Reasons leading to explosion of lead-acid batteries

The explosion of lead-acid batteries is generally caused by improper use. There are many reasons leading to explosion of lead-acid batteries. The reasons for the explosion of lead-acid batteries are detailed below.

1. Battery shell explosion caused by excessive internal battery pressure

People know from the working principle of lead-acid batteries that during the battery charging, especially due to overcharging at the end of charging, water is decomposed into hydrogen and oxygen, and sharp increase of electrolyte temperature during short circuit, severe sulfurization, and charging will cause large amount of water to evaporate. If the vent hole of liquid hole cover is blocked, the pressure inside the battery will rise very high because there is too much gas to overflow, which will cause the battery tank to deform first. When the internal pressure reaches certain pressure, burst will come from the battery tank cover joint or other weak points, which is a physical process. When the internal pressure of the battery is higher than 0.25MPa, the battery bursts at location of hot air joint of the groove cover or edge and corner with concentrated stress.

2. The battery explodes when hydrogen meets the open flame

The explosion limit of H2 and O2 mixed gas is that H2 accounts for 4%~96% of the volume of mixed gas, and the explosion limit of H2 and air mixed gas is that H2 accounts for 4%~74% of the volume of mixed gas. If 80% of the overcharged amount is used to electrolyze water, and the H2 content inside the battery exceeds the explosion range, an explosion will be formed if exposed to open flame when the hydrogen content in the battery or air accumulates to the explosion limit. This is a kind of chemical reaction.

The study found that the explosion of battery is a branched chain explosion reaction. Too many such explosions occur in the case of overcharging. If virtual solder joints exist in the internal poles and through-wall welding of the battery, the battery has higher possibility of explosion. A qualified battery will not undergo self-heating explosion reaction under normal use conditions. When the battery charging voltage is higher than 14.4V for gasoline vehicles and 28.8V for diesel vehicles, an explosion may occur under condition of simultaneous ignition. Through inspection of vehicles with exploded batteries, most voltage regulators were found to be defective, and the batteries were in a severe overcharge state.