The TrueCharge turns on a fan when the charge current is 20 amps or higher. The fan is quite noisey. However, if you monitor your batteries and charge at appropriate times, you can avoid the noise a night. Operating the batteries closer to a fully discharged state allows you to put more energy back into the batteries in a shorter period of time. This may shorten battery life but reduces the Genset running time for recharging.
All chargers supply a specified maximum current to ALL batteries.
So, if you discharge two banks to near depletion, the TrueCharge will split the current between the two banks. The TrueCharge can supply 12V to the coach while recharge is occurring. This load is also part of the 40 AMP maximum. You will need to add the draw from all sources to calculate recharge times.