Your 2009 MH probably already has a decent charger in it to charge the house batteries. What I do is when the MH is not being used the battery disconnects are off. My batteries last several months through the winter this way. During the summer when I charge the house batteries I plug into shore power while the house batteries are being charged ,I plug a maintainer into a 120v outlet inside the MH and into the 12v plug that goes directly into the chassis battery. If I am going to use the MH I leave it connected until I am ready to leave. If I cant use it for several weeks I will disconnect power and turn disconnects off. Everyone does things differently I just don't like to leave the chargers on for weeks at a time.