Rick- IMO the batt cover is a nice but clumsy thing, and I'd store it for the next owner IIWM. Then, I'd take a look at the various degrees of road filth access the batt compartment has. One place dirt comes in easily is the slot over the jack box; you can close that off w/a rubber sheet (to allow some flex in the head of the jack).
Some openings are needed to allow the battery gassing to dissipate (till you switch to AGM batteries), but perhaps not all of them. Closing some off will help w/the filth. Then just hose out the batt compatment on a warm day when it will dry out, & leave it open to do so. A little baking soda & water in a spray bottle will help neutralize acid built up on batt tops if used before hosing. The cap should be on the engine diagnostic port and all caps tight on batts, and I wouldn't use a spray nozzle, just run clean water over the batts & tray after spraying.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project