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How to Handle Voltage Imbalance in a Lipo Battery Pack for Vehicles?


In just a few years, the application scale of polymer lithium battery packs has expanded from our daily lives to the industrial sector. They are not only used in digital products like laptops and portable CD players but also widely used in fields such as electric bicycles, electric cars, and drones. However, with the increasingly widespread use of polymer lithium battery packs, how should we deal with the problem of voltage imbalance in these batteries?


Method for handling voltage imbalance in polymer lithium-ion battery pack for vehicles

1. Repairing an unbalanced lithium-ion battery requires certain steps and precautions. First, the protection board of the lithium-ion battery needs to be removed in order to check the status of the battery. During the inspection, it is necessary to carefully identify the battery that affects the normal operation of the entire battery pack. In order to find these batteries, you need to bypass the protection board of the battery and directly measure the individual lithium-ion battery cells and record the test results. The entire process needs to be carefully operated to ensure that no further damage or safety issues are caused to the battery pack.

Once the unbalanced batteries are identified, you can begin repairing them. This may include balancing the battery pack, calibrating the battery voltage, or replacing problematic batteries. During the repair process, it is important to carefully record the status of the battery pack and all operations during the repair process. This will help you track the performance of the battery pack and ensure that it operates normally after repair.

Therefore, repairing an unbalanced lithium-ion battery requires not only inspection and recording, but also carefulness and patience. Only in this way can the normal operation and long life of the battery pack be ensured.

2.When performing battery maintenance, if certain batteries are found to have issues, we can charge them individually or test their capacity and internal resistance. This can help detect any differences between them and the rest of the battery pack. If the differences are small, we can try charging these batteries individually. However, if there is a significant difference between the capacity and internal resistance, we need to replace them to avoid affecting the performance and lifespan of the entire battery pack.

3.Before reassembling a battery pack that has been repaired by replacing individual cells or recharging, the capacity of each cell should be evaluated to ensure that it meets the design requirements. This is a crucial step in the repair process, as it ensures that the performance of the battery pack will not be compromised and that the pack will operate as intended. To evaluate the capacity of each cell, the cells should be charged and discharged in a controlled environment, and the results should be compared to the manufacturer’s specifications. If any cells are found to have subpar capacity, they should be replaced before the battery pack is reassembled. The capacity testing process should be repeated after any new cells have been installed to ensure that the repaired battery pack meets the design requirements.

4.To recycle batteries, you need to follow the original procedure, including installing the battery protection board and outer packaging. However, it should be noted that after a period of use, the lithium-ion battery pack may experience an imbalance, which may cause the internal resistance of the entire battery pack to differ from that of a new battery. Therefore, special handling is required when replacing individual batteries. You can consider balancing the battery pack or replacing them one by one to avoid the problem from recurring. In addition, to ensure the safe use of the battery pack, it is recommended that you regularly check the status of the battery pack and perform maintenance as needed. This can extend the service life of the battery pack and provide you with longer-lasting power support.

Note: It is important to note that lithium-ion battery packs often experience imbalances after a period of use, resulting in different internal resistance for the entire battery pack compared to a new battery. When replacing individual cells, special attention should be paid, as simply replacing the cell may result in a repeated problem.

  1. First charge the entire lithium-ion battery pack and perform float charging within 2-3 hours after turning on the light. If the battery is not used for a long time, it can be normally charged for 10 minutes on the protection board (plugged in), and then charged normally.
  2. Remove the circuit and plug of the protection board and mark them. The two wires on the board cannot be restored. Measure the voltage of adjacent pins on the circuit. For 48V, there are 16 voltages, and for 60V, there are 20 voltages. The first negative voltage is the voltage where the battery pack becomes negative from the first row. Find a single string of voltage below 3.50V, determine the positive and negative values, identify the negative value, and mark it.
  3. Use a 4.2V charger to charge single wires with voltages between 3.50V to 3.60V to 3.70V, but someone needs to prevent the overcharging of used lithium-ion batteries.
  4. Insert the cables back in the original order, being careful not to reverse them, and put the battery into use. If the lithium-ion battery pack is continuously used, the capacity of the lithium-ion battery will naturally decrease. This is related to the material characteristics of the lithium-ion battery.
  5. In order to extend the life of the lithium-ion battery pack, it is usually recommended to use a shallow charge and discharge mode for lithium-ion batteries, or to charge excessive lithium-ion batteries that are not used or have insufficient power. The lifespan of lithium-ion batteries is not ideal.

The essence of the capacity reduction and attenuation of lithium-ion battery packs is the decrease in lithium-ion content, mainly due to structural material failure or the deactivation of positive and negative electrode materials, electrolyte degradation, and abuse of lithium-ion batteries. In order to extend the life of lithium-ion batteries, they must be used correctly.

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