Lithium battery Basic knowledge III
1：What is overcharge and how does it affect battery performance?
Overcharge refers to the behavior that the battery will continue to charge after it is fully charged in a certain charging process. Because the capacity of negative electrode is higher than that of positive electrode in design, the gas produced by positive electrode is combined with cadmium produced by negative electrode through diaphragm paper. Therefore, in general, the internal pressure of the battery will not increase significantly, but if the charging current is too large, or the charging time is too long, the oxygen generated is too late to be consumed, it may cause the increase of internal pressure, battery deformation, leakage, and other adverse phenomena. At the same time, its electrical performance will be significantly reduced.
2： What are the control methods of overcharge?
In order to prevent battery overcharge, it is necessary to control the charging end point. When the battery is full, there will be some special information available to judge whether the charging has reached the end point. There are generally six ways to prevent the battery from overcharging:
(1). Peak voltage control: determine the end point of charging by detecting the peak voltage of the battery;
(2). DT / dt control: determine the end point of charging by detecting the change rate of battery peak temperature;
(3). T control: when the battery is fully charged, the difference between the temperature and the ambient temperature will reach the maximum;
(4). - V control: when the battery is fully charged and reaches a peak voltage, the voltage will drop a certain value
(5). Timing control: the charging end point is controlled by setting a certain charging time, generally setting the time required to charge 130% of the nominal capacity;
(6). TCO control: considering the safety and characteristics of the battery, high temperature (excluding high temperature battery) charging should be avoided, so when the battery temperature rises 60, charging should be stopped.