sounds like an alternator, and what you did was like a ghetto load test... only dumping like 30a tops draw on it... does sound like an alternator issue though. most alts charge approx 13.0-14.5 under normal conditions, should be no less than 13.0-13.5 with acc on definately no less than 12.6v cuz thats a battery's norm. check parasitic draw too. disconnect the battery neg terminal connect an ammeter from the neg batt terminal to the cable neg terminal. hold it there and take a reading, let the computers reset it should take under 30 seconds(key off doors closed acc all off!). you should have no more than 30 milliamps, .030A. these grand cherokees are notorious for having the courtesy lights staying on kiling the battery too...
