Other Homework Help

im working on a 2008 jeep commander for my neighbors wife. she got home last night and left her window down because her child was still in the car. when she turned the key to put the window up nothing happened. i went over to check it out. i disconnected the battery for ten minutes. the reconnected it. turned key on and you could hear relays clicking under the hood, the instrument panel lit up and flashed (transmission over temp, and service park assist) but nothing else electrical would work and i could not get my code reader to work. i tested the battery voltage with the key off and it was jumping from anywhere between 2-12 volts. i hooked up jumper cables to her jeep and everything started to work fine. code reader did not pull any codes and the trans over temp and service park assist messages were no longer flashing. the jeep would not start only the starter would click even after 30 minutes. i am having her  get the battery tested today but other than that i am lost as to what the problem might be. her car was only turned off for 5 minutes before this happend.