If you have power when you park it there are two options.
One is a device called Trick-L-Start.. SOME motor homes provide for the charging of the chassis battery off the house converter.. Some do not, this device adds that feature to rigs that do not have it, simple 3 wire hook up, and then you forget it.
NOTE: Some Motor Homes **SHOULD** recharge the chassis off the house, but... due to a defect.. Do not.
The alternative option is a Battery Minder or Battery Tender (Both trade marks) these are simple 2-stage chargers (Absorption/float) and do a fantastic job.
Home is where I park it!