While cleanin' up the engine bay this morning I noticed a whole lot of white lead oxide powder beside and below the battery - terminals were clean (I keep a little dielectric grease on those). About 3/8" of the stuff piled up in the bottom of the plastic battery tray.

I'm guessing this means I have a crack in the battery case? Nothing I can see... but obviously something is escaping the case? My understanding is "powder=not normal".

Can anything besides a battery acid or fumes leak cause this?

 

Time for a new battery, get a good one, jel type if you can, then it won't leak in the future.