The M1097R1 Humvee has dual 12 volt batteries to make the truck 24 volts. Both of our batteries had a low charge state so we removed them and charged each of them overnight on a trickle charger.
We were able to revive the batteries, for now at least, and they are able to start the truck even after sitting for a couple weeks.
While we had the batteries removed we cleaned the battery compartment and hold down strap.