Somebody has asked for a simple design with a full-wave rectification, without the option of charging the batteries using an AC adapter, given that the batteries may be taken out and charged outside. The full-wave rectification may be employed when either the dynamo or lamps electric leads are disconnected from the bicycle frame. The Zeners in the circuit schematic below should be 5W. Other diodes should be 1A or more. The resistors can be 1/8 W. The LED indicates when the lights are powered by the dynamo. The more advanced hub regulator is more efficient than the simple regulators and makes batteries last longer.