Starting , Battery Issues 2006 Denali

[vdubpower]

so if i leave my door open or the rear hatch open for like 10 minutes, the battery dies

 

its not completely dead, because the lights will still go on....when i place my charger pack on it, i still have to hold the ignition down and it will start....

 

if i drive it everyday , it doesnt seem to die, but if i dont drive for a day, or leave the door open, it will die

 

i just had the battery tested, it said 12.75 ,

do i need to replace and it or could it be something else

 

i think it all sstarted a yr ago when i had to use a cig lighter charger to put air in the tire. it died then, and has been on and off since then

 

thanks

[jrrod2004]

maybe a bad cell in the battery. did you check your alternator as well?

[vdubpower]

how do you test an alternator?

 

what symptoms diifferntiate between the 2

[jrrod2004]

My primary guess is that the battery has a bad cell or more. Either that or the alternator is not charging the battery as it should (could be dying). The symptoms you have sound like a bad battery. your battery is there for starting purposes only- once you start the car, the alternator takes over, runs the cars electrical system and recharges the battery- if you start your truck and then disconnect the battery, if your alternator is good, the truck will keep running. bad alternator and the truck will die. note that if your alternator is bad, your car can run off the battery for a while till the battery dies. sure sign of bad alternator = constantly dead battery. I would take both the alternator and battery to the local parts store to have them test both. One of them has to be bad.

 

Edit: did you test the battery with the truck on or off?

[vdubpower]

truck off, took it to local firestones they checked it...infont of me and i saw the reading

 

i was abt to get the interstate mtp 78

 

but they didnt have them in stock

 

whats a good battery to get