, current, and temperature of the nickel-hydrogen storage battery 1 in a measurement step (S2). Then, in step (S6) for calculating the internal pressure decrease rate, the "internal pressure decrease rate" based on the gas absorption rate of the negative electrode is calculated based on the measured temperature. In parallel, in the step of estimating the amount of charge reserve (S4), the "reserve charge amount" is estimated based on the measured voltage, current, and temperature. In step (S5) of calculating the correction value of decrease speed, the "correction value of internal pressure decrease rate" is calculated based on the estimated "charge reserve amount". For this estimation, the relationship between the charge reserve and the gas absorption rate of the negative electrode as shown in FIG. 6 is read in advance into the storage unit 13 (see FIG. 9) of the control device 10 (S1). Then, in step (S7) for calculating the corrected internal pressure drop speed, the "internal pressure drop rate" calculated in step (S5) for calculating the corrected internal pressure drop rate is corrected based on the "correction value for internal pressure drop rate" to make it more accurate. Calculate the appropriate “corrected internal pressure decrease rate”.

Next, in the estimated internal pressure calculation step (S8), the "estimated internal pressure" is calculated from the "corrected internal pressure decrease rate" and the "internal pressure increase rate" calculated based on the temperature.
Furthermore, the negative electrode SOC is estimated in the negative electrode SOC estimation step (S9). Further, in the hydrogen equilibrium pressure calculation step (S10), the "hydrogen equilibrium pressure" of the negative electrode is calculated from the temperature. On the other hand, in the corrected negative electrode hydrogen equilibrium pressure calculation step (S11), the "corrected negative electrode hydrogen equilibrium pressure" is calculated from the relationship between the negative electrode SOC and the negative electrode hydrogen equilibrium pressure.

Then, in the step of calculating the corrected estimated internal pressure (S12), a more accurate "corrected estimated internal pressure" is calculated based on the "negative electrode hydrogen equilibrium pressure".
By calculating the correct "corrected estimated internal pressure" in this way, the control unit appropriately limits the SOC of the nickel-metal hydride storage battery 1 as necessary based on this "corrected estimated internal pressure". Even if the balance changes, depletion of the electrolytic solution can be effectively suppressed.

(Configuration of this embodiment)
A configuration for implementing the control method of this embodiment will be described below.
<Nickel-metal hydride storage battery 1>
FIG. 8 shows a cross-sectional view of part of the battery module 90 of the nickel-metal hydride storage battery of this embodiment. As shown in FIG. 8, the nickel-metal hydride storage battery is a sealed battery that is used as a power source for vehicles such as electric vehicles and hybrid vehicles. As a nickel-metal hydride storage battery mounted on a vehicle, there is known a prismatic sealed secondary battery comprising a battery module 90 configured by electrically connecting a plurality of cells 110 in series in order to obtain a required power capacity. ing.

The battery module 90 has a rectangular parallelepiped rectangular case 300 composed of an integrated battery case 100 capable of accommodating a plurality of cells 110 and a lid body 200 sealing the integrated battery case 100 . It should be noted that the prismatic case 300 can be made of resin.

The integrated battery case 100 that constitutes the rectangular case 300 is made of a synthetic resin material, such as polypropylene or polyethylene, that is resistant to an alkaline electrolyte. A partition wall 120 is formed inside the integrated battery case 100 to partition the plurality of unit cells 110 , and the portion partitioned by the partition wall 120 serves as a battery case 130 for each unit battery 110 . The integrated battery case 100 has, for example, six battery cases 130, of which four are shown in FIG.

In the container 130 thus partitioned, the electrode plate group 140 and the positive electrode current collector plate 150 and the negative electrode current collector plate 160 joined to both sides of the electrode plate group 140 are housed together with the electrolyte.
The electrode plate group 140 is configured by stacking a rectangular positive electrode plate 141 and a rectangular negative electrode plate 142 with a separator 143 interposed therebetween. At this time, the direction in which the positive electrode plate 141, the negative electrode plate 142 and the separator 143 are stacked (the direction perpendicular to the paper surface) is the stacking direction. The positive electrode plate 141 and the negative electrode plate 142 of the electrode plate group 140 protrude to the opposite side portions in the direction of the plate surface (the direction along the plane of the drawing), so that the lead portion 141 a of the positive electrode plate 141 and the negative electrode plate 142 are projected. lead portion 142a is configured. Current collecting plates 150 and 160 are joined to the side edges of these lead portions 141a and 142a, respectively.

In addition, through holes 170 used for connecting the battery containers 130 are formed in the upper part of the partition wall 120 . The through-hole 170 is formed by two connection projections 151 and 161, a connection projection 151 projecting from the top of the current collector plate 150 and a connection projection 161 projecting from the top of the current collection plate 160. A weld connection is made through the through hole 170 . As a result, the electrode plate groups 140 of the battery containers 130 adjacent to each other are electrically connected in series. Of the through-holes 170 , the through-holes 170 located outside the battery containers 130 at both ends are fitted with the positive electrode connection terminal 152 or the negative electrode connection terminal 153 (not shown) above the end sidewalls of the integrated battery container 100 . . The positive electrode connection terminal 152 is welded to the connection protrusion 151 of the current collector plate 150 . The negative electrode connection terminal 153 is welded to the connection protrusion 161 of the current collector plate 160 . The electrode plate group 140 connected in series in this manner, that is, the total output of the plurality of cells 110 is taken out from the positive connection terminal 152 and the negative connection terminal 153 .

On the other hand, the cover 200 constituting the prismatic case 300 has an exhaust valve 210 that reduces the internal pressure of the prismatic case 300 to the valve opening pressure or less, and a sensor mounting hole for mounting a sensor for detecting the temperature of the electrode plate group 140. 220 is provided. The sensor mounting hole 220 allows the temperature of the electrode plate group 140 to be measured by a hole extending through the battery case 130 to the vicinity of the electrode plate group 140 .

The exhaust valve 210 is for maintaining the internal pressure in the integrated battery case 100 below the permissible threshold, and when the internal pressure exceeds the permissible threshold and exceeds the valve opening pressure, , the gas generated inside the integrated battery case 100 is discharged by opening the valve. The internal pressure of the integrated battery container 100 is made uniform in all the battery containers 130 by communication holes (not shown) formed in the partition walls 120 . As a result, the integrated battery container 100 discharges gas until the internal pressure equalized in all battery containers 130 becomes less than the valve opening pressure, and the internal pressure is maintained below the permissible valve opening pressure. become.

<Structure of Electrode Group 140>
<Positive electrode plate 141>
The positive electrode plate 141 is composed of nickel hydroxide and cobalt as active materials. Specifically, to nickel hydroxide, add a conductive agent such as cobalt hydroxide or metallic cobalt powder, and if necessary, add a thickener such as carboxymethylcellulose or a binder such as polytetrafluoroethylene in an appropriate amount to make a paste. process. After that, the paste-like processed product is applied to or filled in a core material such as a three-dimensional porous nickel foam, and then dried, rolled, and cut to form a plate-like positive electrode plate 141. As the nickel foam three-dimensional porous body, one obtained by burning off the foamed urethane after plating the surface of the urethane skeleton of the foamed urethane with nickel is used.

<Negative plate 142>
The negative electrode plate 142 is made of, for example, a misch metal, which is a mixture of rare earth elements such as lanthanum, cerium, and neodymium, and a hydrogen storage alloy containing nickel, aluminum, cobalt, and manganese as constituent elements. In more detail, this hydrogen storage alloy is added with a conductive agent such as carbon black, and if necessary, a thickener such as carboxymethyl cellulose and a binder such as styrene-butadiene copolymer, and is first made into a paste. process. Thereafter, the hydrogen-absorbing alloy thus processed into a paste is applied to or filled in a core material such as a punching metal (active material support), which is then dried, rolled, and cut to form a plate-like negative electrode plate 142 . to form

<Separator 143>
As the separator 143, a nonwoven fabric made of an olefin resin such as polypropylene, or a nonwoven fabric subjected to hydrophilic treatment such as sulfonation as necessary, can be used.

<Assembly of Nickel Metal Hydride Battery 1>
The positive electrode plate 141, the negative electrode plate 142, and the separator 143 are alternately stacked in such a manner that the positive electrode plate 141 and the negative electrode plate 142 protrude in opposite directions with the separator 143 interposed therebetween, thereby forming the rectangular parallelepiped electrode plate group 140. Configure. Then, the outer edges of the lead portions 141a of the positive electrode plates 141 stacked to protrude to one side and the current collector plates 150 are joined by spot welding or the like, and the lead portions 142a of the stacked negative electrode plates 142 to protrude to the other side. and the collector plate 160 are joined by spot welding or the like.

The electrode plate group 140 to which the current collector plates 150 and 160 are welded is housed in each container 130 within the rectangular case 300 . The positive electrode current collector plate 150 and the negative electrode current collector plate 160 of the adjacent electrode plate group 140 are connected by spot welding or the like between the connection protrusions 151 and 161 projecting from the upper portions thereof. Therefore, the electrode plate groups 140 adjacent to each other are electrically connected in series.

A predetermined amount of an alkaline aqueous solution (electrolyte) containing potassium hydroxide as a main component is injected into each battery container 130 , and the opening of the integrated battery container 100 is sealed with a lid 200 . Thus, a battery module 90 having, for example, a rated capacity of "6.5 Ah" is configured, which is composed of a plurality of cells 110 (nickel-metal hydride storage batteries). Such battery modules 90 are further combined, housed in a resin case, mounted with a control device, various sensors, etc., and mounted as a battery pack 24 (see FIG. 9) for vehicle use as a battery for driving a vehicle.

<Control device 10 for nickel-metal hydride storage battery>
FIG. 9 is a block diagram of the control device 10 of the nickel-metal hydride storage battery 1 of this embodiment. The control device 10 of the nickel-metal hydride storage battery 1 will be described with reference to FIG. Here, the case where the nickel-metal hydride storage battery 1 is controlled in the state of the battery pack 24 containing the battery module 90 will be described.

<Control device 10>
The control device 10 can be mounted on the vehicle (onboard) to control the battery module 90 of the vehicle based on real-time or accumulated data.

The control device 10 controls and charges the inverter 20 as a charging device for charging the battery module 90 with current from the motor generator 17 as a power generator. Further, the control device 10 controls the inverter 20 as a power supply device to discharge current from the battery module 90 to the motor generator 17 as a drive motor serving as a load.

The control device 10 includes a current detector 21 that measures the current of the battery module 90, a voltage detector 22 that measures the voltage across the terminals of the battery module 90, and a temperature detector 23 that measures the temperature of the battery module 90. ing.

The temperature detector 23 has a temperature sensor arranged in the sensor mounting hole 220 shown in FIG. The temperature sensor measures the temperature near the electrode plate group 140 of the corresponding cell 110 of the battery module 90 and outputs the measured temperature value to the control device 10 as an electrical signal.

<Control unit 11>
A control unit 11 of the control device 10 is configured as a computer including a CPU, a RAM, a ROM, and an interface for controlling the entire control device 10 .

<Information Acquisition Unit 12>
The information acquisition unit 12 successively acquires the charging current value from the current detector 21, acquires the voltage value from the voltage detector 22, acquires the battery temperature from the temperature detector 23, and stores them.

<Storage unit 13>
The storage unit 13 includes a storage medium in which programs for the control device 10 and necessary data are stored. The program comprises a program that performs the following steps. Step (S1) of acquiring the relationship between the charge reserve and the gas absorption rate. Measurement step (S2). Step (S3) of internal pressure increase speed calculation. A step of estimating the charge reserve amount (S4). Step (S5) for calculating an internal pressure decrease speed correction value. Step (S6) for calculating the rate of decrease in internal pressure. Step (S7) for calculating the corrected internal pressure decrease rate. Estimated internal pressure calculation step (S8). A negative electrode SOC estimation step (S9). A step for calculating the hydrogen equilibrium pressure (S10). A step for calculating the corrected negative electrode hydrogen equilibrium pressure (S11). Step of calculating corrected estimated internal pressure (S12). Judgment step (S13). Negative electrode SOC limitation step (S14). A step of relaxing the negative electrode SOC limit (S15).

Further, a map based on actual measurement data of "the relationship between the charge reserve and the gas absorption rate" is stored in the information acquisition unit 12 as data on which the control is based. In addition, maps of "relationship between temperature and internal pressure increase rate" and "relationship between temperature and internal pressure decrease rate" are also stored. In addition, a map of "relationship between battery voltage and negative electrode SOC" is also stored. A map of "relationship between negative electrode SOC and hydrogen equilibrium pressure" is also stored. A map of "relationship between temperature and hydrogen equilibrium pressure" is also stored.

In addition, a map of "deterioration state of the battery estimated from the usage history of the nickel-metal hydride storage battery 1" and "relationship between the deterioration state of the nickel-metal hydride storage battery 1 and the charge reserve amount" is also stored.
<SOC calculator 14>
The SOC calculator 14 estimates the SOC of the battery module 90 from the voltage measured by the voltage detector 22 and the like. Furthermore, from this, the positive electrode SOC, the negative electrode SOC, and the like are estimated with reference to a map or the like.

<Charging reserve estimation unit 15>
The charging reserve estimating unit 15 estimates the charging reserve and the discharging reserve based on the deterioration information of the battery based on the usage history such as the usage SOC and the temperature of the in-vehicle nickel-metal hydride storage battery acquired and accumulated by the information acquisition unit 12. done.

<Charge/discharge control unit 16>
The charge/discharge control unit 16 monitors the voltage of the battery module 90 , and when the SOC is lower than the threshold, the motor generator 17 generates power to charge the battery module 90 via the inverter 20 . On the other hand, the regenerated current from the motor generator 17 charges the battery module 90 through the inverter 20 when the vehicle is braked. In this case, charging is limited when the current is excessive or the SOC of the battery module 90 is too high. The threshold and the like at this time are stored in the storage unit 13 .

On the other hand, when the vehicle is driven, a necessary current is supplied from the battery module 90 to the motor generator 17 via the inverter 20 in accordance with a command from the vehicle ECU (Electronic Control Unit).

<Method for controlling nickel-metal hydride storage battery>
Next, a method for controlling the nickel-metal hydride storage battery 1 of this embodiment will be described in detail along the flowchart of FIG.

In the control method of the nickel-metal hydride storage battery 1, the control is started by the control device 10 while being mounted on the vehicle.
<Step (S1) of acquiring the relationship between the charge reserve and the gas absorption rate>
A map based on actual measurement data of "the relationship between the charge reserve and the gas absorption rate" is stored in advance in the storage unit 13 as data on the premise of the control. In addition, maps of "relationship between temperature and internal pressure increase rate" and "relationship between temperature and internal pressure decrease rate" are also stored. In addition, a map of "relationship between battery voltage and negative electrode SOC" is also stored. A map of "relationship between negative electrode SOC and hydrogen equilibrium pressure" is also stored. A map of "relationship between temperature and hydrogen equilibrium pressure" is also stored.

In addition, a map of "deterioration state of the battery estimated from the usage history of the nickel-metal hydride storage battery 1" and "relationship between the deterioration state of the nickel-metal hydride storage battery 1 and the charge reserve amount" is also stored.
<Measurement step (S2)>
Next, the control unit 11 of the control device 10 sequentially measures the current of the battery module 90 with the current detector 21 . Also, the voltage between the terminals of the battery module 90 is measured by the voltage detector 22 . Also, the temperature of the battery module 90 is measured by the temperature detector 23 . These are stored in the information acquisition unit 12 .

<Step of Calculating Internal Pressure Increase Rate (S3)>
Next, the control unit 11 reads out the temperature stored in the information acquisition unit 12, and determines the internal pressure increase speed based on the temperature based on the map of “relationship between temperature and internal pressure increase speed” stored in the storage unit 13. Calculate

<Step of estimating charge reserve amount (S4)>
In parallel with this, the charge reserve estimator 15 of the control device 10 estimates the charge reserve amount.

By grasping the deterioration state of the nickel-metal hydride storage battery 1, it is possible to grasp the charge reserve amount of the nickel-metal hydride storage battery. That is, the charge reserve amount is correlated with the discharge capacity of the nickel-metal hydride storage battery 1, and if the discharge capacity of the nickel-metal hydride storage battery decreases due to deterioration of the nickel-metal hydride storage battery, the charge reserve amount decreases.

Since the discharge reserve amount increases according to corrosion of the negative electrode, this can be defined as the increase amount. In addition, since the charge reserve amount decreases as hydrogen is released to the outside of the nickel-metal hydride storage battery 1 through the resin battery case, this can be defined as the decrease amount.

In the example of the present embodiment, the charge reserve amount is obtained in advance by determining the correspondence relationship between the increase/decrease amount of the charge reserve and the temperature, and the "temperature during charging/discharging", "temperature when not charging/discharging", etc. It is grasped by measuring and collating with the above correspondence relationship. More specifically, since “charge reserve=negative electrode capacity−positive electrode capacity−discharge capacity”, the charge reserve estimator 15 of the control device 10 also estimates the negative electrode capacity and the positive electrode capacity.

Further, the increase/decrease amount of the charge reserve has a corresponding relationship not only with the temperature but also with the "accumulated value of the charge/discharge current", the "ΔSOC", the "central SOC", and the like. Therefore, by measuring and estimating these in the usage history of the nickel-metal hydride storage battery 1, it is possible to measure the increase/decrease amount of the charge reserve more accurately.

<Step (S5) for Calculating Internal Pressure Reduction Speed Correction Value>
Here, based on the charge reserve amount estimated in the charge reserve amount estimation step (S4), how the decrease in the charge reserve amount affects the internal pressure drop rate is expressed in the form of an internal pressure drop rate correction value. calculate.

Specifically, the "relationship between the charge reserve and the gas absorption rate" as shown in FIG. Calculate with reference to a map based on data.

<Step (S6) of internal pressure decrease rate calculation>
The control unit 11 reads out the temperature stored in the information acquisition unit 12, and determines the internal pressure drop based on the temperature based on the map (not shown) of the "relationship between temperature and internal pressure drop rate" stored in the storage unit 13. Calculate speed.

<Step of Calculating Corrected Internal Pressure Decrease Speed (S7)>
The control unit 11 corrects the "internal pressure decrease speed" calculated in the internal pressure decrease rate calculation step (S6) with the "internal pressure decrease rate correction value" calculated in the internal pressure decrease rate correction value calculation step (S5). , to calculate the “corrected internal pressure decrease speed”.

In this embodiment, it is calculated by the following formula (6).
Corrected internal pressure decrease speed = internal pressure decrease speed × internal pressure decrease speed correction value (6)
Here, the "internal pressure drop rate" is the internal pressure drop rate calculated based on the battery temperature calculated in step (S6) for calculating the internal pressure drop rate. The "internal pressure decrease speed correction value" is the "internal pressure decrease speed correction value" calculated in step (S5) for calculating the internal pressure decrease speed correction value.

<Step of Calculating Estimated Internal Pressure (S8)>
Based on the "internal pressure increase rate" calculated in the internal pressure increase rate calculation step (S3) and the corrected internal pressure decrease rate calculated in the corrected internal pressure decrease rate calculation step (S7), the control unit 11 estimates up to now The current "estimated internal pressure" is calculated from the "estimated internal pressure" that has been set.

<Step of Negative SOC Estimation (S9)>
The control unit 11 also reads out the terminal voltage of the battery module 90 acquired by the voltage detector 22 stored in the information acquisition unit 12 . Along with this, the “negative electrode SOC” based on the battery voltage is calculated from a map (not shown) of “relationship between battery voltage and negative electrode SOC” stored in the storage unit 13 .

<Step of Calculating Hydrogen Equilibrium Pressure (S10)>
Here, the hydrogen equilibrium pressure [MPa] is calculated from a map (not shown) of "relationship between temperature and hydrogen equilibrium pressure" based on the temperature measured in step (S2) of temperature measurement.

<Step of calculating the corrected negative electrode hydrogen equilibrium pressure (S11)>
FIG. 10 is a graph showing a PCT curve showing the relationship between the negative electrode SOC [%] and the hydrogen equilibrium pressure [MPa] at different temperatures. Based on the PCT characteristics of hydrogen storage alloys (Pressure-Composition-Temperature, pressure-composition isotherm of hydrogen storage alloys, JIS H7201:2007), changes in hydrogen equilibrium pressure [MPa] due to changes in negative electrode SOC [%] are shown. ing. A graph is created for each temperature.

FIG. 12 is a conventional one-dimensional map showing the relationship between temperature and hydrogen equilibrium pressure [MPa]. In the conventional technique, the calculation of the hydrogen equilibrium pressure [MPa] as in the hydrogen equilibrium pressure calculation step (S10) is based only on the temperature, as shown in FIG. In this case, the temperature is "medium", so the hydrogen equilibrium pressure is determined to be "P2".

However, the hydrogen equilibrium pressure is greatly affected not only by the temperature but also by the negative electrode SOC as shown in the PCT curve shown in FIG. Therefore, in the present embodiment, not only the temperature but also the relationship between the negative electrode SOC [%] and the hydrogen equilibrium pressure [MPa] as shown in FIG. 10 is considered.

FIG. 11 is a two-dimensional map showing the relationship between temperature, negative electrode SOC [%], and hydrogen equilibrium pressure [MPa]. In the present embodiment, a two-dimensional map of the negative electrode SOC estimated in the negative electrode SOC estimation step (S9) and the “relationship between temperature, negative electrode SOC, and hydrogen equilibrium pressure” shown in FIG. do. With this, the hydrogen equilibrium pressure [MPa] estimated more easily and more accurately is calculated. In the example of FIG. 11, the temperature is "medium", so if it is a different dimension map as shown in FIG. 12, it would be "P2". However, considering the negative electrode SOC, the hydrogen equilibrium pressure is determined to be "P5" because the negative electrode SOC is "medium" on the two-dimensional map.

<Step of Calculating Corrected Estimated Internal Pressure (S12)>
In the estimated internal pressure calculation step (S8), the "estimated internal pressure" is calculated from the "internal pressure increase rate" and the "corrected internal pressure decrease rate" corrected by the charge reserve. The "corrected estimated internal pressure" is calculated by correcting the "estimated internal pressure" based on the "corrected hydrogen equilibrium pressure" calculated in the corrected negative electrode hydrogen equilibrium pressure calculation step (S11).

That is, the "corrected estimated internal pressure" is a value estimated taking into consideration all of the battery temperature, the decrease in the charge reserve, the negative electrode SOC, and the like.
<Step of Judgment (S13)>
<Step of Limiting Negative SOC (S14)>
The state of the nickel-metal hydride storage battery 1 is determined based on the "corrected estimated internal pressure" thus calculated. When this "corrected estimated internal pressure" exceeds the upper threshold value max, the upper limit value of the SOC band used for the nickel-metal hydride storage battery 1 is restricted in order to reduce the risk of valve opening (S14). This is because by limiting the upper limit of the SOC band to be used, the generation of new gas is suppressed and the internal pressure is lowered.

<Step of Alleviating Negative SOC Limitation (S15)>
On the other hand, if this "corrected estimated internal pressure" is below the lower limit threshold min, it is determined that the internal pressure is sufficiently low and the risk of opening the valve is low, and the upper limit of the SOC band used for the nickel-metal hydride storage battery 1 is restricted. Relax (S15). This is to make full use of the capacity of the nickel-metal hydride storage battery 1 by relaxing restrictions on the SOC band to be used.

<When threshold value min≦corrected estimated internal pressure≦threshold value max>
If threshold value min≦corrected estimated internal pressure≦threshold value max (S13: YES), the current limit is maintained and the process ends (end). After that, the control device 10 repeats the steps S1 to S12 as necessary to control the nickel-metal hydride storage battery 1 .

(Action of Embodiment)
Since the nickel-metal hydride storage battery control method of the present embodiment has the configuration described above, it has the following effects.

That is, the control device 10 calculates the "corrected estimated internal pressure" that is estimated taking into account all of the battery temperature, the amount of decrease in the charge reserve, the negative electrode SOC, and the like.
Since this "corrected estimated internal pressure" is an internal pressure that is estimated with higher accuracy than in the conventional technology, it is possible to perform appropriate control according to the actual internal pressure of the nickel-metal hydride storage battery 1.

Based on this highly accurate "corrected estimated internal pressure", the control device 10 limits the SOC band used by the nickel-metal hydride storage battery 1. FIG. That is, when the "corrected estimated internal pressure" is higher than the preset upper limit threshold max, the upper limit of the SOC band used by the nickel-metal hydride storage battery 1 is restricted. By limiting the upper limit of the SOC band, the gas generated in the nickel-hydrogen storage battery 1 is suppressed. By suppressing the generation of gas, the risk of valve opening can be effectively avoided. By avoiding the opening of the valve, depletion of the electrolytic solution due to the opening of the valve can be suppressed. This avoids depletion of the electrolyte in the separator (separator dryout), an increase in internal resistance, and a decrease in capacity. Therefore, according to the control method of the nickel-hydrogen storage battery 1 of this embodiment, the battery life can be improved.

(Effect of Embodiment)
The method for controlling a nickel-metal hydride storage battery according to this embodiment has the following effects.
(1) It is possible to estimate the internal pressure of the battery with high accuracy, avoid liquid drying due to valve opening based on the estimated internal pressure, and suppress battery failure.

(2) Since the internal pressure of the battery is estimated from the "internal pressure increase rate" and the "internal pressure decrease rate", the internal pressure can be accurately estimated. In particular, the "internal pressure drop rate" uses the "corrected internal pressure drop rate" that takes into account the decrease in the charge reserve, so the internal pressure can be estimated more accurately.

(3) Decrease in charge reserve can be determined based on deterioration of the battery, so more accurate estimation can be made.
(4) Since the estimated internal pressure is estimated using the "corrected negative electrode hydrogen equilibrium pressure" corrected with reference to the hydrogen equilibrium pressure, more accurate estimation can be performed.

(5) Since the "corrected negative electrode hydrogen equilibrium pressure" is estimated by referring to not only the temperature but also the negative electrode SOC, an accurate hydrogen equilibrium pressure can be estimated.
(6) Since the "corrected negative electrode hydrogen equilibrium pressure" is estimated using a two-dimensional map of temperature and negative electrode hydrogen equilibrium pressure, it can be easily and accurately estimated by an in-vehicle control device without imposing a burden. .

(7) When the internal pressure is expected to rise based on the estimated internal pressure, the SOC to be used is limited, so the generation of gas is effectively suppressed, and the rise in internal pressure can be suppressed. Therefore, the risk of valve opening can be reduced.

(8) On the other hand, if the estimated internal pressure falls below the predetermined threshold, the upper limit of the SOC that is restricted can be relaxed. Therefore, the performance of the nickel-metal hydride storage battery 1 can be effectively exhibited within a range in which the nickel-metal hydride storage battery 1 does not bear the risk of opening the valve.

(9) The control of the nickel-metal hydride storage battery 1 is automatically performed by the control device 10, which is an in-vehicle computer.
(10) The control device 10 of the nickel-hydrogen storage battery 1 can be implemented in a general ECU. For this reason, it can be easily implemented only by introducing a program without a special device. Moreover, no special cost is incurred for implementing the control method of the present embodiment.

(11) The present embodiment is not limited to new vehicles, and can be introduced to existing vehicles without any particular improvement or addition of equipment.
(Modification)
The above embodiment can also be implemented as follows.

The nickel-metal hydride storage battery 1 of the present embodiment is an assembled battery including the battery module 90 for vehicle use, but the purpose is not limited to vehicle use. Also, the shape is not limited, and the shape is not limited to a columnar shape.

* Further, the nickel-metal hydride storage battery 1 is not limited to the battery module 90, and may be a single battery.
○Temperature [°C], SOC value [%], charge/discharge rate [C], current value [A], voltage value [V], time [s], hydrogen equilibrium exemplified in this embodiment The pressure [MPa] and the like are examples and are optimized by those skilled in the art according to the characteristics of the target battery. The thresholds max, min are similarly optimized.

〇The flow chart is an example, and those skilled in the art can change the order of these procedures, add procedures, or omit them.
○ For example, in the present embodiment, the "corrected negative electrode hydrogen equilibrium pressure" is divided into the step of estimating the negative electrode SOC (S9), the step of calculating the hydrogen equilibrium pressure (S10), and the step of calculating the corrected negative electrode hydrogen equilibrium pressure (S11). However, these may be processed collectively.

○ In addition, the calculation of the "charge reserve", "internal pressure increase rate", "internal pressure decrease rate", "negative electrode SOC", "hydrogen equilibrium pressure", etc. in the embodiment is an example, and the calculation method etc. are not limited.

○ In the present embodiment, the negative electrode SOC is estimated in the negative electrode SOC estimation step (S9). Here, the "negative electrode SOC" based on the battery voltage is calculated from a map (not shown) of "relationship between battery voltage and negative electrode SOC". Instead of this, for example, it may be estimated from the relationship between the negative electrode capacity, the discharge reserve amount, and the positive electrode SOC.

○ Further, the control of the internal pressure is not limited to the limitation of the negative electrode SOC, and may be controlled by the voltage and current of the battery.
○ Further, it goes without saying that a person skilled in the art can add, delete, and change the configuration without departing from the scope of the claims.

REFERENCE SIGNS LIST 1 NiMH storage battery 10 NiMH storage battery control device 11 Information acquisition unit (map/battery usage history)
DESCRIPTION OF SYMBOLS 12... SOC calculation part 13... Charge control part 14... Control part 15... Storage part (program)
DESCRIPTION OF SYMBOLS 16... Charge reserve estimation part 17... Motor generator 20... Inverter 21... Current detector 22... Voltage detector 23... Temperature detector 24... Battery pack 90... Battery module 100... Integrated battery container 110... Single battery 120... Partition wall 130... Battery case 140 Electrode plate group 141 Positive electrode plate 141a Lead portion 142 Negative electrode plate 142a Lead portion 143 Separator 150 Current collector 151 Connection protrusion 152 Connection terminal 153 Connection terminal 160 Current collector 161 ... Connection protrusion 170 ... Through hole 200 ... Lid body 210 ... Exhaust valve 220 ... Sensor mounting hole 300 ... Rectangular case
max: Upper limit threshold for corrected estimated internal pressure
min: Lower limit threshold for corrected estimated internal pressure

Claims (14)

In alkaline secondary batteries,
an internal pressure reduction rate calculation step of calculating an internal pressure reduction rate based on the gas absorption rate of the negative electrode;
a charge reserve amount estimation step of estimating the charge reserve amount;
an internal pressure decrease speed correction value calculation step of calculating an internal pressure decrease speed correction value based on the charge reserve amount estimated in the charge reserve amount estimation step;
Compensated internal pressure decrease speed calculation for calculating a corrected internal pressure decrease speed by correcting the internal pressure decrease speed calculated in the internal pressure decrease speed calculation step based on the internal pressure decrease speed correction value calculated in the internal pressure decrease speed correction value calculation step. A control method for an alkaline secondary battery, comprising: The step of calculating the internal pressure decrease speed correction value includes:
2. The method of controlling an alkaline secondary battery according to claim 1, wherein the internal pressure drop rate correction value is calculated based on a relational expression in which the internal pressure drop rate decreases as the charge reserve decreases. The step of calculating the internal pressure decrease speed correction value includes:
An internal pressure drop rate correction value is calculated based on a map created in advance based on the measured values of the internal pressure drop rate decreasing as the charge reserve amount decreases, which was acquired in the step of acquiring the relationship between the charge reserve and the gas absorption rate. 2. The method of controlling an alkaline secondary battery according to claim 1, wherein: The step of calculating the corrected internal pressure decrease rate includes:
The method for controlling an alkaline secondary battery according to any one of claims 1 to 3, wherein the corrected internal pressure decrease rate is calculated by: corrected internal pressure decrease rate = internal pressure decrease rate x internal pressure decrease rate correction value. The alkaline secondary battery according to any one of claims 1 to 4, wherein the step of calculating the internal pressure decrease rate calculates the internal pressure decrease rate based on the gas absorption rate of the negative electrode based on the battery temperature. control method. The alkaline secondary according to any one of claims 1 to 5, wherein the step of estimating the charge reserve amount uses at least one of battery voltage, current, and temperature to estimate the charge reserve amount. Battery control method. a corrected internal pressure decrease rate calculated by the step of calculating the corrected internal pressure decrease rate of the alkaline secondary battery;
Estimated internal pressure calculation for calculating the estimated internal pressure of the alkaline secondary battery from the internal pressure increase rate calculated from the internal pressure increase rate calculation step based on the measurement step of measuring the voltage, current, and temperature of the alkaline secondary battery 7. The method for controlling an alkaline secondary battery according to any one of claims 1 to 6, comprising steps. For the estimated internal pressure of the alkaline secondary battery calculated in the step of calculating the estimated internal pressure of the alkaline secondary battery,
a negative electrode SOC estimation step of estimating the negative electrode SOC based on the relationship between the voltage of the alkaline secondary battery and the negative electrode SOC and the voltage;
a negative electrode hydrogen equilibrium pressure calculation step of calculating the negative electrode hydrogen equilibrium pressure from the temperature;
calculating a corrected negative electrode hydrogen equilibrium pressure from the relationship between the negative electrode SOC and the negative electrode hydrogen equilibrium pressure,
8. The method of controlling an alkaline secondary battery according to claim 7, further comprising a step of calculating a corrected estimated internal pressure of the alkaline secondary battery based on the negative electrode hydrogen equilibrium pressure. . In the step of calculating the corrected negative electrode hydrogen equilibrium pressure,
9. The method of controlling an alkaline secondary battery according to claim 8, wherein a two-dimensional map based on a PCT curve is used to calculate the hydrogen equilibrium pressure according to the temperature and the negative electrode SOC. The alkaline secondary pressure is determined by comparing the corrected estimated internal pressure with a preset internal pressure threshold based on the corrected estimated internal pressure calculated in the calculating step. 10. The method of controlling an alkaline secondary battery according to claim 8 or 9, wherein control is performed so as to limit the usage SOC of the battery. When the corrected estimated internal pressure exceeds the internal pressure threshold as compared with the upper limit of the internal pressure threshold set in advance, the negative electrode SOC limit is controlled so as to limit the upper limit of the usable SOC of the alkaline secondary battery. 11. The method for controlling an alkaline secondary battery according to claim 10, comprising the steps of: When the corrected estimated internal pressure is less than the internal pressure threshold as compared with a preset lower limit of the internal pressure threshold, the negative electrode SOC is controlled to relax the upper limit of the use SOC of the alkaline secondary battery. 12. The method of controlling an alkaline secondary battery according to claim 10, further comprising a step of relaxing restrictions. The alkaline secondary battery control method according to any one of claims 1 to 12, wherein the alkaline secondary battery is a nickel-metal hydride storage battery. The method for controlling an alkaline secondary battery according to any one of claims 1 to 13, wherein the alkaline secondary battery is an in-vehicle battery for driving a vehicle.

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