Most of the time, this is just an SAE-style Battery Tender lead right to the battery. Chances are that if the bike is one of my personal rides, it doesn't get used as much as I'd like. And I hate to buy batteries, which is why I have, oh, six or seven Battery Tenders around the garage. Pretty much any time a bike sits for more than a few days, it goes on the 'tender. But there are other reasons: I have a couple of small pigtails made up, one to convert the SAE two-pin connector to a USB socket for charging my phone and one a round coaxial cable for heated gear. Because, well, at my advanced age I hate to be uncomfortable.