Nickel-metal hydride battery control method and control device

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

[Technical Field]

[0001] 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 generation of Ni2O3H. [Background technology]

[0002] Hybrid vehicles and other vehicles equipped with electric motors use power stored in secondary batteries to drive the motors. Nickel-metal hydride batteries, among other secondary batteries, are widely used in vehicles because they are capable of charging and discharging large currents.

[0003] It is known that such nickel-metal hydride batteries can suffer from a memory effect depending on their operating conditions, which can cause the positive electrode potential of the battery to fall below a predetermined lower limit or rise above a predetermined upper limit, resulting in side reactions at the positive electrode and deterioration of the positive electrode.

[0004] FIG. 1 is a graph showing the relationship between the abundance ratio [%] of Ni2O3H (nickel oxide) in the positive electrode and the battery capacity ratio [%]. As shown in FIG. 1, there is a problem that, among reactions, particularly in nickel-metal hydride batteries, as the abundance ratio [%] of Ni2O3H (nickel oxide) in the positive electrode increases, the battery capacity ratio [%] irreversibly decreases. Furthermore, the inventors have clarified that, as shown in graph L0 in FIG. 8, once Ni2O3H is generated, the capacity rapidly decreases as the total discharge capacity [Ah] increases. Therefore, Patent Document 1 discloses the following invention that suppresses the generation of Ni2O3H.

[0005] In alkaline storage batteries using nickel hydroxide in the positive electrode, repeated charge and discharge may produce electrochemically inactive Ni2O3H under certain conditions. Therefore, in the invention disclosed in Patent Document 1, when the current density is 100 [A / m 2], a battery has been proposed that appropriately controls the positive electrode potential so that Ni2O3H is below a specified amount when charging and discharging with a total amount of electricity of 10 kAh within the SOC range of 20 to 80%.

[0006] Such an invention is expected to suppress the generation of Ni2O3H. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-233423 Summary of the Invention [Problem to be solved by the invention]

[0008] However, nickel-metal hydride batteries for vehicles are used under harsh conditions, and may deviate from the conditions described in Patent Document 1. The inventors have found that even if a small amount of Ni2O3H is generated, the battery capacity decreases, and furthermore, if the battery is used continuously while this Ni2O3H is generated, the battery capacity may decrease rapidly. For this reason, it is necessary to quickly identify signs that Ni2O3H is likely to be generated and take appropriate action.

[0009] In conventional technology, structural analysis such as XRD of disassembled electrode plates is commonly used to confirm the generation of Ni2O3H in nickel-metal hydride batteries with a certain usage history. However, this method is a destructive test, which makes it virtually impossible to reuse the battery. Another conventional technology is dQ / dV detection, which measures the amount of Co elution, a measure of degradation. However, because this is a destructive test in the over-discharge region below 1 V, it cannot be used to control nickel-metal hydride batteries installed in vehicles.

[0010] Therefore, the problem that the nickel-metal hydride storage battery control method and control device of the present invention aims to solve is to detect signs of Ni2O3H formation, which leads to capacity reduction, and to control the nickel-metal hydride storage battery to suppress the formation of Ni2O3H. [Means for solving the problem]

[0011] In order to solve the above problems, the control method for a nickel-metal hydride battery of the present invention is a control method for a nickel-metal hydride battery performed by a control device that controls the charging and discharging of the nickel-metal hydride battery based on voltage and current, and is characterized in that the control device comprises: an SOC acquisition step of acquiring the SOC of the nickel-metal hydride battery; a charging step of charging the nickel-metal hydride battery at a set rate when the SOC reaches or falls below a set low SOC to acquire a charge curve showing the relationship between battery capacity and battery voltage (OCV); a dQ / dV conversion step of replacing the charge curve with a dQ / dV curve that is a change in capacity relative to a change in voltage; a dQ / dV value accumulation step of accumulating the relationship of the dQ / dV value versus total discharge capacity for each of the charging steps; and a dQ / dV value estimation step of, when the dQ / dV value falls below a set threshold, estimating the dQ / dV value versus the subsequent total discharge capacity based on a point on a plot of the relationship of the dQ / dV value versus total discharge capacity at that time and the relationship of the dQ / dV value versus total discharge capacity acquired previously.

[0012] Furthermore, in the relationship between the dQ / dV value and the total discharge capacity thereafter estimated in the dQ / dV value estimation step, if the dQ / dV value for the set total discharge capacity becomes equal to or less than a set threshold value, the discharge rate of the nickel-metal hydride storage battery can be limited.

[0013] The discharge rate is preferably limited in a set low SOC range, and the set low SOC range may be SOC 50% or less. If the dQ / dV value for the set total discharge capacity estimated in the dQ / dV value estimation step after limiting the discharge rate of the nickel-metal hydride storage battery becomes equal to or less than a set threshold value, the discharge rate of the nickel-metal hydride storage battery can be further limited.

[0014] In the charging step, the set low SOC may be 20 to 40%. In the charging step, the set rate may be 3C or less. The control device for a nickel-metal hydride battery of the present invention includes a voltage measuring device, a current measuring device, and a control device that controls charging and discharging of the nickel-metal hydride battery based on the voltage measured by the voltage measuring device and the current measured by the current measuring device, and is characterized in that the control device executes the following steps: an SOC acquisition step of acquiring the SOC of the nickel-metal hydride battery; a charging step of charging the nickel-metal hydride battery at a set rate when the SOC reaches or falls below a set low SOC to acquire a charge curve showing the relationship between battery capacity and battery voltage (OCV); a dQ / dV conversion step of replacing the charge curve with a dQ / dV curve that is a change in capacity relative to a change in voltage; a dQ / dV value accumulation step of accumulating the relationship of the dQ / dV value versus total discharge capacity for each of the charging steps; and a dQ / dV value estimation step of, when the dQ / dV value falls below a set threshold, estimating the dQ / dV value versus the subsequent total discharge capacity based on the relationship of the dQ / dV value versus total discharge capacity at that time and the relationship of the dQ / dV value versus total discharge capacity acquired previously.

[0015] The nickel-metal hydride battery is a battery for driving a vehicle, and the control device can be suitably implemented when it is mounted on a vehicle. [Effects of the Invention]

[0016] The control method and control device for a nickel-metal hydride battery of the present invention can detect signs of Ni2O3H formation that leads to capacity reduction, and can control the nickel-metal hydride battery to suppress the formation of Ni2O3H. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a graph showing the relationship between the abundance ratio (%) of Ni2O3H in the positive electrode and the capacity ratio (%) of the battery. [Figure 2] Fig. 2(a) is a schematic diagram showing oxygen in a reaction on the particle surface 22b of a particle 22a of the positive electrode active material 2 of a nickel-metal hydride storage battery during charging. Fig. 2(b) is a reaction formula showing the normal main reaction of the positive electrode during discharge and the abnormal side reaction that occurs when oxygen is generated and causes localized "liquid drying up." [Figure 3] 1 is a graph showing a charge / discharge curve of a nickel-metal hydride storage battery. [Figure 4] 1 is a graph showing the slope of the charge / discharge curve of a nickel-metal hydride storage battery as a dQ / dV curve. [Figure 5] 4 is a graph showing a charging curve of forced charging according to the present embodiment. [Figure 6] 3 is a flowchart showing an example of the procedure of a control method for a nickel-metal hydride storage battery according to the present embodiment. [Figure 7] 1 is a block diagram of a control device for a nickel-metal hydride storage battery according to an embodiment of the present invention. [Figure 8] 1 is a graph showing dQ / dV versus total discharge capacity [Ah] of a nickel-metal hydride storage battery according to a conventional control method for a nickel-metal hydride storage battery. [Figure 9] 10 is a graph showing an example of plot points in the procedure of storing plot points (S9) of (total discharge capacity [Ah]) / (dQ / dV). [Figure 10] 10 is a graph showing a straight line in a procedure for estimating (S11) the total discharge capacity EA [Ah] at which dQ / dV=TD is achieved based on the two most recent plot points. [Figure 11] 10 is a graph showing dQ / dV versus total discharge capacity [Ah] of a nickel-metal hydride storage battery after it is determined that "EA≦target total discharge capacity SA (S12)" and "discharge rate limitation (S13)" is performed. [Figure 12]This is a graph showing dQ / dV versus the total discharge capacity [Ah] of a nickel-metal hydride storage battery after "Limiting the discharge rate (S13)" is performed, and it is determined that "EA≦target total discharge capacity SA (S12)" in an estimate based on the plotted point and the two plotted points immediately before that, and then "Limiting the discharge rate (S13)" is performed. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Principle of this embodiment> Hereinafter, a method for controlling a nickel-metal hydride storage battery according to one embodiment of the present invention will be described with reference to FIGS.

[0019] <Prerequisites for this embodiment> The nickel-metal hydride storage battery inspection method of this embodiment aims to detect the formation of Ni2O3H. To this end, the mechanism of Ni2O3H formation will first be explained.

[0020] <Surface of positive electrode active material particles> Fig. 2(a) is a schematic diagram showing oxygen in a reaction on the particle surface 22b of a particle 22a of the positive electrode active material 2 of a nickel-metal hydride storage battery during charging. Fig. 2(b) is a reaction formula showing the normal main reaction of the positive electrode during discharge and the abnormal side reaction that occurs when oxygen is generated and causes localized "liquid drying up."

[0021] <Main reactions at the positive electrode during discharge> The particles 22a of the positive electrode active material 2 change between Ni(OH)2 and β-NiOOH during charging and discharging. For convenience of explanation, the positive electrode active material may be described as Ni(OH)2. The normal main reaction during discharge of a nickel-metal hydride battery is as follows: β-NiOOH is converted to Ni(OH)2 and OH, assuming the presence of HO, as shown in the following formula (1): - In this case, the H2O in the electrolyte is consumed and reduced. OH - acts as an alkaline ion in the alkaline electrolyte 4. In this case, the exchange of ions and electrons does not produce oxygen O2 or hydrogen H2 gases.

[0022] β-NiOOH+H2O+e - →Ni(OH)2+OH - ……(1) <Generation of oxygen due to side reactions and occurrence of "liquid drying up"> Depending on the conditions of use, the potential of the positive electrode may become low. When it reaches the potential for electrolysis of H2O, electrolysis of H2O occurs as a side reaction. In the electrolysis of H2O, O2 is generated at the positive electrode through the reaction shown in equation (2) below.

[0023] 4OH - →O2+2H2O+4e - ……(2) As shown in FIG. 2(a), when the particle surface 22b of the positive electrode active material, Ni(OH)2 / β-NiOOH, becomes low potential due to charging, a side reaction occurs as shown in the above formula (2), and O2 bubbles A are generated on the particle surface 22b of the positive electrode active material. When O2 is generated at the positive electrode during charging, O2 bubbles A adhere to the particle surface 22b of the positive electrode active material. Over time, these O2 bubbles A detach from the particle surface 22b of the positive electrode active material. The area from which the bubbles A detach comes into contact with the alkaline electrolyte 4, and H2O and OH are released. - is supplied.

[0024] However, depending on the conditions, it may take time for the O2 generated on the particle surface 22b of the positive electrode active material to leave the particle surface 22b of the positive electrode active material, as in the case of bubble B. In this way, O2 bubbles such as bubble B attached to the particle surface 22b of the positive electrode active material locally block the alkaline electrolyte. As a result, the H2O and OH on the particle surface 22b of the positive electrode active material may be separated. - This will physically remove the liquid from the area, causing a local "liquid dryness." - does not exist physically.

[0025] <Production of Ni2O3H due to "liquid drying up"> In a normal reaction, H2O is required for the reaction, as shown in equation A in Figure 2(b). However, in the case of "liquid starvation," where H2O is not supplied, an abnormal side reaction occurs when the nickel-metal hydride battery is discharged, resulting in the reaction shown in equation (3) below.

[0026] 16β-NiOOH+4e - →8Ni2O3H+2H2O+O2+4OH - ...(3) In other words, the reaction does not use H2O, but produces H2O instead. The products are Ni2O3H, O2, and OH. - Of these, O2 is absorbed smoothly by the negative electrode through the separator (recombination reaction) as time passes, as shown in equation (4) below, maintaining a closed system. OH - returns to alkaline electrolyte 4.

[0027] 4MH+O2 → 4M+2H2O……(4) Here, Ni2O3H is an electrochemically inactive product, and when it is generated, it accumulates irreversibly, causing problems such as an increase in battery resistance and a decrease in battery capacity. For this reason, the generation of Ni2O3H is considered undesirable and is usually suppressed.

[0028] <Memory effect of nickel-metal hydride batteries> Next, we will explain the memory effect of nickel-metal hydride batteries. It is known that repeated charging and discharging at a low SOC can cause a memory effect in nickel-metal hydride batteries. In battery systems where this memory effect occurs, the voltage shifts toward the noble side during charging. As a result, even at the same SOC, the positive electrode potential increases during charging, making O2 generation particularly likely. On the other hand, during discharge, the discharge curve shifts toward the noble side, resulting in a low positive electrode potential. As a result, localized liquid depletion occurs momentarily at the location where oxygen is generated on the particle surface 22b of the positive electrode active material. When discharging occurs under this condition of H2O deficiency, the discharge voltage shifts to the noble side, resulting in a lower positive electrode potential than usual, approaching the potential for the formation of Ni2O3H. Therefore, Ni2O3H is generated simultaneously with the reaction that generates the missing H2O, as shown in Equation (3) above. The formation of Ni2O3H leads to a rapid capacity loss, as shown in Figure 1.

[0029] <Mechanism of Ni2O3H formation in nickel-metal hydride batteries> As mentioned above, in nickel-metal hydride batteries, the potential of the positive electrode during charging causes oxygen gas (O2) to be generated as a side reaction, which increases the internal pressure of the secondary battery. This O2 causes "liquid starvation," and we analyzed the mechanism by which Ni2O3H is generated.

[0030] The inventors have hypothesized and demonstrated that "liquid starvation" occurs when the drop in positive electrode potential during charging becomes the potential at which oxygen is generated, and when oxygen (O2) gas is actually generated, creating a high internal pressure.

[0031] <Memory effect of in-vehicle nickel-metal hydride batteries> Next, the memory effect of an in-vehicle nickel-metal hydride battery will be described. Hybrid vehicles equipped with an electric motor are driven by the electric power stored in the nickel-metal hydride battery for driving. Among such secondary batteries, an alkaline secondary battery such as a nickel-metal hydride battery can perform charge and discharge with a large current, and thus has been widely used for vehicles. Such an in-vehicle nickel-metal hydride battery may be exposed to a harsh usage environment. For example, charge and discharge may be repeated in a low SOC (State Of Charge) state. For example, when the SOC drops below 40%, the driving force of the motor generator 17 is exhausted. Therefore, the control device 10 operates the engine until, for example, the SOC reaches 60%, and the motor generator 17 generates electricity to rapidly charge the nickel-metal hydride battery in a short time. In such a usage environment, it is known that the memory effect is likely to occur. When the memory effect occurs, the charge curve of the battery shifts upward. That is, even at the same SOC, the positive electrode potential becomes higher. On the other hand, during discharge, the discharge curve of the battery shifts downward. That is, even at the same SOC, the positive electrode potential becomes lower. Then, due to the mechanism described above, the generation of Ni2O3H due to "drying out" is likely to occur.

[0032] <Necessity of control for in-vehicle nickel-metal hydride battery> As shown in Fig. 2(b), once Ni2O3H is generated, it accumulates irreversibly, and as shown in Fig. 1, the capacity of the nickel-metal hydride battery decreases. For such a nickel-metal hydride battery with a reduced capacity, if control corresponding to its deterioration is not performed, the deterioration will further progress. Therefore, an invention has been proposed to suppress the generation of Ni2O3H by controlling an in-vehicle nickel-metal hydride battery, as in Patent Document 1 cited in the description of the prior art.

[0033] <Generation of Ni2O3H and reduction of nickel-metal hydride battery capacity> However, once Ni2O3H is generated, it accumulates irreversibly. This, combined with the memory effect as shown in Figure 1, causes an even greater capacity loss. As the capacity loss progresses, the voltage shifts further to the noble side, creating an environment that is more conducive to the generation of Ni2O3H at an accelerated rate. As a result, as shown in Figure 8, this leads to a rapid decrease in battery capacity with use. For this reason, it is necessary to predict and control the generation of Ni2O3H, even in small amounts, to prevent its generation.

[0034] <Deterioration of nickel-metal hydride batteries due to use and charge / discharge curve> The graph C0 of the charge curve and the graph D0 of the discharge curve of a brand new nickel-metal hydride battery that has never been used have been explained with reference to Figure 3. This charge and discharge curve changes depending on the deterioration caused by use.

[0035] <Deterioration and charging curve> In Figure 3, graph C0 shows the charge curve when charging an unused nickel-metal hydride battery. In contrast, graph C1 shows the charge curve when charging a nickel-metal hydride battery with 1800 Ah used. Graph C2 shows the charge curve when charging a nickel-metal hydride battery with 2920 Ah used. Graph C3 shows the charge curve when charging a nickel-metal hydride battery with 3070 Ah used. Graph C4 shows the charge curve when charging a nickel-metal hydride battery with 3080 Ah used.

[0036] Graph C1 shows the charging curve when charging a nickel-metal hydride battery with a usage history of 1800 [Ah]. Note that graphs C0 to C4 all show the same conditions: charging from a fully discharged battery with a module voltage of 6.0 [V] and an SOC of 0 [%] at a charge rate of 1 / 3C until the battery is fully charged to an SOC of 100 [%]. The characteristics of a charged nickel-metal hydride battery change with use due to factors such as degradation of the active material. Graph C1 is compared with the charging curve C0 of an unused nickel-metal hydride battery. When charging is started from an SOC of 0 [%], the module voltage [V] reaches approximately 8.9 [V], which is not significantly different from graph C0. However, the change in module voltage [V] relative to the increase in battery capacity [Ah] is different. Immediately after charging begins, when the battery capacity [Ah] is approximately 2.7 [Ah], graph C1 has a lower module voltage [V] than graph C0, and when the battery capacity exceeds approximately 2.7 [Ah], graph C1 has a higher module voltage [V] than graph C0.

[0037] Looking at the slope of the graphs, graph C0 is roughly horizontal near the inflection point IPc, while graph C1 consistently maintains a slope above a certain level. <Deterioration of nickel-metal hydride batteries due to use and the dQ / dV curve> Figure 4 is a graph showing the slope of the charge / discharge curve of a nickel-metal hydride storage battery as a dQ / dV curve. As shown in Figure 4, when these slopes are expressed as dQ / dV curves, graph C0 becomes graph RC0, and graph C1 becomes graph RC1.

[0038] As explained above, graph RC0 based on graph C0 shows a peak of approximately +30 for dQ / dV when the module voltage [V] is approximately 8.35 [V]. In contrast, graph RC1 based on graph C1 shows a very gentle peak of approximately +7 for dQ / dV when the module voltage [V] is approximately 8.35 [V].

[0039] Graph C2 in Figure 3 shows the charging curve when charging a nickel-metal hydride battery with a usage history of 2920 [Ah]. In this case, a higher module voltage [V] is shown at the beginning of charging than graph C1. Graph C3 also shows a battery with a usage history of 3070 [Ah], but an even higher module voltage [V] at the beginning of charging than graph C2. Graph C4 then shows an even higher module voltage [V] at an even earlier timing than graph C3.

[0040] As can be seen from the above, repeated charging and discharging at a high current in the usage history indicates that the active material has deteriorated, resulting in a higher module voltage [V] at a lower battery capacity [Ah]. This means that even when the same battery capacity [Ah] is charged, the SOC [%] of a deteriorated nickel-metal hydride battery is higher. Furthermore, deteriorated nickel-metal hydride batteries tend to have a higher SOC [%]. This means that the potential within the nickel-metal hydride battery is conducive to oxygen generation, creating an environment conducive to the production of Ni2O3H.

[0041] For example, in graphs C0 and C1, the usage history is from 0 [Ah] to 1800 [Ah], which is 1800 [Ah] more charge / discharge cycles, but the module voltage [V] at the same electrical capacity [Ah] is not significantly different. However, in graphs C3 and C4, the usage history is from 3070 [Ah] to 3080 [Ah], and even though only 10 [Ah] of charge / discharge cycles have been performed, a clear increase in module voltage [V] can be seen. In other words, it can be seen that once nickel-metal hydride batteries begin to deteriorate over a long usage history, the deterioration accelerates, causing a rapid decrease in capacity.

[0042] <dQ / dV in this embodiment> FIG. 5 is a schematic graph showing the charging curve of the forced charging of this embodiment. In this embodiment, when the SOC of the nickel-metal hydride storage battery falls below 40[%], the vehicle control device automatically performs forced charging at a constant charging rate of 3C until the SOC reaches 60[%] in order to ensure remaining capacity. Here, the average value of dQ / dV from SOC 40[%] to SOC 60[%] is taken as the dQ / dV value in the charging step. In other words, the difference in capacity between SOC 60[%] and SOC 40[%] is taken as V, which is the OCV at SOC 60[%]. 60 [V] and SOC40[%] OCV V 40 This is the value obtained by dividing the difference in voltage [V]. In this way, the dQ / dV value is obtained under constant conditions: the SOC at the start of charging, the SOC at the end of charging, and a charge rate of 3C. Therefore, the dQ / dV values ​​obtained here can be compared over time. In other words, changes in deterioration can be accurately detected.

[0043] As mentioned above, this dQ / dV value also decreases when Ni2O3H is produced in the nickel-metal hydride battery. <Principle of the nickel-metal hydride battery control method according to this embodiment> The principles of the nickel-metal hydride battery control method of this embodiment, discovered by the inventors based on the above findings, can be summarized as follows: First, a charging curve at low SOC of a nickel-metal hydride battery under certain conditions, such as forced charging, is obtained, and dQ / dV is calculated from the curve. The inventors have found that the generation of Ni2O3H in a nickel-metal hydride battery can be estimated based on this dQ / dV value. Furthermore, the inventors have determined that the generation of further Ni2O3H is largely due to the generation of oxygen during rapid discharge at low SOC. By appropriately limiting the discharge rate at low SOC in accordance with the estimated deterioration of the nickel-metal hydride battery based on this, rapid deterioration can be avoided and the required lifespan of the nickel-metal hydride battery can be secured.

[0044] (Configuration of this embodiment) <Nickel-metal hydride battery> The nickel-metal hydride storage battery that is the premise of this embodiment will be briefly described below. The nickel-metal hydride storage battery of this embodiment is an on-board battery used as a power source for driving vehicles such as hybrid cars. To obtain the required power capacity as a nickel-metal hydride storage battery to be mounted on a vehicle, the battery is made up of a battery module formed by electrically connecting multiple sealed cells in series. In this embodiment, OCV (Open Circuit Voltage) refers to the module voltage of the battery module.

[0045] The battery module has a rectangular parallelepiped case made of a resin and configured to house a plurality of cells and a lid that seals the case.

[0046] The integral battery case that constitutes the rectangular case is made of a synthetic resin material, such as polypropylene or polyethylene, that is resistant to alkaline electrolyte. The interior of this integral battery case is formed with partition walls that separate the multiple cells, and the sections separated by these partition walls form battery cases for each cell. The integral battery case may contain, for example, six battery cases.

[0047] <Configuration of electrode plate group> The compartmented battery case contains an electrode group, positive and negative current collectors joined to both sides of the electrode group, and an electrolyte. The electrode group is composed of rectangular positive and negative electrode plates stacked together with a separator between them. The electrode groups of adjacent battery cases are electrically connected in series. The total output of the series-connected electrode groups, i.e., the multiple unit cells, is taken from the positive and negative electrode connection terminals.

[0048] <Positive electrode> The positive electrode plate uses a three-dimensional porous nickel foam made of a porous metal, Ni or Ni alloy, as the base material. The positive electrode substrate has a three-dimensional network structure with pores surrounded by this network. The positive electrode substrate is manufactured, for example, by plating the urethane skeleton surface of urethane foam with nickel and then burning the urethane foam. The positive electrode plate includes a positive electrode composite layer containing Ni(OH)2 and Co as active materials. Specifically, granular nickel hydroxide is first processed into a paste by adding 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. The paste is then filled into the network pores of the positive electrode substrate to form a positive electrode composite layer. The resulting product is then dried, rolled, and cut to form a plate-shaped positive electrode plate.

[0049] <Negative electrode> The negative electrode plate is constructed using a hydrogen storage alloy containing nickel, aluminum, cobalt, and manganese as its active material. Specifically, the hydrogen storage alloy is first processed into a paste by adding a conductive agent such as carbon black, and optionally a thickener such as carboxymethyl cellulose or a binder such as a styrene-butadiene copolymer. The paste-like hydrogen storage alloy is then applied to or filled into a core material such as a punched metal (active material support), which is then dried, rolled, and cut to form a similarly plate-shaped negative electrode plate.

[0050] <Separator> As the separator, a nonwoven fabric of an olefin resin such as polypropylene, or a nonwoven fabric which has been subjected to hydrophilic treatment such as sulfonation as required, can be used.

[0051] The battery module of the nickel-metal hydride storage battery of this embodiment has the above-described configuration. <Control device for nickel-metal hydride storage battery according to this embodiment> Next, we will briefly explain an example of a control device for a nickel-metal hydride battery, which is the premise of this embodiment. The control method of this embodiment, which can detect signs of rapid deterioration of a nickel-metal hydride battery and control it, is suitable for use in nickel-metal hydride batteries mounted on vehicles for driving. Therefore, we will briefly explain here a control device for such a nickel-metal hydride battery as a secondary battery for driving a vehicle.

[0052] <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 battery of this embodiment. The control device 10 for the nickel-metal hydride battery will be described with reference to Fig. 7. Note that here, the nickel-metal hydride battery is controlled in the state of a battery pack that houses a battery module 90.

[0053] <Control device 10> The control device 10, which is a battery control device, is mounted on a vehicle and can control the vehicle's battery module 90 on-board in real time or based on accumulated data. This control device corresponds to the control device of the present invention that controls the charging and discharging of the nickel-metal hydride storage battery based on the voltage measured by the voltage measuring device and the current measured by the current measuring device.

[0054] The control device 10 controls the inverter 20, which serves as a charging device, to charge the battery module 90 with current from the motor generator 17, which serves as a power generator. The control device 10 also controls the inverter 20, which serves as a power supply device, to discharge current from the battery module 90 to the motor generator 17, which serves as a drive motor that serves as a load.

[0055] 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 terminal voltage of the battery module 90, and a temperature detector 23 that measures the temperature of the battery module 90. The current detector 21 corresponds to the current measuring device of the present invention, and the voltage detector 22 corresponds to the voltage measuring device of the present invention.

[0056] The temperature detector 23 includes a temperature sensor. The temperature sensor measures the temperature near the electrode plate group of the corresponding single cell in the battery module 90 and outputs the measured temperature value to the control device 10 as an electrical signal.

[0057] <Control unit 11> The control unit 11 of the control device 10 is configured as a computer including a CPU, RAM, ROM, and interface for controlling the entire control device 10.

[0058] <Information acquisition unit 12> The information acquisition unit 12 sequentially acquires the charge and discharge current values from the current detector 21, the voltage value from the voltage detector 22, and the battery temperature from the temperature detector 23 and stores them.

[0059] <Storage unit 13> The storage unit 13 includes a storage medium in which programs and necessary data of the control device 10 are stored. The program includes a program for executing the flowchart shown in FIG. 6.

[0060] Also, in the storage unit 13, as data for the premise of control, a “threshold value” of the dQ / dV value and the like are stored in advance. <dQ / dV calculation unit 14> The dQ / dV calculation unit 14 estimates the change in the battery capacity [Ah] from the battery module 90 charged and discharged by the charge and discharge control unit 16 and generates a charging curve from the open circuit voltage (OCV) [V] which is the module voltage. In this case, since the battery capacity [Ah] is an in-vehicle battery, it is difficult to accurately measure the battery capacity [Ah] by charging and discharging from a complete discharge of SOC0[%] to a full charge of SOC100[%]. Therefore, the battery capacity [Ah] is estimated within a range of SOC[%] where problems are unlikely to occur in the operation of the vehicle. In this embodiment, when the SOC reaches a low SOC of 40%, the charge rate is fixed at 3C, and the dQ / dV value is acquired using the battery control of the vehicle that forcibly charges up to SOC60%. For this reason, it is possible to detect the deterioration of the nickel-metal hydride battery by comparing the dQ / dV values acquired under the same conditions in time series.

[0061] <Judgment part 15> The determination unit 15 compares the dQ / dV value calculated by the dQ / dV value calculation unit 14 with a pre-stored threshold value to determine whether the on-board nickel-metal hydride battery will be able to complete its set lifespan. The control unit 11 also limits the discharge conditions of the battery module 90 when the SOC is low, depending on the amount of Ni2O3H produced estimated from the dQ / dV value, thereby suppressing rapid deterioration of the nickel-metal hydride battery. This procedure extends the lifespan of the nickel-metal hydride battery so as not to impede vehicle operation, and controls the battery to complete its set lifespan.

[0062] <Charge / discharge control unit 16> The charge / discharge control unit 16 monitors the voltage of the battery module 90, and if the SOC drops below a threshold of 40%, it generates electricity using the motor generator 17 and charges the battery module 90 via the inverter 20 at a charge rate of 3C until the SOC reaches 60%. In this embodiment, the vehicle's battery control itself is used to obtain a charge curve when charging under certain conditions. Then, by obtaining a dQ / dV value from this, a dQ / dV value that can be compared over time is obtained, which is a technical feature.

[0063] Meanwhile, as another normal control, the charge / discharge control unit 16 charges the battery module 90 by supplying a regenerative current from the motor generator 17 via the inverter 20 when braking the vehicle. In this case, the charge / discharge control unit 16 limits charging if there is an excessive current or if the SOC of the battery module 90 is too high. The threshold value and the like for this purpose are stored in the storage unit 13. In this embodiment, the charge / discharge is controlled so that the potential of the positive electrode is set to a potential at which O2 is not generated, so as to prevent the generation of Ni2O3H.

[0064] On the other hand, when the vehicle is being driven, the charge / discharge control unit 16 supplies the necessary current from the battery module 90 to the motor generator 17 via the inverter 20 in response to a command from the vehicle's ECU (Electronic Control Unit).

[0065] In particular, when the determination unit 15 detects deterioration of the nickel-metal hydride storage battery, the charge / discharge control unit 16 suppresses the rapid generation of Ni2O3H by, for example, avoiding rapid discharge when the SOC is low.

[0066] <Procedure of the nickel-metal hydride battery control method according to this embodiment> Fig. 6 is a flowchart showing an example of the procedure of the control method for a nickel-metal hydride storage battery of this embodiment. Next, an outline of the procedure for predicting the generation of Ni2O3H and preventing the generation of Ni2O3H through control using the control method for a nickel-metal hydride storage battery of this embodiment will be described with reference to the flowchart of Fig. 6.

[0067] <Outline of procedure> First, as a preliminary step, "threshold setting step (S1)" sets an appropriate threshold value according to the characteristics of the nickel-metal hydride battery to be controlled. Next, during vehicle operation, "SOC estimation (S2)" obtains the SOC that will be the basis for control. Then, "SOC ≦ 40%? (S3)" determines whether the current SOC is in a low SOC state. If the SOC is low, "forced charging / charging curve acquisition (S4)" performs forced charging to restore the remaining capacity of the nickel-metal hydride battery, while obtaining the amount of charging energy and the OCV of the nickel-metal hydride battery at that time. Then, while monitoring the SOC using the "SOC estimation (S5)" procedure, if "SOC > 60%? (S6)" is reached, "charging ends (S7)".

[0068] The process "calculates dQ / dV from the acquired charging curve (S8)" and "storages the plot points of (total discharge capacity [Ah]) / (dQ / dV) (S9)." If "dQ / dV≦T W (S10)" then "based on the two most recent plot points, dQ / dV = T DThe total discharge capacity EA [Ah] is estimated (S11) so that the target total discharge capacity SA is equal to or less than the target total discharge capacity (S12). If the result is that EA is equal to or less than the target total discharge capacity SA, then it is predicted that the target nickel-metal hydride battery will not last as long as the target total discharge capacity [Ah] under the current control. Based on this prediction, the discharge rate is limited (S13) to suppress deterioration of the nickel-metal hydride battery.

[0069] After this, if it is predicted that the target nickel-metal hydride storage battery will not last until the target total discharge capacity [Ah] even after the discharge rate is limited again in the steps S2 to S12, "limitation of discharge rate (S13)" is performed again. By repeating this procedure, the discharge rate is limited so that the nickel-metal hydride storage battery will last until the target total discharge capacity [Ah]. Each step will be explained in detail below.

[0070] <Threshold setting step (S1)> The characteristics of the nickel-metal hydride battery to be used are obtained in advance. Here, a charge curve from full discharge to full charge from SOC 0 [%] to SOC 100 [%] as shown in FIG. 3 is obtained, and this is converted into a dQ / dV curve as shown in FIG. 4, and the deterioration level of the nickel-metal hydride battery is measured. Then, a threshold value is determined based on the relationship between these deterioration levels and the dQ / dV value. In this embodiment, the threshold value is the dQ / dV value when the battery is forcibly charged at a charge rate of 3C with an SOC of 40 to 60 [%].

[0071] The dQ / dV value at which the dQ / dV value begins to rapidly decrease relative to the total discharge capacity [Ah] is called the "warning threshold T W For example, in this embodiment, dQ / dV is set to 40. This alert threshold T W If it is smaller, there is a high possibility that Ni2O3H will be generated.

[0072] In addition, the dQ / dV value that indicates the limit of the nickel-metal hydride battery is called the "limit threshold T D For example, in this embodiment, dQ / dV=20. The dQ / dV value is set as this "limit threshold T DIf it is smaller than 」, Ni2O3H may rapidly occur.

[0073] Also, the target total discharge capacity of the nickel - hydrogen storage battery is set as 「target total discharge capacity SA」. This is the remaining life expected for the battery when mounted on a vehicle. In this embodiment, the target total discharge capacity SA = 4000 [Ah] is set.

[0074] <SOC Estimation (S2)> The control device 10 estimates the current SOC based on the voltage OCV from the voltage detector 22. This procedure corresponds to the 「step of obtaining SOC」 of the present invention.

[0075] <SOC≤40[%]? (S3)> The control device 10 determines whether the obtained SOC is 「SOC≤40[%]」. That is, it determines whether the nickel - hydrogen storage battery has reached the set low SOC and whether forced charging is necessary. Here, if it is not 「SOC≤40[%]」, (S3: NO) continue monitoring by estimating SOC (S2). On the other hand, if it is 「SOC≤40[%]」 (S3: YES), perform forced charging (S4).

[0076] <Forced Charging - Charging Curve Acquisition (S4)> Figure 3 is a graph showing an example of the charging curve in forced charging (S4). This procedure corresponds to the 「charging step」 of the present invention. In the case of this embodiment, in forced charging (S4), as shown in Figure 7, a motor - generator 17 generates electricity by an internal combustion engine (not shown), and this is converted into a direct - current by an inverter 20 to charge the battery module 90 until SOC reaches 60%. The charging rate at this time is constantly adjusted to 3C by the charge - discharge control unit.

[0077] During the execution of this forced charging, based on the current and voltage obtained by the current detector 21 and the voltage detector 22, the dQ / dV calculation unit 14 calculates the charging curve, which is the relationship between the open - circuit battery voltage OCV and the SOC, and stores it in the storage unit 13.

[0078] <SOC Estimation (S5)> The dQ / dV calculation unit 14 sequentially estimates the SOC at that time according to the progress of the started forced charging.

[0079] <soc>60[%]?(S6)> Here, it is determined whether "SOC>60[%]" or not (S6). That is, it is determined whether the nickel-metal hydride storage battery has escaped from a low SOC. If it is determined that "SOC>60[%]" is not the case (S6: NO), it is determined that the low SOC has not yet been overcome, and forced charging (S4) continues. On the other hand, if it is determined that "SOC>60[%]" is the case (S6: YES), it is determined that the nickel-metal hydride storage battery has escaped from a low SOC.

[0080] <Charging End (S7)> If it is determined that "SOC>60[%]" (S6: YES) and that the nickel-metal hydride battery has escaped from the low SOC state, the forced charging (S4) is terminated (S7).

[0081] <Calculate dQ / dV from the acquired charging curve (S8)> As shown in Figure 5, during forced charging (S4), the increase in OCV of the nickel-metal hydride battery, V 60 -V 40 =ΔV [V] and the increase in capacity of the nickel-metal hydride storage battery ΔQ [Ah] are calculated. 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 stores the average dQ / dV value in the storage unit 13. This procedure corresponds to the "dQ / dV calculation step" of the present invention.

[0082] <(Total discharge capacity [Ah]) / (dQ / dV) plot point storage (S9)> 9 is a graph showing an example of plot points in the procedure of storing plot points (S9) of (total discharge capacity [Ah]) / (dQ / dV). The vertical axis represents dQ / dV [Ah / V], and the horizontal axis represents total discharge capacity [Ah].

[0083] As shown in FIG. 9, for example, during the first forced charge after the start of use, the relationship between the total discharge capacity [Ah] and the dQ / dV value is accumulated. That is, a plot point P0 where (total discharge capacity [Ah], (dQ / dV)) = (0, 60) is plotted. The next plot point P1 is approximately (300, 51), and the next plot point P2 is approximately (700, 43). The next plot point P3 is approximately (1100, 34). In reality, too many plot points to fit in FIG. 9 are plotted, but in FIG. 9 they are extremely simplified for the purpose of explaining the concept. This procedure corresponds to the "dQ / dV value accumulation" step of the present invention.

[0084] <dQ / dV≦T W ?(S10)> Next, "dQ / dV≦T W In other words, it is determined whether the dQ / dV value is below the warning threshold T W It is judged whether or not dQ / dV≦T W If it is not true (S10: NO), the steps from S2 to S9 are repeated. W If it is "YES" (S10:YES), the process proceeds to the next step S11.

[0085] In this embodiment, the alert threshold T W The plot point P2 shown in FIG. 9 is approximately (700, 43), so the alert threshold T W The next plot point P3 is approximately (1100, 34), so the alert threshold T W It is below 40.

[0086] <dQ / dV=T based on the two most recent plot points D Estimate the total discharge capacity EA [Ah] (S11) dQ / dV≦T W If " (S10: YES), dQ / dV = T based on the two most recent plot points D The total discharge capacity EA [Ah] is estimated (S11). D is the dQ / dV value for satisfying the minimum battery performance. When the dQ / dV value is lower than the threshold value T D , the nickel-hydrogen storage battery cannot exhibit sufficient performance.

[0087] FIG. 10 is a graph showing a prediction straight line L1 in the procedure for estimating (S11) the total discharge capacity EA [Ah] at which dQ / dV = T D based on the two most recent plotted points. Here, the plotted point P3 shown in FIG. 9 is a plotted point below the warning threshold value T W which is 40. Also, the plotted point P2 is the plotted point plotted immediately before that. Therefore, a straight line connecting this plotted point P2 and the plotted point P3 is defined as the prediction straight line L1. When this prediction straight line L1 is extended, it reaches the threshold value T D . The total discharge capacity [Ah] at this time is defined as the estimated total discharge capacity EA [Ah].

[0088] In the example shown in FIG. 10, the estimated total discharge capacity EA [Ah] is approximately 1800 [Ah]. That is, assuming that the discharge rate allowed for the current nickel-hydrogen storage battery is controlled to 3C, it can be estimated that the nickel-hydrogen storage battery will become unusable when the total discharge capacity [Ah] reaches 1800 [Ah] under this control. This procedure corresponds to the "step of estimating the dQ / dV value" of the present invention.

[0089] <Is EA ≤ target total discharge capacity SA? (S12)> Next, it is determined whether "EA ≤ target total discharge capacity SA" (S12). If it is determined that "EA ≤ target total discharge capacity SA" is not satisfied (S12: NO), the procedures from S2 to S11 are repeated as they are. On the other hand, if "EA ≤ target total discharge capacity SA" is satisfied (S12: YES), the process proceeds to the procedure for restricting the next discharge rate (S13).

[0090] Here, the target total discharge capacity SA in this embodiment is set to 4000 [Ah]. Meanwhile, the estimated total discharge capacity EA [Ah] estimated in S11 was approximately 1800 [Ah]. In other words, with the current control of the nickel-metal hydride storage battery, it is estimated that the nickel-metal hydride storage battery will become unusable when the total discharge capacity [Ah] reaches 1800 [Ah], meaning that the target total discharge capacity SA of 4000 [Ah] will not be reached.

[0091] <Discharge rate limit (S13)> As shown in Figure 10, with the current control of nickel-metal hydride batteries, i.e., a method that allows a discharge rate up to 3C, it is estimated that the nickel-metal hydride batteries will become unusable when the total discharge capacity [Ah] reaches 1800 [Ah]. Therefore, it is necessary to change the current control method that allows a discharge rate up to 3C.

[0092] Therefore, the inventors have confirmed through experiments that Ni2O3H is more likely to be generated by discharging at a high rate when the SOC is low. Therefore, when the SOC is below 50%, for example, the current discharge rate of 3C is limited to a lower discharge rate, for example, 2C (S13).

[0093] FIG. 11 is a graph showing dQ / dV versus total discharge capacity [Ah] of a nickel-metal hydride battery after it has been determined that "EA≦target total discharge capacity SA (S12)" and "Limitation of discharge rate (S13)" has been performed. Until now, in control that allows a discharge rate up to 3C, it is thought that the battery will follow a progression like the predicted line L1 in the future. Therefore, if the discharge rate is limited to, for example, 2C when the SOC is below 50%, the deterioration of the nickel-metal hydride battery is expected to follow the predicted line L2. However, in reality, it is unknown at this stage what kind of deterioration will occur. Therefore, in the control method for a nickel-metal hydride battery of this embodiment, the process returns to "Estimation of SOC (S2)" and "Calculation of dQ / dV=T based on the two most recent plot points" is performed. D The procedure up to step (S11) is performed to determine whether the total discharge capacity SA is equal to or less than the predetermined value.

[0094] FIG. 12 shows an estimate based on two plot points, P4 plotted after "Limiting the Discharge Rate (S13)" and the immediately preceding plot point P3. It also shows a state in which it is determined that "EA≦target total discharge capacity SA (S12)." The graph also shows the dQ / dV value versus the total discharge capacity [Ah] of the nickel-metal hydride storage battery after "Limiting the Discharge Rate (S13)."

[0095] 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 in FIG. 11, it can be predicted that degradation has been suppressed by limiting the discharge rate (S13), but the predicted straight line L2 has not yet been obtained. It is only at the stage (S9) when a new plot point P4 is acquired after limiting the discharge rate (S13) that the predicted straight line L2 can be obtained (S11).

[0096] As shown in Fig. 12, according to the predicted line L2 obtained based on plot points P3 and P4, the estimated total discharge capacity EA [Ah] is approximately 2600 [Ah]. In other words, the discharge rate currently permitted for the nickel-metal hydride storage battery is limited and controlled to 2 C. If this control is continued, it can be estimated that the nickel-metal hydride storage battery will become unusable when the total discharge capacity [Ah] reaches 2600 [Ah] (S11).

[0097] 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 limited again (S13), and the discharge rate is further limited from 2C when the SOC is 50% or less to, for example, 1C.

[0098] In this case, when the next plot point is obtained, for example, the predicted line L3 is obtained, and the estimated total discharge capacity EA [Ah] exceeds the target total discharge capacity SA of 4000 [Ah]. In this way, the above procedure is repeated so that the estimated total discharge capacity EA [Ah] does not become the target total discharge capacity SA of 4000 [Ah].

[0099] (Action of this embodiment) The operation of the nickel-metal hydride battery control method of this embodiment is as follows. First, the nickel-metal hydride battery is forcibly charged from a low SOC of 40% (SOC) to an SOC of 60% (SOC) at a charge rate of 3C. The charging curve for this forcible charging is obtained, and the dQ / dV is calculated from the curve. By obtaining the dQ / dV value during this forcible charging under constant charging conditions, the dQ / dV values ​​can be compared over time. This allows for accurate estimation of the generation of Ni2O3H in the nickel-metal hydride battery. Furthermore, the generation of Ni2O3H is largely due to the generation of oxygen during rapid discharge at low SOC. Therefore, the discharge rate below an SOC of 50% is appropriately and gradually limited according to the estimated deterioration of the nickel-metal hydride battery. This control prevents rapid deterioration in the onboard nickel-metal hydride battery and ensures the required life of the nickel-metal hydride battery.

[0100] (Effects of this embodiment) (1) The control method and control device for a nickel-metal hydride storage battery according to the present embodiment can accurately estimate the generation of Ni2O3H, which causes a decrease in capacity, and accurately detect signs of deterioration.

[0101] (2) Furthermore, based on the accurately detected signs of deterioration, control can be performed to suppress the subsequent generation of Ni2O3H in the nickel-metal hydride battery, thereby preventing a sudden decrease in capacity.

[0102] (3) The inventors discovered that the generation of Ni2O3H is primarily due to the generation of oxygen during rapid discharge at low SOC. For this reason, control is performed by limiting the discharge rate at low SOC (e.g., 50% or less). Therefore, at high SOC (e.g., SOC above 50%), no discharge restriction is performed, so in the case of an in-vehicle nickel-metal hydride battery, the impact on driving can be reduced.

[0103] (4) Such control is possible if the OCV of the nickel-metal hydride battery is known, so it can be easily controlled even for the drive nickel-metal hydride battery installed in a hybrid vehicle. (5) Control is performed repeatedly in real time, which helps to avoid situations where vehicle operation suddenly stops.

[0104] (6) In particular, the dQ / dV value is calculated based on a charging curve with a fixed charging condition called "forced charging." This allows accurate comparison of dQ / dV values ​​over time. This has the effect of preventing even the slightest deterioration changes in nickel-metal hydride batteries from being overlooked as signs of deterioration.

[0105] (Variation) The above embodiment can also be implemented as follows. In the embodiment, the plot point P n and the previous plot point P n-1 Based on the predicted line L n However, the present invention is not limited to this, and the two points may be selected based on time, or may be selected based on dQ / dV, instead of just before.

[0106] The number of plotted points is not limited to two, but three or more points may be selected and the predicted line L may be calculated using the least squares method or the like. Furthermore, in the above embodiment, for the purpose of visual explanation, a plot point P is selected on a graph of total discharge capacity [Ah]-dQ / dV to obtain the predicted line L. However, this is not limited to this, and it goes without saying that it is not necessary to create a graph itself, and an embodiment in which calculations are performed and controlled within the control device 10 is also included.

[0107] The numerical ranges for dQ / dV, OCV [V], SOC [%], total discharge capacity [Ah], etc. shown in this embodiment are merely examples. The present invention is not limited to these, and those skilled in the art can appropriately optimize the ranges depending on the configuration and characteristics of the target nickel-metal hydride storage battery.

[0108] The threshold can be set with an appropriate margin, taking into account the degree of safety. The control device 10 shown in Figure 7 is an example, and is not limited to this configuration. The functions of the control device 10 may be performed by an ECU of the vehicle. Alternatively, the control device 10 may be provided independently within the battery pack.

[0109] In this embodiment, the present invention has been described using a nickel-metal hydride storage battery mounted on a hybrid vehicle (HV) as an example, but it is not limited to hybrid vehicles (HV), and can also be implemented in electric vehicles (EV), plug-in hybrid vehicles (PVH), fuel cell vehicles (FV), etc. Furthermore, it can be suitably applied to batteries for ships and aircraft. It can also be applied to stationary batteries.

[0110] The flowchart shown in FIG. 6 is an example of an implementation of this embodiment, and it goes without saying that a person skilled in the art can change the order of the steps, add or delete steps, or modify the implementation.

[0111] It goes without saying that even if the present invention is not described in the embodiments, a person skilled in the art can add, delete, or modify the configuration of the present invention without departing from the scope of the claims. [Explanation of symbols]

[0112] A...Air bubbles B...Air bubbles 2...Cathode active material 22a...particle 22b…Particle surface 4...Alkaline electrolyte 10...Control device 11...Control unit 12…Information acquisition department 13...Memory unit (programs, maps, etc.) 14...dQ / dV calculation section 15…Judgment section 16...Charge / discharge control unit 17...Motor generator 20...Inverter 21...Current detector 22...Voltage detector 23...Temperature detector 24...Battery pack 90...Battery module T W ...alert threshold T D …critical threshold EA: Estimated total discharge capacity SA: Target total discharge capacity OCV: Open battery voltage P, P0, P1, ~P n ...plot points L, L1, L2, L3...Predicted straight lines< / soc>

Claims

1. A control method for a nickel-metal hydride battery performed by a control device that controls charging and discharging of the nickel-metal hydride battery based on voltage and current, comprising: the control device acquires an 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 lower, and obtaining a charging curve showing the relationship between battery capacity and battery voltage OCV; a dQ / dV calculation step of calculating a dQ / dV value that is an average of a change in the increment dV of the battery voltage OCV and a change in the increment dQ of the battery capacity corresponding to the increment dV of the battery voltage OCV based on the charging curve; a dQ / dV value accumulation step of accumulating the relationship of the dQ / dV value with respect to the total discharge capacity EA for each charging step; and a dQ / dV value estimation step of, when the dQ / dV value becomes equal to or less than a set warning threshold value T W, estimating the dQ / dV value for the subsequent total discharge capacity EA based on the relationship of the dQ / dV value for the total discharge capacity EA at that time and a point obtained by plotting the relationship of the dQ / dV value for the total discharge capacity EA obtained previously.

2. A total discharge capacity EA at which the dQ / dV value becomes a limit threshold value T D , which is the dQ / dV value for satisfying a minimum battery performance, is estimated based on two points, the plot point estimated in the step of estimating the dQ / dV value and the subsequent plot point of the dQ / dV value against the total discharge capacity EA, and it is determined whether the total discharge capacity EA is equal to or less than a target total discharge capacity SA. If it is determined that the total discharge capacity EA is equal to or less than the target total discharge capacity SA, 2. The method for controlling a nickel-metal hydride battery according to claim 1, further comprising limiting a discharge rate of the nickel-metal hydride battery.

3. 3. The method for controlling a nickel-metal hydride battery according to claim 2, wherein the discharge rate is limited in the set low SOC region.

4. 4. The method for controlling a nickel-metal hydride battery according to claim 3, wherein the set low SOC region is an SOC of 50% or less.

5. The method for controlling a nickel-metal hydride battery according to any one of claims 2 to 4, characterized in that, when the dQ / dV value for the total discharge capacity EA thereafter estimated in the dQ / dV value estimation step after limiting the discharge rate of the nickel-metal hydride battery becomes equal to or less than the limit threshold value T D, the discharge rate of the nickel-metal hydride battery is further limited.

6. In the charging step, 6. The method for controlling a nickel-metal hydride storage battery according to claim 1, wherein the set low SOC is 20 to 40%.

7. In the charging step, 7. The method for controlling a nickel-metal hydride storage battery according to claim 1, wherein the set rate is 3C or less.

8. a voltage measuring device, a current measuring device, and a control device that controls 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 acquires an 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 lower, and obtaining a charging curve showing the relationship between battery capacity and battery voltage OCV; a dQ / dV calculation step of calculating a dQ / dV value that is an average of a change in the increment dV of the battery voltage OCV and a change in the increment dQ of the battery capacity corresponding to the increment dV of the battery voltage OCV based on the charging curve; a dQ / dV value accumulation step of accumulating the relationship of the dQ / dV value with respect to the total discharge capacity EA for each charging step; a step of estimating a dQ / dV value, in which when the dQ / dV value becomes equal to or less than a set warning threshold value T W, the step of estimating the dQ / dV value for the total discharge capacity EA thereafter is executed based on the relationship of the dQ / dV value for the total discharge capacity EA at that time and the relationship of the dQ / dV value for the total discharge capacity EA previously obtained.

9. 9. The nickel-metal hydride battery control device according to claim 8, wherein the nickel-metal hydride battery is a battery for driving a vehicle, and the control device is mounted on the vehicle.

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