Made the mistake of wiring my first set of grips directly to the battery. I altered the wiring after leaving them on not once but TWICE !! Fairly simple process. Remove the live supply feeding the grips fuse holder from the battery and connect it to a switched live going into the back of the fusebox. To find the live side of the fuse in the fusebox, remove the fuse and check for 12v with a meter or small 12v bulb with the ignition on. Headlight fuse is a good one to aim for. There's no point wiring to the load/out side of the fusebox fuse as your grips will have their own one and you would then need to uprate the fuse in the fusebox to accommodate the extra load. Depending on the bike, there might even be an accessory connector for exactly this type of purpose (if you can find it !) that you could use instead. Never faffed around with a relay, overcomplicated for what's probably no more than a 3A current draw. The additional load should be negligible to cause any problems overloading the switching contacts of the ignition switch.