Thanks. I will be getting rid of wet cell batteries for exactly that reason - their lack of efficiency. The lithiums are going to cost some dough tho. It will be expensive to get the rig fully fitted out. This all is also the reason why I'm looking at flatbeds.
The Wynns explain they connect the gray and cleaned black water to increase their gray water range which that dump at stations. They have a new rig for which the black tank have never been used.