Airburst

I took the bulb out of a Union dynamo headlight today, and the rating stamped on the bulb was 6 volts. The rating stamped on the lense of the light is 3.6 volts. What's with the difference in voltage ratings?

Thanks in advance

CaptCarrot

pass, but most dynamos emit 6V and 3W, and most incandescent bulbs for dynamos are 3W or 2.4W (when used in conjunction with a 0.6W rear light)

Airburst

Ah, I didn't know what the output of a standard generator was, I thought it was 3.6 volts. If it's 6 volts, I guess I'll be fine giving the light 6 volts from a battery, which is what I plan on doing. Thanks!

CaptCarrot

Going back to the original question, the difference may just be due to the lens of a battery light being used in a dynamo light (especially if the manufacturer makes the same style of light to be powered from 2 different sources).

ATEOTD - the rating on the bulb denotes the power that the bulb will accept. The rating on the lens or housing is normally down to the heat generated by the bulb to prevent melting or fire. Although at those voltages it is not as bad as say a 100W bulb in 60W rated lamp shade.

One other thought is that the rating on the lens may actually be "VA" which is Volt Amps (crudely the Wattage). That 3.6 could be 3.6W and not 3.6V

Airburst

Ah, am I possibly going to melt the light by running it at 6 volts? Roughly what sort of speed does a bike with a tyre dynamo have to move for the dynamo to actually output 6 volts? I'm thinking the lamp may be able to withstand the heat from running at 6v, but only when there's air flowing over it to cool it. Am I overthinking this?

And I hadn't thought of the VA thing, but it also says 2.4 watts underneath the voltage rating, so that can't be it.