Drained Battery

I was wondering if anyone can help me here; I have a 99 Windstar 3.8L with 150,000kms on it, when I shut the van off I have power to my radio and power windows for 10 mins or till one of the doors are opened, if I sit inside of it and let it go till the 10mins are up and the radio shut off, when I go to try and start it the battery is dead and I have to jump it, I was wondering is it the battery or something else that's just draining the battery alot, not sure how old the battery is cause I bought the van used, it does start up fine any other time tho, any help would be great, thanks

The 10-minutes-or-until-a-door-opens feature is a handy factory feature. The interior lights will also turn themselves off after awhile (20 minutes, IIRC) if a door is left open.

If the battery is unable to start the engine after only 10 minutes of radio use, I suspect the battery is dying. A voltmeter will tell you if it's hanging on. Get a decent digital multimeter ($20 or less for basic models) and learn to use it; it's a valuable tool.

Note that other problems (dirty battery connections, starter problems, etc.) can cause similar symptoms.