400 mile electric RV

I do think hybrids are the future for RVs, at least the higher end ones. Electric motors make the same torque at 0RM as they do at full speed, 0RPM is where you really need the the HP of a ICE, not at top end, aside from hill climbing. The other thing is , once you climb the hill and are descending, you can get much of that energy back with an EV instead of wasting it in the brakes or Jake. For around town and in the park Pure EV will be nice , quiet and no fumes, on the highway, I do think you'll still need a diesel Genset, but that can be pretty efficient since it can run at a fixed , most optimum RPM. For example, a Tesla X needs 15kWh to maintain 60MPH for an hour. An RV is probably double that, so generating 10Kwh can extend the range of a 120kWH battery from 4hrs to 6 hrs of driving. You can stop and rapid charge, or boondock way far from a charger and let the genset bring it up slowly.