Well, actually, it could be the starter. I had a starter kill a battery once. Out running errands, stopped at a store, did my thing, came out to move on, inserted the key, turned it, and everything went black. It killed the battery so dead it wouldn't even register the LCD mileage display on the dash board.
I do hope you got the polarity right, flipping that could get really expensive. Assuming that is ok, you can only look around for the cause. The bad smell is likely melted/burned insulation somewhere. Might also be the incinerated carcass of whatever varmint chewed the wrong wire.
This will take some serious hands-on wire tracing.