skridlov: The idea exists since exactly 120 years now and was in service between 1910 and 1924 called GeVeCo. The biggest modern battery-swapping project
Better Place went bankrupt in 2013. They erected 21 robotic swapping stations in Israel and 17 in Denmark.
Apparently Tesla Model S is also capable of battery swapping but only one swapping station was built and Tesla seems to have abandoned the project due to low demand and high costs compared to regular fast-charging.
For helicopters I think with today's battery technology, the way to go is gas turbine generated electricity. Buffer battery for peak loads / takeoff power. 5 minutes purely electric flying ability for emergency landing in case of engine failure.
