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Car battery testing over double 12 volts??

I can't process how this is happening. I have an old car battery in one of my cars. It is worn out enough that it died on the first freeze that we had, sitting 2-3 days without starting. Said battery has also been leaking a bit of acid from around the terminals, and they are corroded.

So, lately, the alternator belt has been squealing if I slow to an idle (1993 Geo Metro), and the airbag light randomly flashes. The alternator belt is not worn and is torqued properly. I've noticed other electrical oddities such as the gas gauge going up and down (at almost the same rate as the throttle/RPM increase/decrease).

Finally, I pulled it this evening and threw another tested good (checked

12.7 v) battery in the car. I am about to go drive to my evening shift at work. I decided to test the old battery with the same voltage tester, and it tested at 27 V!! I can't find any info on a web search about this issue.

I checked it twice, and even put it on a charger for a minute to see if that would make a difference. The cheap HF trickle charger showed "fully charged"... then it tested at 27.2 V after unplugging it. Hopefully it hasn't damaged the ECM in the car, or something.

Does anyone know how the voltage of a 12 V car battery can double or more, just with regular usage? Possibly the cells in the battery shorting, or something? I thought that shorted cells decreased the voltage, not increased it. What an odd issue; thanks for the insight.

Reply to
Michael Trew
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Possible voltage regulator problem. Other issues:

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Another interesting link:

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Reply to
AMuzi

Was it a Fluke?

What did it test as with a small load?

--scott

Reply to
Scott Dorsey

I jumped the gun. The voltage meter was on the wrong setting. I didn't think that the meter was on the wrong setting, because the newer battery that I pulled out of another car happened to test at exactly 12.7 V on that same wrong setting. What a coincidence.

I pulled the new battery from a car that slid down my back dirt alley 2 weeks ago. I haven't bothered to pull the car out yet... my come-along isn't enough to pull it out.

Anyway, that car that slid down, the dirt hillside was in contact with the rocker panel firmly, and I guess that TOTALLY drained that battery. On the correct setting, the new battery just tested at 2.some volts... yikes.

I have the new battery on a little 1 amp charger now, maybe it will come around by tomorrow. I was very confused after my first post, when the car would not start at all. Yep, I guess 2 volts will do that.

Reply to
Michael Trew

Because you had it on the AC setting and it wasn't a Fluke?

--scott

Reply to
Scott Dorsey

Yes. I believe it was set to "200" A/C instead of "20" D/C.

Surprisingly, I was able to use a huge old heavy duty battery charger to bring the 2.4 volt battery (the new one) back to life. Hopefully I didn't damage it too much by letting it drain down that far.

Reply to
Michael Trew

Slow charge it.

Reply to
Xeno

I had it on a 1 amp trickle charger all night, it didn't do a thing after 12 hours. I put it on full-blast on my old Silver Beauty charger,

10 minutes cranked the car over, and drove around town. Hopefully that didn't damage it too much.
Reply to
Michael Trew

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