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Can a car alternator overcharge?

By Li Chenyu / hcfire360 November

Not exactly. But the voltage regulator can let too much voltage reach the battery.
Check for example:
1. Using a voltmeter, check battery voltage at rest. Should read +- 12.6 V.
2. Check voltage at idle. Should read +-13.6 V.
3. Increase motor speed. Should not go over 14.5 V (that's the use of a volt. reg.). If so, could be a faulty volt. reg.
A persistent over 15 V. output will ruin the battery.