I have an AC generator of 6V AC and 9W power output. It is on an old bicycle motor a BSA winged wheel. I intend to run nicelite 3-6V DC LED lights rated at 1W each one red one white. I appreciate I can use Schottky diodes to make a bridge rectifier to convert the AC.  I also need the option of holding the energy charge into capacitors or batteries? To give me a stationary light's when the engine isn't running or I run out of fuel and end up cycling along at night time.

I realise I could use a switch to go between generated output and stored energy. But realize automatic switching employing the right Transistor could be utilised.