Yesterday I got a battery powered handlebar mount light prototype built using the Endorstar, Luxeon Rebel 3up star, pictured in the previous post. I’m using a heavily heat-sinked 3/4″ copper cap to hold the LED and lens, and a proto-typing board to hold a partially assembled driving circuit. The batteries are 3 Lithium Polymer cells that I picked up from Sparkfun.com wired in series to give 11.1 volts. (each cell is 3.7, just as the Lithium Ion’s). The special thing about Lithium Polymer cells is that they have a very high power/weight ratio. In other words, they weigh very little. NiCd batteries have a power/weight ratio of 150Watts/kg, Li-ion’s are up to 340Watts/kg, and Li-Poly’s are up to 7100Watts/kg. (that’s an unsupported wikipedia reference) Li-Poly’s also have a 99.8% charge/discharge, which is significantly better than any other battery chemistry’s.
The next step is to mount it to a bike and see how the beam shape is, see how far it throws, and see if I can get away with running at 800-1000mA without overheating it, and see what effect air flow has on heat dissipation. I’m cutting it close by having such a small heat sink on this LED, but it is also an experiment.