I bought a new 3 year battery about 3 months ago from autozone and recently it died completely. The keyless entry didnt even work. So I jumped it off and drove it to autozone so they could test it and said it had a 45% charge so I let it run a little longer to get more charge on the battery so that they could test the alternator, which turned out to be fine. So I drove it home and this this morning I tried to crank it up and it was dead yet again. I have made sure no interior lights or anything were left on. I have no idea what the problem is. Please help!!

 

We will assume that what the store told you is true, that battery indeed was "discharged", and that it "charged up", and that your alternator is putting out full power. Since you did not mention your model and year, can't tell you the amps.

But when turned off the truck battery should read 13.2 volts or above. When cranked, it will increase to 13.8 - 14.2 volts.

Now when you turn it off, there are things that keep running, like alarm system, clock, radio memory, etc. But usually it is a larger drain that kills the battery. It sounds like you don't have a voltmeter handy, so here is a shade tree method. With tuck not running, remove + battery terminal. Take a tail light bulb and hold it where metal sleeve of the base touches the (+) post. Touch the battery terminal to a base contact on the bulb. If you have a substantial drain the bulb will light. You can then pull fuses to isolate this.

 

thank you very much I'll give that a try.

oh, and mine is a 2002 D2.

thanks again !

 

What is the cold cranking , CCA, rating on your battery? Did you have some one recharge the battery after it died, driving it a little won't give you much if any of a charge unless driven for 2 to 3 straight hours.
Get it started and go back to where you bought that battery, have them do a charging test. The system needs to be between 13.6 and 14.4 volts or you have a problem.

 

basically you have to do a draw test to find out what is causing the problem. you need a multimeter that reads Amps and then you have to test the system. it should only be 30 milliamp draw.