2001 Villager having issues!!

First off .... this is my mother in-laws van not mine. Saturday her and my mother went to visit a family member for a few minutes. Well my mom was in the car listening to the radio and the van just died. Well when the mother in-law tried to start of course it didn't start .... BUT after she removed the key all dummy lights, dome light, went crazy. They couldn't even jump start it the battery was that dead. So they went and got another battery and it started right up. Could it be something else that is draining the battery? I have also noticed when I have drove it that while sitting still the rpms will go up, and it tries to lunge forward... different problem all together? or same problem? I told her to take it to auto zone or something to have it tested but she hasn't done it yet. Also was told it is blowing oil somewhere. I have not personally looked at it yet to see if I can see where the oil is coming from.:shakehead

Find out if the alternator is working to start with.

Many odd electrical problems come from a bad ground lead. Check the black wire from the battery to the frame/engine. Check to see if the terminals on the battery are corroded. Sometimes the acid will leak from the battery and leach into the black and red wires on the terminals. This will reduce the efficiency and impeed charging. If the wires are alright, then pull the alternator and have it tested. What most people don't understand is that sitting in a vehicle that is at idle with all the accessories on will drain the battery. At idle the engine is not spinning fast enough to charge the car's battery even with everything off. If the battery is weak to start with then it would not take much to kill it.