As part of your weekly PMCS, make it a point to open the battery compartment access doors on your HYEX to look for wet areas. That moisture quickly mixes with dirt and sand to create corrosion.
Look for any rust inside the compartment, especially on the bottom plate that supports the batteries in place. Report any you find to your mechanic.
Corrosion in the HYEX battery box
Remove the batteries to eyeball the condition of the battery box itself. Any water or acid that collects underneath causes the bottom plate to rust and deteriorate.
Next, use a wire brush to scrape off rust and old paint. After a good cleaning, protect any bare metal with bituminous coating compound, NSN 8030-00-290-5141.