Could be the alternator not putting out or the battery not taking the charge. Have both load tested.
Could also be an excessive drain being created by an electrical short with the electrical system.
The computer controls the field generation of the alternator-if it fails to control the field circuit it will overcharge or undercharge the battery.
Get a test light disconnect the battery positive cable-put test light between the disconnected cable and battery positive post-if there's a short circuit the test light will lit up. Now to find where that short is coming from start removing fuses one at a time, when the test light turns off-that's where the problem circuit is.
For the battery and alternator:
Get a voltmeter read the battery voltage before you start it up record it-it should read 12.4volts and up. Now start the jeep up, the reading now should be 13.5 to 15.5 volts if not the alternator or the field generation driver in the computer.
www.eautorepair.net if you need repair manuals see below
Wednesday, November 14th, 2007 AT 4:44 AM