So just got a 1985 Vette that had a new battery out in a few months ago. The power was running fine for the first week until yesturday I had to jump it. In idle the voltage goes down to 11.3 and a red light will pop up until I accelerate and it goes up to 13v. I'm guessing in the 11's is not normal for the battery? I'm thinking it may be possible that the battery died yesterday because I left a Bluetooth adapter in the ciggerate lighter for an hour, although it was fine while leaving it plugged in over night. Or maybe because the passenger door didn't shut all the way again? With the battery being new, is there anything someone may suggest to be the issue? And at what voltage is normal while idling?

 

Either a loose belt or a bad alternator.

Since it seems to be charging at all I'd check the belt first.

You should be ~14.2 volts under power and no less than 13 at idle.

 

Have the alternator and battery tested at a parts house. It is free. Dan

 

Most likely a bad alternator killing the battery.

 

There's a similar conversation over in C4 Tech that might be worth a look. https://www.corvetteforum.com/forums...est-steps.html

 

Or KILLED? Took someone I knew 5 batteries changed in a short period of time, relatively, before figuring it out. He brought the battery in for warranty, they gave him a new one, few months later, here we go again and he kept a tender on it at night. IIRC, they got fed up of doing it and insisted that he bring the car in and they found a bad alternator. He never came back for that after they sold him an alternator.

 

FYI, a (flooded lead-acid) battery (when disconnected) reading 12.2 volts is completely discharged. And, a (static) battery reading 12.6 volts is fully charged. If the voltage is below 12 volts, the battery is severely discharged. Furthermore, it is recommended that you NOT attempt to use the alternator to recharge a battery that is severely discharged as the load on the alternator is likely enough to possibly fry the rectifier too! Recharge the battery with a battery charger first. The alternator can handle normal loads like headlights, motors, and normal charging chores. But, a severely discharged battery or (worse!) a battery with a dead cell will tax the alternator beyond its intended design and it may damage it as well.

Just went through this last week. Suddenly battery dead. With the doors shut and the under hood lights disconnected, measure the current between the battery post and the battery cable. (configure your VOM for measuring AMPERAGE according to the VOM's manual). Normal C4 static current drain is ~ 21-23mA (.021-.023A). More than that e.g., especially above an ampere of so will kill a battery over night.)

However, if you are not equipped to do the testing yourself, the recommendation to take it to someplace e.g., AutoZone or O'Riliey's, etc, where they can do a complete analysis of the charging and load testing of the system is the way to go.

 

Don't you just love it when new members come on and ask a question and never even read or comment on the answers that people took time to write. Dan

 

Hey so super late response but just wanted to come back and say thanks for mentioning the alternator, that was the issue and the voltage has been normal ever since I replaced it.

 

For real

 

I got a new alternator on Amazon for less than $60 . Not worth screwing around for less than the cost of a battery.