Drones usually have a shortcoming when it comes to the payload and the time they can stay in the air. The average consumer drone’s flight time is 20 to 25 minutes at best before you have to bring the drone back for a battery swap. Thus, a probable solution to this could be mid-air refueling. It is easier to do this with liquid fuel instead of batteries. Researchers have come up with a solution at UC Berkeley. The solution consists of a secondary drone that carries a swappable battery to the mother drone.

swappable battery

In theory, it appears to be a simple concept. In practice, though, you really have two drones. The main drone and a smaller one that carries the battery back and forth. Of course, one would also need a way for the drones to find each other and dock. In an experimental setting, a big quadcopter, which weighs 820 grams, is carrying its own 2.2 Ah lithium-polymer battery that by itself gives it a flight time of about 12 minutes. Each little quadcopter weighs 320 g, including its own 0.8 Ah battery plus a 1.5 Ah battery as cargo. However, the smaller ones can’t keep themselves in the air for that long. However, as delivering batteries to the main drone is their sole task, it can be doable.

How does it work?

The smaller quadrotor takes a position about 30 centimeters above a passive docking tray mounted on top of the bigger drone, as each flying battery approaches the main quadrotor. Slowly and gradually, it then descends to about 3 cm above, waits for its alignment to be just right. It then drops down, landing on the tray which helps align its legs with electrical contacts. Later, when the connection is made, the main quadrotor is able to power itself completely from the smaller drone’s battery payload.

Each swappable battery can power the main quadrotor for about 5 minutes, and then it flies off and a new flying battery takes its place. If everything goes well, the main quadrotor only uses its primary battery during the undocking and docking phases. While testing, the flight time was boosted from 12 minutes to nearly an hour. As this needs to happen in a motion-capture environment, it is a constraint for the researchers who are trying to figure out the maneuver to work outside. Sometimes, an issue also occurs when the primary drone is moving. There are potential applications in situations where continuous monitoring by a drone is important—one could argue that switching off two identical drones might be a simpler way of achieving that, but that again requires two drones as opposed to just one plus a bunch of relatively simple and inexpensive flying batteries.