First of all my knowledge of electronics is very limited, so please bear with me.
I am looking to charge AA batteries from a bicycle dynamo for when I am on a global cycle tour. My dynamo is a Schmidt SON 28 Dynamo hub, which I believe outputs 6 volts. So presumably it would be a good solution to charge 5 batteries (1.2 x 5 = 6V)?
The problem is I have read that the output voltage from a dynamo can greatly fluctuate depending on speed, so my research has led me to believe that I need to use a full wave rectifier. Any suggestions for this?
Secondly I want the charger to stop charging when the batteries are charged and turn on an LED indicating they are charged. Any ideas how to achieve this? Would something like an attiny85 (I have one of these) do the job? Or are there simpler / better solutions?
Thirdly, does anyone have a circuit diagram that may work? I have searched extensively for a circuit diagram, but can’t find anyone else who has done a similar project.