A standard 12V lead-acid car battery is not the same hazard as a household mains circuit, and simply touching its two terminals with wet hands is not a sound explanation of a fatal shock. The more relevant hazards are a short circuit, corrosive electrolyte and gas produced during charging.
How can a 12V car battery injure you?
If a metal tool or jewelry bridges the terminals, the battery can deliver enough current to heat the metal and cause severe burns. Lead-acid electrolyte is corrosive, and charging can release explosive gas. Keep metal objects away from the terminals, use eye protection, and follow the battery and charger instructions in a ventilated area. OSHA’s battery-charging rule describes protective requirements for workplace charging areas.
Are hybrid and electric-car batteries different?
Yes. Hybrid and electric vehicles have high-voltage traction systems that can cause lethal electric shock. NHTSA advises that these systems require special precautions; do not touch or service high-voltage components unless you are trained and equipped for that work.
If lead-acid electrolyte contacts skin or eyes, start flushing immediately with clean water. For eye exposure, continue flushing while seeking urgent medical care and contacting Poison Control. Do not delay flushing to identify the battery or try to neutralize acid on the body. If there is smoke or fire, move to safety and contact emergency services.
Sources: OSHA: 29 CFR 1926.441 — Batteries and Battery Charging; OSHA: Sulfuric Acid Chemical Hazards; NHTSA: Electric and Hybrid Vehicles — Batteries, Charging & Safety
