What is overcharging and how does it affect battery performance?

Overcharging refers to the behavior of a battery being fully charged after a certain charging process before continuing to charge.

Due to the higher capacity of the negative electrode compared to the positive electrode during design, the gas generated by the positive electrode passes through the separator paper and combines with the cadmium generated by the negative electrode. Therefore, in general, the internal pressure of the battery will not increase significantly. However, if the charging current is too high or the charging time is too long, the generated oxygen cannot be consumed in time, which may cause adverse phenomena such as internal pressure increase, battery deformation, leakage, etc. Meanwhile, its electrical performance will also significantly decrease.

What is over discharge and how does it affect battery performance?

After discharging the stored power inside the battery, if the voltage reaches a certain value, continuing to discharge will cause overdischarge. The discharge cut-off voltage is usually determined based on the discharge current. The discharge of 0.2C-2C is generally set at 1.0V/unit, while the discharge of 3C or above, such as 5C or 10C, is set at 0.8V/unit. Overdischarge of the battery may have catastrophic consequences, especially for high current or repeated overdischarging, which has a greater impact on the battery. Generally speaking, overdischarging can increase the internal pressure of the battery, damage the reversibility of the positive and negative active materials, and even if charged, only partial recovery can be achieved, resulting in a significant decrease in capacity.

What problems will occur when batteries of different capacities are used together?

If different capacities or old and new batteries are mixed together for use, there may be phenomena such as leakage and zero voltage. This is due to the difference in capacity during the charging process, which causes some batteries to be overcharged while others are not fully charged. When discharging, some batteries with higher capacity are not fully discharged, while those with lower capacity are overdischarged. This vicious cycle results in battery damage leading to leakage or low (zero) voltage.