Lithium battery protection measures

- Jul 30, 2019-

When charging a lithium battery, be sure to set the upper voltage limit to take into account the battery life, capacity, and safety. The optimal charging voltage is limited to 4.2V. Lithium batteries should also have a lower voltage limit when discharging. When the cell voltage is lower than 2.4V, some materials will start to be destroyed. Since the battery will self-discharge, the voltage will be lower for a longer period of time. Therefore, it is best not to put it at 2.4V until it stops. During the period from 3.0V to 2.4V, the lithium battery releases only about 3% of the battery capacity. Therefore, 3.0V is an ideal discharge cutoff voltage. In charge and discharge, in addition to the voltage limit, current limitation is also necessary. When the current is too large, lithium ions do not reach the cell and accumulate on the surface of the material.

When these lithium ions obtain electrons, crystals of lithium atoms are generated on the surface of the material, which is dangerous as overcharge. In case the battery case is broken, it will explode. Therefore, the protection of the lithium ion battery must include at least three factors: the upper limit of the charging voltage, the lower limit of the discharging voltage, and the upper limit of the current. In the general lithium battery pack, in addition to the lithium battery core, there will be a protective plate, which is mainly to provide these three protections. However, these three protections of the protection board are obviously not enough, and the global lithium battery explosion is still frequent. To ensure the safety of the battery system, a more careful analysis of the cause of the battery explosion must be performed.