The car sat for a few weeks and the battery appeared to have died. I had to jump start the car to get it running, it fired right up and I drove the car for about 30 minutes. Once I had returned home I left the car idling in the garage and about 5 minutes later it died, no power and would not restart.

The car is a 96 LT4 and it is curently sitting in the garage with no power. Does this sound like a battery or an alternator problem?

Thanks for any ideas.

 

Battery. You need to have the battery charged and tested.

 

I would also check for corroded battery cables.

 

If your alternator wasn't working the red battery symbol light on the dash would have lit up when you drove the car. Driving your car for 30 minutes will not put much of a charge in the battery. Lead acid batteries don't like sitting for long periods of time (4+ wks) and as they discharge the plates collect lead sulphate. Lead sulphate is a good insulator and fully sulphated batteries are door stops. You might try charging your battery with a battery charger for 24 hours and you might also measure the leakage current from your battery with everything off in the car. GM says leakage current must not be more than 50 milliamps. Batteries at the end of their life will not hold a charge and this might also be your problem. How old is the battery? If it is at 1/2 or more of its guarantee period, it is suspect.
NEVER leave your car parked for long periods, buy a battery tender and connect it to your battery (it is safe to leave your battery connected in the car) so that your battery is kept charged. Every time you fully discharge a car battery and charge it up it looses its amp hour capacity and soon you have the equivalent of a motorcycle battery.
Disconnecting the battery will not work either because lead acid batteries self discharge up to 1% each day even disconnected.

 

 

Sounds like the battery

 

It's probably the battery, but you may want to have the alternator checked out. Alternators are not designed to charge dead/failed batteries. They are for maintaining a properly supplied electrical system, not as a substitution for an inadequate power supply. If possible, always try to use a battery charger to recharge a battery before you start it. If it won't take a charge or drops its charge during starting, you have a bad battery and you won't end up smoking your alternator.

 

Thanks for the help guys! I pulled the battery took it to NTB where it was bought and it had a dead cell, they replaced it no questions asked. Came home installed it and she is back up and running. I am going to get a battery charger/conditioner this week to keep her charged and ready when she sits covered in the garage.