On the longer rides battery consumption of my portable electronics becomes an issue. Phone, GPS, MP3 player and Bluetooth Helmet (at the moment three of those items are actually one in the same) all run down all too quickly.
I had originally planned to install a marine grade 12VDC accessory outlet somewhere, but dangling cables and plugs shaking free sounds like a really bad idea on a bike. A solution from Princess Auto presented itself in the form of a Weatherproof USB outlet (for $6.99 no less).
After some pondering I finally decided that I’d locate the plug in the trunk, and if I did need to charge my phone I could just lock it in the trunk (as it spits everything to the bluetooth in the helmet anyway), and if I run a gps I can snake a cable up along the gas tank with few issues.
For installation I had planned to tap the battery, switching the power using a relay wired to the marker light. A bad relay forced me to cheat, running the USB outlet off the marker light circuit (a draw of 5VDC 450mA shouldn’t cause any issues, and I can cannibalize the wiring when I get a replacement relay).
So for now, it seems to work just fine, and I can stop checking the status of my phone battery so often.