Quote:
Originally Posted by haigha
… I'm a little concerned because this guy says the battery should read around 12.5 V before starting (even after leaving the high beams on for 5 minutes). What do you think?
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I wouldn't think that the battery voltage is a problem. The only way to test it properly is with the car off, using a multi-meter on the jump terminal under the hood/bonnet. When you check the voltage via the car's hidden menu or OBD there is a significant electrical load on the battery - all the computer modules are awake, the fuel pump is running etc. It will read at least 0.5v lower than the no-load voltage, maybe more.
BUT, if it take 15 seconds for the alternator to start putting out a decent voltage after starting the car, I'd be worried. That's way too long - it should output the full 13.8-14.2v near-instantly. Sounds like the alternator or rectifier/regulator is on the way out - which could eventually kill your new battery.