Dodge Ram Electronic Problem Battery or Not?

[Aluminum]

I have a 1997 Dodge Ram 2500, Its been sitting for a while so when I went to start it no suprise the battery was dead. I jumped it and took it for a little drive, ran perfectly fine then all of a sudden went dead it just quit the idle never changed or anything so I'm guessing the problem is the battery or alternator the truck ran good and strong for atleast 5 minutes before it quit, and I never charged the battery or anything but the voltometer was above half when it was running and when it quit and i turned the key nothing no crank no noise just nothing! I'm guessing its the battery since just a jump kept it going for a few minutes. What do you guys think?

EDIT: I jumped it again and same think ran then quit after a few minutes. And nothing in the truck was on no air no lights no radio so nothing for using power

 

[BAILEY1]

The next time it quits, tap on the ECU and see if it fires back up.

 

[HolyRamBatman]

Start it up and immediately unhook the battery. You could also try a voltage test on the battery. Before, during and after startup.