What is overcharge and overdischarge? What are the dangers of lithium batteries?

What is overcharge and overdischarge? What are the dangers of lithium batteries?


Overcharge means that when the lithium-ion battery is overcharged, the charging voltage exceeds the set voltage, such as the rated voltage of the battery is 3.7V, and the full voltage is 4.2±0.05V. That is, the highest voltage is 4.25V. If it exceeds 4.25V, it is called overcharge. What harm will overcharge do to the battery?

When overcharged, the battery voltage rises rapidly with the increase of polarization, which will cause irreversible changes in the structure of the positive active material and decomposition of the electrolyte, generate a large amount of gas, and release a large amount of heat, resulting in a sharp increase in the battery temperature and internal pressure, and the internal diaphragm. Melting or shrinking, resulting in a short circuit between the positive and negative materials, there are hidden dangers such as explosion and combustion.


Overdischarge refers to the discharge when the voltage reaches the rated voltage and continues to discharge. For example, the rated discharge voltage of a ternary lithium battery is 3.2V. If it continues to discharge below 3.2V, it is overdischarge. What harm does overdischarge have on the battery?

After the battery has discharged the internal stored power, after the voltage reaches a certain value, continuing to discharge will cause over-discharge. Over-discharge of the battery may bring catastrophic consequences to the battery, especially the impact of high-current over-discharge or repeated over-discharge on the battery. bigger. Generally speaking, overdischarge will increase the internal pressure of the battery, the reversibility of the positive and negative active materials will be destroyed, the electrolyte will decompose, the negative electrode lithium will be deposited, and the resistance will increase. 

👉How to avoid overcharging or overdischarging the battery?👈

One: Use the lithium battery special protection board (BMS) to work with the battery. The protection board can protect the battery from overcharging or overdischarging. The smart version can also set the charging voltage and discharging voltage, which can better protect the battery.

Two: Use the matching lithium battery charger, do not use fast charging.

Three: When the battery voltage reaches the voltage set by the protection board, the protection board will power off to protect the battery, but the lithium battery will fall back and the voltage will rise, which will be higher than the voltage set by the protection board. It can no longer be used at this time. Repeated use will cause irreversible damage to the battery.

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