I ride an electric bicycle that uses a 48V battery for it's energy source and there have been times when it would have been convenient to have a USB charging port (for charging my phone or any other other device that can recharge from a USB port). So I built this USB charging port (basically a DC-to-DC converter capable of handling up to 60V input voltage). I used the OSH Park circuit board prototyping service which worked perfectly. I wrote an instructable about the build here:
http://www.instructables.com/id/A-USB-Charging-Port-for-an-Electric-Bicycle
Regards,