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Battery problem

3365 Views 13 Replies 5 Participants Last post by  yan7gin
Hey guys, I have a 1988 f250 7.3 and my gear shifter broke off right above the transmission (zf5) so I welded it back. I removed both battery negative cables before I started. The next couple of mornings I went to start the truck and had low voltage. Like 5.3 volts on the cranking battery. So I had the alt checked and the stator came back as bad, luckily it was still under warranty so I replaced it. The next morning, same thing low voltage but this time it was .3 volts. I took the battery to Walmart to have it checked , it was less than a year old. After waiting 1hr and a half it came back good. So I get back home and check amp draw with everything off( even underhood light) and I had a 3.5 amp draw. I checked every in cab fuse one at a time with no change. I had to leave for work shortly after. As I return this weekend I bought a new voltage regulator from advance. Hooked it up and no fix, the amp draw is now dang near 5 amps. I'm needing help with this one guys. Oh and my battery light is on as well.
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Ok guys I was doing more reading and I disconnected both battery negative cables to read amperage and it went from 5 amps with the drivers side battery still connected to virtually zero when disconnected. Could it be that I've had a bad battery this entire time? The voltage reads 11.64v right now.
If you are testing the batteries then isn't a better method to check Voltage on each fully disconnected battery than to test Amps?

Unhook positive and negative cables for each battery. Fully charge each battery with a wall mounted charger. Unhook charger. Check voltage. Allow to sit overnight and check voltage again. It should still be atleast 12.6 or higher.
Ok I took the drivers side battery to advance auto this morning. Turns out it's good, the guy said it was just low voltage, they charged it, I took it home and swapped the batteries. Now I have no problems. No current draw and every thing is back up to snuff. So far..
Its not typical to have only one of your batteries at 5.3 volts.

These batteries are hooked up in (EDIT: Parallel) and after a few days of sitting like yours were, they should have both been near the same voltage.

The fact you had such a large amp draw probably indicates a voltage imbalance between the two batteries. You said you had the "starter" battery (primary battery) charged and tested and it was reported "good". Did you do anything with the other battery? You should really have it charged and tested as well.
Parallel. Connecting batteries in series ADDs their voltage; connecting them in parallel adds their AMPERAGE (or Amp-hours).Disconnect EITHER terminal from EITHER battery (one is enough) while you measure voltage across each battery's posts.
Senior moment. Thanks for catching it.

As for either terminal from either battery, you won't ever break me of the habit of removing negative first. (Unless I am working on our Ford Jubilee).
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