My idea is to build a electronic system for my bike to supply my phone and lights with energy. I want to use a Dynamo (6 V, 3 W) to charge a USB Powerbank. From its two USB ports I want to charge my phone and run the front and back light. As a front light I want to power a 3 W high-power LED with ~3,75 V @ 0.6 A. As a backlight I want to use ~3 red LEDs with 0.02 A at around 2 V.
The setup should be as energy-efficient as possible and easy to repair.
First problem: How to charge the powerbank via the USB-Port with 6 V? Is it sustainable to charge the powerbank with 6 V instead of 5 V? I could drop the voltage through resistors, but that would generate 0.5 W (???) of heat. What options do I have here?
Second problem: How to wire the lights the most efficient way? I used the high-power LED with two 1 Ω resistor to run it at around 0.6 A, however, that seems way to inefficient to me. What is a better way here? Maybe connect the high-power LED in some way with the red LEDs?