Yes and No, but mostly No.
The new Amazon indoor drone probably uses inductive charging (https://www.theverge.com/2020/9/25/21455197/amazon-ring-drone-home-security-surveillance-sidewalk-halo-privacy). The use case is solid for that device but in general no.
Why I claim NO:
- If the battery is warm do not charge, inductive adds heat so that is a danger. This type of charging creates a lot of heat as waste, so a drone coming in [literally] hot is a fire hazard.
- Generally speaking inductive charging is VERY inefficient, realistic 10-20% efficiency (don't believe the hype)
- The engineering expense is probably not worth it, no true benefit for the market.
Yes it is possible but not very practical, not very safe, not very efficient.
As for inductive charging - as in mechanical energy turned into power (like an alternator) - that happens all the time. I use a punch and "auto-rotate" on drones to limp back to the launch site when the battery is low (via FPV and rate controls not available on most drones). This is accomplished via "active braking" (or any other name scraped up) - in short the motors can turn into mini alternators and feed voltage back into the system, used to slow down props for key maneuvers. I have pulled some miracle landings using this dangerous method.
Capacitors are similar to batteries except they have 2 big differences:
1: Caps can not hold a charge for long (seconds or minutes)
2: Caps can discharge really fast - as in instantly. They were used for flash bulbs "back in the day", I have built near deadly DC tasers from caps.
Caps as a battery is not really possible. There are some hybrid technology I have read about, but nothing mainstream AFIK.
Caps in drones are very often used for voltage smoothing - specifically taking out noise caused by the ESC+weak electrical system, poor grounds, and other noise on the circuit.
Charging "in flight" is still out of reach. Matternet has a limited use example of the full charging station (https://mttr.net/images/Matternet.New_Station_Unveil.2020.03.10.pdf). Problems are many, here are a few:
- Proximity is an issue - inductive "wireless" charging requires things to be pretty close (inch or less generally).
- Right now it is far too difficult to get enough power unless you transform the use. One can trickle charge a phone because a typical iPhone under load is ~500mah draw (tiny). A drone is many, or tens of, amps hovering so you would need to exit the trickle charging "wifi" approach and lean towards directed energy (beam focusing), such as microwave (type of energy). You would also need to change the power reception and conversion on unit. Wireless power still eludes science for any practical use where power is high and range is preferred, even at only a few feet.
I can not underscore enough how poor wifi efficiency is currently. Claims of 60-75% are lab results - I have run tests on my chargers and I am quite unimpressed in performance. Convenience is high.
Danger is real - my wifi chargers all suggest NOT sleeping with the charger near bed or a minimum 20cm distance.
It is always important to underscore how drones are generally at peak technology. Anything that would improve drones and is not a weight or cost factor has been tried or is in the mix. We keep looking for innovation, and it comes, but if inductive wifi charging was valuable to the market we would see that happen.