wiring in heated grips on a 2015 T100 Bonneville

Where is the best place on a 2015 T100 Bonneville to wire in a set of heated grips? I have had them wired up to the sidelight in the headlamp shell but have now disconnected them to see if this is causing an issue with my battery which appears to lose about half a volt every night. I have been advised there could be a 'drain' on my battery somewhere and as the heated grips are the only extra attachment on the bike I thought i would try this first. I do not want to wire them directly to the battery in case i leave them switched on and flatten the battery

Thanks

David

 

I have had Oxford heated grips before and they were really good but this time i chose Daytona grips as they have quite a slim profile on the bars and they do work well. I don't know if these would cut off when the ignition is switched off. I might try attaching them to the battery first then see if they do cut out. Thanks