Volts (V), Amperes (A) and Watts (W) are all units of electricity.
V = W / A
A = W / V
W = V x A
Most Bicycle dynamos (often incorrectly called generators) put out alternating current (AC).
Most are 6 volts and 3 watts. However 2.4 watt versions are also common. Older dynamos may be either 6 volt or 12 volt. Vintage Sturmey-Archer Dynohubs put our 6 volts but only 2 watts. This is more than enough for modern LED lights.
Incandescent bulbs are OK with this, but LED bulbs require direct current (DC) or they will burn out immediately!
Either way you will see blinking at slow speeds. It is more noticeable with LEDs because there is no residual glow like the filament of an incandescent bulb.
All LED lights have a rectifier, which flips one side of the AC over, making DC. The flashing will still be there but twice as fast.
Everyone knows how bright a 100 watt light bulb looks. However, watts aren't a good way to tell the brightness of a light source. Most street lights are 100 watts for example.
Bulb quality, material, the inert gasses inside the bulb (Krypton or Halogen), reflector and lenses all contribute to light output. The units Lumen, Lux and Foot-Candle are used to determine actual brightness. You could purchase a Lux Meter or just come into our shop and try out the lights in person. Many of the new LED lights are amazingly bright.
It is our opinion that many bike lights are TOO BRIGHT! Especially for trail use, where bikes come at you head-on.
Our staff commutes by bike all year long, so we have first-hand experience of what works.