I used A123 batteries in my electric helicopter a decade ago. They're still going strong and you could charge them in 8 minutes. They were unfussy and the combination of batteries/motor gave a better power to weight ratio than an IC engine. It was only in energy density that they fell short.
The obvious solution to the fast-charge problem is to have a large battery on slow charge from the mains. If you take somebody for an hour's lesson then charge in 10 minutes from the ground-based battery then you will only need a 17kW mains supply - assuming you need 1/5 the energy of petrol for an equivalent flight. Expensive, but probably cheaper and easier than trying to swap batteries in and out of the aircraft which is the other solution that has been proposed.