I have a 2003 Chevy blazer just put a brand new battery in and the next day I had to jump it. I took to autozone and battery was at 45 % at the time they said they couldn't check alternator ( im assuming the car was just running off of the battery for a brand new battery to be that low) so I took alternator off and took back to autozone and it passed. what else could be my problem

 

sounds like maybe a bad battery - wouldn't be the first time a new one was bad

 

The battery tested good also

 

It may be that something is being left on. Do you have an amp for a sub or anything lie that that may not turn off when the car does?

 

im kinda having the same problem with my blazer im researching on anything it could be because I turn and make sure all lights are off they say it could be mixed or messed up fuses that's has to be connected to the radio or something

 

I'm having the same issue with my 94 full size. I went through 3 AC delco batteries, all of which were good and a new alternator and still having problems with battery/power/alternator not charging the battery. Still cant find any solutions..