What Causes Smoke from a Car Battery?

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Smoke from a battery is caused by damaged separators and sparking between electrode plates. Here are the detailed explanations: 1. Battery Working Principle: From the perspective of internal operation and structure, a battery consists of alternating anode (PbO2) plates and cathode (Pb) plates separated by insulating separators. Immersed in electrolyte (dilute sulfuric acid), these plates generate 2V of electricity. Batteries require frequent charging and discharging, causing the active materials on the plates to repeatedly expand and contract with volume changes. The separators prevent short circuits between anode and cathode plates while allowing ion flow. 2. Fault Analysis: When separator quality is poor (e.g., containing impurities), ions crossing the separator may release these impurities. Excessive electrolyte impurities (from impure water or unsealed battery caps allowing contamination) can cause plate short circuits. High short-circuit currents can scorch separators, worsening the short circuit in a vicious cycle. As damaged separator areas expand, smoke emerges through battery vent holes, resulting in visible smoke emission.