A method and device for detecting battery life

Abstract

The present application discloses a battery life detection method and device, the battery life detection method includes fully charging the battery with a preset first current; then discharging the battery with a preset starting current for a preset discharge time, and recording the battery voltage V1; S1: fully charging the battery with a preset first current; S2: discharging the battery with a preset vehicle equipment working current; S3: fully charging the battery with a preset first current; S4: discharging the battery with a preset starting current for a preset discharge time, and recording the battery voltage V2; repeating steps S1-S4 until V1-V2> the starting voltage threshold, it is determined that the battery is at the end of its service life, and the number of repetitions N is the maximum number of times the battery is charged. The present application simulates the workflow of an actual car battery so that the detected battery life is consistent with the actual battery life, thereby being able to accurately monitor the battery usage.

Description

Technical Field

[0001] The present invention relates to the technical field of battery life detection, and in particular to a battery service life detection method and device. Background Art

[0002] Currently in the lithium-ion battery industry, the test results of cycle testing (charging and discharging with a fixed current for several cycles to a specified capacity retention rate, such as 80% SOHc) plus calendar life (storage at different SOC states of charge at a specified temperature until the capacity retention rate reaches a specified value, such as 80% SOHc) are usually used to simulate the service life of the battery.

[0003] However, the above method is time-consuming and requires a lot of testing resources. In addition, the test method only considers the capacity retention rate and calendar life of the battery, but does not test the battery according to the actual battery workflow, resulting in a certain error between the actual battery life and the service life obtained by the test. Summary of the invention

[0004] The present invention provides a battery service life detection method, which solves the technical problem that there is a certain error between the battery service life in actual use and the service life obtained by detection.

[0005] According to one aspect of the present invention, a method for detecting battery life is provided, comprising:

[0006] Fully charging the battery with a preset first current;

[0007] Then discharge the battery with a preset starting current for a preset discharge time, and record the battery voltage V1;

[0008] S1: Fully charging the battery with the preset first current;

[0009] S2: Discharge the battery with the preset vehicle equipment working current;

[0010] S3: Fully charging the battery with the preset first current;

[0011] S4: After discharging the battery for a preset discharge time using the preset starting current, the battery voltage V2 is recorded;

[0012] Steps S1-S4 are repeatedly executed until V1-V2>the starting voltage threshold, and it is determined that the battery is at the end of its service life, and the number of repetitions N is the maximum number of times the battery is charged.

[0013] Optionally, the step of fully charging the battery with the preset first current and the step of discharging the battery with the preset vehicle-mounted device working current both include:

[0014] Leave the battery for a preset cooling time.

[0015] Optionally, the preset cooling time is greater than or equal to 10 minutes.

[0016] Optionally, before step S3, the method further includes:

[0017] S21: Repeat steps S1-S2 M times;

[0018] Repeat steps S1-S4 until V1-V2> the start voltage threshold, and then determine that the battery is at the end of its service life, and the number of repetitions N is the maximum number of times the battery is charged, including:

[0019] Repeat steps S1-S4 until V1-V2> the start voltage threshold, and then determine that the battery is at the end of its service life, and M*(N-1) is the maximum number of battery charging times, and N is the number of repetitions.

[0020] Optionally, M is greater than or equal to 50.

[0021] Optionally, the battery is a 12V lithium battery.

[0022] Optionally, the preset first current is 3C-10C; the preset starting current is 10C-20C; and the preset vehicle-mounted equipment operating current is 30mA-100mA.

[0023] Optionally, the preset discharge time is 100s-140s; the preset cooling time is greater than or equal to 10 minutes.

[0024] Optionally, the start voltage threshold is 0-100mV.

[0025] According to another aspect of the present invention, a battery service life detection device is provided, comprising:

[0026] A first charging unit, used to fully charge the battery with a preset first current;

[0027] A first discharge unit, used for discharging the battery with a preset starting current for a preset discharge time, and recording the battery voltage V1;

[0028] A second charging unit, used to fully charge the battery with the preset first current;

[0029] The second discharge unit is used to discharge the battery with a preset vehicle-mounted equipment working current;

[0030] A third charging unit, used to fully charge the battery with the preset first current;

[0031] A third discharging unit, used to discharge the battery with the preset starting current for a preset discharging time and then record the battery voltage V2;

[0032] The judging unit is used to repeatedly execute the operations in the second charging unit, the second discharging unit, the third charging unit and the third discharging unit in sequence until V1-V2>the starting voltage threshold, and judge that the battery is at the end of its service life, and the number of repetitions N is the maximum number of charging times of the battery.

[0033] The technical solution of the embodiment of the present invention simulates the working process of an actual automobile battery, such as simulating the working process of the battery using a large current to start the vehicle and using a small current to supply various on-board devices when the vehicle is running, so that the service life of the battery detected is consistent with the actual battery life, thereby accurately monitoring the battery usage. In addition, the present application determines whether the battery has reached the end of its service life by judging whether the value of V1-V2 is greater than the starting voltage threshold, that is, after the battery loses a certain battery capacity, the starting voltage generated by the battery when the vehicle is started again must be able to start the vehicle, which is more practical and eliminates the need to use time-consuming and meaningless detection methods such as calendar life.

[0034] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 is a flow chart of a battery life detection method provided according to Embodiment 1 of the present invention;

[0037] Figure 2 is another flow chart of a battery life detection method provided according to the second embodiment of the present invention;

[0038] Figure 3 A flowchart of a specific application of a battery life detection method provided in Embodiment 3 of the present invention;

[0039] Figure 4 It is a structural schematic diagram of a battery service life detection device provided according to Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0041] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0042] Embodiment 1

[0043] Figure 1 This is a flow chart of a battery life detection method provided in the first embodiment of the present invention. This embodiment is applicable to the case of performing life tests on low-voltage lithium batteries or other low-voltage batteries. The method can be performed by a battery life detection device, which can be implemented in the form of hardware and / or software, and can be configured in an electronic device. Figure 1 As shown, the method includes:

[0044] S01. Fully charge the battery with a preset first current.

[0045] When charging the battery, the battery can be fully charged using a suitable preset first voltage according to the capacity of the battery to be charged, ensuring that the battery is fully charged within a certain period of time. That is, if the battery capacity is large, a larger voltage can be used for charging; if the battery capacity is small, a corresponding smaller voltage can also be used for charging. The battery can be fully charged in a shorter period of time, thereby shortening the time of the entire battery detection process.

[0046] S02. After discharging the battery with a preset starting current for a preset discharge time, record the battery voltage V1.

[0047] The preset starting current is determined according to the actual discharge current of the battery when the car is started, and the preset discharge time is determined according to the discharge time of the battery when the car is started. The exemplary preset starting current may be equal to the discharge current of the battery when the car is started, and the preset discharge time may be equal to the discharge time of the battery when the car is started. The present application can simulate the discharge process of the battery of the car, by discharging the battery with a preset starting current, simulating the large current discharge of the battery when the car is started; and by discharging the battery with a starting current for a preset discharge time, simulating the continuous discharge of the battery when the car is started, and recording the voltage of the battery at this time. Since the battery is at full capacity at this time, the battery voltage of the battery at this time is greater than the voltage required to start the car.

[0048] S1, fully charging the battery with a preset first current;

[0049] After recording the battery voltage V1 when the car is started with the battery at full capacity, the battery can be charged and discharged cyclically, that is, the charging and discharging process of simulating the actual operation of the car can be repeated many times. First, the battery can be fully charged with a suitable preset first current to ensure that the battery is fully charged within a certain period of time.

[0050] S2, discharge the battery with the preset vehicle equipment working current;

[0051] Among them, the preset vehicle-mounted equipment working current is less than the preset starting current. The preset vehicle-mounted equipment working current is determined according to the vehicle-mounted equipment working current. When the battery is fully charged, the discharge of the battery during normal operation of the car can be simulated, that is, the battery is only used to power the vehicle-mounted equipment on the car. At this time, the discharge of the battery is compared with the discharge of the battery when the car is started. It should be discharged with a smaller discharge current. Therefore, in the specific detection process, the detection personnel can set the corresponding preset vehicle-mounted equipment working current according to the actual vehicle-mounted equipment working current, so that the battery is discharged with the preset vehicle-mounted equipment working current.

[0052] S3, fully charging the battery with a preset first current;

[0053] S4, after discharging the battery with a preset starting current for a preset discharge time, record the battery voltage V2;

[0054] After the battery is discharged with the preset vehicle equipment working current, it can be fully charged again and then discharged with the preset starting current for the preset discharge time. The battery voltage recorded at this time is the battery voltage recorded after the battery has gone through a complete actual charge and discharge process.

[0055] S5, determine whether the value of V1-V2 is greater than the starting voltage threshold. If yes, continue to step S6, if no, return to step S1.

[0056] S6. It is determined that the battery is at the end of its service life, and the number of times N of repetitions of S1-S4 is the maximum number of times the battery is charged.

[0057] Repeat steps S1-S4, that is, the battery has gone through N complete actual charge and discharge processes. The voltage V2 recorded at this time is the battery voltage after the battery has been discharged with a large current again after going through N complete actual charge and discharge processes. At this time, the battery has lost a certain amount of capacity. In order to determine whether the battery has entered the end of its service life, it can be determined whether the voltage generated by the current capacity of the battery when the car is started meets the starting voltage of the car's motor, that is, the minimum capacity of the battery must be able to meet the battery to start the car. Therefore, it can be set that when V1-V2> the starting voltage threshold, it is determined that the battery is at the end of its service life. The starting voltage threshold is the starting voltage when the battery is full of capacity minus the critical value of the voltage required to start the car. Of course, the starting voltage threshold here can also be set to an empirical value, or set according to the needs of the tester.

[0058] In addition, in order to simulate the actual use process of the battery as much as possible, the present application can discharge the battery with a preset vehicle-mounted equipment working current after the battery is fully charged, and discharge the fully charged battery with a preset starting current. The total number of charging times is the number of times the battery is charged from an empty state to a full state, that is, the number of repetitions of step S1. Therefore, when it is detected that V1-V2>the starting voltage threshold, the maximum number of charging times of the battery is N times.

[0059] The technical solution of the embodiment of the present invention simulates the working process of an actual automobile battery, such as simulating the working process of the battery using a large current to start the vehicle and using a small current to supply various on-board devices when the vehicle is running, so that the service life of the battery detected is consistent with the actual battery life, thereby accurately monitoring the battery usage. In addition, the present application determines whether the battery has reached the end of its service life by judging whether the value of V1-V2 is greater than the starting voltage threshold, that is, after the battery loses a certain battery capacity, the starting voltage generated by the battery when the vehicle is started again must be able to start the vehicle, which is more practical and eliminates the need to use time-consuming and meaningless detection methods such as calendar life.

[0060] Embodiment 2

[0061] Figure 2 This is a flow chart of a battery life detection method provided by the second embodiment of the present invention. In this embodiment, the battery voltage V2 is not recorded repeatedly, but M battery charging and discharging processes are grouped together, and V2 is recorded once after each group, so as to reduce the test process and quickly complete the battery life detection. Figure 2 As shown, the method includes:

[0062] 201. Fully charge the battery with a preset first current, and place the battery for a preset cooling time.

[0063] After the battery is fully charged with the preset first current, the temperature of the battery surface will increase. In order to make the recorded voltage more accurate, the battery can be left for a period of time to reduce the battery surface temperature and then the next step can be performed after the battery returns to normal temperature.

[0064] 202. After discharging the battery with a preset starting current for a preset discharge time, the battery voltage V1 is recorded;

[0065] 203. Fully charge the battery with a preset first current, and place the battery for a preset cooling time.

[0066] It should be noted that after each battery charge, the battery surface may generate heat. Therefore, the battery can be left for a while and then proceed to the next step after the battery cools down in order to obtain more accurate test results.

[0067] 204. Discharge the battery with a preset vehicle equipment operating current, and leave the battery for a preset cooling time.

[0068] It should be noted that when the battery is discharged with the preset vehicle-mounted equipment working current, the battery surface will also heat up because the battery is in a long working state. Therefore, the battery needs to be left for a certain period of time to facilitate the next step. The preset cooling time in this application can be set according to the detection requirements. For example, it can be set to an empirical value of 30 minutes, and of course it can be appropriately extended or shortened.

[0069] 205. Determine whether the number of repetitions of steps 203-204 reaches M times. If so, continue to execute step 206. If not, return to execute step 203.

[0070] In the present application, step 203 and step 204 may be repeated M times, i.e., M times of battery full charge and emptying may be set as a group. For example, 50 times may be set as a group. After the battery is fully charged, it is then discharged with a preset vehicle-mounted device working current. After repeating 50 times, the battery voltage V2 after high current discharge is recorded again, so as to reduce multiple measurements of V2. Of course, the number of repetitions of steps 203-204 may be set according to actual needs, for example, it may be set to 100 or 200.

[0071] 206. Fully charge the battery with a preset first current, and place the battery aside for a preset cooling time.

[0072] 207. After discharging the battery with a preset starting current for a preset discharge time, record the battery voltage V2.

[0073] 208. Determine whether V1-V2 is greater than the starting voltage threshold. If so, execute step 209; if not, return to execute step 203.

[0074] 209. It is determined that the battery is at the end of its service life, and M*(N-1) is the maximum number of times the battery can be charged, and N is the number of times steps 203-207 are repeated.

[0075] It should be noted that steps 203-207 will be repeated, that is, the battery will be fully charged and discharged in groups of M times. After repeating M times, the battery will be fully charged again. The battery voltage V2 after the preset starting current is discharged for the preset discharge time is recorded. With this method, there is no need to record V2 every time the battery is filled and discharged. Due to the differences in the battery's own process or manufacturing process, it is difficult to keep the battery life consistent. Therefore, the actual detection does not need to be too precise. In this regard, the present application can be grouped into 50 or 100 times of full-discharge, and V2 is recorded once after each group of full-discharge of the battery is completed, so that the number of times the voltage V2 is recorded is reduced, thereby reducing the detection time. The number of repeated charge and discharge times M of the present application can also be set according to the detection needs.

[0076] In addition, when V1-V2>starting voltage threshold, the battery may be at the end of its service life, that is, the discharge voltage of the battery when starting the car is lower than the critical value of the voltage required to start the car. Therefore, M*N cannot be directly used as the final charging number of the battery, but M*(N-1) is used as the maximum charging number of the battery.

[0077] Of course, when the minimum maximum charging times of the battery are known, the number of V2 detections before the minimum maximum charging times can be omitted. For example, assuming that the battery can be charged at least 1000 times, V2 detection does not need to be performed before 1000 times, but V2 detection is performed from 1000, and then M times of full charge-empty are grouped as one, and V2 is measured after one group, which can reduce the number of V2 measurements.

[0078] The technical solution of the embodiment of the present invention simulates the working process of an actual automobile battery, such as simulating the battery using a large current to start the vehicle, and using a small current to supply various on-board devices when the car is running, so that the service life of the battery detected is consistent with the actual battery life, thereby accurately monitoring the battery usage. In addition, the present application reduces the impact of the battery temperature on subsequent steps by setting the battery aside for a preset cooling time. And by taking M times of full charging and emptying as a group, and measuring the starting voltage V2 of the battery after one group, the number of measurements of V2 can be reduced, thereby completing rapid detection and obtaining more accurate detection data.

[0079] Embodiment 3 of the present invention provides a specific application example, such as Figure 3 As shown in the figure, the specific process of life detection of 12V lithium battery includes:

[0080] 301. Fully charge a 12V lithium battery to 100% SOC at a current of 3C-10C and leave it for 30 minutes.

[0081] It should be noted that when charging a 12V lithium battery as the starting power source for a car, it is necessary to complete the fast charge within 20 minutes, so a high rate current of 3C-10C can be used for charging. In order to fully dissipate the heat of the battery, the 12V lithium battery can be left for 30 minutes after being fully charged to allow the battery to cool down.

[0082] 302. Discharge the 12V lithium battery with a starting current of 10C-20C for 120 seconds and record the battery voltage V1.

[0083] It should be noted that since the 12V lithium battery needs to reach a specified voltage in a short time before starting the vehicle, the 12V lithium battery can be discharged with a pulse current of 10C-20C and the battery voltage V1 during discharge should be recorded.

[0084] 303. Fully charge a 12V lithium battery to 100% SOC at a current of 3C-10C and leave it for 30 minutes.

[0085] 304. Discharge the 12V lithium battery to 0% SOC at a current of 30mA-100mA and leave it for 30 minutes.

[0086] It should be noted that, since the 12V lithium battery is usually discharged at a current of 30mA-100mA when used as a power source for vehicle-mounted equipment, the 12V lithium battery can be discharged at a current of 30mA-100mA in this embodiment. Since the battery will also generate a certain amount of heat during the discharge process, the 12V lithium battery can be left for 30 minutes after being discharged to allow the battery to cool down.

[0087] 305. Determine whether the number of repetitions of steps 303-304 reaches 100. If so, continue to execute step 306. If not, return to execute step 303.

[0088] 306. Then fully charge the 12V lithium battery to 100% SOC with a current of 3C-10C and leave it for 30 minutes.

[0089] 307. Discharge the 12V lithium battery with a starting current of 10C-20C for 120 seconds and record the battery voltage V2 at this time.

[0090] 308. Determine whether V1-V2 is greater than 100mV. If so, continue to execute step 309; if not, return to execute step 303.

[0091] 309. It is determined that the battery is at the end of its service life, and 100*(N-1) is the maximum number of times the battery can be charged, and N is the number of times steps 303-307 are repeated.

[0092] It should be noted that, for the case where a 12V lithium battery is used as the starting power source for a car, this embodiment can be used as a group of 100 full-discharge cycles, that is, after the battery is discharged and then filled for 100 times, the battery voltage V2 after the 12V lithium battery is discharged with the starting current is recorded, that is, if the battery is repeatedly filled and discharged for 1000 times, only 10 times of V2 need to be recorded, which greatly reduces the number of times V2 is recorded, thereby reducing the battery detection time. In addition, if when V1-V2>100mV, the number of times V2 is recorded is 10 times, then the maximum number of times the battery can be charged is 950 times, where the starting voltage threshold is 100mV, which is an empirical value here.

[0093] Embodiment 4

[0094] Figure 4 This is a schematic diagram of the structure of a battery life detection device provided by Embodiment 3 of the present invention. Figure 4 As shown, the device comprises:

[0095] The first charging unit 401 is used to fully charge the battery with a preset first current.

[0096] The first discharging unit 402 is used for discharging the battery with a preset starting current for a preset discharging time and then recording the battery voltage V1.

[0097] The second charging unit 403 is used to fully charge the battery with a preset first current.

[0098] The second discharging unit 404 is used to discharge the battery with a preset vehicle-mounted equipment working current.

[0099] The third charging unit 405 is used to fully charge the battery with a preset first current.

[0100] The third discharging unit 406 is used to discharge the battery with a preset starting current for a preset discharging time and then record the battery voltage V2.

[0101] The judging unit 407 is used to repeat the steps in the second charging unit, the second discharging unit, the third charging unit and the third discharging unit N times until V1-V2> the starting voltage threshold, and judge that the battery is at the end of its service life, and N is the maximum number of charging times of the battery.

[0102] Optionally, the device further comprises:

[0103] The cooling unit is used to place the battery for a preset cooling time after the battery is fully charged with a preset first current and after the battery is discharged with a preset vehicle-mounted equipment working current.

[0104] Optionally, the device further comprises:

[0105] A repeating unit is used for repeating the steps in the second charging unit 403 to the second discharging unit 404 M times after executing the steps in the second discharging unit 404.

[0106] The judgment unit 407 can also be used to repeatedly execute the operations in the second charging unit 403, the second discharging unit 404, the repeating unit, the third charging unit 405 and the third discharging unit 406 in sequence until V1-V2>the starting voltage threshold, and it is judged that the battery is at the end of its service life, and M*(N-1) is the maximum number of charging times of the battery, and N is the number of repetitions.

[0107] The battery life detection device provided in the embodiment of the present invention can execute the battery life detection method provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0108] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0109] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A battery life detection method, characterized in that: include: Fully charging the battery with a preset first current; Then discharge the battery with a preset starting current for a preset discharge time, and record the battery voltage V1; S1: Fully charging the battery with the preset first current; S2: Discharge the battery with the preset vehicle equipment working current; S3: Fully charging the battery with the preset first current; S4: After discharging the battery for a preset discharge time using the preset starting current, the battery voltage V2 is recorded; Steps S1-S4 are repeatedly executed until V1-V2>the starting voltage threshold, and it is determined that the battery is at the end of its service life, and the number of repetitions N is the maximum number of times the battery is charged.

2. The battery life detection method according to claim 1, characterized in that: The step of fully charging the battery with the preset first current and discharging the battery with the preset vehicle-mounted equipment working current both includes: Leave the battery for a preset cooling time.

3. The battery life detection method according to claim 2, characterized in that: The preset cooling time is greater than or equal to 10 minutes.

4. The battery life detection method according to claim 1, characterized in that: Before step S3, the method further includes: S21: Repeat steps S1-S2 M times; The steps S1-S4 are repeatedly performed until V1-V2> the starting voltage threshold, and it is determined that the battery is at the end of its service life, and the number of repetitions N is the maximum number of times the battery is charged, including: Repeat steps S1-S4 until V1-V2> the start voltage threshold, and then determine that the battery is at the end of its service life, and M*(N-1) is the maximum number of battery charging times, and N is the number of repetitions.

5. The battery life detection method according to claim 4, characterized in that: M is greater than or equal to 50.

6. The battery life detection method according to any one of claims 1 to 5, characterized in that: The battery is a 12V lithium battery.

7. The battery life detection method according to claim 6, characterized in that: The preset first current is 3C-10C; the preset starting current is 10C-20C; and the preset vehicle-mounted equipment operating current is 30mA-100mA.

8. The battery life detection method according to claim 6, characterized in that: The preset discharge time is 100s-140s; the preset cooling time is greater than or equal to 10 minutes.

9. The battery life detection method according to claim 6, characterized in that: The starting voltage threshold is 0-100mV.

10. A battery life detection device, characterized in that: include: A first charging unit, used to fully charge the battery with a preset first current; A first discharge unit, used for discharging the battery with a preset starting current for a preset discharge time, and recording the battery voltage V1; A second charging unit, used to fully charge the battery with the preset first current; The second discharge unit is used to discharge the battery with a preset vehicle-mounted equipment working current; A third charging unit, used to fully charge the battery with the preset first current; A third discharging unit, used to discharge the battery with the preset starting current for a preset discharging time and then record the battery voltage V2; The judging unit is used to repeatedly execute the operations in the second charging unit, the second discharging unit, the third charging unit and the third discharging unit in sequence until V1-V2>the starting voltage threshold, and judge that the battery is at the end of its service life, and the number of repetitions N is the maximum number of charging times of the battery.

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