What kind of accident is a battery explosion?
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A driver at a certain workplace needed to charge the battery of his electric bike while working. When he thought the charging time was sufficient, he went to check it, and suddenly the battery exploded; fragments from the battery’s plastic casing flew toward his face, causing a fracture in his nasal bone. What type of accident is it? How to prevent it?
The hydrogen content in the battery has reached the explosive limit. Avoid overcharging while charging. According to the working principle of lead-acid batteries, the active material at the positive electrode is lead dioxide, while the active material at the negative electrode is sponge lead. The electrolyte is a dilute sulfuric acid solution. When the battery is charged to 70%~80% of its capacity, oxygen begins to be produced at the positive electrode; when charging is nearly complete at around 90%, hydrogen starts to be produced at the negative electrode. Hydrogen is a flammable and explosive Class A substance; its explosion limit in air is 4.1% to 74.1%, and its ignition temperature is around 450°C. As a result, the hydrogen concentration in the charging chamber can easily reach the explosion limit, leading to combustion and explosion upon exposure to a fire source. For example, on July 3, 1991, an explosion occurred in the lead-acid battery room of a power plant, resulting in the death of one maintenance worker and severe damage to the charging equipment and batteries. The main cause of the accident was the failure of the battery ventilation system, which led to the accumulation of hydrogen inside the area; furthermore, the inspector violated safety rules by smoking during his inspection, and an open flame triggered the explosion.