Originally Posted by
cyccommute
I've got to agree with mrbubbles on USB. USB is relatively new and isn't any kind of standard, de facto or otherwise, especially when you consider what the market has to offer. Midrange lights aren't in the $60 to $100 range anymore. That's high end compared to what's available for $20. Even weak "cheap" lights that run on AA are expensive (and worthless, IMO) compared what's available on the market. The Cree's that are currently available put out 10 times the light that the "cheap" lights put out for about half the cost. There's a little more bother in charging and maintaining them but that's minimal.
Just look at headlights on Amazon. There are basically three groups. "Cheap" lights, usually with no mention of lumen rating: AA or AAA batteries. Brand name lights (Cygolite, Niterider, Serfas, MagicShine) up to 1000 lumen: all USB. Everything rated 1000 lumen and above (both brand name and China): all with custom chargers.
It's quite simple. Custom chargers are a hassle. USB is convenient, and, if you make a rechargeable headlight, the only reason not to do USB is if you need a big battery that would take forever to charge through USB. And you only need it if you have a very powerful light.