Powerdynamo brings new ignition & light
|What good are 100 or even 150 Watts if your light bulb still
sheds a miserly 35 or even 15 watts.
Most vintage bikes have bulbs (as shown in the picture, for dimensions see here) with a socket called BA20d and an output between 15 and 35 watts.
When you use our 12 volts systems, you should upgrade your bulb to a 40/45 one.