Lead acid battery thermal runaway fault analysis When the battery is charged:
There is a cumulative increase in battery temperature. When the heat accumulates to a certain extent during the warming process, the battery terminal voltage will suddenly decrease, forcing the current to increase suddenly, and the phenomenon of high battery temperature and damage to the battery is called thermal runaway.
1. Fault symptoms:
When charging, especially to the end, the charger does not turn green, and the battery is seriously hot, if the charging current is measured, it will be found that the current is high and there is no downward trend. When the heating is serious, the gas extraction pressure is too high, which will cause the battery shell to be heated and deformed until the battery is scrapped.
2. Fault cause:
A. Battery water loss
After water loss, the ultra-fine glass fiber separator in the battery shrinks, making the adhesion with the positive and negative plates very poor, the internal resistance increases, and the heat increases during the charging and discharging process. After the preceding process, the heat generated inside the battery can only be dissipated through the battery slot. If the heat dissipation is less than the heat, the temperature rises. As the temperature rises, the overpotential of the battery gas evolution decreases, the volume of gas evolution increases, a large amount of oxygen in the positive electrode passes through the "channel", reacts on the surface of the negative electrode, emits a large amount of heat, and causes the temperature to rise rapidly, forming a vicious cycle, the so-called "thermal runaway". The final temperature reaches more than 80℃, that is, deformation occurs. At the same time, the largest heat capacity in the battery is water, after the loss of water, the heat capacity of the battery is greatly reduced, and the heat generated makes the temperature of the battery rise quickly.
B. Single case lag
If a group of batteries or a single-cell battery is seriously backward, under the condition that the constant voltage value of the charging is unchanged, the voltage of the lagging cell does not rise or rises slowly, and the charging voltage of other good cells is relatively high, it will heat up; The same group of batteries have a battery backward, will also lead to a group of other good batteries due to overcharging heat, will produce thermal runaway problem
C. The charging voltage is too high
The charging voltage of some inferior chargers is higher than the specified value, increasing battery evolution, and the battery will also produce thermal runaway.
D Oxygen circulation is smooth
The oxygen precipitated from the positive plate directly acts on the negative plate, and the heat generated can not be discharged in time, forming a thermal runaway.
