I would like to design a system that switches from a 36V primary DC source to a back up 36V battery source. I would like the system to be light weight because it will be attached to a tethered drone. The drone motors draw around 80A of current. I also want the switching response time to be almost zero. Or is there already a component that does the following job?

 

Verbal descriptions are almost useless when it comes to evaluating possible solutions to a problem. A schematic diagram of what you have in mind would be most helpful. For example, does the 2.88 kW of power flow along the tether? What gauge wire is used to transport that amount of power. How much does it weigh when the drone is at the design altitude. What conditions will cause you to switch between the primary DC source and the backup battery source?