So....
In October, I drove back out to the home town and picked up my dad's truck. It'd been sitting there for a year since he had his stroke and passed away, but it was still in decent (if damp and a bit mildewy) shape and I brought it back home. I don't have need to drive it very often so I have to make a point of going out and starting it up once a week or so just to keep the fluids circulating and the battery charged.
Tonight we got home from running some errands and I fired up the truck before bringing in the groceries and stuff. It started just fine and I left it to run while I put stuff away, let the dog out, etc.
About three hours later I'm watching tv and trying to figure out what the noise is outside...
Guess the battery is charged up.