Power battery full life cycle overcharge protection method

Abstract

The invention discloses a power battery full life cycle overcharge protection method comprising the following steps: S1, through a battery cycle life test, obtaining a charging target monomer voltage VqN and a charging target monomer current IqN, and recording the charging target monomer voltage VqN and the charging target monomer current IqN in a parameter comparison table; s2, in the charging process of the power battery, voltage values of all the single battery cells in the power battery are collected in real time, and the highest real-time voltage value Vmax in all the single battery cells is obtained through calculation; s3, the current number of charging cycles of the power battery is confirmed, and the charging target monomer voltage VqN and the charging target monomer current IqN at the current number of charging cycles are obtained by looking up the parameter comparison table; s4, calculating a difference value between the VqN and the Vmax, maintaining the original charging current of the power battery for charging when the difference value is greater than a threshold value X, and executing a step S5 when the difference value is less than or equal to the threshold value X; s5, setting the requested charging current as IqN or reducing the requested charging current to IqN, and stopping charging until Vmax is greater than or equal to VqN; the invention has the advantages of better protecting the power battery and prolonging the service life of the power battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery management, and in particular relates to a method for protecting a power battery from overcharging throughout its life cycle. Background Art

[0002] With the continuous development of new energy vehicles, lithium-ion power batteries are being used more and more widely. However, power batteries also have some safety hazards, such as overcharging, overdischarging, short circuit and other problems. Overcharging means that the power battery is charged for a long time through the charger, causing the actual voltage of the power battery to exceed the rated voltage.

[0003] Overcharging of power batteries can lead to reduced power battery capacity, shortened life, heating, fire and other problems. Currently, there are two main types of power battery overcharging protection: hardware protection and software protection:

[0004] 1. Hardware protection is achieved through the battery management system (BMS) and other circuit components, which directly monitor the voltage, current and temperature of the battery and take action when overcharging occurs;

[0005] 2. Software protection is achieved by embedding software in the charger and battery management system (BMS). These software algorithms can process and analyze sensor data in real time and make corresponding protection decisions.

[0006] In the actual charging process, if the charging target cell voltage fails to be updated in time or is updated inaccurately, the power battery may continue to charge when charging should be stopped, and the overcharging problem still exists. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for overcharging protection of a power battery during its entire life cycle, which can better protect the power battery and extend the service life of the power battery.

[0008] The technical solution adopted by the present invention to solve the above technical problems is: a method for overcharging protection of a power battery during its entire life cycle, comprising the following steps:

[0009] S1. Take the battery cells of the same batch and model as the power battery as the charging target, and obtain the charging target single cell voltage VqN and charging target single cell current IqN at different charging cycle times through the battery cycle life test, and record them in the parameter comparison table;

[0010] S2. During the charging process of the power battery, the voltage values ​​of all the single cells in the power battery are collected in real time, and the highest real-time voltage value Vmax among all the single cells is calculated;

[0011] S3, confirm the current charging cycle number of the power battery, and check the parameter comparison table to obtain the charging target single cell voltage VqN and the charging target single cell current IqN at the current charging cycle number;

[0012] S4, calculating the difference between VqN and Vmax, when the difference is greater than the threshold value X, maintaining the original charging current of the power battery for charging, when the difference is less than or equal to the threshold value X, executing step S5;

[0013] S5. Set the requested charging current to IqN or reduce it to IqN until Vmax ≥ VqN, then stop charging.

[0014] Preferably, in step S3, the current number of charging cycles of the power battery is calculated according to the following formula:

[0015] N=C 累积 / C 标称

[0016] Where N is the current charging cycle number, C 累积 The cumulative charge and discharge capacity C of the power battery 累积 , C 标称 It is the nominal capacity of the power battery.

[0017] Preferably, in step S4, the value range of X is 20±5 mV.

[0018] Preferably, in step S5, the charging current is reduced to IqN according to the following formula:

[0019]

[0020] T N =K1×T N-1

[0021] Where, I(t) is the charging current at time t, I initial is the original charging current, T N is the total time for the charging current to decrease in the current charging cycle, t is the current time, 0≤t≤T N , T N-1 It is the total time for the charging current to decrease in the last charging cycle. K1 is a constant, 0<K1<1.

[0022] Preferably, K1 satisfies: 0.7≤K1≤0.9.

[0023] Preferably, in the process of decreasing the requested charging current to IqN, if VqN≥K2×Vmax, K2 is a constant, and 0.95≤K2<1, the requested charging current is set to IqN.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1. By taking the cells of the same batch and model as the power battery as the charging target and conducting a cycle life test, the charging target single cell voltage and charging target single cell current are obtained, and a parameter comparison table is made. During actual use, the power batteries of the same batch and model can dynamically update the charging current according to the parameter comparison table, so that each charging can be completed at the most appropriate time to avoid overcharging, thereby better protecting the power battery and extending the service life of the power battery;

[0026] 2. By reducing the requested charging current to IqN, the instantaneous current drop during the charging process can be avoided, which may have an adverse effect on the safety and performance of the power battery, and help further extend the service life of the power battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The process of the present invention is shown in FIG. Figure 1 ;

[0028] Figure 2 The process of the present invention is shown in FIG. Figure 2 . DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0030] Embodiment A:

[0031] like Figure 1 and Figure 2 As shown, a method for overcharging protection of a power battery throughout its life cycle comprises the following steps:

[0032] S1. Take the battery cells of the same batch and model as the power battery as the charging target, and obtain the charging target single cell voltage VqN and charging target single cell current IqN at different charging cycle times through the battery cycle life test, and record them in the parameter comparison table;

[0033] Cycle times Charging target single cell voltage Charging target single cell current 1 VqV Iq1 2 VqV Iq2 3 V Q Iq3 4 V Q Iq4 5 V Q Iq5 …… …… …… N VqV Iq

[0034] S2. During the charging process of the power battery, the voltage values ​​of all the single cells in the power battery are collected in real time, and the highest real-time voltage value Vmax among all the single cells is calculated;

[0035] S3, confirm the current charging cycle number of the power battery, and check the parameter comparison table to obtain the charging target single cell voltage VqN and the charging target single cell current IqN at the current charging cycle number;

[0036] S4, calculating the difference between VqN and Vmax, when the difference is greater than the threshold value X, maintaining the original charging current of the power battery for charging, when the difference is less than or equal to the threshold value X, executing step S5;

[0037] S5. Set the requested charging current to IqN, and stop charging when Vmax≥VqN.

[0038] In step S3, the current number of charging cycles of the power battery is calculated according to the following formula:

[0039] N=C 累积 / C 标称

[0040] Where N is the current charging cycle number, C 累积 The cumulative charge and discharge capacity C of the power battery 累积 , C 标称 It is the nominal capacity of the power battery.

[0041] In step S4, the value range of X is 20±5 mV, preferably 20 mV.

[0042] Embodiment B:

[0043] The rest is the same as that of Embodiment A, except for step S5. In this embodiment, step S5 is to reduce the requested charging current to IqN until Vmax≥VqN, and then stop charging.

[0044] Specifically, the charging current is reduced to IqN according to the following formula:

[0045]

[0046] T N =K1×T N-1

[0047] Where, I(t) is the charging current at time t, I initial is the original charging current, T N is the total time for the charging current to decrease in the current charging cycle, t is the current time, 0≤t≤T N , T N-1 is the total time for the charging current to decrease in the last charging cycle, K1 is a constant, 0<K1<1. Preferably, K1 satisfies: 0.7≤K1≤0.9. The charging current is linearly decreased to IqN, achieving a smooth transition, avoiding the current drop during the charging process and causing adverse effects on the safety and performance of the power battery.

[0048] In this embodiment, in the process of reducing the requested charging current to IqN, if VqN≥K2×Vmax, K2 is a constant, and 0.95≤K2<1, the requested charging current is set to IqN, which is a constraint condition.

[0049] The advantages of this embodiment are:

[0050] 1. By setting constraints, it is possible to avoid the situation where Vmax reaches VqN before the charging current drops to IqN. That is, the power battery must be charged according to the preset VqN at the end of the charging stage to ensure that each charging can be completed at the most appropriate time.

[0051] 2. The charging current drops to IqN and cooperates with the constraints to achieve dynamic regulation. Even if the current drops instantly, the current drop span can be reduced, reducing the adverse effects on the power battery, which helps to further extend the service life of the power battery.

[0052] Embodiment 1,

[0053] S1. Take a single battery cell as the charging target, and obtain the charging target cell voltage VqN and charging target cell current IqN at different charging cycle times through the battery cycle life test, and record them in the parameter comparison table;

[0054] S2. Take multiple cells of the same batch and model to form a power battery. During the fast charging of the power battery, collect the voltage values ​​of all single cells in the power battery in real time, and calculate the highest real-time voltage value Vmax among all single cells;

[0055] S3, confirm the current charging cycle number of the power battery, and check the parameter comparison table to obtain the charging target single cell voltage VqN and the charging target single cell current IqN at the current charging cycle number;

[0056] S4, calculating the difference between VqN and Vmax, when the difference is greater than 20 mV, maintaining the original charging current of the power battery for charging, when the difference is less than or equal to 20 mV, executing step S5;

[0057] S5. Set the requested charging current to IqN, and stop charging when Vmax≥VqN.

[0058] Record the capacity retention rate of the power battery, as shown in the following table:

[0059] Serial number Number of cycles Charging capacityAh Discharge capacityAh Capacity retention rate % 1 0 6.16 5.94 100.00 2 500 6.10 5.92 99.60 3 1000 6.03 5.90 99.30 4 1500 6.01 5.88 99.00 5 2000 5.99 5.85 98.50 6 2500 5.98 5.80 97.60 7 3000 5.96 5.77 97.20 8 3500 5.92 5.73 96.40 9 4000 5.83 5.69 95.75 10 4500 5.76 5.63 94.81

[0060] Embodiment 2,

[0061] S1. Take a single battery cell as the charging target, and obtain the charging target cell voltage VqN and charging target cell current IqN at different charging cycle times through the battery cycle life test, and record them in the parameter comparison table;

[0062] S2. Take multiple cells of the same batch and model to form a power battery. During the fast charging of the power battery, collect the voltage values ​​of all single cells in the power battery in real time, and calculate the highest real-time voltage value Vmax among all single cells;

[0063] S3, confirm the current charging cycle number of the power battery, and check the parameter comparison table to obtain the charging target single cell voltage VqN and the charging target single cell current IqN at the current charging cycle number;

[0064] S4, calculating the difference between VqN and Vmax, when the difference is greater than 20 mV, maintaining the original charging current of the power battery for charging, when the difference is less than or equal to 20 mV, executing step S5;

[0065] S5. Reduce the requested charging current to IqN until Vmax ≥ VqN, and then stop charging.

[0066] Record the capacity retention rate of the power battery, as shown in the following table:

[0067] Serial number Number of cycles Charging capacityAh Discharge capacityAh Capacity retention rate % 1 0 6.16 5.94 100.00 2 500 6.11 5.93 99.62 3 1000 6.04 5.91 99.33 4 1500 6.02 5.89 99.04 5 2000 6.00 5.87 98.54 6 2500 5.99 5.82 97.65 7 3000 5.98 5.79 97.26 8 3500 5.94 5.75 96.51 9 4000 5.85 5.71 95.92 10 4500 5.78 5.65 95.08

[0068] Comparative Example 1

[0069] A power battery includes multiple battery cells of the same batch and model, which are charged according to conventional fast charging.

[0070] Record the capacity retention rate of the power battery, as shown in the following table:

[0071]

[0072]

[0073] According to the recorded results, the number of cycles when the capacity retention rate of the power batteries in Example 1, Example 2 and Comparative Example 1 is lower than 95% is shown in the following table:

[0074] Number of cycles Example 1 4391 Example 2 4522 Comparative Example 1 3907

[0075] Taking the common strategy in the market as an example, the power battery is charged at a fixed charging target single cell voltage throughout its life cycle. When the cumulative mileage of the power battery (corresponding to the cumulative charge and discharge capacity or number of cycles) reaches a certain level, the power battery will decay. If it is still charged according to the charging target single cell voltage set at the beginning, it is easy to cause the power battery to be overcharged due to insufficient redundant capacity. However, this technical solution continuously updates the charging current for charging according to the use of the power battery throughout its life cycle, so that the power battery ends charging at the most appropriate time each time, thereby completing overcharge protection, which is conducive to extending the battery life by about 12-16%.

[0076] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for overcharging protection of a power battery during its entire life cycle, characterized in that: The following steps are involved: S1. Take the battery cells of the same batch and model as the power battery as the charging target, and obtain the charging target single cell voltage VqN and charging target single cell current IqN at different charging cycle times through the battery cycle life test, and record them in the parameter comparison table; S2. During the charging process of the power battery, the voltage values ​​of all the single cells in the power battery are collected in real time, and the highest real-time voltage value Vmax among all the single cells is calculated; S3, confirm the current charging cycle number of the power battery, and check the parameter comparison table to obtain the charging target single cell voltage VqN and the charging target single cell current IqN at the current charging cycle number; S4, calculating the difference between VqN and Vmax, when the difference is greater than the threshold value X, maintaining the original charging current of the power battery for charging, when the difference is less than or equal to the threshold value X, executing step S5; S5. Set the requested charging current to IqN or reduce it to IqN until Vmax ≥ VqN, then stop charging.

2. A method for overcharging protection of a power battery during its entire life cycle according to claim 1, characterized in that: In step S3, the current number of charging cycles of the power battery is calculated according to the following formula: N=C 累积 / C 标称 Where N is the current charging cycle number, C 累积 The cumulative charge and discharge capacity C of the power battery 累积 , C 标称 It is the nominal capacity of the power battery.

3. A method for overcharging protection of a power battery during its entire life cycle according to claim 1, characterized in that: In step S4, the value range of X is 20±5 mV.

4. A method for overcharging protection of a power battery during its entire life cycle according to claim 1, characterized in that: In step S5, the charging current decreases to IqN according to the following formula: T N =K1×T N-1 Where, I(t) is the charging current at time t, I initial is the original charging current, T N is the total time for the charging current to decrease in the current charging cycle, t is the current time, 0≤t≤T N , T N-1 It is the total time for the charging current to decrease in the last charging cycle. K1 is a constant, 0<K1<1.

5. A method for overcharging protection of a power battery during its entire life cycle according to claim 5, characterized in that: K1 satisfies: 0.7≤K1≤0.

9.

6. A method for overcharging protection of a power battery during its entire life cycle according to claim 5, characterized in that: In the process of decreasing the requested charging current to IqN, if VqN≥K2×Vmax, K2 is a constant, and 0.95≤K2<1, the requested charging current is set to IqN.

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