I have a 95' Plymouth Voyager, and had it sitting for six months in KY, when I was living in Denver. The batterie was dead, and someone jumped it for me, but I forgot to turn off the radio and thus no more radio.
No big deal, except, it's draining the batterie.
I have a brand new batterie in it. I had it sitting yet again for a long time. Since May. I thought the transmission was out, but now it's looking like it could very well be merely the filter needing changed out. So I am going to buy a filter today, and some ATF+4 transmission fluid and see what that does. I jumped the batterie again, and reved the engine.
the radio makes a crackling sound when I rev it real hard. But the radio is both shorted out and turned off. So why's it still trying to get juice?
What can I do, so I can preserve my batterie?

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America just went to hell.

Disconnect the battery when the vehicle is going to sit for weeks or months at a time. You can also connect a small charger or battery keeper to provide a slight charge during the time the battery is sitting. There are electrical devices in the vehicle that will take a small amount of current from the battery even when the vehicle is turned off. These will deplete the battery if given enough time. Also, don't let the battery sit outside in freezing temperatures for more than a day or so without some charger connected to it. It's also possible that, if the radio was damaged during the jump start, it may be drawing more current than normal. You may want to pull the Radio fuse from the fuse panel. Hope this helps.

I also had a 1995 Voyager.Although mine did not sit as long as yours between driving times so the battery always had a full charge.My biggest problem came when I disconnected the battery for maintenance or replacement.The van would start up,run and go down the road about one mile and then stall out.It would start right up again and run fine and then stall out again.I found out later that once you disconnect the battery without supplying current to the computer you wipe out all the operating codes.The van then needs to relearn the codes and for the most part it will.It may take about half hour of driving but it worked for me.If not, the dealer can reprogram the computer with the factory codes.A good auto store can supply you with a cut off switch attached to the battery posts so when your not using the van the battery won't be drained.But again remember about the codes being wiped out with no power.Another option is a solar powered trickle charger that plugs into the cigarette lighter socket.It will maintain a charge to the van's battery but only if parked outside in sunlight.Even new batteries go bad in a short time but before you go out and buy another have yours load tested after trickle charging it for 24 hours.The radio,some have an anti theft built in.Once you delete power, the code to the radio it has to be reprogramed by the dealer.Transmission?Take the van down to an auto center and have them flush the system and replace the the filter.If you have slippage this should cure the problem.A good rule of thumb?Every 25,000 miles.One last thing after the flush" no, not the toilet"the trans.Electrical problems can have an effect on how the trans operates so also check the TPI sensor.Most of your problems seem to come from low or no voltage.I wish my life were that simple.Good luck.