The motor controller is now being controlled by the Arduino and power is running safely through the new power/relay board. Woot! I'm working on the Safety piece of the throttle control (to keep unlicensed chair drivers from flipping it over or accelerating too harshly). Should have that completed by tomorrow.
The relay board has a booboo in it. The 12V Accessory is supposed to only work when the 24V system is energized. Sadly, I wired it after the main (24V) power switch. The electricity is taking the easiest way to ground, which is NOT through the 12V relay coil. Stupid electrons. @Phillysteak527 I might need some of your professional electronics design expertise to do this the right way. I'm bumping up against the limits of me hobbyist knowledge here.
I'll have to come up with another solution for that part of the power board, but, in the meantime, the stuff that matters is working perfectly!
Almost ready to drive!!