11 Volts on my truck battery? Huh?

[RobertD]

I put my meter on my truck battery, and I read 11 volts. I start it, and when running it still reads 11 volts.

1968 Ford truck.

Am I going crazy? That makes no sense to me. At rest it should be over 12, and running should be 13-14...

Starter works, truck runs, though I do have some gremlin in there that is making my radio intermittent sometimes.

For you betting folks, is it my multimeter, or is it something in the electrical? I'll get my other meter out next time I head to my mother's where I left it. Need to pick up some other tools anyway.

 

[itsid]

well.. car batteries will die at around 10 V..
but if it starts it should read 12V at least..

I'm not sure you can loose a volt or two on a multimeter (I can't imagaine a way to do so)

What I CAN imagine is, that your ground in fact isn't zero but +2V or something.
maybe even because of your radio (like you have the perma-+ set correctly and the switched-+ to ground or maybe just a speaker or something)

So first thing to check: remove the radio completely, and recheck the voltages;
if all is within reasonable values, refer to the radio's manual to check it's wiring.

'sid

 

[firemanjim]

You have a short somewhere causing a small constant discharge. Disconnect the radio, and read the battery again . Make sure that your chassis ground is good, and a ground wire to the body. (are your lights kinda dim?)

 

[RobertD]

If it is a constant discharge, that must be a great battery since I go weeks without driving the truck.

update: OK so tested my 4runner with this meter, and it came back with high 11 low 12 at rest. It's digital and it kinda would fluctuate between the two before settling on 12. After start, read 13.

Retest the truck. 11 at rest. 13 running. So that is good, but still odd. Going to keep my eye on this.

I started looking into this because I bought a MSD ready-to-run distributor, these are ones that don't use an ignition box. Doesn't work, sounds like a dead miss. Sent it back, they tested it, said it's fine. Talked with the techs more, and they say it needs a solid 12 V to run correctly, and that I should check into that. So I have installed a switched relay direct from the battery to run it whenever I get around to re-install it. As you can imagine installing and uninstalling distributors all day just really isn't the most fun thing when it's 95 degrees so I delayed until this weekend!

Here's another weird thing. If I touch the neg post and the positive tester touching the oil residue on the top of the battery, I read 5-7 volts. I didn't clean it, it's dark and I can do all that tomorrow, but just something odd I noticed.

Anyhoooo, that's the update for now.

 

[firemanjim]

https://www.oelcheck.de/en/knowledg...charges-in-hydraulic-oils-and-lubricants.html
Maybe the explanation for the oil thing.....

 

[itsid]

I'm not exactly sure it being a short (or creeping current) it's more like a false potential.
something that doesn't cause too much troubles (else the truck wont start I assume) or is capable of draining a battery...
just something that messes with more sensible electronics..

like hm.. like adding a tripple A battery to your ground wire the wrong way around.;
so you ended up with that small 1.5V potential in reverse (measuring 10.5 instead of 12V)
True it cannot be such battery for multiple reasons, but you know what I mean hopefully

I think an even quicker test would be to remove/disconnect the battery, then check the battery connectors for a voltage with a multimeter.

'sid

 

[machinist@large]

If it is a constant discharge, that must be a great battery since I go weeks without driving the truck.

update: OK so tested my 4runner with this meter, and it came back with high 11 low 12 at rest. It's digital and it kinda would fluctuate between the two before settling on 12. After start, read 13.

Retest the truck. 11 at rest. 13 running. So that is good, but still odd. Going to keep my eye on this.

It sounds like you might have a cell going out, which can lead to funky voltage even when the rest of the system is OK. As for your meter, definitely double check it; contrary to popular belief, just because its digital doesn't mean it's accurate.

As for the battery itself, see below....

........Here's another weird thing. If I touch the neg post and the positive tester touching the oil residue on the top of the battery, I read 5-7 volts. I didn't clean it, it's dark and I can do all that tomorrow, but just something odd I noticed........

If it's conducting current, then it's not oil, it's battery acid. That adds to my thoughts about you having a bad cell in the battery, most likely one of the end one's. Pop the cap's and check the fluid levels; unless you have a true sealed gel cell type, then the odds are high that the cap's are removable. Go from there, and keep us advised.

 

[machinist@large]

Any luck on the electrical front?

 

[fowler]

Look for hot battery
Misshapen sides of battery

Think its on the way out

How old is the battery
They only have a 3 yr life expectancy

 

[RobertD]

We had a dang monsoon yesterday in this part of the state, so I haven't re-tested it. I'll check it later. I didn't think about the battery acid issue. That makes a lot of sense, and makes sense why it would read low. The battery is probably 4 years old by now, maybe older. I don't drive the truck a lot, but it's always started strong. Probably time for a new one soon in both my vehicles.