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Battery on fire

After a 5 minute drive, my 2000 Lexus(recently purchased) car stopped/ battery was flaming/cables were fried. I put the fire out(extinguisher from near-by store). Some say the “battery shorted out” is this true/possible?

It could have shorted out internally, or it could have been overcharged by a bad alternator, which would cause hydrogen gas to be generated and any old spark could have triggered it.

The short is much more likely than hydrogen igniting. Any accumulation of hydrogen would simply go poof! and leave no further damage. But a short circuit, entirely possible, would turn cables red hot and then they can ignite nearby plastic. A careful inspection might determine the cause of the short.

Loose battery terminals can cause a fire too. Most times they won’t but it has happened. I’ve only caught a few that were smoking.