Amazon’s plan to use drones to deliver packages is an amazing idea. But turning it into reality involves solving difficult technical problems.

One of the biggest challenges is the limited battery power on board the drone.

As if being loyal to Murphy’s laws, batteries are notorious for running low just when they are needed most, such as when a drone is in flight.

Amazon has been wary of this possibility and has invented this on-board battery charger for drones. The battery charger is powered by a combustion engine that may also be used to directly drive the drone’s propellers.

A computer on the drone calculates the estimated flight duration and checks whether there is enough charge in the battery to provide power for that duration. Only when there isn’t enough battery, the combustion engine is started to drive a generator which then charges the battery to the required level.

By making sure there is sufficient battery power available on the drone at all times, this invention makes Amazon’s Prime Air not only to take flight but also sustain it.

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