Car battery testing over double 12 volts??

[Michael Trew]

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.

[AMuzi]

Possible voltage regulator problem. Other issues:
https://gear4wheels.com/why-is-your-car-battery-voltage-too-high/


Another interesting link:
https://mechanics.stackexchange.com/questions/45283/is-15v-too-high-for-a-standard-car-battery

--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[Scott Dorsey]

Michael Trew <michae...@att.net> wrote:
>
>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.

Was it a Fluke?

What did it test as with a small load?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Michael Trew]

On 12/23/2021 21:07, Scott Dorsey wrote:
> Michael Trew<michae...@att.net> wrote:
>>
>> 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.
>
> Was it a Fluke?
>
> What did it test as with a small load?
> --scott

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.

[Scott Dorsey]

Michael Trew <michae...@att.net> wrote:
>On 12/23/2021 21:07, Scott Dorsey wrote:
>> Michael Trew<michae...@att.net> wrote:
>>>
>>> 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.
>>
>> Was it a Fluke?
>>
>> What did it test as with a small load?
>
>

>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.

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

[Michael Trew]

On 12/24/2021 15:24, Scott Dorsey wrote:
> Michael Trew<michae...@att.net> wrote:
>> On 12/23/2021 21:07, Scott Dorsey wrote:
>>> Michael Trew<michae...@att.net> wrote:
>>>>
>>>> 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.
>>>
>>> Was it a Fluke?
>>>
>>> What did it test as with a small load?
>>
>>
>> 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.
>
> Because you had it on the AC setting and it wasn't a Fluke?
> --scott

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.

[Xeno]

Slow charge it.

--
Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

[Michael Trew]

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.