Battery keeps going dead

[Jamie Miles]

About a week ago, I tried to start my car and the battery was dead. I charged it up, and the car started right up no problem. It was dark out, and I noticed that everytime I came to a stop the headlights and dash lights in the car got very dim. When I took off again, the headlights brightened back up, so I knew the alternator was at least doing something.

When I shut the car off the next time, I tried to restart it and the battery was dead again. The next day I jumped the car off again and got out the volt meter. The voltage at the alternator was fluctuating back and forth between 14.6 and 18.9 volts.

I decieded to replace the voltage regulator. The voltage at the alternator is now holding steady at 18.9 volts. That seems WAY too high to me? I drove the car around several miles (should have been enough to recharge the battery), and whenn I got back home, you guessed it, the battery is dead once again.

I am at a loss as to what is going on here. If I am getting 18.9 volts at the alternator, and the headlights brighten up when you rev the car up, why will it not recharge the battery? The battery itself is only about 4 months old.

The car is a 1973 Maverick that I am bringing back to life. It had sat in someones back yard in South Carolina since 1992 when I got it. I have driven the car quite a bit in the past 6 months, and this problem just started last week.

 

[wallaka]

Sounds like a shot battery. You need to have it load tested to be sure, otherwise check your ground wires.

 

[fb71]

yup, sounds like the battery has an open cell. Age of the battery is not important, as some are just pure junk. Some of the worst have been all of the JCI brands (Johnson Controls Inc), such as DieHard, Delphi, and several others I can't recall right now. Exide isn't that great either. I have several different brands of 24F batteries cut open and drained, to show my students. The best by far is Interstate. Huge intercell welds, the most surface area per plate, the most secure mounting of each cell to fight vibration. These are only my observations and opinion. However, I have an Interstate battery that is 10 years old, and it spent 4 of those fully discharged while sitting in a car under an oak tree. 24 hours on a charger, and its been back in service for the past 3 years.

 

[fordconvert]

Check all your connections also. I think the regulator grounds through the case so make sure you have a clean spot near one of the mounting screws. Look at the connectors in the block make sure they are clean and tight. You can jam a small flat screwdriver in the block to release the connectors to clean them better. If there is a bad connection at the regulator it can confuse the thing and make it run the voltage up that high. Even with a bad battery 18.9 seems high. Also check you engine to body ground strap and battery cables.

 

[66 Fastback]

The battery need to be fully charged before making a regulator reading/conclusion. However the voltage does seem high.
Having said that, I had a small short somewhere in my harnes on my '61 Vette. I went through several lifetime warranty alternators, regulators and had several Die Hard Batteries replsced. Sears always took reading and certified it before it left there shop. But the slow leak persisted. I had to unhook the battery each time I parked to make sure I would have a battery. When Sear finally balked at replacing the battery for the 4th time, I bought a new harness and rewired the car and went back to the stock generator. It's an expensive bullet to bite, but I have not had a problem since then.
Doug

 

[Shrinkdude]

I had a similar problem with the battery not getting charged but saw no "charging" volts at the battery. I found 2 problem areas in my wiring, one at a plug where the wires go to the alternator and the other at the voltage regulator. Double check your connections to make sure that they aren't any bad spots.