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In some of the videos, you can hear what sounds like a leaf blower running in the background. It actually is a leaf blower motor, running the generator to power the robot. I refer you back to the quotes from the tekkies above, in particular regarding the subject of drones carrying a person.
I ask you to remember the nuclear battery that the Terminator robot had, because we don’t have anything remotely like that.
Hence these larger robots require an ICE (internal combustion engine) and generator to do any serious amounts of work.

Think about your rechargeable electric drill or electric weed whacker.
You have about 15-30 minutes continuous use, under normal load, if you have a fully charged, large battery.
Then you have to swap a new one in.

Now imagine running the actuators, servos, sensors, step motors and the computers and software for one of these robots on lithium batteries.
In the big ones, they don’t even try –
they have an ICE/generator within the chassis.