Presumably ICE generator means internal combustion engine? When I Google it the only thing that comes up is something that generates ice cubes. How would running a gen set to charge a battery pack in flight work? Assuming that say 60hp (40 odd kw) is being drawn in cruise, then a similar input would surely be required or the battery depletion would only be slowed by some degree. Happy to hear if there is something that makes that equation more favourable.
With at least one car manufacturer claiming they will be all electric in a couple of years, maybe there are some quantum leaps coming in battery technology. True that road vehicles are less weight critical, but current battery cars (not hybrids) lose a lot of space to the cell storage.