I have a '04 chevy 4500 hauler that sits for a week or two at a time without being started. Just recently it has been losing 100% of the charge, sometimes. every one in a while it is grave yard dead. Is this a short some where or bad batterys? To get it started it takes a battery charger and another truck both hooked up for about 10 minutes. After it starts and runs for about an hour its fine to shut off and restart for daily use.

Sounds like a bad battery. If one of them is bad it'll kill the other one too. That would be the 1st thing I'd check.

Do you have any aftermarket electronic items installed in your truck?

I've got the same thing now. I've had my 2500 for about 3 months and it's sat for a week at a time without any issue. Last saturday, I parked it outside and didn't touch it until Tuesday of this week and all of a sudden it's completely dead. I didn't do anything different then I normally do besides parking it outside instead of in the garage. Don't know what the deal is, but now I have to start it everyday to get the battery charged up a bit or it'll be dead. I let it idle for 2 hours on Tuesday, 45 min on Wednesday, and 2 hours last night and still won't get past approximately 12 volts. Once I start her up and run her for a minute or two, she jumps right up to 14.4.

I took it to checker to have them check out the batteries on tuesday, and the guy kept getting an error on the device he was using to test the batteries and told me to keep turning on my lights. Finally he got the drivers side battery to read properly and said it looked fine, showing 680 joules I believe on a 770 battery and that it was charging normally from the alternator. He didn't retest the passenger side battery, so don't know if that ones the issue or not.

No aftermarket electronics as well.

You have to disconnect the ground to batteries to test. Without doing that they may show OK. I bet you have a bad battery.:cool:

the only aftermarket draw could be a red light on brake controller. I just had a edge programmer installed, but the problem was going on before that. thanks for the replies, I am going to swap out both batterys.