While the Trik-L-Start will do the job there's a better solution. Use a voltage controlled relay like the Blue Sea ACR to connect the start battery and the house battery. It will monitor the voltage and when the solar panel gets the house battery voltage up it will connect the batteries and allow the starting battery to charge also. When the sun goes down and the voltage falls it will disconnect them.
The benefit from this is that when driving down the road it will work the same way and allow the engine alternator to recharge the house batteries.
It seems like the MH should have been set up for the engine to recharge the house anyway so you may already have a similar device. It may be as simple as changing the wiring or reprogramming it to have it act both ways on charging.
