Originally Posted by
Leisesturm
Isn't life fraught enough, what with needing to keep track of credit card due dates and staying on top of the slow puncture in the front tire? Do you really need to figure out how to get a 5v light system to run off a 3.7v Li-Ion battery pack?
Rechargable USB "emergency packs" for phones are tiny. RayOVac, at least, also makes a 4AA box with USB output.