JP6779808B2 - Secondary battery deterioration judgment method and secondary battery deterioration judgment device - Google Patents

Description

The present invention relates to a method for determining deterioration of a secondary battery for determining the performance of a secondary battery using an aqueous electrolyte, and a device for determining deterioration of the secondary battery.

Conventionally, in a secondary battery using an aqueous electrolytic solution such as a nickel hydrogen secondary battery, a positive electrode plate, a negative electrode plate and a separator are laminated so that a separator is interposed between the positive electrode plate and the negative electrode plate to form an electrode plate. The ones that made up the group are known. In such a group of electrode plates, if a metal foreign substance is present between the electrodes, a micro short circuit may occur between the negative electrode plate and the positive electrode plate. In particular, once used, the secondary battery is reused because there is a risk that metal foreign matter may get caught between the plates or break the separator due to vibration of the usage environment or expansion due to charging / discharging. Sometimes it is desirable to exclude batteries with such deterioration. Therefore, Patent Document 1 describes an example of a method for inspecting a secondary battery for determining the presence or absence of a minute short circuit in the secondary battery.

In the method for inspecting a secondary battery described in Patent Document 1, first, the secondary battery is adjusted to an arbitrary SOC (charge state: State Of Charge) and the voltage drop amount during the aging process is measured. It has a measurement process. In addition, the inspection method of the secondary battery is repeated a plurality of times, and the secondary battery is charged by an arbitrary amount of current to adjust to an SOC different from the SOC of the voltage drop measurement up to the previous time, and during the aging process. A second voltage drop measuring step for measuring the voltage drop of the above is provided. Further, the inspection method of the secondary battery includes the first estimation step of calculating the first estimated SOC from the voltage drop amount and the reference line in the first voltage drop measuring step, and the first estimated SOC for each of the first estimated SOCs. It is provided with a second estimation step of calculating a second estimated SOC by adjusting the amount of current in the voltage drop measuring step of 2. Then, the inspection method of the secondary battery is to compare the actual measurement line showing the relationship between the voltage drop amount in each voltage drop measurement process and the primary / secondary estimated SOC with the reference line, and to make a minute short circuit. It includes a determination step for determining the presence or absence.

Japanese Unexamined Patent Publication No. 2014-6205

In recent years, with the increase in hybrid vehicles and electric vehicles, it is necessary to determine with high accuracy whether or not many secondary batteries can be reused. For example, the secondary battery inspection method described in Patent Document 1 is a method of comparing a predetermined reference line with an actual measurement line measured from a secondary battery to be determined, and therefore is a determination target at the time of determination. Since the unique discharge characteristics of the secondary battery cannot be taken into consideration, the improvement of the determination accuracy may be restricted.

The present invention has been made in view of such circumstances, and an object of the present invention is a method for determining deterioration of a secondary battery capable of determining deterioration of the secondary battery with higher accuracy, and a method for determining deterioration of the secondary battery. The purpose is to provide a deterioration determination device for the above.

The method for determining the deterioration of a secondary battery that solves the above problems is a method for determining the deterioration of a secondary battery containing an aqueous electrolyte, and is aging when the charge amount of the secondary battery is the first remaining capacity. The step of acquiring the first voltage drop amount in the process and the aging process when the remaining capacity of the charge amount of the secondary battery is the second remaining capacity which is the remaining capacity lower than the first remaining capacity. In the step of acquiring the second voltage drop amount and the step of comparing the first voltage drop amount with the second voltage drop amount, the second voltage drop amount is compared with the first voltage drop amount. When the voltage drop amount of the above is larger than a predetermined ratio, the present invention includes a step of determining that the secondary battery has deteriorated.

The secondary battery deterioration determination device that solves the above problems is a secondary battery deterioration determination device that determines the deterioration of the secondary battery containing the aqueous electrolyte, and the charge amount of the secondary battery is the first remaining amount. The first voltage drop acquisition unit that acquires the first voltage drop in the aging process when the capacity is high, and the remaining capacity in which the remaining capacity of the charge amount of the secondary battery is lower than the first remaining capacity. The second voltage drop amount acquisition unit that acquires the second voltage drop amount in the aging process when the second remaining capacity is, and the first voltage drop amount and the second voltage drop amount. For comparison, the secondary battery is provided with a determination unit for determining that the secondary battery has deteriorated when the second voltage drop is larger than a predetermined ratio with respect to the first voltage drop.

According to such a method or configuration, each voltage drop amount in the two remaining capacities acquired by the process of leaving the secondary battery to be discharged, that is, the so-called aging process, is acquired, and based on each acquired voltage drop amount. The deterioration of the secondary battery is determined. In this determination, the first voltage drop amount and the second voltage drop amount are compared, and when the second voltage drop amount is larger than a predetermined ratio with respect to the first voltage drop amount, the secondary battery Is determined to have deteriorated. That is, the second voltage drop is not compared with the preset specified value, but with the first voltage drop that includes the tendency related to the inherent discharge characteristics of the secondary battery itself. .. That is, by comparing the first voltage drop amount and the second voltage drop amount, which include the tendency related to the own unique discharge characteristic, the deterioration state of the secondary battery is the state of the secondary battery. It will be possible to obtain with higher accuracy according to. Specifically, according to a comparison between the first voltage drop amount and the second voltage drop amount, at least the discharge characteristic due to the memory effect of the secondary battery to be determined is determined in determining the deterioration state. Will be considered.

As a preferred method, when the first voltage drop amount is "D1", the second voltage drop amount is "D2", and the predetermined ratio is "R1" which is a value larger than 1, " When the value calculated by "D2-D1 x R1" is larger than the set specified value, it is assumed that the second voltage drop amount is larger than the predetermined ratio with respect to the first voltage drop amount.

According to such a method, the secondary battery is deteriorated based on the magnitude of the second voltage drop amount being larger than a predetermined ratio larger than 1 with respect to the first voltage drop amount. It can be determined that.

As a preferred method, the first remaining capacity is 15% or more of the total capacity of the secondary battery, and the second remaining capacity is 2% or less of the total capacity of the secondary battery.
Since the secondary battery is often used in the range of 40 to 60% of the total capacity for automobiles, for example, the remaining capacity of the reused secondary battery is often 15% or more. Therefore, as in this method, if the remaining capacity is 15% or more as the amount of voltage drop including the tendency related to the inherent discharge history of the secondary battery itself, the first with the remaining capacity having a small influence of deterioration is used. If the voltage drop amount is 2% or less, the effect of the second voltage drop amount, in which the effect of deterioration due to a minute short circuit is large, can be obtained.

As a preferred method, the predetermined ratio is changed according to the magnitude of the first voltage drop amount.
The mode of deterioration of the secondary battery can be estimated according to the magnitude of the first voltage drop. Therefore, according to such a method, deterioration can be appropriately determined by changing a predetermined ratio according to the mode of deterioration of the secondary battery.

As a preferred method, the deterioration of the secondary battery is determined to be a defect due to a minute short circuit.
The amount of voltage drop when the remaining capacity decreases is greatly affected by the minute short circuit. Therefore, according to such a method, deterioration of the secondary battery due to a minute short circuit can be determined.

As a preferred method, the secondary battery is a nickel metal hydride secondary battery.
In a nickel-metal hydride secondary battery, when the remaining capacity is large, the effect of the memory effect is large on the voltage drop amount, while when the remaining capacity is small, the effect of a minute short circuit is large on the voltage drop amount. Therefore, according to such a method, the deterioration determination is made in a place where the influence of the minute short circuit is large by acquiring the second voltage drop amount when the second remaining capacity is smaller than the first remaining capacity. The effects of micro short circuits will be taken into account in the results.

According to the present invention, the deterioration determination of the secondary battery can be performed with higher accuracy.

The schematic diagram which shows the schematic structure about one Embodiment which embodied the deterioration determination apparatus of a secondary battery. The graph which shows the relationship between the remaining capacity and the voltage of the secondary battery which is the deterioration determination target in the same embodiment. The graph which shows the relationship between the relationship between two voltage drops and the deterioration determination when the remaining capacity is different in the same embodiment.

An embodiment in which a secondary battery deterioration determination device using the secondary battery deterioration determination method is embodied will be described with reference to FIGS. 1 to 3. Here, the secondary battery is a nickel-hydrogen secondary battery, and the nickel-hydrogen secondary battery is mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and is used as a power source for a traveling motor of the vehicle.

First, an outline of reuse of a nickel-metal hydride secondary battery will be described.
Generally, in a nickel-metal hydride secondary battery, the ratio [%] of the remaining capacity (remaining capacity) to the fully charged battery capacity is indicated by SOC (charged state: System of Charge). In general, nickel-metal hydride secondary batteries mounted on vehicles are regulated to charge and discharge within the SOC range defined as the range of use (for example, between 40% and 60%). Further, if the SOC of the nickel-metal hydride secondary battery falls below the range of use, there is a high possibility that the deterioration state will progress quickly. Therefore, the discharge of the nickel-metal hydride secondary battery is regulated so as not to fall below the range of use, and the charge is regulated so as not to exceed the range of use. Therefore, the SOC of the nickel-metal hydride secondary battery is usually maintained within the range of use or close to the range of use even after use. In the present embodiment, when the unit is [Ah], it is expressed as the remaining capacity, and when the unit is the ratio [%], it is expressed as SOC.

In addition, there are many nickel-metal hydride secondary batteries installed in vehicles that can be reused depending on the usage environment and usage conditions. Reuse of nickel-metal hydride secondary batteries also leads to reduction of cost and environmental load. On the other hand, once used nickel-metal hydride secondary batteries have different vibrations from the usage environment, temperature rise in the usage state, expansion and contraction of the electrode plate due to charging and discharging, and the like. Therefore, in order to reuse it, it is necessary to inspect each battery to determine whether or not there is a problem. For example, one of the problems that occurs in a nickel-metal hydride secondary battery once used is a minute short circuit. Micro-short circuits are caused by metal foreign matter getting caught between the plates or breaking the separator. After manufacturing, the occurrence is eliminated in the manufacturing process, etc., but after use. In the case of a nickel-metal hydride secondary battery, it may occur due to the usage environment and usage conditions. Further, each nickel-metal hydride secondary battery has a unique discharge characteristic due to a memory effect or the like based on a discharge history, a charge history, or the like. Therefore, even when inspecting for defects, it is preferable that the unique discharge characteristics of each battery are taken into consideration in the inspection. Therefore, it is preferable that the presence or absence of a minute short circuit can be appropriately determined for the reusable nickel-metal hydride secondary battery while considering the unique discharge characteristics caused by the memory effect of each battery.

Therefore, in the present embodiment, a device for determining deterioration including a minute short circuit of a nickel-metal hydride secondary battery that can appropriately determine the presence or absence of a minute short circuit while considering the unique discharge characteristics caused by the memory effect of each battery and the like. Is illustrated. The deterioration determination device of the nickel hydrogen secondary battery acquires the first voltage drop amount based on the aging process when the charge amount of the secondary battery is the first remaining capacity, and then charges the secondary battery. The second voltage drop amount is acquired based on the aging process when the remaining capacity of the amount is the second remaining capacity, which is the remaining capacity lower than the first remaining capacity. Then, when the first voltage drop amount and the second voltage drop amount are compared and the second voltage drop amount is larger than a predetermined ratio with respect to the first voltage drop amount, the secondary battery deteriorates. Is determined to have occurred. The remaining capacity may be SOC.

Next, the nickel-metal hydride secondary battery will be described in detail with reference to FIG.
As shown in FIG. 1, the nickel-metal hydride secondary battery is configured as a battery module 10 in which a plurality of cell cells 100 (cells 1 to 6 101 to 106) are connected in series. The battery module 10 includes a positive electrode terminal 11 in which cells 101 to 106 are electrically connected in series, and a negative electrode terminal 12 as input / output terminals used for charging and discharging. The positive side wiring PL and the negative side wiring NL, which are external wiring, are connected to the positive electrode terminal 11 and the negative electrode terminal 12, respectively, and an electric motor, a power supply, etc. as a load are connected to the positive side wiring PL and the negative side wiring NL, respectively. It is connected. The battery module 10 is provided with six battery tanks by partitioning the space inside the integrated battery tank by a partition wall, and each battery tank corresponds to each cell 101 to 106. The cell 100 is a separator in which a predetermined number of negative electrode plates 111 containing a hydrogen storage alloy and a predetermined number of positive electrode plates 112 containing nickel hydroxide (Ni (OH) ₂ ) are made of a non-woven fabric of an alkali resistant resin. It includes an electrode group 113 laminated via (not shown). Then, in the cell 100, the negative electrode plate 111 of the electrode group 113 is connected to the current collector plate 114 on the negative electrode side, the positive electrode plate 112 of the electrode group 113 is connected to the current collector plate 115 on the positive electrode side, and potassium hydroxide (KOH) is connected. ) Is a water-based electrolyte whose main component is an electrolytic solution (not shown) and is housed in a resin battery case.

The positive electrode plate 112 includes a foamed nickel substrate which is a metal porous body, a positive electrode active material containing nickel oxide such as nickel hydroxide and nickel oxyhydroxide filled in the foamed nickel substrate, and an additive (conductive agent, etc.). ).

The negative electrode plate 111 has an electrode support made of punching metal or the like, and a hydrogen storage alloy (MH) applied to the electrode support.
Subsequently, with reference to FIG. 1, the deterioration determination device 30 including the deterioration determination method of the nickel hydrogen secondary battery will be described.

The deterioration determination device 30 is a device that determines deterioration of the battery module 10 based on two voltage drops acquired by two different SOCs. Further, the deterioration determination device 30 electrically supplies a voltmeter 23 for measuring the voltage between terminals of the battery module 10, a discharge circuit 26 for discharging the battery module 10, and an ammeter 25 for measuring the current flowing through the discharge circuit 26. It is connected to the.

The voltmeter 23 is connected between the positive electrode terminal 11 and the negative electrode terminal 12 of the battery module 10 via the positive side wiring PL and the negative side wiring NL. The voltmeter 23 measures the voltage between the terminals of the battery module 10 and outputs the measured voltage value to the deterioration determination device 30 as an electric signal.

The discharge circuit 26 is connected between the positive electrode terminal 11 and the negative electrode terminal 12 of the battery module 10 via the positive side wiring PL and the negative side wiring NL. The discharge circuit 26 has an electric load and a switch connected in series with the electric load, and opens and closes the switch based on an instruction signal from the deterioration determination device 30. The discharge circuit 26 opens the circuit between the positive electrode terminal 11 and the negative electrode terminal 12 by opening the switch, and closes the switch to connect the positive electrode terminal 11 and the negative electrode terminal 12 via an electric load. The next battery can be discharged.

The ammeter 25 is connected in series with the discharge circuit 26 between the positive electrode terminal 11 and the negative electrode terminal 12 of the battery module 10 via the positive side wiring PL and the negative side wiring NL. The ammeter 25 measures the current flowing through the discharge circuit 26, and outputs the measured current value to the deterioration determination device 30 as an electric signal.

The deterioration determination device 30 includes a computer having a calculation unit and a storage unit, and various processes such as a process of determining deterioration of the secondary battery through calculation processing in the calculation unit of the program stored in the storage unit or the like. I do. The deterioration determination device 30 obtains the voltage between the terminals of the battery module 10 from each input signal. Further, the deterioration determination device 30 can control the discharge circuit 26, and can, for example, perform constant current (CC) discharge or constant voltage (CV) discharge. That is, the battery module 10 can be discharged and adjusted to a predetermined SOC.

The deterioration determination device 30 includes a voltage drop acquisition unit 31 that acquires a voltage drop, a remaining capacity estimation unit 32 that estimates the remaining capacity of the secondary battery, and a determination unit 33 that determines the deterioration state of the nickel-metal hydride secondary battery. A notification unit 34 for notifying the determination result of the determination unit 33, and a storage unit 35 for storing the information required for the determination process are provided. The storage unit 35 stores the voltage drop amount and the like acquired by the voltage drop amount acquisition unit 31.

The voltage drop acquisition unit 31 acquires the voltage drop based on the voltage acquired before and after the aging process based on the voltage acquired from the voltmeter 23. More specifically, the voltage drop acquisition unit 31 acquires the first voltage drop ΔV12 (unit [V]) when the battery module 10 has the first SOC as the first remaining capacity. Further, the voltage drop acquisition unit 31 has a second voltage drop ΔV34 (unit [unit]) when the SOC of the battery module 10 is the second SOC as the second remaining capacity when the SOC is lower than the first SOC. V]) is acquired, and each acquired voltage drop amount is stored in the storage unit 35. The first SOC is, for example, the SOC of the battery module 10 recovered for reuse. The second SOC is the SOC of the battery module 10 recovered for reuse, but is the SOC after a predetermined time has elapsed from the time when it was the first SOC.

The aging process is a process in which the terminals of the battery module 10 are left open for a predetermined period of time. The voltage drop is the voltage at the start, which is the voltage measured at the start of the aging process, and the voltage at the end, which is the voltage measured after being left for a predetermined period with the positive and negative terminals of the secondary battery open. It is acquired as the difference between them, that is, "voltage drop = start voltage-end voltage". Specifically, the voltage drop acquisition unit 31 acquires the start voltage V1 at the first SOC of the battery module 10, leaves it for a predetermined period, and then acquires the end voltage V2 to start the battery module 10. The first voltage drop amount ΔV12, which is the difference between the hourly voltage V1 and the end voltage V2, is acquired. The SOC of the battery module 10 is the first SOC when the starting voltage V1 is acquired, but is slightly lower than the first SOC when the ending voltage V2 is acquired. Similarly, the voltage drop acquisition unit 31 acquires the start voltage V3 of the battery module 10 at the time of the second SOC, and after leaving it for a predetermined period, acquires the end voltage V4 and obtains the start voltage. The second voltage drop amount ΔV34, which is the difference between V3 and the end voltage V4, is acquired. The SOC of the battery module 10 is the second SOC when the starting voltage V3 is acquired, but is slightly lower than the second SOC when the ending voltage V4 is acquired.

The predetermined period may be set to a period during which the amount of voltage drop can be appropriately obtained. As the predetermined period, for example, about 2 to 3 hours to 1 day is often set, but it may be set shorter than 2 to 3 hours as long as a voltage drop amount suitable for determination can be obtained. However, it may be set longer than one day. The predetermined period can be determined based on experience, experiment, and theory according to the type of the battery module 10 and the like. The first SOC is 15% or more, preferably 20% or more, and more preferably 30% or more. The SOC of the battery module 10 recovered from the vehicle is preferable as the first SOC because adjustments such as charging and discharging are not required. The second SOC has a value smaller than that of the first SOC, may be 2% or less, preferably 1% or less, and more preferably in the vicinity of 0% including 0%. For the secondary battery whose SOC at the time of recovery is smaller than the value suitable for the first SOC, after the charging process is performed so that the SOC becomes an appropriate SOC, the first voltage drop ΔV12 and the second voltage drop The quantity ΔV34 may be obtained. Further, if the first voltage drop amount ΔV12 and the second voltage drop amount ΔV34 suitable for the deterioration determination can be obtained, a predetermined period for acquiring the first voltage drop amount ΔV12 and the second voltage drop amount are obtained. The predetermined period for acquiring the quantity ΔV34 may be the same, or conversely, it may be different. By the way, adjusting the SOC of the battery module 10 reduces the influence of the memory effect generated on the battery module 10. However, since the battery module 10 which has a memory effect at the time of use is likely to have the same memory effect at the time of reuse, the first voltage drop amount ΔV12 is acquired by the SOC at the time of recovery without adjusting the SOC. By doing so, the discharge history and the like are more preferably considered.

The voltage drop amount acquisition unit 31 acquires the voltage drop amount in the order of the first voltage drop amount ΔV12 and the second voltage drop amount ΔV34. If the voltage drops are acquired in this order, the first SOC is larger than the second SOC, so that the secondary battery does not need to be charged when the two voltage drops are acquired. Further, since the SOC of the secondary battery changes only in one direction in which the SOC decreases, the first voltage drop ΔV12 and the second voltage drop in a state where the SOC changes only in the decreasing direction (state in which discharge continues). The quantity ΔV34 and can be obtained. Here, the state in which the SOC changes only in the decreasing direction is a state in which charging is not sandwiched in the middle, and occurs when a load is connected between the terminals and a discharge occurs or when the terminals are open. It is a state in which self-discharge is continuous.

The remaining capacity estimation unit 32 estimates the SOC of the secondary battery. A known method can be used to estimate the SOC. For example, the SOC when discharged to the lower limit voltage of the secondary battery is defined as 0%, and the first SOC and the second SOC can be roughly obtained (estimated) from the integrated electric energy at the time of discharging. In the present embodiment, since the second SOC needs to be smaller than the first SOC, so high accuracy is not required for the estimation of the SOC.

By the way, both the first voltage drop amount ΔV12 and the second voltage drop amount ΔV34 of the battery module 10 have a relationship that increases according to the magnitude of the memory effect. Therefore, the inventors do not determine the deterioration of the battery module 10 based only on the second voltage drop ΔV34 as in the conventional case, but the first voltage drop of the second voltage drop ΔV34. It has been found that the determination accuracy can be improved by performing the determination based on the ratio to ΔV12.

Therefore, the determination unit 33 of the present embodiment determines the deterioration state of the nickel-metal hydride secondary battery based on the relationship between the first voltage drop amount ΔV12 and the second voltage drop amount ΔV34. More specifically, the determination unit 33 determines that the deterioration state is progressing, that is, it is deteriorated when the second voltage drop amount ΔV34 is larger than the predetermined ratio of the first voltage drop amount ΔV12. Specifically, when the first voltage drop amount ΔV12 is set to “D1”, the second voltage drop amount ΔV34 is set to “D2”, and the predetermined ratio is set to “R1” which is a value larger than 1, the following Calculate "Equation 1".

D2-D1 x R1 ... (Equation 1)
Then, when the calculation result of "Equation 1" is larger than the specified value set for the deterioration determination, it is determined that the secondary battery has deteriorated. The predetermined ratio "R1" will be described in detail later, but it can be determined based on experience, experiment, and theory according to the type of the battery module 10 and the like.

The first voltage drop amount ΔV12 will be described with reference to FIGS. 2 and 3.
FIG. 2 is a graph showing the relationship between the remaining capacity (SOC) measured for the six battery modules 10 and the voltage between terminals. In FIG. 2, the first voltage drop amount ΔV12 is a value acquired by the aging process when the specific remaining capacity is, for example, 2 [Ah]. Further, the second voltage drop amount ΔV34 is the case where the terminal voltage is the final voltage estimated to have the remaining capacity “0 Ah”, for example, if the final voltage of one cell is 1 [V], the case is 6 cells. When it is 6 [V], it is a value acquired by the aging process. Of the six battery modules 10, five battery modules 10A to 10E are normal battery modules determined to have no deterioration, and are shown by graphs "A" to "E". One battery module 10F is a defective battery module determined to be deteriorated, and is shown by the graph “F”. At this time, depending on the discharge characteristics caused by the memory effect, for example, when the SOC is 15% to 60%, the heights of the voltages shown by the graphs "A" to "F" in the specific SOC are different. In a normal battery module 10A to 10E, the final voltage at which the SOC becomes 0% is approximately the same, for example, 6V, so that the terminal voltage is high when the SOC is between 15% and 60%. The voltage drop tends to be larger. Further, is the defective battery module 10F the same as the normal battery modules 10A to 10E in the voltage drop amount when the SOC is 15% to 60% with respect to the normal battery modules 10A to 10E due to a minute short circuit or the like? , Tends to be larger.

FIG. 3 shows the first voltage drop amount ΔV12 of the six battery modules 10A to 10F when the remaining capacity is 2 [Ah]. As described above, the amount of voltage drop tends to increase as the voltage between terminals increases, so that the normal battery modules 10A to 10E correspond to the graphs "E" to "A" in descending order of the voltage between terminals. Therefore, the first voltage drop amount ΔV12 is large. Further, in the defective battery module 10F, since the voltage between terminals is the graph "F" corresponding to the graph "D" and the graph "E", the magnitude of the first voltage drop ΔV12 is also the graph "D". It is shown to be between and the graph "E". In FIG. 2, the graph of the defective battery module shows "micro short battery". "Short-circuit battery" means a battery having a minute short circuit.

That is, the first voltage drop amount ΔV12 is set as a large value in the order of the graphs “E”, “F”, “D”, “C”, “B”, and “A” when the remaining capacity is 2 [Ah]. To be acquired.
The second voltage drop amount ΔV34 of the battery module 10 will be described.

In the aging process after the SOC reaches the final voltage estimated to be "0%" (remaining capacity is "0Ah"), the amount of voltage change between the normal battery modules 10A to 10E and the defective battery module 10F ( It is known that there is a difference in the amount of voltage drop).

That is, in the normal battery modules 10A to 10E, after reaching the final voltage, normal self-discharge occurs. Since the voltage between terminals at this time is lower than the voltage at the time of measurement of the first voltage drop amount ΔV12, the second voltage drop amount ΔV34 acquired by the aging process does not become a very large value.

On the other hand, the defective battery module 10F tends to have a large amount of self-discharge even after reaching the final voltage. Therefore, the second voltage drop amount ΔV34 acquired by the aging process tends to be a large value. More specifically, in the cell 100 included in the defective battery module 10F, the voltage during the aging process continues to decrease due to the delicate conductive path between the positive and negative electrodes. Therefore, as the second voltage drop amount ΔV34, a value larger than the second voltage drop amount ΔV34 acquired from the normal battery modules 10A to 10E can be obtained. In addition, the defective battery module 10F may have a reduced final voltage due to rapid autolysis.

Further, when the battery modules 10A to 10F are at the final voltage, the value of the second voltage drop ΔV34 acquired by the aging process tends to be larger in the battery module 10 having a larger value of the first voltage drop ΔV12. It is in. It is considered that this is due to the influence of the charge history and the discharge history of the battery module 10, for example, the influence caused by the memory effect. Therefore, for example, when trying to determine a defect of the battery modules 10A to 10F by comparing the second voltage drop amount ΔV34 with a predetermined value (for example, the threshold value L2 in FIG. 3), the battery modules 10A to 10C It will be included in the good product area (second good area). On the other hand, the battery modules 10D to 10F including the battery modules 10D and 10E, which are good products but have a large memory effect, are included in the defective product region (second defective region). That is, there is room for improvement in the accuracy of determining deterioration of the battery module 10.

Further, when the SOC is in a range (low range) lower than the use range (low range), the first voltage drop amount ΔV12 and the second voltage drop amount ΔV34 are greatly affected by the minute short circuit. Therefore, by acquiring the second voltage drop ΔV34 at an SOC lower than the first voltage drop ΔV12, the determination result can be made suitable for the defect determination due to the minute short circuit in the battery module 10. The probability of being able to do it increases. Even if the cause of the defect is not a minute short circuit, if the value of the second voltage drop ΔV34 is large, it can be inferred that some inconvenience has occurred in the battery module 10, so it is preferable to determine it as a defect.

In view of the above, the inventors set the first SOC for acquiring the first voltage drop ΔV12 in a range larger than about 15%, and set the second SOC for acquiring the second voltage drop ΔV34. It has been found that the battery module 10 having a possibility of a minute short circuit can be determined by "D2-D1 x R1" shown in the formula 1 when the value is set to a range including 0%.

That is, in the case of the normal battery modules 10A to 10E, the first voltage drop amount ΔV12 “D1” is acquired as a value including the memory effect. Further, in the case of the normal battery modules 10A to 10E, the second voltage drop amount ΔV34 “D2” is also acquired as a value including the memory effect. Then, the ratio "R1" of the acquired "D1" and "D2" is obtained as a substantially constant value. Therefore, for example, if the value of "R1" is made larger than a certain value, the result of Equation 1 "D2-D1 x R1" can be obtained as a value of "0" or less.

On the other hand, in the case of the defective battery module 10F, the first voltage drop amount ΔV12 “D1” is acquired as a value including the memory effect. On the other hand, in the case of the defective battery module 10F, the second voltage drop amount ΔV34, “D2”, is acquired with a large value that is more affected by the voltage drop due to the minute short circuit, although it includes the memory effect. Therefore, "D2" is acquired as a larger value than "D1". Therefore, if the value of "R1" set for the normal battery modules 10A to 10E is applied to the defective battery module 10F, the result of the formula 1 "D2-D1 x R1" is larger than "0". Obtained as.

The determination line L1 in FIG. 3 is a line indicating “D2 = D1 × R1”. The determination line L1 indicates that if the first voltage drop ΔV12 is large, the battery module 10 is a good product even if the second voltage drop ΔV34 is large. That is, the quality of the battery module 10 can be determined by reflecting the influence of the charging history of the battery modules 10A to 10F, for example, the memory effect.

The value of "R1" may be adjusted. More specifically, "R1" is adjusted within a range in which the calculation result of Equation 1 is "0" or negative in the case of normal battery modules 10A to 10E and positive in the case of defective battery module 10F. You may. By such adjustment, the region below the determination line L1, that is, the region where the calculation result is "0" or negative becomes the first good region where it can be determined that the battery modules 10A to 10E are normal. On the contrary, the range above the determination line L1, that is, the range where the calculation result is positive is the first defective region that can be determined to be the defective battery module 10F.

The y-intercept may be added to "D2 = D1 x R1" based on experience, experiment, theory, and the like. Further, if the normal battery modules 10A to 10E and the defective battery modules 10F can be discriminated, the result of "D2-D1 x R1" is compared with the specified value for quality determination and is equal to or less than the specified value. If it is, it is normal, and if it exceeds the specified value, it may be determined that it is defective. Since it is considered that the values of "R1", y section, default value, etc. differ individually depending on the battery capacity, battery performance, etc. of the battery module 10, experience is experienced for each battery module 10 to be determined for the presence or absence of a minute short circuit. It is preferable to determine based on experiments, theories, etc.

The operation of this embodiment will be described with reference to FIG.
First, the voltage drop acquisition unit 31 acquires the first voltage drop ΔV12 under the first SOC, with the SOC at that time as the first SOC for the recovered battery module 10. The voltage drop acquisition unit 31 measures the starting voltage V1 and then measures the ending voltage V2 after leaving the terminals open for a predetermined period (aging process). Then, the voltage drop amount acquisition unit 31 calculates the first voltage drop amount ΔV12 by “starting voltage V1-end voltage V2” and stores it in the storage unit 35.

After that, the voltage drop acquisition unit 31 monitors the SOC estimated by the remaining capacity estimation unit 32, and lowers the SOC of the recovered battery module 10 to the second SOC. The second SOC is reduced to such a size that a difference suitable for deterioration determination can be obtained. Specifically, the second SOC is set to a value near 0%. The SOC of the battery module 10 may be adjusted by leaving the terminals open, or the SOC may be adjusted by discharging using the discharge circuit 26.

Then, the voltage drop acquisition unit 31 acquires the second voltage drop ΔV34 when the SOC of the battery module 10 becomes the second SOC. First, the voltage drop acquisition unit 31 measures the starting voltage V3, and then measures the ending voltage V4 after leaving the terminals open for a predetermined period (aging process). After that, the voltage drop amount acquisition unit 31 obtains the second voltage drop amount ΔV34 by “starting voltage V3-end voltage V4” and stores it in the storage unit 35.

The determination unit 33 determines "D2-D1 x R1" based on the value "D1" of the first voltage drop amount ΔV12 stored in the storage unit 35 and the value "D2" of the second voltage drop amount ΔV34. calculate. Then, the determination unit 33 determines that the battery module 10 is normal if the calculation result is "0" or negative, and conversely, determines that the battery module 10 is defective if the calculation result is positive. To do. Further, the determination result is notified to another device as a signal, or is notified to the user by display or sound via the notification unit 34.

As described above, according to the secondary battery deterioration determination device using the secondary battery deterioration determination method of the present embodiment, the effects described below can be obtained.
(1) Each voltage drop amount in the first SOC and the second SOC acquired by the process of leaving the battery module 10 to be discharged, that is, the so-called aging process, is acquired, and the battery is based on each acquired voltage drop amount. Deterioration of the module 10 is determined. In this determination, the first voltage drop amount ΔV12 and the second voltage drop amount ΔV34 are compared, and the second voltage drop amount ΔV34 is a predetermined ratio “R1” with respect to the first voltage drop amount ΔV12. When is also large, it is determined that the secondary battery has deteriorated. That is, the second voltage drop ΔV34 is not compared with the preset specified value, but is compared with the first voltage drop ΔV12 including the tendency related to the inherent discharge characteristic of the secondary battery itself. Will be done. That is, by comparing the first voltage drop ΔV12 and the second voltage drop ΔV34, which include the tendency related to their own unique discharge characteristics, the state of deterioration of the secondary battery is determined by the secondary battery. It will be possible to obtain with higher accuracy according to the state of. Specifically, according to a comparison between the first voltage drop amount ΔV12 and the second voltage drop amount ΔV34, at least the discharge caused by the memory effect of the battery module 10 to be determined is determined for the deterioration state. Characteristics are taken into account.

(2) The battery module 10 is deteriorated based on the fact that the magnitude of the second voltage drop amount ΔV34 is larger than a predetermined ratio “R1” which is larger than 1 with respect to the first voltage drop amount ΔV12. It can be determined that.

(3) Since the SOC of the battery module 10 for automobiles is often used in the range of 40 to 60%, the SOC of the battery module 10 to be reused is often 15% or more. Further, as the voltage drop amount including the tendency related to the unique discharge history of the secondary battery itself, if the remaining capacity is 15% or more, the first voltage drop amount ΔV12 in SOC with less influence of deterioration is acquired. can do. Further, if it is 2% or less, the influence of the second voltage drop amount ΔV34, in which the influence of deterioration due to the minute short circuit appears greatly, can be greatly obtained.

(4) The amount of voltage drop when the SOC drops is greatly affected by the minute short circuit. Therefore, the deterioration of the battery module 10 due to the minute short circuit can be determined.
(5) In the battery module 10, when the SOC is high, the effect of the memory effect is large on the voltage drop amount, while when the SOC is low, the effect of the minute short circuit is large on the voltage drop amount. Therefore, by acquiring the second voltage drop amount ΔV34 at the time of the second SOC lower than the first SOC, the deterioration judgment is made in the place where the influence of the minute short circuit is large, and the influence of the minute short circuit is more considered in the judgment result. Will be done.

(Other embodiments)
The above embodiment can also be implemented in the following embodiments.
-In the above embodiment, the case where the deterioration determination device 30 is connected to the voltmeter 23, the discharge circuit 26, and the ammeter 25 is illustrated. However, not limited to this, the deterioration determination device may not be connected to an ammeter or a discharge circuit as long as the voltage drop amount and the SOC can be estimated.

-In the above embodiment, the battery module 10 is composed of six cell cells 100, but it may be composed of a plurality of cell cells other than six. Further, the battery module may be composed of a single battery.

-In the above embodiment, the case where the secondary battery is a nickel hydrogen secondary battery has been illustrated, but the present invention is not limited to this, and the secondary battery is nickel cadmium secondary as long as it is an alkaline secondary battery using an aqueous electrolyte. It may be a rechargeable battery or the like.

-In the above embodiment, the case where the adjusted predetermined ratio "R1" is set is illustrated. However, the present invention is not limited to this, and a predetermined ratio “R1” may be changed based on the first voltage drop amount. For example, if the first voltage drop amount is large, the predetermined ratio may be reduced, and conversely, if the first voltage drop amount is small, the predetermined ratio may be increased. As a result, even in the case where the first voltage drop amount changes slightly significantly, the determination can be appropriately performed.

-In the above embodiment, the case where the deterioration determination method of the secondary battery is applied to the battery module 10 has been illustrated, but the present invention is not limited to this, and the deterioration determination method of the secondary battery is combined with a single battery or a plurality of battery modules. It may be applied to a battery pack. When the battery pack is determined to be defective, the battery pack may be disassembled into a battery module to determine deterioration. In this case, when it is determined that the battery pack is normal, it is not necessary to disassemble the battery pack, so that the determination is easy and quick.

-In the above embodiment, the case where the secondary battery is used as a power source for an automobile has been illustrated. However, the present invention is not limited to this, and the secondary battery may be used as a power source other than the automobile such as various moving bodies and fixed bodies as long as it is used as a power source.

10, 10A to 10F ... Battery module, 11 ... Positive terminal, 12 ... Negative terminal, 23 ... Voltage meter, 25 ... Current meter, 26 ... Discharge circuit, 30 ... Deterioration judgment device, 31 ... Voltage drop acquisition unit, 32 ... Remaining capacity estimation unit, 33 ... determination unit, 34 ... notification unit, 35 ... storage unit, 100 ... cell battery, 101-106 ... cell, 111 ... negative electrode plate, 112 ... positive electrode plate, 113 ... electrode group, 114 ... current collection Plate, 115 ... Current collector plate, NL ... Negative side wiring, PL ... Positive side wiring.

Claims (7)

This is a method for determining the deterioration of a secondary battery containing an aqueous electrolyte.
The step of acquiring the first voltage drop amount by the aging process when the charge amount of the secondary battery is the first remaining capacity, and
A step of acquiring a second voltage drop amount by an aging process when the remaining capacity of the charge amount of the secondary battery is a second remaining capacity which is a remaining capacity lower than the first remaining capacity.
In the step of comparing the first voltage drop amount and the second voltage drop amount, when the second voltage drop amount is larger than a predetermined ratio with respect to the first voltage drop amount, A method for determining deterioration of a secondary battery, comprising a step of determining that the secondary battery has deteriorated. When the first voltage drop amount is "D1", the second voltage drop amount is "D2", and the predetermined ratio is "R1" which is a value larger than 1, "D2-D1x". The first aspect of claim 1, wherein when the value calculated in "R1" is larger than the set specified value, the second voltage drop amount is larger than the predetermined ratio with respect to the first voltage drop amount. How to judge the deterioration of the secondary battery. The first remaining capacity is 15% or more of the total capacity of the secondary battery.
The method for determining deterioration of a secondary battery according to claim 1 or 2, wherein the second remaining capacity is 2% or less of the total capacity of the secondary battery. The method for determining deterioration of a secondary battery according to any one of claims 1 to 3, wherein the predetermined ratio is changed according to the magnitude of the first voltage drop. The method for determining deterioration of a secondary battery according to any one of claims 1 to 4, wherein the deterioration of the secondary battery is determined to be defective due to a minute short circuit. The method for determining deterioration of a secondary battery according to any one of claims 1 to 5, wherein the secondary battery is a nickel hydrogen secondary battery. A secondary battery deterioration determination device that determines the deterioration of a secondary battery containing an aqueous electrolyte.
A first voltage drop acquisition unit that acquires a first voltage drop in the aging process when the charge amount of the secondary battery is the first remaining capacity.
A second voltage for acquiring a second voltage drop in the aging process when the remaining capacity of the charge amount of the secondary battery is the second remaining capacity, which is the remaining capacity lower than the first remaining capacity. With the descent amount acquisition section,
The secondary battery is compared with the first voltage drop amount and the second voltage drop amount, and when the second voltage drop amount is larger than a predetermined ratio with respect to the first voltage drop amount. A deterioration determination device for a secondary battery, which is provided with a determination unit for determining that deterioration has occurred.