JP2023119270A - Nickel-hydrogen storage battery control method and control device - Google Patents

Abstract

To exercise control so as to detect a symptom of Ni2O3H generation that incurs a capacity reduction and suppress Ni2O3H generation in a nickel-hydrogen storage battery.SOLUTION: First, a threshold is set (S1), and SOC is acquired (S2). Then, a determination is made whether SOC≤40% is satisfied(S3), and if it is low SOC, a charge curve is acquired while carrying out forcible charging (S4). When SOC>60% is reached (S6) while monitoring the SOC (S5), charging is terminated (S7). dQ/dV is calculated from the charge curve (S8), and (total discharge capacity [Ah])/(dQ/dV) plot points are stored (S9). When dQ/dV≤TW(S10) is reached, a total discharge capacity EA[Ah] at which dQ/dV=TD is reached is estimated on the basis of the most recent two plot points (S11). If EA≤target total discharge capacity SA (S12) is satisfied, discharge rates are limited (S13) so as to suppress degradation.SELECTED DRAWING: Figure 6

Description

The present invention relates to a control method and control device for a nickel-metal hydride storage battery, and more particularly to a control method and control device for a nickel-metal hydride storage battery that suppresses the formation of Ni ₂ O ₃ H.

A hybrid vehicle or the like equipped with an electric motor drives the electric motor with electric power stored in a secondary battery. Among such secondary batteries, nickel-metal hydride storage batteries are widely used for vehicles because they can charge and discharge large currents.

It is known that such a nickel-metal hydride storage battery has a memory effect depending on the usage conditions. As a result, the positive electrode potential of the battery tends to become lower than the predetermined lower limit potential or higher than the predetermined upper limit potential, so that a side reaction occurs at the positive electrode, which can deteriorate the positive electrode.

FIG. 1 is a graph showing the relationship between the existence ratio [%] of Ni ₂ O ₃ H (nickel oxide) in the positive electrode and the capacity ratio [%] of the battery. As shown in FIG. 1, among the reactions, especially in a nickel-metal hydride storage battery, when the abundance ratio [%] of Ni ₂ O ₃ H (nickel oxide) in the positive electrode increases, the capacity ratio [%] of the battery irreversibly increases. ] is reduced. In addition, the present inventors found that once Ni ₂ O ₃ H is produced, as shown in the graph L ₀ shown in FIG. 8, the capacity decreases rapidly as the total discharge capacity [Ah] increases. It revealed that. Therefore, Patent Document 1 discloses the following invention for suppressing the formation of Ni ₂ O ₃ H.

In an alkaline storage battery using nickel hydroxide for the positive electrode, electrochemically inactive Ni ₂ O ₃ H may be generated depending on the conditions by performing charging and discharging under repeated charging and discharging conditions. Therefore, in the invention disclosed in Patent Document 1, the current density is 100 [A/m ² ], the SOC is within the range of 20 to 80 [%], and the total amount of electricity is 10 [kAh]. In this case, a battery has been proposed in which the positive electrode potential is appropriately controlled so that the Ni ₂ O ₃ H content is less than or equal to a specified amount.

Such an invention can be expected to suppress the formation of Ni ₂ O ₃ H.

JP 2011-233423 A

However, nickel-metal hydride storage batteries for vehicles, in particular, are used under harsh conditions, and may deviate from the conditions of use described in Patent Document 1 in some cases. The inventors of the present invention have found that if a certain amount of Ni ₂ O ₃ H is produced, even if it is very small, the capacity of the battery will decrease, and if the Ni ₂ O ₃ H is continuously produced, the battery will It was found that the capacity can drop rapidly. For this reason, it is necessary to quickly grasp signs that Ni ₂ O ₃ H is likely to be generated and take appropriate measures.

Regarding the continuation of the use of a nickel-metal hydride storage battery with a certain usage history in the prior art, as a technique for confirming the formation of Ni ₂ O ₃ H, for example, structural analysis such as XRD of electrode plates after decomposition is common. However, since this method is a destructive test, there is a problem that reuse of the battery is substantially impossible. There is also a conventional dQ/dV detection technique for measuring the Co elution amount, which is a type of deterioration level. However, since it is a destructive inspection in the over-discharge region below 1V of the cell, there is a problem that it cannot be used for controlling the nickel-metal hydride storage battery mounted on the vehicle.

Therefore, the problem to be solved by the control method and control device for a nickel-metal hydride storage battery of the present invention is to detect a sign of the generation of Ni ₂ O ₃ H that leads to a decrease in capacity, and to control the generation of Ni ₂ O ₃ H in the nickel-metal hydride storage battery. It is to control so as to suppress generation.

In order to solve the above-mentioned problems, a method for controlling a nickel-metal hydride storage battery according to the present invention is a method for controlling a nickel-metal hydride storage battery that is performed by a control device that controls charging and discharging of the nickel-metal hydride storage battery based on voltage and current, wherein the control The device performs an SOC acquisition step of acquiring the SOC of the nickel-metal hydride storage battery, and when the SOC reaches a set low SOC or less, charges the nickel-metal hydride storage battery at a set rate and indicates the relationship between the battery capacity and the battery voltage OCV. A charging step of acquiring a charging curve, a dQ/dV conversion step of replacing the charging curve with a dQ/dV curve that is a capacitance change with respect to a voltage change, and a relationship of the dQ/dV value with respect to the total discharge capacity of the charging Steps of dQ/dV value accumulation accumulated for each step, and when the dQ/dV value becomes equal to or less than the set threshold value, the relationship of the dQ/dV value with respect to the total discharge capacity at that time, and the previously acquired and a dQ/dV value estimation step of estimating the dQ/dV value for the subsequent total discharge capacity based on plotted points representing the relationship of the dQ/dV value for the total discharge capacity.

Further, in the relationship of the dQ/dV value with respect to the total discharge capacity estimated in the step of estimating the dQ/dV value, when the dQ/dV value with respect to the set total discharge capacity is equal to or less than the set threshold value, the nickel metal hydride It is possible to limit the discharge rate of the storage battery.

It is preferable that the discharge rate is limited in a set low SOC region. Further, the set low SOC region can be SOC 50[%] or less.
In the subsequent dQ/dV value for the total discharge capacity estimated in the step of estimating the dQ/dV value after limiting the discharge rate of the nickel-metal hydride storage battery, the dQ/dV value for the set total discharge capacity becomes equal to or less than the set threshold. In this case, the discharge rate of the nickel-hydrogen storage battery can be further limited.

In the charging step, the set low SOC can be 20 to 40 [%]. In the charging step, the set rate may be 3C or less.
The nickel-metal hydride storage battery control device of the present invention controls charging and discharging of the nickel-metal hydride storage battery based on a voltage measuring device, a current measuring device, and the voltage measured by the voltage measuring device and the current measured by the current measuring device. The control device includes an SOC acquisition step of acquiring the SOC of the nickel-metal hydride storage battery, and when the SOC reaches a set low SOC or less, the nickel-metal hydride storage battery is charged at a set rate to restore the battery A charging step of acquiring a charging curve showing the relationship between capacity and battery voltage OCV, a dQ / dV converting step of replacing the charging curve with a dQ / dV curve that is a capacity change with respect to voltage change, and a dQ for the total discharge capacity. A dQ/dV value accumulation step of accumulating a /dV value relationship for each step of the charging, and a dQ/dV value for the total discharge capacity at that time when the dQ/dV value becomes equal to or less than a set threshold value. and a dQ/dV value estimation step of estimating the dQ/dV value for the subsequent total discharge capacity based on the previously obtained relationship of the dQ/dV value for the total discharge capacity. and

The nickel-metal hydride storage battery is a battery for driving a vehicle, and can be suitably implemented when the control device is mounted on the vehicle.

The method and apparatus for controlling a nickel-metal hydride storage battery of the present invention detect a sign of the generation of Ni ₂ O ₃ H, which leads to a decrease in capacity, and control the generation of Ni ₂ O ₃ H in the nickel-metal hydride storage battery to be suppressed. be able to.

4 is a graph showing the relationship between the abundance ratio (%) of Ni ₂ O ₃ H in the positive electrode and the capacity ratio (%) of the battery. FIG. 2(a) is a schematic diagram showing oxygen in reaction during charging of the particle surfaces 22b of the particles 22a of the positive electrode active material 2 of the positive electrode of the nickel-metal hydride storage battery. FIG. 2(b) is a reaction formula showing a normal main reaction of the positive electrode during discharge and an abnormal side reaction when oxygen is generated and local "liquid depletion" occurs. 4 is a graph showing charge/discharge curves of a nickel-metal hydride storage battery. 4 is a graph showing the slope of the charging/discharging curve of the nickel-metal hydride storage battery as a dQ/dV curve. 4 is a graph showing a charging curve for forced charging according to the present embodiment; 4 is a flow chart showing an example of the procedure of a method for controlling a nickel-metal hydride storage battery according to the present embodiment; 1 is a block diagram of a control device for a nickel-metal hydride storage battery according to this embodiment; FIG. 4 is a graph showing dQ/dV with respect to the total discharge capacity [Ah] of a nickel-metal hydride battery according to a conventional nickel-metal hydride battery control method. FIG. 10 is a graph showing an example of plot points in the procedure of (total discharge capacity [Ah])/(dQ/dV) plot point storage (S9); FIG. 4 is a graph showing a straight line in the procedure for estimating (S11) the total discharge capacity EA [Ah] that satisfies dQ/dV= _TD based on the two most recent plotted points; 4 is a graph showing dQ/dV with respect to the total discharge capacity [Ah] of the nickel-metal hydride storage battery after it is determined that "EA≦target total discharge capacity SA (S12)" and "discharge rate limitation (S13)" is performed. After "limiting the discharge rate (S13)", it is further determined that "EA ≤ target total discharge capacity SA (S12)" in estimation based on the plotted point and the two plotted points immediately before that, and further 4 is a graph showing dQ/dV with respect to the total discharge capacity [Ah] of the nickel-metal hydride storage battery after "limiting the discharge rate (S13)";

<Principle of this embodiment>
A control method for a nickel-metal hydride storage battery according to the present invention will be described below using one embodiment with reference to FIGS. 1 to 12. FIG.

<Assumptions of this embodiment>
The method for inspecting a nickel-metal hydride storage battery according _to the present embodiment aims at detecting the formation of _Ni2O3H . Therefore, first, the mechanism of formation of Ni ₂ O ₃ H will be described.

<Surface of Particles of Positive Electrode Active Material>
FIG. 2(a) is a schematic diagram showing oxygen in reaction during charging of the particle surfaces 22b of the particles 22a of the positive electrode active material 2 of the positive electrode of the nickel-metal hydride storage battery. FIG. 2(b) is a reaction formula showing a normal main reaction of the positive electrode during discharge and an abnormal side reaction when oxygen is generated and local "liquid depletion" occurs.

<Main reaction at positive electrode during discharge>
Particles 22a of positive electrode active material 2 change between Ni(OH) ₂ and β-NiOOH due to charging and discharging. For convenience of explanation, Ni(OH) ₂ may be used as a representative positive electrode active material. A normal main reaction during discharge of a nickel-metal hydride storage battery is that Ni(OH) ₂ and OH ⁻ are produced from β-NiOOH on the premise of the presence of H ₂ O, as shown in the following equation (1). In this case, H ₂ O in the electrolyte is consumed and reduced. OH ⁻ acts as an alkali ion of the alkaline electrolyte 4 . In this case, the exchange of ions and electrons does not generate gases such as oxygen O ₂ and hydrogen H ₂ .

β-NiOOH+H ₂ O+e ⁻ →Ni(OH) ₂ +OH ⁻ (1)
<Generation of Oxygen and Occurrence of “Liquid Depletion” Due to Side Reaction>
Depending on the conditions of use, the potential of the positive electrode may become low. When the potential for electrolysis of H ₂ O is reached, electrolysis of H ₂ O occurs as a side reaction. In the electrolysis of H ₂ O, O ₂ is generated at the positive electrode by the reaction represented by the following formula (2).

4OH ⁻ →O ₂ +2H ₂ O+4e ⁻ (2)
As shown in FIG. 2(a), when the particle surface 22b of the positive electrode active material of Ni(OH) ₂ /β-NiOOH, which is the positive electrode active material, becomes a low potential due to charging, the potential as shown in the above equation (2) is reached. A side reaction occurs, and O ₂ bubbles A are generated on the particle surface 22b of the positive electrode active material. When O ₂ is generated at the positive electrode during charging, bubbles A of O ₂ adhere to the particle surface 22b of the positive electrode active material. The O ₂ bubbles A separate from the particle surface 22b of the positive electrode active material over time. Then, the place where the air bubble A has left comes into contact with the alkaline electrolyte 4, and H ₂ O and OH ^- are supplied.

However, depending on the conditions, it may take time for the O ₂ generated on the particle surfaces 22b of the positive electrode active material to leave the particle surfaces 22b of the positive electrode active material like the bubbles B. Thus, the O ₂ bubbles such as the bubbles B adhering to the particle surface 22b of the positive electrode active material block the alkaline electrolyte locally. As a result, the H ₂ O and OH ⁻ on the particle surface 22b of the positive electrode active material are physically removed, and the portion is locally “liquid dried”. Neither H ₂ O nor OH ^— are physically present here.

<Generation of Ni ₂ O ₃ H by “liquid drying”>
Then, in a normal reaction, H ₂ O is required for the reaction as shown in formula A _in FIG. A side reaction occurs, resulting in a reaction such as the following formula (3).

16β-NiOOH+4e ⁻ →8Ni ₂ O ₃ H+2H ₂ O+O ₂ +4OH ⁻ (3)
In other words, it reacts without using H ₂ O and produces H ₂ O on the contrary. As products at that time, Ni ₂ O ₃ H, O ₂ and OH ⁻ are generated. Of these, O ₂ is smoothly absorbed by the negative electrode (recombination reaction) through the separator as shown in formula (4) below as time elapses, maintaining a closed system. OH ⁻ returns to the alkaline electrolyte 4 .

4MH+ _O2 →4M+ _2H2O (4)
Here, Ni ₂ O ₃ H is an electrochemically inactive product, and when Ni ₂ O ₃ H is generated, it accumulates irreversibly, causing an increase in battery resistance and a decrease in battery capacity. is at issue. Therefore, the generation of Ni ₂ O ₃ H is usually suppressed as undesirable.

<Memory effect of nickel metal hydride storage battery>
Next, the memory effect of the nickel-metal hydride storage battery will be explained. It is known that a memory effect occurs in a nickel-metal hydride storage battery when it is repeatedly charged and discharged at a low SOC. In a battery system with a memory effect, the voltage shifts to the noble side during charging. As a result, even if the SOC is the same, the potential of the positive electrode increases during charging, making it particularly easy for O ₂ to be generated. On the other hand, since the discharge curve shifts to the base side during discharge, the positive electrode potential is low. As a result, at the place where oxygen is generated on the particle surface 22b of the positive electrode active material, the dryness of the liquid occurs locally instantaneously. When discharging is performed in a state in which H ₂ O is insufficient, the discharge voltage shifts to the base, and the positive electrode potential stays lower than usual, thereby approaching the generation potential of Ni ₂ O ₃ H. Therefore, Ni ₂ O ₃ H is produced at the same time as the reaction that attempts to produce insufficient H ₂ O as shown in the above formula (3). The formation of Ni ₂ O ₃ H causes a rapid capacity decrease as shown in FIG.

<Mechanism of Ni ₂ O ₃ H Generation in Nickel Metal Hydride Battery>
As described above, in the nickel-hydrogen storage battery, Ni ₂ O ₃ H generates oxygen O ₂ gas as a side reaction of charging due to the potential of the positive electrode during charging, and the internal pressure of the secondary battery rises. The O ₂ causes "liquid depletion", and the mechanism by which Ni ₂ O ₃ H is produced was analyzed.

The present inventor presumes that "liquid depletion" occurs when the decrease in positive electrode potential during charging becomes the potential for oxygen generation, and when oxygen O ₂ gas is actually generated and the internal pressure is high. and proved this.

<Memory effect of in-vehicle nickel-metal hydride storage battery>
Next, the memory effect of the in-vehicle nickel-metal hydride storage battery will be described. A hybrid vehicle or the like equipped with an electric motor drives the electric motor with electric power stored in a driving nickel-metal hydride storage battery. 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. Such in-vehicle nickel-metal hydride storage batteries may be exposed to harsh operating environments. For example, charging and discharging may be repeated in a low SOC (State Of Charge) state. For example, when the SOC falls below 40%, the motor generator 17 runs out of drive power. Therefore, by operating the engine until the SOC reaches 60%, for example, by the control device 10, the motor generator 17 generates power to quickly charge the nickel-metal hydride storage battery in a short time. It is known that a memory effect is likely to occur in such a usage environment. The memory effect causes a positive shift in the battery charge curve. That is, even if the SOC is the same, the positive electrode potential becomes higher. On the other hand, during discharge, the discharge curve of the battery shifts to the base. That is, even if the SOC is the same, the positive electrode potential becomes lower. Then, Ni ₂ O ₃ H is likely to be generated due to "dryness" due to the mechanism described above.

<Necessity for control of in-vehicle nickel-metal hydride storage batteries>
As shown in FIG. 2(b), once Ni ₂ O ₃ H is generated, it is irreversibly accumulated, resulting in a decrease in the capacity of the nickel-metal hydride storage battery as shown in FIG. Such a nickel-metal hydride storage battery whose capacity has decreased will deteriorate further if control is not carried out according to the deterioration. Therefore, as in Patent Document 1 cited in the description of the prior art, an invention has been proposed that suppresses the generation of Ni ₂ O ₃ H by controlling a nickel-metal hydride storage battery mounted on a vehicle.

<Generation of Ni ₂ O ₃ H and Decrease in Capacity of Nickel Metal Hydride Storage Battery>
However, once Ni ₂ O ₃ H is generated, it accumulates irreversibly. Then, as shown in FIG. 1, coupled with the memory effect, the capacity decrease progresses further. As the capacity decrease progresses, the voltage further shifts to the noble side, creating an environment in which Ni ₂ O ₃ H is likely to be generated at an accelerated rate. As a result, as shown in FIG. 8, the capacity of the battery is abruptly decreased with use. Therefore, it is necessary to predict the generation of Ni ₂ O ₃ H even if it is a small amount, and avoid the generation by control.

<Deterioration of Ni-MH storage batteries due to use and charge/discharge curves>
Graph C0 of the charge curve and graph D0 of the discharge curve of a new nickel-metal hydride storage battery with no usage history have been described with reference to FIG. This charge/discharge curve changes according to deterioration due to use.

<Degradation and charge curve>
In FIG. 3, graph C0 shows a charging curve during charging of an unused nickel-metal hydride storage battery. On the other hand, graph C1 shows a charging curve when charging a nickel-metal hydride storage battery using 1800 Ah. Graph C2 shows a charge curve during charging of a nickel-metal hydride storage battery that uses 2920 Ah. Graph C3 shows a charge curve during charging of a nickel-metal hydride storage battery using 3070 Ah. Graph C4 shows a charge curve during charging of a nickel-metal hydride storage battery using 3080 Ah.

Graph C1 shows a charge curve when a nickel-metal hydride storage battery with a usage history of 1800 [Ah] is charged. In all graphs C0 to C4, the charging conditions are the same, from a fully discharged module voltage of 6.0 [V] at SOC 0 [%] to a charging rate of 1/3 C, until fully charged at SOC 100 [%]. The characteristics of the charged nickel-metal hydride storage battery change due to deterioration of the active material and the like due to use. Graph C1 is compared with the charging curve C0 of an unused nickel-metal hydride storage battery. By comparison, when charging is started from SOC 0 [%], there is not much difference from graph C0 in that the module voltage [V] is approximately 8.9 [V] and SOC 100 [%]. However, the change in module voltage [V] with respect to the increase in battery capacity [Ah] is different. When the battery capacity [Ah] is about 2.7 [Ah] immediately after the start of charging, the graph C1 shows that the module voltage [V] is lower than the graph C0, and when the battery capacity exceeds about 2.7 [Ah], the graph C1 is higher than the module voltage [V] from the graph C0.

Looking at the slope of the graph, the slope of the graph C0 is almost horizontal near the inflection point IPc. On the other hand, the graph C1 consistently maintains a constant slope or more.
<Deterioration of Ni-MH storage battery due to use and dQ/dV curve>
FIG. 4 is a graph showing the slope of the charge/discharge curve of the nickel-metal hydride storage battery as a dQ/dV curve. As shown in FIG. 4, when these slopes are represented by dQ/dV curves, graph C0 becomes graph RC0 and graph C1 becomes graph RC1.

Here, in the graph RC0 based on the graph C0, as described above, the module voltage [V] was approximately 8.35 [V] and the value of dQ/dV showed a peak of approximately +30. On the other hand, in graph RC1 based on graph C1, the value of dQ/dV shows an extremely gentle peak of approximately dQ/dV=+7 near approximately 8.3 [V].

Graph C2 shown in FIG. 3 shows a charge curve when a nickel-metal hydride storage battery having a usage history of 2920 [Ah] is charged. In this case, the module voltage [V] is higher than the graph C1 at the early stage of charging. Further, graph C3 has a usage history of 3070 [Ah], but shows a higher module voltage [V] than graph C2 at the early stage of charging. Graph C4 shows a higher module voltage [V] than graph C3 at an earlier timing.

As described above, in the history of use, when charging and discharging were repeated at a large amount of current, the deterioration of the active material progressed, and the module voltage [V] increased with a small battery capacity [Ah]. I can confirm. This shows that even if the same battery capacity [Ah] is charged, the SOC [%] of the deteriorated nickel-metal hydride storage battery is higher. Also, a deteriorated nickel-metal hydride storage battery tends to have a higher SOC [%]. This means that the potential in the nickel-metal hydride storage battery is such that oxygen is likely to be generated, and the environment is such that Ni ₂ O ₃ H is likely to be generated.

For example, in the graphs C0 and C1, the usage history repeats many charges and discharges from 0 [Ah] to 1800 [Ah] and 1800 [Ah], but the module potential [V] at the same electric capacity [Ah] is not much different. However, in the graphs C3 and C4, a clear increase in the module voltage [V] can be confirmed even though the usage history is only 10 [Ah] from 3070 [Ah] to 3080 [Ah]. . In other words, it can be understood that once the deterioration of the nickel-metal hydride storage battery begins to progress as the usage history becomes longer, the deterioration progresses at an accelerated pace, causing a rapid capacity decrease.

<dQ/dV of this embodiment>
FIG. 5 is a schematic graph showing a charging curve for forced charging according to the present embodiment. In this embodiment, when the SOC of the nickel-metal hydride storage battery falls below 40%, the charging rate is automatically reduced by the vehicle control device until the SOC reaches 60% in order to secure the remaining capacity. Forced charging is performed by keeping the voltage constant at 3C. Here, the average value of dQ/dV from SOC 40[%] to SOC 60[%] is used as the dQ/dV value in the charging step. That is, the difference in capacity between SOC 60 [%] and SOC 40 [%] was divided by the voltage difference between V 60 [V], which is the OCV of SOC ₆₀ [%], and V ₄₀ [V], which is the OCV of SOC 40 [%]. value. In this way, the dQ/dV value is acquired under the constant conditions of the SOC at the start of charging, the SOC at the end of charging, and the charging rate of 3C. Therefore, the dQ/dV values obtained here can be compared in time series. That is, it is possible to accurately detect changes in deterioration.

This dQ/dV value also decreases when Ni ₂ O ₃ H is produced in the nickel-hydrogen storage battery, as described above.
<Principle of Control Method for Nickel Metal Hydride Storage Battery of Present Embodiment>
Here, the principle of the method for controlling the nickel-metal hydride storage battery according to the present embodiment discovered by the inventors based on the above knowledge is summarized as follows. First, a charging curve at a low SOC of the nickel-metal hydride storage battery under a certain condition of forced charging is acquired, and dQ/dV is calculated from this. The inventors have found that it is possible to estimate the production of Ni ₂ O ₃ H in the nickel-metal hydride storage battery based on this dQ/dV value. In addition, the present inventors have found that the further generation of Ni ₂ O ₃ H is largely caused by the generation of oxygen during rapid discharge at low SOC. By appropriately limiting the discharge rate at low SOC according to the deterioration of the nickel-metal hydride storage battery estimated based on this, rapid deterioration is avoided and the necessary life of the nickel-metal hydride storage battery is ensured.

(Configuration of this embodiment)
<Nickel metal hydride storage battery>
A nickel-metal hydride storage battery, which is the premise of this embodiment, will be briefly described below. The nickel-metal hydride storage battery of this embodiment is a vehicle-mounted battery used as a power source for driving a vehicle such as a hybrid vehicle. It is a battery consisting of a battery module configured by electrically connecting a plurality of single cells, which are sealed batteries, in series in order to obtain a required power capacity as a nickel-metal hydride storage battery mounted on a vehicle. OCV (Open Circuit Voltage) in this embodiment means the module voltage of the battery module.

A battery module has a rectangular parallelepiped prismatic case composed of an integrated battery case capable of accommodating a plurality of cells and a lid body for sealing the integrated battery case. A resin-made case can be used for this rectangular case.

The integrated battery case that constitutes the rectangular case is made of a synthetic resin material, such as polypropylene or polyethylene, that is resistant to an alkaline electrolyte. A partition wall is formed inside the integrated battery case to partition a plurality of cells, and the portion partitioned by the partition wall serves as a battery case for each battery. The integrated battery case has, for example, six battery cases.

<Structure of Electrode Group>
In the compartmentalized container, an electrode plate group, and a positive electrode collector plate and a negative electrode collector plate joined to both sides of the electrode plate group are accommodated together with an electrolytic solution. The electrode plate group is configured by laminating a rectangular positive electrode plate and a negative electrode plate with a separator interposed therebetween. Electrode groups of adjacent battery cases are electrically connected in series. The total output of the series-connected electrode plate group, ie, the plurality of single cells, is taken out from the positive connection terminal and the negative connection terminal.

<Positive plate>
For the positive electrode plate, a foamed nickel three-dimensional porous body made of Ni or a Ni alloy, which is a porous metal, is used as a positive electrode base material. The positive electrode substrate has a bone portion having a three-dimensional network structure and a hole portion surrounded by the bone portion. The positive electrode substrate is manufactured, for example, by nickel-plating the surface of the urethane skeleton of foamed urethane and then burning off the foamed urethane. The positive plate comprises a positive composite layer containing Ni(OH) ₂ and Co as active materials. Specifically, to granular nickel hydroxide, add an appropriate amount of a conductive agent such as cobalt hydroxide or metallic cobalt powder, and if necessary, a thickener such as carboxymethyl cellulose or a binder such as polytetrafluoroethylene, and then paste it. processed into a shape. After that, the paste-like processed material is filled into the mesh-like holes of the positive electrode substrate to form a positive electrode mixture layer. After that, it is dried, rolled, and cut to form a plate-like positive electrode plate.

<Negative plate>
The negative electrode plate 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. After that, 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 into a plate-like negative electrode plate. Form.

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

The battery module of the nickel-metal hydride storage battery of this embodiment has the configuration described above.
<Control Device for Nickel Metal Hydride Storage Battery of Present Embodiment>
Next, an example of a control device for a nickel-metal hydride storage battery, which is a premise of the present embodiment, will be briefly described. The control method of the present embodiment, which can detect signs of rapid deterioration of a nickel-metal hydride storage battery and can control it, can be suitably applied to a nickel-metal hydride storage battery mounted on a vehicle for driving. Therefore, here, a control device for such a nickel-metal hydride storage battery as a secondary battery for driving a vehicle will be briefly described.

<Control device 10 for nickel-metal hydride storage battery>
FIG. 7 is a block diagram of the control device 10 for the nickel-metal hydride storage battery of this embodiment. The control device 10 for the nickel-metal hydride storage battery will be described with reference to FIG. Here, the nickel-metal hydride storage battery is controlled in the state of the battery pack containing the battery module 90 .

<Control device 10>
A control device 10, which is a battery control device, is mounted on a vehicle and can control a battery module 90 of the vehicle in real time or based on accumulated data so-called onboard. This control device corresponds to a control device that controls charging and discharging of the nickel-hydrogen storage battery based on the voltage measured by the voltage measuring device and the current measured by the current measuring device of the present invention.

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. This current detector 21 corresponds to the current measuring device of the present invention. The voltage detector 22 corresponds to the voltage measuring device of the invention.

The temperature detector 23 has a temperature sensor. The temperature sensor measures the temperature in the vicinity of the electrode plate group of the corresponding unit cell in 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 sequentially acquires charge/discharge current values from the current detector 21, voltage values from the voltage detector 22, and 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 includes a program for executing the flowchart shown in FIG.

In addition, the storage unit 13 stores in advance the “threshold” of the dQ/dV value and the like as data on which control is performed.
<dQ/dV calculator 14>
The dQ/dV calculator 14 estimates a change in battery capacity [Ah] from the battery module 90 charged and discharged by the charge/discharge controller 16, and generates a charge curve from the module voltage OCV [V]. . In this case, since the battery capacity [Ah] is a vehicle-mounted battery, it is impossible to accurately measure the battery capacity [Ah] by charging and discharging from a fully discharged SOC of 0 [%] to a fully charged SOC of 100 [%]. Have difficulty. Therefore, the battery capacity [Ah] is estimated within the SOC [%] range in which problems in vehicle operation are unlikely to occur. In this embodiment, when the SOC becomes a low SOC of 40[%], the charging rate is kept constant at 3C, and the dQ/dV value is acquired using the vehicle battery control that forcibly charges the SOC to 60[%]. are doing. Therefore, deterioration of the nickel-metal hydride storage battery can be detected by comparing the dQ/dV values acquired under the same conditions in time series.

<Determination unit 15>
The determination unit 15 compares the dQ/dV value calculated by the dQ/dV value calculation 14 with a pre-stored threshold value to determine whether or not the on-vehicle nickel-metal hydride storage battery can complete the set life. In addition, the control unit 11 restricts the conditions for discharging when the SOC of the battery module 90 is low according to the amount of Ni ₂ O ₃ H produced estimated from the dQ/dV value, thereby preventing rapid deterioration of the nickel-metal hydride storage battery. suppress In this procedure, the life of the nickel-metal hydride storage battery is extended so that the operation of the vehicle is not hindered, and control is performed so that the set battery life can be completed.

<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 value of 40[%], the motor generator 17 generates power and the charge rate is changed to 3C through the inverter 20. to charge the battery module 90 until the SOC reaches 60 [%]. In this embodiment, the battery control itself of the vehicle is used to obtain the charging curve when charging is performed under certain conditions. A technical feature is that by obtaining the dQ/dV value from this, a dQ/dV value that can be compared in time series can be obtained.

On the other hand, the charge/discharge control unit 16 charges the battery module 90 by supplying regenerated current from the motor generator 17 through the inverter 20 during braking of the vehicle as other normal control. In this case, the charge/discharge control unit 16 limits charging 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 . Further, in the present embodiment, charging and discharging are controlled so that the potential of the positive electrode becomes a potential at which O ₂ is not generated so that Ni ₂ O ₃ H is not generated.

On the other hand, when the vehicle is driven, the charge/discharge control unit 16 supplies necessary current 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).

In particular, when the determination unit 15 detects deterioration of the nickel-metal hydride storage battery, the charge/discharge control unit 16 prevents rapid generation of Ni ₂ O ₃ H by, for example, avoiding rapid discharge when the SOC is low. Suppress.

<Procedure of control method for nickel-metal hydride storage battery of the present embodiment>
FIG. 6 is a flow chart showing an example of the procedure of the method for controlling the nickel-metal hydride storage battery of this embodiment. Next, the flow chart of FIG. 6 outlines the procedure for predicting the generation of Ni ₂ O ₃ H and avoiding the generation of Ni ₂ O ₃ H by control using the method for controlling a nickel-metal hydride storage battery according to the present embodiment. will be described with reference to

<Overview of procedure>
First, as a preparation, an appropriate threshold is set according to the characteristics of the nickel-metal hydride storage battery to be controlled in a "threshold setting step (S1)". Next, in operation of the vehicle, the SOC, which is the basis of control, is acquired by "SOC estimation (S2)". Then, it is determined whether or not the current SOC is in a low SOC state by "SOC≤40%? (S3)". If the SOC is low, in "forced charging/charging curve acquisition (S4)", in order to recover the remaining capacity of the nickel-metal hydride storage battery, while performing forced charging, the charging power amount at that time and the OCV of the nickel-metal hydride storage battery to get Then, while monitoring the SOC in the procedure of "SOC estimation (S5)", when "SOC > 60%? (S6)", "end charging (S7)".

Along with "calculating dQ/dV from the acquired charging curve (S8)", "(total discharge capacity [Ah])/(dQ/dV) plot point storage (S9)" is performed.
If "dQ/dV≤T _W (S10)", "estimate the total discharge capacity EA [Ah] that satisfies dQ/dV=T _D based on the two most recent plot points (S11)". As a result, if "EA ≤ target total discharge capacity SA (S12)", it is predicted that the target nickel-metal hydride storage battery will not have a life up to the target total discharge capacity [Ah] under the current control. . Degradation of the nickel-metal hydride storage battery is suppressed by performing "restriction of the discharge rate (S13)" based on this prediction.

After that, in the procedure from S2 to S12 again, if it is predicted that the target nickel-metal hydride storage battery will not have a life up to the target total discharge capacity [Ah] even with the control that limits the discharge rate, Discharge rate limitation (S13)” is performed. By repeating this procedure, control is performed to limit the discharge rate so that the nickel-metal hydride storage battery has a life up to the target total discharge capacity [Ah]. Each procedure will be described in detail below.

<Threshold Setting Step (S1)>
The characteristics of the nickel-metal hydride storage battery to be used are obtained in advance. Here, a charge curve from complete discharge to full charge from SOC 0 [%] to SOC 100 [%] as shown in FIG. Measure the degree of deterioration of the nickel-metal hydride storage battery. Then, the threshold is determined based on the relationship between the degree of deterioration and the dQ/dV value. In this embodiment, the dQ/dV value when forced charging is performed at a charging rate of 3C at an SOC of 40 to 60[%] is used as the threshold.

The dQ/dV value at which the dQ/dV value begins to decrease rapidly with respect to the total discharge capacity [Ah] is set as the "warning threshold value T _W ". For example, in this embodiment, dQ/dV=40. If it is smaller than this warning threshold _TW , the possibility of Ni ₂ O ₃ H being generated increases.

Also, the dQ/dV value indicating the limit of the nickel-metal hydride storage battery is set as the "limit threshold _TD ". For example, in this embodiment, dQ/dV=20. If the dQ/dV value is smaller than this "critical threshold T _D ", Ni ₂ O ₃ H may be generated rapidly.

Also, the target total discharge capacity of the nickel-metal hydride storage battery is set as the "target total discharge capacity SA". This is the remaining life expectancy of the battery when mounted in a vehicle. In this embodiment, the target total discharge capacity SA is set to 4000 [Ah].

<SOC estimation (S2)>
Control device 10 estimates the current SOC based on voltage OCV from voltage detector 22 . This procedure corresponds to the "SOC acquisition step" of the present invention.

<SOC≤40[%]? (S3)>
The control device 10 determines whether or not the obtained SOC satisfies "SOC≦40[%]". That is, it is determined whether the nickel-metal hydride storage battery has reached the set low SOC and forced charging is necessary. Here, if it is not "SOC≤40[%]" (S3: NO), monitoring is continued by estimating the SOC (S2). On the other hand, if "SOC≤40[%]" (S3: YES), forced charging (S4) is performed.

<Acquisition of forced charging/charging curve (S4)>
FIG. 3 is a graph showing an example of a charging curve in forced charging (S4). This procedure corresponds to the "charging step" of the present invention. In the case of this embodiment, the forced charging (S4) is performed by the internal combustion engine (not shown) in FIG. do. The charge rate at this time is adjusted to be 3C by the charge/discharge controller.

During execution of this forced charging, the dQ/dV calculator 14 calculates a charging curve that is the relationship between the open battery voltage OCV and the SOC based on the current and voltage obtained by the current detector 21 and the voltage detector 22. and stored in the storage unit 13.

<SOC estimation (S5)>
The dQ/dV calculator 14 sequentially estimates the SOC at that time according to the progress of the forced charging that has started.

<SOC> 60 [%]? (S6)>
Here, it is determined whether or not "SOC>60[%]" (S6). That is, it is determined whether or not the nickel-metal hydride storage battery has exited the low SOC. Here, if it is determined that "SOC>60[%]" is not true (S6: NO), it is assumed that the low SOC has not yet been overcome, and forced charging (S4) is continued. On the other hand, if it is determined that "SOC>60[%]" (S6: YES), it is determined that the nickel-metal hydride storage battery has exited the low SOC.

<End of charging (S7)>
If it is determined that "SOC>60[%]" (S6: YES) and the nickel-metal hydride storage battery has exited the low SOC, forced charging (S4) is terminated (S7).

<Calculation of dQ/dV from Acquired Charging Curve (S8)>
As shown in FIG. 5, during the forced charging (S4), the increment V ₆₀ −V ₄₀ =ΔV [V] in the OCV of the nickel-metal hydride storage battery and the increment ΔQ [Ah] in the capacity of the nickel-metal hydride storage battery are calculated. be done. Then, the dQ/dV calculation unit 14 divides ΔQ [Ah] during the forced charging by ΔV [V] to calculate the average dQ/dV value during the forced charging (S4), and the storage unit 13 memorize to This procedure corresponds to the "dQ/dV conversion step" of the present invention.

<(Total discharge capacity [Ah])/(dQ/dV) plot point storage (S9)>
FIG. 9 is a graph showing an example of plot points in the procedure of (total discharge capacity [Ah])/(dQ/dV) plot point storage (S9). The vertical axis indicates dQ/dV [Ah/V], and the horizontal axis indicates total discharge capacity [Ah].

As shown in FIG. 9, for example, when forced charging is performed for the first time after the start of use, the relationship between the total discharge capacity [Ah] and the dQ/dV value is accumulated. That is, the plot point _P0 of (total discharge capacity [Ah], (dQ/dV))=(0, 60) is plotted. The next plotted point _P1 is approximately (300, 51), and the next plotted point _P2 is approximately (700, 43). The next plotted point _P3 is approximately (1100,34). In practice, more plot points than shown in FIG. 9 are plotted, but they are extremely omitted in FIG. 9 for explanation of the concept. This procedure corresponds to the "dQ/dV value accumulation" step of the present invention.

<dQ/ _dV≤TW ? (S10)>
Next, it is determined whether or not "dQ/dV≤T _W " (S10). That is, it is determined whether or not the dQ/dV value has reached the warning threshold _TW based on deterioration due to use. If not "dQ/dV≤T _W " (S10: NO), the procedure from S2 to S9 is repeated. If “dQ/dV≦T _W ” (S10: YES), proceed to the next step of S11.

In this embodiment, the warning threshold _TW is set to dQ/dV=40. Here, the plotted point _P2 shown in FIG. 9 is approximately (700, 43), so it does not reach 40, which is the warning threshold _TW . The next plotted point, _P3 , is approximately (1100, 34), so it is below the warning threshold _TW of 40.

<Estimate the total discharge capacity EA [Ah] where dQ/dV= _TD based on the two most recent plot points (S11)>
If “dQ/dV≦T _W ” (S10: YES), the total discharge capacity EA [Ah] that satisfies dQ/dV= _TD is estimated based on the two most recent plotted points (S11). Here, the “limit threshold T _D ” is the dQ/dV value for satisfying the minimum battery performance. When the dQ/dV value falls below the limit threshold _TD , the nickel-metal hydride storage battery cannot exhibit sufficient performance.

FIG. 10 is a graph showing the expected straight line _L1 in the procedure for estimating (S11) the total discharge capacity EA [Ah] that satisfies dQ/dV= _TD based on the two most recent plotted points. Here, the plotted point _P3 shown in FIG. 9 is the plotted point below 40, which is the warning threshold _TW . Also, the plot point _P2 is the plot point plotted immediately before. Therefore, the straight line connecting the plotted points _P2 and _P3 is defined as the expected straight line _L1 . As this predicted straight line _L1 is extended, it reaches the limit threshold _TD . The total discharge capacity [Ah] at this time is assumed to be the estimated total discharge capacity EA [Ah].

In the example shown in FIG. 10, the estimated total discharge capacity EA [Ah] is approximately 1800 [Ah]. In other words, if the discharge rate allowed for the current nickel-metal hydride storage battery is controlled to 3C, under this control, the nickel-metal hydride storage battery will be discharged when the total discharge capacity [Ah] reaches 1800 [Ah]. We can assume that it will be unusable. This procedure corresponds to the "dQ/dV value estimation step" of the present invention.

<EA≦target total discharge capacity SA? (S12)>
Next, it is determined whether or not "EA≦target total discharge capacity SA" (S12). If it is determined that "EA≦target total discharge capacity SA" is not satisfied (S12: NO), the procedure from S2 to S11 is repeated. On the other hand, if "EA≤target total discharge capacity SA" (S12: YES), the process proceeds to the next procedure for limiting the discharge rate (S13).

Here, the target total discharge capacity SA of this embodiment is set to 4000 [Ah]. On the other hand, the estimated total discharge capacity EA [Ah] estimated in S11 was approximately 1800 [Ah]. That is, in the current control of the nickel-metal hydride storage battery, it is estimated that the nickel-metal hydride storage battery cannot be used when the total discharge capacity [Ah] reaches 1800 [Ah]. It means that a certain 4000 [Ah] cannot be reached.

<Restriction of Discharge Rate (S13)>
As shown in FIG. 10, in the current control of the nickel-metal hydride battery, that is, the method of allowing the discharge rate up to 3C, the nickel-metal hydride battery becomes unusable when the total discharge capacity [Ah] reaches 1800 [Ah]. It is estimated to be. Therefore, it is necessary to change the control method that allows the current discharge rate up to 3C.

Therefore, the present inventors have confirmed by experiments that Ni ₂ O ₃ H is easily generated by discharging at a high rate when the SOC is low. Therefore, for example, when the SOC is 50% or less, the current discharge rate of 3C is limited to a lower discharge rate, for example, 2C (S13).

FIG. 11 is a graph showing dQ/dV with respect to the total discharge capacity [Ah] of the nickel-metal hydride storage battery after it is determined that "EA ≤ target total discharge capacity SA (S12)" and the "discharge rate limit (S13)" is performed. be. It is considered that the control that allows a discharge rate up to 3C so far follows a transition like the future prediction straight line _L1 . Therefore, if the discharge rate at an SOC of 50% or less is limited to, for example, 2C, the deterioration of the nickel-metal hydride storage battery is expected to follow the expected straight line _L2 . However, it is unclear what kind of deterioration actually occurs at this stage. Therefore, in the control method of the nickel-metal hydride storage battery of the present embodiment, returning to "Estimation of SOC (S2)" again, "Total discharge capacity SA where dQ/dV= _TD based on the two most recent plot points ] is performed until the step (S11).

FIG. 12 shows estimation based on two plotted points, plotted point _P4 and immediately preceding plotted point _P3 after the "discharge rate limitation (S13)". Further, it shows a state in which it is determined that "EA≦target total discharge capacity SA (S12)". And, it is a graph showing the dQ/dV value with respect to the total discharge capacity [Ah] of the nickel-metal hydride storage battery after "limiting the discharge rate (S13)".

Then, a predicted straight line _L2 is obtained from the newly acquired plot point _P4 and the immediately preceding plot point _P3 . At the stage of FIG. 11, it can be expected that deterioration could be suppressed by restricting the discharge rate (S13), but the expected straight line _L2 has not yet been obtained. After the discharge rate is restricted (S13) and the new plot point _P4 is obtained (S9), the predicted straight line _L2 can be obtained for the first time (S11).

As shown in FIG. 12, the estimated total discharge capacity EA [Ah] is approximately 2600 [Ah] according to the predicted straight line _L2 obtained based on the plotted points _P3 and _P4 . In other words, the discharge rate allowed for current nickel-metal hydride storage batteries is limited and controlled to 2C. Under this control, it can be estimated that the nickel-metal hydride storage battery will become unusable when the total discharge capacity [Ah] reaches 2600 [Ah] (S11).

As a result, the estimated total discharge capacity EA [Ah] of 2600 [Ah] is less than the target total discharge capacity SA of 4000 [Ah] (S12: NO). Therefore, the discharge rate is restricted again (S13), and the discharge rate at SOC 50% or less, which had been restricted to 2C, is further restricted to, for example, 1C.

In such a case, when the next plot point is obtained again, for example, the predicted straight line _L3 is obtained, and the estimated total discharge capacity EA [Ah] exceeds the target total discharge capacity SA of 4000 [Ah]. ing. In this manner, the above procedure is repeated so that the estimated total discharge capacity EA [Ah] does not reach the target total discharge capacity SA of 4000 [Ah].

(Action of this embodiment)
The operation of the nickel-metal hydride storage battery control method of the present embodiment is as follows. First, forced charging is performed from SOC 40[%], which is the low SOC of the nickel-metal hydride storage battery, to SOC 60[%] at a charge rate of 3C. A charge curve in this forced charge is acquired, and dQ/dV is calculated from this. By acquiring the dQ/dV value in forced charging under this constant charging condition, it is possible to compare the dQ/dV values in time series. Therefore, it is possible to accurately estimate the production of Ni ₂ O ₃ H in the nickel-metal hydride storage battery. Further generation of Ni ₂ O ₃ H is largely caused by the generation of oxygen during rapid discharge at low SOC. Therefore, according to the estimated deterioration of the nickel-metal hydride storage battery, the discharge rate of SOC 50[%] or less is appropriately limited stepwise. By performing such control, there is an effect of avoiding rapid deterioration of the on-vehicle nickel-metal hydride storage battery and securing the necessary life of the nickel-metal hydride storage battery.

(Effect of this embodiment)
(1) The method and apparatus for controlling a nickel-metal hydride storage battery according to the present embodiment can accurately estimate the production of Ni ₂ O ₃ H, which causes a decrease in capacity, and accurately detect signs of deterioration.

(2) Further, it is possible to control the generation of Ni ₂ O ₃ H in the nickel-metal hydride storage battery after that based on the accurately detected sign of deterioration. Therefore, a rapid capacity decrease can be avoided.

(3) The inventors have found that the generation of Ni ₂ O ₃ H is largely caused by the generation of oxygen during rapid discharge at low SOC. Therefore, control is achieved by limiting the discharge rate at low SOC (eg, below 50%). Therefore, at a high SOC (for example, an SOC exceeding 50%), discharge is not restricted, so in the case of an in-vehicle nickel-metal hydride storage battery, the impact on running can be reduced.

(4) Since such control is possible if the OCV of the nickel-metal hydride storage battery is known, it is possible to easily control even the drive nickel-metal hydride storage battery mounted on the hybrid vehicle.
(5) Since control is performed repeatedly in real time, it is possible to avoid situations such as sudden stoppage of vehicle operation.

(6) In particular, the dQ/dV value is calculated based on a charging curve in which the charging condition of "forced charging" is constant. Therefore, the dQ/dV values can be accurately compared in time series. Therefore, there is an effect that even a slight change in deterioration of the nickel-metal hydride storage battery is not overlooked as a sign.

(Modification)
The above embodiment can also be implemented as follows.
○ In the embodiment, the predicted straight line _Ln is generated based on the plotted point _Pn and the immediately preceding plotted point Pn _-1 . However, the present invention is not limited to this, and two points may be selected based on time, or may be selected based on dQ/dV.

○ Moreover, the selection of the plot points is not limited to two points, but three or more points may be selected and the predicted straight line L may be obtained by the method of least squares or the like.
○Furthermore, in the above embodiment, for visual explanation, plot point P is selected on the graph of total discharge capacity [Ah]-dQ/dV to obtain expected straight line L. However, the present invention is not limited to this, and of course the creation of the graph itself is not necessary, and it goes without saying that a mode in which calculation is performed inside the control device 10 and controlled is included.

○ Numerical ranges such as dQ/dV, OCV [V], SOC [%], and total discharge capacity [Ah] exemplified in the present embodiment are examples. The present invention is not limited to this, and can be appropriately optimized according to the configuration and characteristics of the target nickel-metal hydride storage battery by those skilled in the art.

○ The threshold can be set with an appropriate margin in anticipation of safety.
(circle) the control apparatus 10 shown in FIG. 7 is an example, and is not limited to such a structure. The control device 10 may perform its functions by means of the ECU of the vehicle. It can also be provided independently within the battery pack.

〇 In this embodiment, the nickel-metal hydride storage battery installed in a hybrid vehicle (HV) was used as an example to describe the present invention. ), a fuel cell vehicle (FV), or the like. Furthermore, it can be suitably applied to batteries for ships and aircraft. Furthermore, it can also be applied to a stationary battery.

○ The flowchart shown in FIG. 6 is an example of implementation of this embodiment, and it is needless to say that a person skilled in the art can change the order of the procedures, add, delete, or change the procedures.

○ Needless to say, even if the present invention is not described in the embodiments, it is possible for those skilled in the art to add, delete, or change the configuration without departing from the scope of the claims.

A... Bubble B... Bubble 2... Positive electrode active material 22a... Particle 22b... Particle surface 4... Alkaline electrolytic solution 10... Control device 11... Control unit 12... Information acquisition unit 13... Storage unit (program, map, etc.)
DESCRIPTION OF SYMBOLS 14... dQ/dV calculation part 15... Judgment part 16... Charge/discharge control part 17... Motor generator 20... Inverter 21... Current detector 22... Voltage detector 23... Temperature detector 24... Battery pack 90... Battery module _TW ... Warning threshold _TD ... Limit threshold EA ... Estimated total discharge capacity SA ... Target total discharge capacity OCV ... Open battery voltage P, P ₀ , P ₁ , ~ P _n ... Plot points L, L ₁ , L ₂ , L ₃ ... Forecast straight line

Claims (9)

A nickel-metal hydride battery control method performed by a control device that controls charging and discharging of a nickel-metal hydride battery based on voltage and current, comprising:
The control device includes an SOC acquisition step of acquiring the SOC of the nickel-metal hydride storage battery;
a charging step of charging the nickel-metal hydride storage battery at a set rate when the SOC reaches a set low SOC or less, and obtaining a charge curve showing the relationship between the battery capacity and the battery voltage OCV;
a dQ/dV conversion step of replacing the charge curve with a dQ/dV curve that is a capacitance change with respect to a voltage change;
a dQ/dV value accumulation step of accumulating the relationship of the dQ/dV value to the total discharge capacity for each charging step;
When the dQ/dV value becomes equal to or less than the set threshold, the relationship between the dQ/dV value with respect to the total discharge capacity at that time and the relationship between the previously acquired dQ/dV value with respect to the total discharge capacity are plotted. and a dQ/dV value estimation step of estimating the dQ/dV value for the subsequent total discharge capacity based on the above. In the relationship of the dQ/dV value with respect to the total discharge capacity estimated in the step of estimating the dQ/dV value, when the dQ/dV value with respect to the set total discharge capacity is equal to or less than the set threshold, the nickel-metal hydride storage battery 2. The method of controlling a nickel-metal hydride storage battery according to claim 1, wherein the discharge rate is limited. 3. The method of controlling a nickel-metal hydride storage battery according to claim 2, wherein the discharge rate is limited in a set low SOC region. 4. The method of controlling a nickel-metal hydride storage battery according to claim 3, wherein the set low SOC region is SOC 50[%] or less. In the subsequent dQ/dV value for the total discharge capacity estimated in the step of estimating the dQ/dV value after limiting the discharge rate of the nickel-metal hydride storage battery, the dQ/dV value for the set total discharge capacity becomes equal to or less than the set threshold. 5. The method of controlling a nickel-metal hydride battery according to claim 2, further comprising limiting the discharge rate of the nickel-metal hydride battery when the battery is discharged. In the charging step,
The method for controlling a nickel-metal hydride storage battery according to any one of claims 1 to 5, wherein the set low SOC is 20 to 40 [%]. In the charging step,
The method for controlling a nickel-metal hydride storage battery according to any one of claims 1 to 6, wherein the set rate is 3C or less. a voltage measuring device, a current measuring device, and a control device for controlling charging and discharging of a nickel-metal hydride storage battery based on the voltage measured by the voltage measuring device and the current measured by the current measuring device,
The control device includes an SOC acquisition step of acquiring the SOC of the nickel-metal hydride storage battery;
a charging step of charging the nickel-metal hydride storage battery at a set rate when the SOC reaches a set low SOC or less, and obtaining a charge curve showing the relationship between the battery capacity and the battery voltage OCV;
a dQ/dV conversion step of replacing the charge curve with a dQ/dV curve that is a capacitance change with respect to a voltage change;
a dQ/dV value accumulation step of accumulating the relationship of the dQ/dV value to the total discharge capacity for each charging step;
When the dQ/dV value becomes equal to or less than the set threshold value, based on the relationship of the dQ/dV value with respect to the total discharge capacity at that time and the previously obtained relationship of the dQ/dV value with respect to the total discharge capacity, and a dQ/dV value estimation step of estimating the dQ/dV value for the total discharge capacity thereafter. 9. The nickel-metal hydride storage battery control device according to claim 8, wherein the nickel-metal hydride storage battery is a battery for driving a vehicle, and the control device is mounted on the vehicle.

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