Bad Voltage Regulator?

[ausgezeichnet]

Here is my current situation:

1. While running above idle, the voltage hangs around 12.95-13.0V
2. After driving the car for 15 minutes, the battery gets hot. More than just warm, but not hot enough that you can't touch it.
3. One hour after fully charging the battery and disconnecting the negative terminal, the battery voltage drops to 11.70V

The alternator light does not light, this is the second red top optima battery with the same problem and I had the alternator rebuilt 2 years ago.

My guess is that the voltage regulator is bad and has over charged and damaged the battery. My question is this: Could a damaged battery prevent a high voltage reading while running even of the voltage regulator was actually producing a higher voltage? If not, what could produce my current situation?

Thanks.

[john walker's workshop]

your voltage should be 13.8 to 14.2. if the battery gets hot at your low charge rate, there must be a poor connection somewhere, like the negative ground strap to body, trans to body, positive cable at the starter or the clamps at the battery. that can also cause your low charge rate.

[ausgezeichnet]

Thanks John. When I dropped the engine and transaxle last year I cleaned all the ground connections you mentioned. I also double-checked them today and they are all tight. I did a load test and go some interesting results.

I started the car with 10.75V on the battery. It was a little sluggish but it started. With he RPM’s at about 1500 I got a voltage of 13.55. I turned on the high beams and the voltage dropped momentarily and then went back up to 13.55V. I turned off the lights and tried the test again. but by now the max reading was 13.30V. I turned on the lights and it dropped below 12V and stayed there. It only when back to 13.30 when I turned off the lights. I continued repeating the test with the same results.

Can a bad voltage regulator cause low voltage or does it sound like my alternator is bad?