Adding additional load to any existing systems circuit is never a good idea...especially with CFM's minimal standards. It will cause not only voltage drops across all systems but most likely cause additional heating of poorly designed connectors and internal harness connections. With that said...nothing wrong with using that circuit as a relay trigger for the lights. A relay's coil only take around 6 milliamps and that..won't effect anything. The power source for the light itself will come straight from the battery then. Of course that little LED will only pull something less then 4 amps which you could do as I did..tie it into the accessory circuit without a relay. Its fused and keyed power. Just need a switch.