I'm not much into trying to make a backyard lighting system for my bike when I could buy one for the price it would take to jerryrig something and then maybe not work right.

So for $48 you could buy Cygolite Metro with dual beam 13 watts total with a battery life of 5 hrs on one beam or 2.5 on both. Only problem with this light for some people, but not for me, is that it runs off of 6D batteries which can either be the throwaway kind of the rechargeble kind. The battery pack can either fasten to your top frame or to the handlebar like a handlebar bag. It's fast and easy to connect and disconnect the light from it's mount and the battery pack fastens on with velcro. Reason I like this light is because I'm not tied to a wall. Or for another $20 Cygolite makes a couple of rechargeable water bottle type of models you can choose from