TWI785841B - Battery diagnostic device, battery diagnostic method, battery diagnostic program product - Google Patents

Abstract

An object of the present invention is to provide a technology capable of accurately determining the state of deterioration of a storage battery within a practical time. According to the battery diagnostic device of the present invention, during the rest period after charging the battery, the first fluctuation amount of the voltage value of the battery is obtained, and the value of the voltage value is determined by subtracting the internal resistance of the battery from the first fluctuation amount. For the influence caused, calculate the state of deterioration without the influence of the aforementioned internal resistance (refer to FIG. 8 ).

Description

Battery diagnostic device, battery diagnostic method, battery diagnostic program product

The present invention relates to techniques for diagnosing storage batteries.

The number of storage batteries on the market is increasing. In order to properly use the battery, it is necessary to grasp the state of deterioration (State of Health, hereinafter abbreviated as SOH) of the battery. SOH can be represented by the current capacity equivalent to the initial capacity of the battery. One method of judging the state of deterioration is to discharge the battery from a fully charged state to an empty state, and calculate the capacity during the period. In this method, in order to calculate the state of deterioration, it is necessary to discharge the storage battery intentionally, so it may not be practical in some cases. Especially in applications such as electric vehicles, electric charges are wasted unnecessarily due to discharge.

The following Patent Documents 1 to 3 describe more practical methods for judging the state of deterioration. In these documents, during the rest period after the charging operation is completed, the deterioration state is calculated using the change in the battery voltage during the period from the cessation of the charging operation until a certain time elapses. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-094710 [Patent Document 2] Japanese Patent Laid-Open No. 2020-003218 [Patent Document 3] Japanese Patent Laid-Open No. 2019-219389

[Problem to be Solved by the Invention]

The methods described in Patent Documents 1 to 3 may include the influence of the internal resistance of the battery in the fluctuation amount of the battery voltage used for calculating the deterioration state. When the battery voltage is affected by the internal resistance, it is impossible to obtain a battery voltage suitable for determining the deterioration state, so the accuracy of the deterioration state judgment may decrease.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technology capable of accurately determining the deterioration state of a storage battery within a practical time. [Means for solving problems]

According to the battery diagnosis device of the present invention, the first fluctuation amount of the voltage value of the storage battery is obtained during the rest period after the charging operation of the storage battery is performed, and the value of the voltage value is calculated by subtracting the internal resistance of the storage battery from the first fluctuation amount. For the influence caused, calculate the deterioration state without the influence of the aforementioned internal resistance. [Effect of Invention]

According to the battery diagnosis device according to the present invention, it is possible to accurately determine the deterioration state of the storage battery within a practical time.

＜Implementation Type 1＞

FIG. 1 is a diagram showing a configuration example of a charger 1 according to Embodiment 1 of the present invention. In this embodiment, the charger 1 has the role of the rechargeable battery module 2 , and the battery has the role of a battery diagnosis device for determining the deterioration state of the battery module 2 .

The voltage sensor 31 measures the voltage value output by the battery module 2 , and outputs the measurement result to the acquisition unit 11 . The temperature sensor 32 measures the temperature of the battery module 2 and outputs the measurement result to the acquisition unit 11 . The current sensor 33 measures the current value output by the battery module 2 , and outputs the measurement result to the acquisition unit 11 . The voltage sensor 31 /temperature sensor 32 /current sensor 33 can also be formed as a part of the charger 1 or the battery module 2 , or can be formed as a module separate from these.

FIG. 2 is a diagram showing another configuration example of the charger 1 according to Embodiment 1 of the present invention. The battery module 2 may be controlled by the battery management system 34 . The battery management system 34 obtains the current value/temperature/voltage value of the battery module 2 in order to control the battery module 2 . That is, the acquisition unit 11 can acquire these values from the battery management system 34 .

FIG. 3 is a diagram illustrating the internal configuration of the calculation unit 12 . The calculation unit 12 has a block for calculating the threshold value I_thresh and a block for calculating the SOH which will be described later. The acquisition unit 11 sends the voltage value V, current value I, and temperature T of the battery module 2 to each calculation block. The SOH calculation block calculates the SOH of the battery module 2 using the I_thresh obtained by the I_thresh calculation block, and outputs the result. The calculation steps of each calculation block will be described later.

FIG. 4 is a flow chart illustrating the procedure for calculating I_thresh by the I_thresh calculation block (calculation unit 12). Hereinafter, each step in FIG. 4 will be described.

(Figure 4: Step S401) The I_thresh calculation block determines whether the charger 1 starts charging the battery module 2. For example, the start of charging can be detected when the charging current flowing into the battery module 2 exceeds a certain threshold. The start of charging can also be detected by other appropriate methods.

(Figure 4: Step S402) The I_thresh calculation block calculates (estimates) the internal resistance of the battery module 2 during the period after the charging operation of the battery module 2 is started. The specific procedure for calculating the internal resistance will be described later.

(Figure 4: Step S403) The I_thresh calculation block calculates I_thresh using the threshold data 131 stored in the storage unit 13 . A specific calculation program and an example of the threshold data 131 will be described later. The memory unit 13 may be a component of the charger 1 or may be formed separately from the charger 1 . The I_thresh calculation block outputs the calculated I_thresh.

FIG. 5 is a diagram illustrating the steps of estimating the internal resistance of the battery module 2 at S402. When the charging operation starts, the charging current rises from 0 to I_ch. The output voltage of the battery module 2 rises sharply at the start of the charging operation, and then rises gently thereafter. The I_thresh calculation block obtains the voltage variation ΔV_ch during the period Δt_ch during which the output voltage rises sharply. The I_thresh calculation block calculates the estimated value R_est of the internal resistance by the following formula: R_est= ΔV_ch/I_ch.

FIG. 6 shows a configuration example of the threshold data 131 . The threshold value 131 holds V_R_thresh as a value unique to each battery module 2 . I_thresh is an inherent value of each battery module 2 , so the I_thresh calculation block refers to the threshold value data 131 to obtain I_thresh for each battery module 2 . Specifically, I_thresh is calculated according to the following formula: I_thresh=V_R_thresh/R_est. V_R_thresh, for example, can be obtained through experiments in advance and recorded in the threshold data 131 first.

FIG. 7 is a flow chart illustrating the procedure of the SOH calculation block (calculation unit 12 ) to calculate the SOH. Hereinafter, each step in FIG. 7 will be described.

(Figure 7: Step S701) The SOH calculation block determines whether the charging operation of the battery module 2 is completed. Specifically, when the charging current I_charge of the battery module 2 turns from a value greater than 0 to 0, the charging operation ends. Alternatively, the charger 1 may receive a notification that the charging operation is completed. If the charging operation is not completed, it waits until it is completed. When it ends, go to S702.

(Figure 7: Step S702) The SOH calculation block determines whether the charging current I_charge (the charging current value before turning to 0) at the time point when the charging operation ends is less than I_thresh. When I_charge is not less than I_thresh, return to S701. If the I_thresh is not reached, the process proceeds to S703.

(Figure 7: Step S703) The SOH calculation block acquires the fluctuation amount ΔV of the output voltage of the battery module 2 during the period from the time point when the charging operation is completed until a specific time period. A specific example of ΔV will be described using the diagrams described later.

(Figure 7: Step S704) The SOH calculation block calculates the SOH using the degradation state data 132 stored in the storage unit 13 . The specific calculation steps and examples of the degradation state data 132 will be described later. The SOH calculation block outputs the calculated SOH.

FIG. 8 is a diagram illustrating specific examples of S702 to S703. When the charging operation of the battery module 2 is about to end, the charger 1 gradually reduces the charging current I_charge as shown in FIG. 8 , and at the same time keeps the charging voltage constant. At the end of the charging action, I_charge changes from a value greater than 0 to 0. If the value before I_charge turns to 0 is I_thresh, proceed to Y in S702. With this operation, in the constant voltage/variable current charging method (the method of gradually reducing the charging current), the following procedure can be implemented according to the voltage fluctuation at the end of the charging operation.

The SOH calculation block acquires the variation ΔV of the battery voltage during the period from the end of the charging operation until the specified time Δt elapses. Δt is the necessary time until the influence of the internal resistance of the battery module 2 on the battery voltage becomes sufficiently small, and in a typical battery module 2, it is approximately 2 seconds or less, and may be 1 second or less (for example, several ms to hundreds of seconds) ms).

As shown enlarged in the lower right of FIG. 8 , Δt may also be a value with a certain time range. That is, the influence of the internal resistance on the battery voltage should be within a certain range, and this makes Δt a value with a certain allowable range. The SOH calculation block obtains the voltage change ΔV during the period Δt within this range. By using ΔV within this range to calculate SOH, in addition to eliminating the influence of internal resistance, there is an advantage that SOH can be calculated in a very short time after the end of charging.

FIG. 9 shows a configuration example of the degradation state data 132 . The deterioration state data 132 is data describing the relationship between ΔV and SOH in each battery module 2 . In the SOH calculation block, in S703 , the obtained ΔV can be used to calculate the SOH by referring to the degradation state data 132 .

＜Implementation Type 1: Induction＞ With regard to the charger 1 of the first embodiment, Δt is used from the time when the charging operation of the battery module 2 is completed until the influence of the internal resistance of the battery module 2 on the battery voltage becomes sufficiently small. The SOH of the battery module 2 is calculated based on the variation ΔV of the battery voltage between the two. Thereby, accurate SOH can be obtained without the influence of internal resistance.

With respect to the charger 1 of the present embodiment 1, a charger 1 is used in which the influence of the internal resistance of the battery module 2 on the battery voltage falls within a specific range from the time when the charging operation of the battery module 2 is completed until the elapse of time. The SOH of the battery module 2 is calculated by the variation ΔV of the battery voltage for a long time (approximately within 1 second to 2 seconds) up to the time point. In this way, in addition to eliminating the influence of internal resistance, SOH can be calculated in a very short time after the end of charging.

＜Implementation Type 2＞ FIG. 10 is a flow chart illustrating a procedure for calculating SOH by the charger 1 according to Embodiment 2 of the present invention. It is the same as Embodiment 1 except for the calculation procedure of calculating blocks by SOH. The SOH calculation block implements a new step S1001 between S703 and S704 in FIG. 7 . Other calculation procedures are the same as in Figure 7.

(FIG. 10: Step S1001) The SOH calculation block uses the temperature characteristic data 133 stored in the storage unit 13 to correct the temperature characteristic of the battery module 2 . That is, the ΔV of the current temperature of the battery module 2 is corrected to the value ΔV_norm of the standard temperature T_norm of the battery module 2 . An example of the correction procedure will be described later.

FIG. 11 shows an example of temperature characteristic data 133 . The relationship between the temperature of the battery module 2 and ΔV can be represented by a linear function (ΔV=mT+c). As for the temperature characteristics of the battery module 2 , with the temperature of the battery module 2 , the slope m of the aforementioned linear function does not change but the intercept c does. The temperature characteristic data 133 is data describing the temperature characteristic, and the above-mentioned linear function is described with each SOH.

The temperature characteristic data 133 describes the relationship between ΔV of the current temperature T of the battery module 2 and the value ΔV_norm of the standard temperature T_norm (for example, 25° C.) of the battery module 2 by the aforementioned linear function. The SOH calculation block can calculate ΔV_norm by referring to the part corresponding to the temperature T of the temperature characteristic data 133 using the temperature T of the battery module 2 , the measured value of ΔV and the standard temperature T_norm. Specifically, by solving the simultaneous equations, the following formula can be used to calculate: ΔV_norm=m(T_norm-T)+ΔV.

Even if the battery temperature changes, the slope m does not change, so the aforementioned calculation formula remains the same regardless of the battery temperature. That is to say, the SOH calculation block is not affected by the value of the intercept c, and can be obtained by the above calculation formula ΔV_norm.

The SOH calculation block calculates SOH by referring to the degradation state data 132 by using the ΔV_norm after correcting ΔV to the value ΔV_norm of T_norm. Thereby, for example, even when the surrounding temperature of the battery module 2 deviates greatly from the standard temperature, accurate SOH can be obtained.

＜Implementation Type 2: Induction＞ Regarding the charger 1 of the second embodiment, the temperature characteristic data 133 is used to convert ΔV of the current temperature T of the battery module 2 into a value ΔV_norm of the standard temperature T_norm of the battery module 2, and use the converted value to calculate SOH . Thereby, even when the surrounding temperature of the battery module 2 deviates greatly from the standard temperature, accurate SOH can be obtained.

In the second embodiment, the linear function (ΔV=mT+c) describing the temperature characteristic data 133, the intercept changes when the battery temperature changes, but the slope does not change. That is, without being affected by the battery temperature, ΔV can be converted to the value ΔV_norm of the standard temperature by a simple calculation formula.

＜Implementation Type 3＞ FIG. 12 is a flow chart illustrating the procedure for calculating the SOH of the charger 1 according to Embodiment 3 of the present invention. It is the same as Embodiment 1-2 except the calculation procedure of calculating the block by SOH. The SOH calculation block implements a new step S1201 between S703 and S704 in FIG. 7 . Furthermore, in the third embodiment, S702 is omitted. Other calculation procedures are the same as those in Fig. 7 or Fig. 10 . Here, an example in which S1201 is implemented after S1001 using the same calculation program as in FIG. 10 is shown.

(Figure 12: Step S1201) In the third embodiment, S702 is not implemented, so ΔV may include the influence of the internal resistance of the battery module 2 . Here, in the SOH calculation block, its influence is removed by ΔV in this step. Specifically, the voltage drop caused by the estimated value R_est of the internal resistance is removed by the following formula: ΔV'=ΔV-(I_charge×R_est). R_est can be estimated by the procedure described in Embodiment 1. The SOH calculation block calculates SOH by using ΔV' in S704.

＜Implementation Type 3: Induction＞ With regard to the charger 1 of the third embodiment, regardless of whether the charging current I_charge after the completion of the charging operation is less than the threshold value I_thresh, the amount of voltage variation ΔV after the completion of the charging until a specific time elapses is obtained. By using this The calculation of SOH by ΔV is different from Embodiment 1 because there is no need to wait until Δt elapses from the end of the charging operation, so SOH can be calculated more quickly.

<Modification of the present invention> In the above embodiment, because the influence caused by the temperature characteristics of the battery module 2 is removed, the SOH can be calculated only when the temperature of the battery module 2 is at the standard temperature (or within the allowable range before and after it). Thereby, correct SOH can be obtained without correcting the temperature characteristic.

In the above embodiments, an example in which the charger 1 operates as a battery diagnostic device is described, but the functional units corresponding to the acquisition unit 11 and the calculation unit 12 do not necessarily have to be arranged in the charger 1 . That is, as long as the voltage value/current value/temperature of the battery module 2 can be acquired, these functional parts can be arranged in any place. Furthermore, there is no need to directly connect these functional parts to the battery module 2 .

In the above embodiments, the battery module 2 was exemplified as a storage battery, but the present invention can also be applied to other storage batteries. For example, the unit size of the storage battery applicable to the present invention is not limited to a battery module, but may also be a battery cell or a battery pack. The composition of the accumulator can also be arbitrary. For example, it can be a lithium iron phosphate battery (LFP), a spherical nano-carbon fiber (MNC) battery, or a battery with other components.

1: Charger 11: Acquisition department 12: Calculation department 13: Memory Department 131:Threshold data 132:Deterioration status data 133: Temperature characteristic data 2: Battery module 31: Voltage sensor 32: Temperature sensor 33: Current sensor 34:Battery management system

[ Fig. 1 ] is a diagram showing a configuration example of a charger 1 according to Embodiment 1. [ Fig. 2 ] is a diagram showing another configuration example of the charger 1 according to the first embodiment. [FIG. 3] is a figure explaining the internal structure of the calculation part 12. [FIG. [ FIG. 4 ] is a flowchart illustrating the steps of calculating I_thresh by the I_thresh calculation block (calculation unit 12 ). [FIG. 5] It is a figure explaining the procedure of estimating the internal resistance of the battery module 2 in S402. [FIG. 6] A configuration example of threshold value data 131 is shown. [FIG. 7] It is a flow chart explaining the procedure of calculating SOH by the SOH calculation block (calculation part 12). [FIG. 8] It is a figure explaining the specific example of S702-S703. [ FIG. 9 ] shows a configuration example of the deterioration state data 132 . [ Fig. 10 ] is a flow chart illustrating the procedure for calculating SOH in the charger 1 of Embodiment 2. [FIG. 11] An example of temperature characteristic data 133 is shown. [ Fig. 12 ] is a flow chart illustrating the procedure for calculating the SOH of the charger 1 according to the third embodiment.

Claims (14)

A battery diagnostic device for diagnosing the state of deterioration of a battery; comprising: an acquisition unit for obtaining a voltage value output by the battery and a current value output by the battery, and a calculation unit for calculating the state of deterioration by using the voltage value and the current value; the calculation The unit obtains the first fluctuation amount of the voltage value during the rest period after the charging operation of the storage battery, the calculation unit uses the first fluctuation amount to calculate the degradation state, and the calculation unit calculates the degradation state by By removing the influence of the internal resistance of the storage battery on the voltage value from the first fluctuation amount, the degradation state without the influence of the internal resistance is calculated; the internal resistance is used from the start time point of the charging operation of the storage battery The second fluctuation amount of the voltage value is estimated until a specific time point during the charging operation is performed. In the battery diagnostic device according to claim 1, the calculation unit judges whether or not the degradation state determination condition that the current value is below a threshold value is satisfied at the time point when the charging operation of the storage battery is stopped, and the calculation unit judges whether the degradation state determination is satisfied. In the case of conditions, the fluctuation amount of the voltage value during the period from the time point when the charging operation is stopped until the elapse of a specific time is obtained as the first fluctuation The quantity, the aforementioned specific time, is the length of time from the time point when the aforementioned charging operation is stopped to the time point when the influence of the aforementioned internal resistance on the aforementioned voltage value is controlled within a specific range. According to the battery diagnosis device of claim 2, the aforementioned specific time is within 2 seconds. In the battery diagnostic device according to claim 2, the calculation unit calculates the threshold value using the estimated internal resistance. The battery diagnostic device according to claim 2, wherein the battery diagnostic device is further equipped with a storage unit that stores threshold data describing the relationship between the internal resistance and the threshold for each of the aforementioned batteries, and the calculation unit uses the threshold data described in accordance with the aforementioned threshold data. The relationship computes the aforementioned threshold. The battery diagnostic device according to claim 1, wherein the battery diagnostic device further includes a storage unit storing degradation state data describing the relationship between the first fluctuation amount and the degradation state for each of the storage batteries, and the calculation unit operates according to the degradation state. The aforementioned relationship described by the state data calculates the aforementioned degradation state. In the battery diagnostic device according to claim 1, the storage battery has a temperature characteristic that changes the first fluctuation amount according to the temperature of the storage battery, and the obtaining unit further obtains the storage battery temperature, the calculation unit corrects the first fluctuation amount according to the temperature characteristic, and the calculation unit calculates the deterioration state using the corrected first fluctuation amount. According to the battery diagnostic device of claim 7, the calculation unit converts the relationship between the measured temperature of the battery and the first variation in the correction to the standard temperature of the battery and the temperature characteristic according to the temperature characteristics. The relationship between the standard values of the aforementioned first fluctuation amount of the standard temperature is obtained by converting the aforementioned first fluctuation amount into the value of the aforementioned standard temperature. In the battery diagnosis device according to claim 7, the temperature characteristic is a linear function representing the relationship between the temperature of the battery and the first variation, and the temperature characteristic has a function corresponding to the temperature of the battery, and the above 1 The property that the intercept of a subfunction varies but the slope does not. In the battery diagnosis device according to claim 1, the calculation unit, regardless of the current value, obtains the fluctuation amount of the voltage value during the period from the time when the charging operation is stopped until a specific time elapses, as the first fluctuation The calculation unit calculates the deterioration state without the influence of the internal resistance by removing the influence of the internal resistance of the storage battery included in the first variation on the voltage value. In the battery diagnostic device according to claim 10, the calculation unit obtains the start of the charging operation for the storage battery. The second fluctuation amount of the voltage value between the start time point and the specified time point during the charging operation, the calculation unit uses the second fluctuation amount to estimate the internal resistance, and the calculation unit uses the second fluctuation amount to estimate the internal resistance. By removing the influence of the estimated internal resistance on the voltage value from the first variation, the degradation state excluding the influence of the internal resistance is calculated. In the battery diagnostic device according to claim 1, the calculation unit calculates the degradation state only when the temperature of the battery is within a specific range. A method for diagnosing a battery, diagnosing the deterioration state of the storage battery; comprising: the steps of obtaining the voltage value output by the storage battery and the current value output by the storage battery, and the step of calculating the degradation state by using the voltage value and the current value; The step of the state is to obtain the first fluctuation amount of the aforementioned voltage value during the rest period after the charging operation of the aforementioned storage battery, and in the step of calculating the aforementioned degradation state, use the aforementioned first fluctuation amount to calculate the aforementioned degradation state, and calculate the aforementioned degradation state The step of calculating the degradation state without the influence of the internal resistance by removing the influence of the internal resistance of the storage battery on the voltage value from the first variation; From the start time point of the battery to a specific time point during the period when the aforementioned charging action is implemented The second fluctuation amount of the aforementioned voltage value is estimated. A battery diagnosis program product, which causes a computer to execute the process of diagnosing the deterioration state of the storage battery; causes the computer to execute: the steps of obtaining the voltage value output by the storage battery and the current value output by the storage battery, and using the voltage value and the current value to calculate the aforesaid The step of degraded state; in the step of calculating the aforementioned degraded state, make the aforementioned computer perform the step of obtaining the first fluctuation amount of the aforementioned voltage value during the rest period after charging the aforementioned storage battery, and in the step of calculating the aforementioned degraded state, use The aforementioned computer executes the step of calculating the aforementioned degradation state using the aforementioned first fluctuation amount, and in the step of calculating the aforementioned degradation state, the aforementioned computer is executed to remove the influence of the internal resistance of the storage battery from the aforementioned first fluctuation amount on the aforementioned voltage value, A step of calculating the aforementioned degradation state without the influence of the aforementioned internal resistance; the aforementioned internal resistance uses the aforementioned voltage between the start time point when the charging operation of the aforementioned storage battery is started and the specified time point during the implementation of the aforementioned charging operation The second variation of the value is estimated.

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