G Warwick, Plugging in, Aviation Week & Space Technology, 8 September 2014, p 52

In Slovenia, Pipistrel Aircraft has flown its ‘Watts Up’ two-seat trainer aircraft, fitted with an 85 kW electric motor of 14 kg and  6.5 kW/kg power density, together with a 17 kWh battery pack that recuperates 13% of its energy on every approach.   The battery can be recharged in 30 minutes, and replaced within a few minutes.   Endurance is 1 hour plus 30 minutes reserve.