Just a note on my battery operation...
I opened the power-plug end of the battery, and saw that it's the negative wire from the battery that goes via the key-switch. I took out the + and - spades from the power plug, so that I didn't damage the plastic plug itself, and desoldered both + and minus in addition to the wires to the key-switch.
Then I re-soldered the negative from the battery directly to the negative spade, and the positive from the battery to the positive spade, together with a thinner wire, about 7cm long, which I soldered to one point on the key-switch. Then I soldered a 40cm long thinner wire on the other point on the key-switch, and threaded it through a small hole i'd drilled close to the power-plug. I also fastened a tie-strap on the wire on the inside...
I attached a connector at the end of the thin wire, which then connects to the thin red + wire on the controller, together with the battery-meter wire from the throttle...
I had to use a blow-torch to de-solder and solder the + and - spades on the power connector, due to its size; my 40W solder-iron wasn't up to the task.
I think GM should have done it this way from the start, except that where I used a thinner wire directly out of the battery-box, they should have a third connection point in the plug itself...