I really don't understand all this stuff about battery capacity and fan horse-power but I know I mistakenly bought a 2006 Monaco diplomat in which the previous owner had converted to an electric fan system. It had four fans installed in a frame that required major modifications to the shroud to fit it in. It had a manual switch in the drivers compartment and it worked great on flat ground. But I live in the west and we have hills. Even a short climb caused overheating and bigger ones resulted in all kinds of warnings and in one case the engine finally cut out.
We spent many days (even weeks) residing in various repair shops where we replaced thermostats, radiators until we finally found our way to Source Engineering who rebuilt the shrouding and installed a new fan in the MH. Ever since it has worked great. I'm sure we saved a little gas using the electric fan but I would never go back to it. That 400 HP engine works fantastically. You paid a huge up charge to buy a DP for all kinds of good reasons. Why would you want to cripple it just to reduce mileage a little bit. Just buy a front gas engined van chassis class C and be done with it.
'06 Monaco Diplomat
'06 Jeep Wrangler Toad