Thanks to advancements in lithium battery technology, lithium-ion batteries have experienced explosive growth. However, this growth has also brought some usage issues. Recently, a friend reported to me that their lithium-ion battery experienced a decrease in capacity after only a short period of use, and asked me what the reason might be. Today, I'll explain it to you.
When this happens, many people's first reaction is to wonder if it's a battery quality issue. However, besides the aging and degradation of the cells themselves, a more common and important factor contributing to reduced capacity in lithium-ion battery packs is the imbalance of charge within the series-connected cells due to different self-discharge rates. This ultimately leads to reduced capacity and shorter battery life. Based on my experience repairing lithium-ion batteries, over half of them experience capacity loss due to charge imbalance. In some cases, the battery voltage drops below 2.0V, meaning the battery is nearing the end of its life and cannot be recharged.
So, what methods can be used to resolve the imbalance in the charge level of a lithium-ion battery and restore it to normal?
1. First, charge the entire battery pack by float charging for 2 to 3 hours after the indicator light turns on. If the battery pack has been left discharged for a long time and can no longer be charged, you can directly charge it for 10 minutes by bypassing the protection board (using the discharge port), and then charge it normally.
2. Disconnect the ribbon cable from the protection board. Before disconnecting, please mark the connector. For boards with two ribbon cables, the cables must not be reversed. Measure the voltage between adjacent pins on the ribbon cable. If it's 48V, there will be 16 voltage readings; if it's 60V, there will be 20. The first voltage series starting from the negative terminal is the voltage between the negative terminal of the battery pack and the first ribbon cable, and so on. Find the single series with a voltage below 3.50V, determine its positive and negative terminals, and mark them.
3. Use a 3.6V charger to charge single strings with a voltage below 3.50V to 3.60 to 3.70V. However, someone must be present to prevent overcharging from damaging the batteries.
