Batteries not charging...

[geez_al]

I everyone, I ran into a problem that is sort of confusing me.

My bus has been sitting now for a few months. I've been running it
every few weeks to kep everything charged and lubricated but the last
time, I left the inverter on and it drained the batteries all the way
down to about 10 volts and I had to jump start it.

The alternator is working as normal when running but it seems the
batteries just can't hold a charge. Even after running for extended
peroids of time (trip to Mississippi from NM) when the engine is off,
the low volt relay still trips.

Any suggestions? I don't think there is a short anywhere.

Thanks,

Al S.
1981 31ft FC
NM