I have this car for almost 20 days know. It's an automatic 05 Cobalt sedan.
2.2

Three days after buying it, I put in a new battery of 1000 amps. Since two days ago when I start the car it acts like a dead battery, but the engine runs. I have a Voltage meter and it marks 12.00, 12.27, 12.67, (red light) and it's like crazy until it gets to 13.8, 14.1, 13.0, 12,8 etc. (after running it for 13 minutes or so).

I turn off the auto lights, and the voltage comes up a little higher. I don't know if it has the original alternator. I had a Montero and sold it because of this, I changed 3 alternators in one year. What can it be?
New to this kind of car also.

What do you think?

 

you know you are suppose to charge a new battery first before installing it into a car right? new batteries don't come charged

 

False.

 

Its not a deep cycle battery is it ?the type used for a boat.If so they require a different charger than is in the car.
And yes the battery is charged when you get it but cant hurt to put it on a charger for a while and see if it helps.
The altenator should be putting out like 14.7 volts at say 2000 rpm if not it should be replaced unless the pcm is regulating it for some reason.

 

Thanks for the responses. What is the pcm?

 

the last battery i bought had to be charged before instillation, as per directions on the battery

 

I have NEVER got a battery that i needed to charge first.