I don't think the efficiency of the electric motor is the issue here. The article about the Taurus G4 mentions that cruise power is around 1/5 of take off power - so would be about 17 kW for the Pipistrelle if that was similar. However, average power has to be less because the trainer needs a reserve in its 17 kWh battery after an hour's flight. The G4 had to fly fast for the challenge but the Pipistrelle doesn't as a trainer. I think two issues are -
1. What can realistically be achieved using the 17 kWh battery in an hour's flight whilst retaining a 30 minute reserve? I suspect less than a 152 with a tank of fuel.
And
2. How do you put around 12 kWh of charge back into the battery in an hour? From a 230 volt ( European) supply you need 50 amps and from a US 110 volt supply, 100 amps assuming negligible losses. Those sorts of supplies will need to be specially provided. A flying school with several planes would need proportionally more. The literature does say that the batteries are quickly replaceable, so maybe the solution is to have multiple batteries charging more slowly but battery packs won't be cheap.
Difficult to see how this technology can be developed for a tourer where you can 'recharge' with enough Avgas for, say, 4 hours flight in 5 minutes...
Last edited by Andrewgr2; 28th Aug 2014 at 14:33.
Reason: Clarification of power use.