A charging method and system for extending the life of power batteries

Abstract

This invention relates to a charging method and system for extending the life of a power battery, comprising the following steps: 1) During charging, the current charging current and the highest single-cell voltage of the power battery are collected, and the corresponding open-circuit voltage is determined from the current power battery SOC based on a pre-obtained correspondence between the power battery SOC and open-circuit voltage; 2) The voltage difference is obtained by subtracting the highest single-cell voltage from the open-circuit voltage, and compared with the product of the current charging current and the current internal resistance of the power battery; when the voltage difference exceeds the set range of the product of internal resistance, the SOH of the power battery is iteratively adjusted so that the voltage difference is within the set range of the product of internal resistance; the charging current of the power battery is adjusted according to the adjusted SOH; the method for obtaining the current internal resistance of the power battery is to determine the current internal resistance of the power battery based on the pre-obtained correspondence between the power battery SOC, SOH, temperature and the power battery internal resistance, using the current power battery SOC, SOH and temperature.

Description

Technical Field

[0001] This invention relates to a charging method and system for extending the life of a power battery, belonging to the field of electric vehicle power devices, and particularly to a charging method for power batteries. Background Technology

[0002] Compared with traditional vehicles, new energy vehicles currently have problems such as range anxiety, long charging time, and short battery life. In particular, the short battery life is a problem. The cost of batteries accounts for more than 40% of the cost of the whole vehicle. Generally, after 3-5 years of operation, the battery life of new energy vehicles will degrade to less than 80% of the new battery capacity. After 3-5 years, customers will face significant cost losses due to battery replacement.

[0003] Every battery in a new energy vehicle has a MAP (Charging Matrix Table) for temperature and State of Charge (SOC). At a specific SOC and temperature, the MAP determines the battery's maximum charging capacity. The Battery Management System (BMS) then adjusts the charging current based on this capacity to ensure the battery reaches a safe charging current. Current technology requires the charging current to be lower than a set value. This is because different SOCs and temperatures correspond to different charging currents. As batteries age, their capacity decreases, leading to different charging rates at the same current. A normal charging rate for a new battery may be too high for an older battery, potentially causing overcurrent, overvoltage, or lithium plating when the older battery requests charging current from the MAP. This not only affects battery life but also poses safety risks.

[0004] The existing technology adjusts the charging current by calculating a battery life factor (SOH) ranging from 0% to 100% before charging (SOH is the percentage of the battery's current capacity to its rated capacity; a new battery has an SOH of 100%, which decreases as the battery ages). During charging, the charging current is obtained from the MAP table and multiplied by the SOH to reduce the charging current based on the battery's lifespan and prevent overcurrent. As the battery ages, its capacity decreases, its internal resistance increases, and its SOH also decreases. The charging current obtained by multiplying the charging current by the SOH also decreases, preventing overcharging and lithium plating in aging batteries. However, the accuracy of SOH calculation remains a challenge in the industry. When the SOH of a battery is too high, the charging current obtained by multiplying the charging current by the SOH will also be too high, leading to overcharging and lithium plating. This results in increased internal resistance and a reduction in usable active lithium ions, ultimately causing the lithium battery capacity to prematurely decay to the end of its lifespan. Summary of the Invention

[0005] The purpose of this invention is to provide a charging method and system for extending the life of power batteries, in order to solve the problem of lithium plating in batteries due to overcurrent during charging, which ultimately affects battery life.

[0006] To achieve the above objectives, the present invention includes:

[0007] The present invention provides a charging method for extending the life of a power battery, comprising the following steps:

[0008] 1) During the charging process, the current charging current and the highest single cell voltage of the power battery are collected. At the same time, based on the pre-obtained correspondence between the power battery SOC and the open circuit voltage, the corresponding open circuit voltage is determined from the current power battery SOC.

[0009] 2) The voltage difference is obtained by subtracting the highest single-cell voltage and the open-circuit voltage, and compared with the product of the current charging current and the current internal resistance of the power battery; when the voltage difference exceeds the set range of the product of the internal resistance, the SOH of the power battery is iteratively adjusted so that the voltage difference is within the set range of the product of the internal resistance; the charging current of the power battery is adjusted according to the adjusted SOH.

[0010] The method for obtaining the current internal resistance of the power battery is to determine the current internal resistance of the power battery based on the pre-obtained correspondence between the power battery's SOC, SOH, temperature and internal resistance, using the current power battery's SOC, SOH and temperature.

[0011] This invention provides a charging method to extend the life of a power battery. During the charging process of a new energy vehicle, the current charging current and the highest single-cell voltage of the power battery are collected. Based on the correspondence between the state of charge (SOC) and open-circuit voltage of the power battery, which has been calibrated in the laboratory before the new energy vehicle leaves the factory, the corresponding open-circuit voltage is determined according to the current SOC of the power battery.

[0012] After determining the open-circuit voltage, the highest single-cell voltage is also obtained. The difference between the two is the voltage difference. This voltage difference is then compared with the product of the current charging current and the internal resistance of the power battery. The product of the current charging current and the internal resistance of the power battery is the voltage of the power battery at the current charging current. Comparing this voltage with the voltage difference allows us to determine whether the internal resistance of the power battery is appropriate.

[0013] Furthermore, the internal resistance of the power battery is also obtained from a pre-prepared table calibrated in the laboratory, corresponding to the power battery's SOC, SOH, temperature, and internal resistance. Since the power battery's SOC and temperature are fixed, the internal resistance is only related to the SOH. Therefore, by checking whether the battery's internal resistance is appropriate, one can determine whether the corresponding SOH is accurate and adjust the SOH accordingly.

[0014] Further, the method for obtaining the current charging current of the power battery in step 1) is as follows: after the vehicle is charged, the stored system SOC is read and the battery temperature is obtained. Based on the correspondence between the stored system SOC, battery temperature and charging current, the MAP current is determined by the currently stored system SOC and battery temperature. The current charging current of the power battery is obtained by multiplying the MAP current and the current SOH.

[0015] Furthermore, before obtaining the current charging current of the power battery, a first current value is calculated based on the current reduction coefficient and MAP current when the power battery is faulty; the minimum value between the product of the MAP current and the current SOH and the first current value is taken as the current charging current of the power battery.

[0016] Similarly, based on the MAP table corresponding to the SOC, battery temperature, and charging current calibrated in the laboratory, the MAP current can be determined according to the system SOC and battery temperature stored in the system. The current charging current of the power battery is obtained by multiplying the SOH of the power battery and the MAP current. In addition, the first current value is obtained by multiplying the current reduction factor during power battery failure by the MAP current. The first current value and the product of the MAP current and the current SOH are compared, and the smaller value is taken as the current charging current of the power battery. This current charging current is reported to the charging station as the allowable charging capacity of the power battery. The charging station charges according to this current, which has reduced the risk of overcurrent to a certain extent.

[0017] Furthermore, in step 2), when the voltage difference is greater than the set range of the product of internal resistances, SOH is lowered so that the voltage difference is within the set range of the product of internal resistances.

[0018] When the voltage difference is less than the set range of the product of internal resistances, the battery internal resistance is larger and the corresponding SOH is smaller. Thus, the smaller SOH multiplied by the current charging current of the power battery will result in a smaller actual charging current. Using this actual charging current for charging will not cause battery overcurrent, and therefore will not affect battery life.

[0019] However, when the voltage difference exceeds the set range of the product of internal resistances, the battery's internal resistance is smaller, resulting in a larger SOH. Multiplying the larger SOH by the current charging current of the power battery will yield a larger actual charging current. Using this actual charging current for charging will cause battery overcurrent. Therefore, the SOH must be lowered until the voltage difference falls within the set range of the product of internal resistances. Multiplying the SOH at this point by the current charging current of the power battery will then prevent battery overcurrent.

[0020] Furthermore, in step 2), the set range is determined by the electrical connection material, electrical connection length, and cross-sectional area of ​​the electrical connection between each cell in the power battery through an offline calibration method.

[0021] Different cells within a power battery are connected by aluminum bars. Other materials can also be used to connect different cells. Different connection materials, lengths, and cross-sectional areas between cells result in varying resistances. Therefore, by setting a range so that the voltage difference falls within a predetermined range of the product of internal resistances, the battery's internal resistance is considered accurate, and consequently, the corresponding State of Harm (SOH) is also accurate.

[0022] The present invention also provides a charging system for extending the life of a power battery, including a controller, the controller performing the following steps to implement a charging method for extending the life of a power battery.

[0023] 1) During the charging process, the current charging current and the highest single cell voltage of the power battery are collected. At the same time, based on the pre-obtained correspondence between the power battery SOC and the open circuit voltage, the corresponding open circuit voltage is determined from the current power battery SOC.

[0024] 2) The voltage difference is obtained by subtracting the highest single-cell voltage and the open-circuit voltage, and compared with the product of the current charging current and the current internal resistance of the power battery; when the voltage difference exceeds the set range of the product of the internal resistance, the SOH of the power battery is iteratively adjusted so that the voltage difference is within the set range of the product of the internal resistance; the charging current of the power battery is adjusted according to the adjusted SOH.

[0025] The method for obtaining the current internal resistance of the power battery is to determine the current internal resistance of the power battery based on the pre-obtained correspondence between the power battery's SOC, SOH, temperature and internal resistance, using the current power battery's SOC, SOH and temperature.

[0026] The present invention also provides a charging system for extending the life of power batteries. During the charging process of new energy vehicles, the current charging current and the highest single cell voltage of the power battery are collected. Based on the correspondence between the state of charge (SOC) and open circuit voltage of the power battery, which has been calibrated in the laboratory before the new energy vehicle leaves the factory, and the correspondence is stored in the controller in the battery management system, the controller determines the corresponding open circuit voltage based on the current SOC of the power battery.

[0027] After determining the open-circuit voltage, the highest single-cell voltage is also obtained. The difference between the two is the voltage difference. This voltage difference is then compared with the product of the current charging current and the internal resistance of the power battery. The product of the current charging current and the internal resistance of the power battery is the voltage of the power battery at the current charging current. Comparing this voltage with the voltage difference allows us to determine whether the internal resistance of the power battery is appropriate.

[0028] Furthermore, the internal resistance of the power battery is also obtained from a pre-prepared table calibrated in the laboratory, corresponding to the power battery's SOC, SOH, temperature, and internal resistance. This table is also stored in the controller of the battery management system. Since the power battery's SOC and temperature are fixed, the internal resistance is only related to the SOH. Therefore, by checking whether the battery's internal resistance is appropriate, it is possible to determine whether the corresponding SOH is accurate, and thus adjust the SOH accordingly.

[0029] Further, the method for obtaining the current charging current of the power battery in step 1) is as follows: after the vehicle is charged, the stored system SOC is read and the battery temperature is obtained. Based on the correspondence between the stored system SOC, battery temperature and charging current, the MAP current is determined by the currently stored system SOC and battery temperature. The current charging current of the power battery is obtained by multiplying the MAP current and the current SOH.

[0030] Furthermore, before obtaining the current charging current of the power battery, a first current value is calculated based on the current reduction coefficient and MAP current when the power battery is faulty; the minimum value between the product of the MAP current and the current SOH and the first current value is taken as the current charging current of the power battery.

[0031] Similarly, based on the MAP table corresponding to the SOC, battery temperature, and charging current calibrated in the laboratory, the MAP current can be determined according to the system SOC and battery temperature stored in the system. The current charging current of the power battery is obtained by multiplying the SOH of the power battery and the MAP current. In addition, the first current value is obtained by multiplying the current reduction factor during power battery failure by the MAP current. The first current value and the product of the MAP current and the current SOH are compared, and the smaller value is taken as the current charging current of the power battery. This current charging current is reported to the charging station as the allowable charging capacity of the power battery. The charging station charges according to this current, which has reduced the risk of overcurrent to a certain extent.

[0032] Furthermore, in step 2), when the voltage difference is greater than the set range of the product of internal resistances, SOH is lowered so that the voltage difference is within the set range of the product of internal resistances.

[0033] When the voltage difference is less than the set range of the product of internal resistances, the battery internal resistance is larger and the corresponding SOH is smaller. Thus, the smaller SOH multiplied by the current charging current of the power battery will result in a smaller actual charging current. Using this actual charging current for charging will not cause battery overcurrent, and therefore will not affect battery life.

[0034] However, when the voltage difference exceeds the set range of the product of internal resistances, the battery's internal resistance is smaller, resulting in a larger SOH. Multiplying the larger SOH by the current charging current of the power battery will yield a larger actual charging current. Using this actual charging current for charging will cause battery overcurrent. Therefore, the SOH must be lowered until the voltage difference falls within the set range of the product of internal resistances. Multiplying the SOH at this point by the current charging current of the power battery will then prevent battery overcurrent.

[0035] Furthermore, in step 2), the set range is determined by the electrical connection material, electrical connection length, and cross-sectional area of ​​the electrical connection between each cell in the power battery through an offline calibration method.

[0036] Different cells within a power battery are connected by aluminum bars. Other materials can also be used to connect different cells. Different connection materials, lengths, and cross-sectional areas between cells result in varying resistances. Therefore, by setting a range so that the voltage difference falls within a predetermined range of the product of internal resistances, the battery's internal resistance is considered accurate, and consequently, the corresponding State of Harm (SOH) is also accurate. Attached Figure Description

[0037] Figure 1 This is a graph showing the change of static voltage as a function of SOC during charging of the battery cells of this invention.

[0038] Figure 2 This is a flowchart illustrating the process of preventing battery overcurrent in this invention.

[0039] Figure 3 This is a graph showing the relationship between battery internal resistance and temperature and SOC at different SOH values ​​according to the present invention. Detailed Implementation

[0040] The present invention will now be described in further detail with reference to the accompanying drawings.

[0041] Method Implementation Examples:

[0042] This invention provides a charging method to extend the lifespan of a power battery. By analyzing actual battery lifespan and laboratory battery cycle life, this invention reveals that the battery lifespan in actual vehicles degrades significantly faster than in laboratory cycles. One reason for this is that charging with a current exceeding the battery's actual charging capacity accelerates battery lifespan degradation. As the battery ages, its actual withstand current decreases. Therefore, in actual charging, the charging current is multiplied by the battery lifespan factor (SOH) to reduce the charging current. If, after a certain degree of battery aging, the battery lifespan factor should be 60%, but the calculated factor is 70%, then multiplying the charging current by the factor still exceeds the battery's actual charging capacity, leading to accelerated battery lifespan degradation.

[0043] Based on this, the present invention proposes a charging method to extend the life of a power battery, under the premise that the SOH calculation is inaccurate, by adjusting the charging current to meet the actual charging capacity of the battery, thereby preventing battery overcurrent.

[0044] This invention calculates the allowable charging current for the battery during vehicle charging. This calculation considers cell lifespan, system fault current limiting coefficient (β), and the battery system wiring harness withstand capability. During charging, the individual battery cell voltage, charging current, and SOC are collected in real-time. The difference between the collected individual battery cell voltage and the battery static voltage (OCV) is calculated. Simultaneously, the battery internal resistance is looked up using the calculated SOH, SOC, and temperature. The difference between the individual battery cell voltage and the battery static voltage is compared with the product of the charging current and the battery internal resistance. If this difference is outside the range of the product of charging current and battery internal resistance, it indicates that the battery internal resistance does not match the actual value, further indicating that the SOH does not match the actual value. Therefore, the SOH needs to be readjusted and recalculated. If the difference is within the range of the product of charging current and battery internal resistance, it indicates that the battery internal resistance and SOH match the actual value. Charging is then performed according to the charging current calculated based on the current SOH and battery internal resistance until charging is complete. Figure 2 As shown, the specific steps are as follows.

[0045] 1) Determine the correlation coefficient.

[0046] After the vehicle starts charging, the battery system obtains the current state of charge (SOC) of the battery and collects the current battery temperature. Based on the correspondence between SOC, battery temperature and charging current calibrated in the laboratory, the current charging current is determined by the current SOC and battery temperature, i.e., the charging current is obtained from the MAP table. The specific correspondence is shown in Table 1.

[0047] Table 1. Relationship between allowable charging current and temperature / SOC (Map Table)

[0048]

[0049] 2) Calculate SOH.

[0050] Calculate SOH using lithium iron phosphate batteries as an example:

[0051] ① Ensure that the battery's SOC is low enough before charging;

[0052] like Figure 1 As shown, the horizontal axis represents the battery's state of charge (SOC), and the vertical axis represents the battery's static voltage (OCV). An SOC above 30% corresponds to a cell voltage plateau. During this plateau, even small voltage fluctuations can lead to significant differences in SOC, resulting in inaccurate initial SOC calculations and consequently, inaccurate SOH calculations. Therefore, SOH calculations are generally performed when the SOC is below 30%. When the SOC is below 30%, even small changes in OCV can cause significant differences in SOC, making the calculated SOH more accurate. Therefore, it is essential to ensure that the battery's SOC is sufficiently low before charging, ideally below 30%.

[0053] ② Charging ends when the battery is fully charged, at which point the corresponding SOC is 100%;

[0054] ③ Calculate SOH using the SOC difference;

[0055] Assuming the battery's State of Charge (SOC) is 20% before charging and 100% after a full charge, the difference between 20% and 100% SOC, ΔSOC, is 80%. The current battery capacity is calculated by dividing the actual amount of charge delivered between 20% and 80% by the corresponding ΔSOC value (80%). Dividing this current capacity by the battery's original factory capacity gives the battery's State of Balance (SOH).

[0056] 3) Calculate the charging current.

[0057] The calculated lower limit of the battery life coefficient is multiplied by the charging current obtained from the MAP meter, i.e., SOH × MAP. Then, the current reduction coefficient β caused by the fault under fault conditions is multiplied by the charging current obtained from the MAP meter, i.e., β × MAP. The current allowable charging current I of the current harness is also collected. 线束 Compare SOH×MAP, β×MAP, and I 线束 The minimum value among the three values ​​is used as the charging current for the battery's allowable charging capacity and is then transmitted to the charging station. The charging station then charges the battery according to this minimum current value.

[0058] 4) Collect the highest single-cell voltage and obtain the OCV based on the current SOC.

[0059] The battery system acquires the voltage of all individual cells within the battery, but only uploads the highest, lowest, and average individual cell voltages. And based on... Figure 1 As shown, each SOC of the battery corresponds to an OCV, and the corresponding OCV is obtained based on the current SOC of the battery.

[0060] 5) Calculate the difference between OCV and the highest single-cell voltage, and compare it with the product of the battery's allowable charging current and the battery's internal resistance.

[0061] The highest single-cell voltage is V max The highest single-cell voltage is different at any given moment, as it is acquired in real time and changes with charging time. OCV is the battery's static voltage, a constant value; only one OCV corresponds to a given SOC.

[0062] Calculate V max The difference in -OCV is compared with X×I×R and Y×I×R. Where X and Y are the safe charging coefficients, I is the charging current allowed by the battery's charging capacity, and R is the battery's internal resistance. For example... Figure 3 As shown, the battery system stores a table showing the correspondence between different SOC, SOH, temperatures, and battery internal resistances. The current battery internal resistance, R, is obtained based on the current battery SOC, SOH, and current battery temperature.

[0063] 6) Adjust SOH based on the comparison results.

[0064] X and Y are safety charging coefficients because different cells within the battery are connected by aluminum bars. Besides aluminum bars, other materials can also be used to connect different cells. Different connection materials, lengths, and cross-sectional areas between different cells all result in different resistances. Therefore, X and Y are set safety charging coefficients, based on the calculated V... max If the difference between -OCV and R is within the range of X×I×R and Y×I×R, it is assumed that the battery internal resistance matches the actual value. Since the current SOC and temperature are fixed, the battery internal resistance is only related to SOH. When the battery internal resistance matches the actual value, it means that the calculated SOH value is appropriate. Therefore, the final charging current calculated by multiplying SOH by the charging current of the battery's allowable charging capacity is accurate and will not affect the battery life.

[0065] If the calculated V max If the difference between -OCV and the actual value is outside the range of X×I×R and Y×I×R, then the calculated battery internal resistance is considered inconsistent with the actual value, indicating that the calculated SOH value is inaccurate. This is especially true in the V range. maxWhen the difference between -OCV and Y×I×R is greater than Y×I×R, it indicates that the battery's internal resistance is too low. This means the current SOC and the corresponding current SOH at the current temperature are too high, resulting in a lower battery internal resistance. Consequently, the final charging current calculated by multiplying the current SOH by the battery's allowable charging current will also be too high, thus affecting battery life. Therefore, it is necessary to reduce the SOH and recalculate until V... max If the difference between -OCV and X×I×R and Y×I×R is within the range, then the SOH calculation is considered correct, and the final charging current is obtained before adjusting the charging.

[0066] System Implementation Example:

[0067] The present invention also provides a charging system for extending the life of a power battery. The system uses a controller in a battery management system. The controller executes corresponding steps to realize a charging method for extending the life of the power battery. This method has been clearly described in the method embodiments and will not be repeated here.

Claims

1. A charging method for prolonging the life of a power cell, characterized in that, The method comprises the following steps: 1) During the charging process, the current charging current and the highest single cell voltage of the power battery are collected, and the corresponding open circuit voltage is determined according to the correspondence between the SOC of the power battery and the open circuit voltage obtained in advance, and the corresponding open circuit voltage is determined according to the current SOC of the power battery; 2) The voltage difference is obtained by subtracting the highest single cell voltage from the open circuit voltage, and is compared with the product of the current charging current and the current internal resistance of the power battery; When the voltage difference exceeds the set range of the product of the internal resistance, the SOH of the power battery is iteratively adjusted so that the voltage difference is within the set range of the product of the internal resistance, at which time the internal resistance of the power battery corresponds to the actual value; and the charging current of the power battery is adjusted according to the adjusted SOH; The method for obtaining the current internal resistance of the power battery is to determine the current internal resistance of the power battery according to the correspondence among the SOC, SOH, temperature and internal resistance of the power battery obtained in advance, and the current internal resistance of the power battery is determined according to the current SOC, SOH and temperature of the power battery.

2. The charging method for prolonging the life of a power cell according to claim 1, characterized in that, In step 1), the method for obtaining the current charging current of the power battery is to read the stored system SOC after the vehicle is charged, obtain the battery temperature, determine the MAP current according to the correspondence among the stored system SOC, battery temperature and charging current, and obtain the current charging current of the power battery according to the product of the MAP current and the current SOH.

3. The charging method for prolonging the life of a power cell according to claim 2, characterized in that, Before obtaining the current charging current of the power battery, a first current value is calculated according to the current drop coefficient and the MAP current when the power battery fails; and the minimum value of the product of the MAP current and the current SOH and the first current value is taken as the current charging current of the power battery.

4. The charging method for prolonging the life of a power battery according to claim 1, characterized in that, In step 2), when the voltage difference is greater than the set range of the product of the internal resistance, the SOH is lowered so that the voltage difference is within the set range of the product of the internal resistance.

5. The charging method for prolonging the life of a power cell according to claim 4, characterized in that, In step 2), the set range is determined by the method of offline calibration of the material, length and cross-sectional area of the electrical connection between the power battery and the power battery.

6. A charging system for prolonging the life of a power cell, characterized in that The controller executes the following steps to realize the charging method for prolonging the service life of the power battery, 1) During the charging process, the current charging current and the highest single cell voltage of the power battery are collected, and the corresponding open circuit voltage is determined according to the correspondence between the SOC of the power battery and the open circuit voltage obtained in advance, and the corresponding open circuit voltage is determined according to the current SOC of the power battery; 2) The voltage difference is obtained by subtracting the highest single cell voltage from the open circuit voltage, and is compared with the product of the current charging current and the current internal resistance of the power battery; When the voltage difference exceeds the set range of the product of the internal resistance, the SOH of the power battery is iteratively adjusted so that the voltage difference is within the set range of the product of the internal resistance, at which time the internal resistance of the power battery corresponds to the actual value; and the charging current of the power battery is adjusted according to the adjusted SOH; The method for obtaining the current internal resistance of the power battery is to determine the current internal resistance of the power battery according to the correspondence among the SOC, SOH, temperature and internal resistance of the power battery obtained in advance, and the current internal resistance of the power battery is determined according to the current SOC, SOH and temperature of the power battery.

7. The charging system for prolonging the life of a power cell according to claim 6, characterized in that, The method for obtaining the current charging current of the power battery in step 1 is as follows: after the vehicle is charged, the stored system SOC is read, the battery temperature is obtained, the MAP current is determined according to the correspondence among the stored system SOC, the battery temperature and the charging current, the product of the MAP current and the current SOH is obtained, and the current charging current of the power battery is obtained according to the product.

8. The charging system for prolonging the life of a power cell according to claim 6, wherein, Before the current charging current of the power battery is obtained, a first current value is also calculated according to the current drop coefficient when the power battery fails and the MAP current; and the minimum value of the product of the MAP current and the current SOH and the first current value is taken as the current charging current of the power battery.

9. The charging system for prolonging the life of a power cell according to claim 6, wherein, In step 2, when the voltage difference is greater than the set range of the product of the internal resistance, the SOH is adjusted downward, so that the voltage difference is within the set range of the product of the internal resistance.

10. The charging system for prolonging the life of a power cell according to claim 9, wherein, In step 2, the set range is determined by the offline calibration method of the material, length and cross-sectional area of the electrical connection between the power battery and each cell.

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