Ours has a 12 volt equalizer switch in the control panel that ties the gen and 12 volt house batteries togeather.

We also have a 24 volt equalizer switch to tie the bus and the house (4 each) togeather as well. Going down the road with the 24 switch on the alternater charges both house banks, 12 and 24. They work the other way as well, we can use these switches to jump start the bus and gen. both, if nessesary.

If we leave the 12 volt switch on with the gen. running the 12 volt house batteries get charged by the gen alternater.