There is a vent hole on the car battery (there is a small hole in the middle of the filler plug of the ordinary battery, and there is a small tube on the maintenance-free battery) to open to the atmosphere. If the battery is not properly maintained and the ventilation holes are blocked, then if the electrical load is too large or a large current discharge is caused by a short circuit, the reaction is intensified, and the hydrogen cannot escape. When the pressure in the battery reaches a certain level, it will explode; If the ventilation is not good, it will accumulate in the battery, and it will burn and explode when it encounters sparks.

The former situation mostly occurs when the battery is in use, and the latter situation mostly occurs when the battery is being charged. The battery will produce hydrogen and oxygen during the charging and discharging process, especially when overcharged, the water is electrolyzed to produce a large amount of hydrogen and oxygen. If the ventilation holes are blocked, the heat and gas generated cannot be dissipated, which will continuously increase the internal temperature and pressure of the battery, which will eventually cause the battery to explode. Therefore, attention should be paid to dredging the ventilation holes in daily maintenance to prevent dirt from blocking the ventilation holes.