Strange Battery

[eLindemann]

My battery reads hardly any voltage, yet my engine is able to run.

I know I'm testing voltage correctly because I just checked my sister's car and voltage came up a perfect 12.1 V (she's having starter issues and one of the first things I know to check is the battery). I only tested my battery out of curiosity. But it doesn't even read 1 V, it reads ~250 mV, even when the engine is running.

I don't know whether to think about changing batteries or not. Ford had checked my battery when I got the recall service done on the cruise control a few months ago.

I've also got A/C problems, and I'm kinda wondering if this may be related.

 

[Ashley_MTX]

I've had enough issues with them that if there's a low battery that I know should be good the first thing I always blame (correctly or not) is the alternator. Some people will tell you it's useless to get it tested at an auto parts place but it can be useful.

Might be completely in the wrong direction but it might rule that out.

 

[RonPorter]

If it's more than a couple of years old, just buy a new battery. That can solve a bunch of weird little (and big) problems.

 

[eLindemann]

Okay, sounds good. I have no idea how old my battery is, but it certainly doesn't look brand-spankin'-new. I guess I'll be picking me up a new battery.

 

[Ashley_MTX]

Yeah it's better than getting stranded in the middle of nowhere with a dead battery. Trust me. I know.

 

[TimboSHO]

If your battery had less than a volt of charge it would be useless. Less than 11v will not start the car, and going below 10 you wouldn't get output from any accesories (lights, etc.). You likely have a bad connection from the point you are testing it to the battery. Clean your terminals and cables and test again. If your car starts, the battery has more than 12v in it, guaranteed.

 

[eLindemann]

If your battery had less than a volt of charge it would be useless. Less than 11v will not start the car, and going below 10 you wouldn't get output from any accesories (lights, etc.). You likely have a bad connection from the point you are testing it to the battery. Clean your terminals and cables and test again. If your car starts, the battery has more than 12v in it, guaranteed.

You see, that's what I thought. My terminals are sparkly clean. I take good care to make sure of that. Which is why the measurements have me dumbfounded.

 

[Racer X]

Where are you testing the voltage?

 

[eLindemann]

At the terminals. If you're asking where in the terminals, I've checked all over them, same reading throughout ~250 mV +- about 20 mV.

 

[Racer X]

Your meter is set for DC and not AC, right?

 

[eLindemann]

Yes. As I had said in my initial post, I checked my sister's battery and that one checked out fine.
Just used the meter again on her car and got the same good reading as earlier (12.1 V), so the multimeter is still good.

 

[Ashley_MTX]

I would take the car somewhere and see if you can get it tested by someone else using at least one other meter. Auto parts stores will do it for free. I know some people will swear up and down that those tests are useless but it might save you however much money by helping you narrow the issue down or rule things out.

 

[SHOZ123]

There is no way the battery is reading under 1v and starting the car.

 

[Racer X]

There is no way the battery is reading under 1v and starting the car.

This.

Have you tried disconnecting the the battery cables and testing?

 

[platoribs]

I've had enough issues with them that if there's a low battery that I know should be good the first thing I always blame (correctly or not) is the alternator. Some people will tell you it's useless to get it tested at an auto parts place but it can be useful.

Might be completely in the wrong direction but it might rule that out.

When an alternator gives it up... and your driving along the interstate... blasting the jambs... wif LED's glowing...

Thaas no dope yo!

 

[eLindemann]

This.

Have you tried disconnecting the the battery cables and testing?

Haven't tried with the cables disconnected, since that should have no effect on the reading. I'll give it a try though.

 

[RonPorter]

Just get a new battery. $50 Duralast from AutoZone are kick-ass. Then check out stuff from there.

If the alternator was crap, it never would have started with a low battery.