Thanks for the replies. Since initially posting, I've found out my bike, a Triumph, has a factory fitted plug connection in the electrical loom to which a DIN / Hella type socket can be attached (via a bracket already part of the frame). So, I'm going to order a DIN / Hella socket and a suitable lead/kit to charge a sat nav. Until a couple pof days ago, I'd not heard of DIN sockets, they look like a smaller version of cigarette lighter sockets. Apparently, a few manufacturers ie Triumph, BMW have these sockets alreaday on the bikes or at least a connection plug which accommodates them...............