Turn on LEGO Mindstorms robot remotely
I know for a fact (from reading the EV3 schematics), the only way to turn on an EV3 is by pressing the center button.

Here are some ideas to work around this issue:


Create another robot that presses the power button.
Create a mechanical device that causes the center button to be pressed all of the time, then create a mechanism to switch battery power.
Solder wires in parallel with the center button and attach this to a device, such as a relay, that can operate the center button electrically.