Battery dead?

FC · 06-03-2020, 11:47 AM

Measured voltage just now having not touched the car at all. It was down to 11.6V. It hesitated a little but started up fine.* Measured voltage while running and got 13.9V, so I guess that confirms that the alternator is working. Shut off the engine after just a couple of minutes and battery voltage read 12.2V.

*WTF? Why was the battery not able to start my car yesterday after 25 minutes of over 3.5krpm driving? Is that not enough and the return drive did the trick to top it off?

Meanwhile, the battery did drop from 12.05V to 11.59V in 24 hours.

Maybe I should disconnect the battery and track it on its own to confirm it's not some parasitic loss.

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06-03-2020, 11:47 AM	#13
FC Solving problems Join Date: Oct 2003 Carmudgeonly Ride: M5 / 718 GTS / Cooper S / GTI / LR4 Location: Metro Boston Posts: 25,248	Measured voltage just now having not touched the car at all. It was down to 11.6V. It hesitated a little but started up fine.* Measured voltage while running and got 13.9V, so I guess that confirms that the alternator is working. Shut off the engine after just a couple of minutes and battery voltage read 12.2V. *WTF? Why was the battery not able to start my car yesterday after 25 minutes of over 3.5krpm driving? Is that not enough and the return drive did the trick to top it off? Meanwhile, the battery did drop from 12.05V to 11.59V in 24 hours. Maybe I should disconnect the battery and track it on its own to confirm it's not some parasitic loss.