If it is a Vanquish or similar 12v SMD led light bar, they are meant to run off a 3s lipo. They are woefully dim on less than 3s and they won't even light up on less than 8 (or so) volts. Running a 3s light bar through the receiver isn't really an option.

The simplest solution is running the light off a small 3s pack wired to a switch to turn it on and off. If you want to control the light from your transmitter, then get one of the turnigy remote switches, it just splices into the positive wire going to the light and handles 3s voltage. I have one wired up on my SCX10 to control the light bar running a 3s pack.

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