This is the 36V rear light found on all of our eZeebikes and on the Alpino range of Wisper bikes. It runs off the 36V battery supply but is not wired directly to it.
In the case of eZeebike this rear light is wired to the front light which has a twin wire going into the battery gauge. Inside the battery gauge the positive cable goes through the light switch and is then soldered onto the 36V part of the PCB inside the battery gauge. The negative cable is soldered straight to the 0V (ground) part of the PCB without any switching. The light specific wiring ends there as the battery gauge gets its power via a cable to the controllor, which is connected to the ezee battery.
On Wisper bikes this rear light connects directly to the wisper controllor.