I've built and currently testing an LED lighting system using a dynamo. Only the dynamo powers the headlight with standard Blinkies used as side and taillights. This was a safety concern, as you never want your taillight going out at stops and they run for 200+ hours on 2 AAA batteries. Here is my current design.
I have included a solar panel for effortless recharging during the day!
This headlight stays on for up to 3 hours without recharging help from the dynamo. If you don’t want to use the dynamo or your in a condition where you cant recharge the batteries while running the light at night and the batteries die and go out at stops the LED driver chip will shutdown the LED preventing damage to both the LED and rechargeable batteries. When you start moving again the chip will automatically turn the LED light back on and will operate exactly like a standard dynamo light. Opening S1 and leaving S2 closed allows recharging the batteries at 500mA or the suggested maximum recharging current for Ni-MH batteries. After batteries have been recharged opening S2 prevents overcharging the batteries. After testing for over 100 hours I've never managed to completely deplete the batteries to the point the chip must shut down the LED even in stop and go town traffic. The LED currently in use is a Luxeon 1-watt Star drawing 350mA allowing for 150mA-recharging current for the batteries when riding above 8 MPH with maximum recharging current generated at 10 MPH with LED on.