The brake lever "power cut-off sensor" according to the Tektro site is a normally-open switch. If it's not running a brake light, you don't need to plug it in to anything. I found some documentation that implies this controller does not have a low voltage take-off so it would be full battery voltage for accessories. But that's 36V. Which is a big number to be wrong about. Some lights that take high voltage then have a lower voltage take-off from the headlight to do lower voltage tail lights. Can you figure out the brands or models of the lights? Do the lights plug into the controller with controls from the head unit? Or did they plug into the battery with their own switch?