The Whatt Meter Electrical Box is complete.
Since the Whatt Meter displays both Amps and Volts, a selector switch is unnecessary. It's true that once both battery clips are installed the rear wheel will turn because the motor will run off the battery, but since the Red Positive clip is within easy reach, I will just use it instead of a switch.
A switch could easily be added, as could a Female Plug to connect to a far off battery.
There are no batteries in the Whatt Meter, nor does it have an on and off switch, or does the Whatt Meter require selecting between Volts and Amps like the Harbor Freight Volt Amp Meter.