Yeah, when the motor is running it is dipping quite a bit. I put my old Motomaster battery that came with the car, and with the lights, and heater running on high it is dipping down a little bit below 12 volts. I think my alternator has the voltage regulator built in, in which case I believe that I would have to replace everything at once.

 

Well, the red-top charged up overnight and passed the load test fine, looks like a wimpy alternator is the culprit.

 

^ BUT do the lights still dim?

 

Some Optimas, when gone "bad", still test good.

It'll charge up, it'll load test fine too.

After charging and the load test, wait 20 minutes, then check it's voltage again. It should be about 12.7 or higher.

Wait 24 hours. Sitting on the bench or disconnected from your car. If it self-discharges in this time, it's done. You can even "see" this happen over the 24 hours, just check voltage every hour or two, and it will consistently drop it's voltage.

At the end of the 24 hours, if it's any more than a few tenths of a volt lower than when you started - Or less than 12.5v - Boat anchor city.

 

Okay thanks Grizz. I am running another battery in my car, so the RedTop has been sitting in the garage overnight. I will take a voltage reading and then check it again tomorrow.