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I own a 2020 Cube Nuroad Race FE bike.

Do you perhaps know what model of hub dynamo this bike has or at least if it's AC or DC? I can't figure it out since there are no markings on it.

Here are a few images of the hub dynamo in question: https://i.stack.imgur.com/sUkAb.jpg

mkrieger1
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Dusan
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3 Answers3

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The standard output of hub dynamos is 6V A.C. and usually 3W, though smaller current outputs are available.

I think it is unlikely that your hub deviates from this well established standard, else it would be incompatible with almost all lights and charging accessories. Of course, as original equipment, the best place to ask the question is your CUBE dealer or the CUBE helpdesk.

You could also hook up the output to an oscilloscope and see what you get out of it. You should expect a sine wave (from an unloaded SP dynohub) or something a bit more triangular maybe. As Chris H demonstrates, the output is 12-15V peak-peak AC with frequency apparently dependant on wheel speed and the design of the hub.

Noise
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    The output from actual hub dynamos is more like sharp alternating spikes, with roughly 0.5A maximum current and maximum voltage somewhere way above 6V if the load has higher resistance than 12 ohms. – ojs May 23 '22 at 13:07
  • @ojs how's the lamp dealing with it? Plenty large capacitor and Zener diode as limiter? Nice side effect that standing light comes almost free. – gschenk May 23 '22 at 13:20
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    @gschenk the spikes go both ways (i.e. it's AC, but not sinusoidal) so you need a bridge rectifier. Then the cheapest dynamo lights flicker, but better ones have enough of a capacitor to smooth that out. Standlight supercapacitor circuits re more complex (though I keep meaning to try building a basic one as I have a spare supercap and a flickering cheap light). – Chris H May 23 '22 at 13:30
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    You could also hook up the output to an oscilloscope and see what you get out of it. I have in the past, and you don't. I'll see if I can get a picture – Chris H May 23 '22 at 13:32
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    @ChrisH I'd like to know that: https://bicycles.stackexchange.com/questions/84024/output-of-a-hub-dynamo-measured-with-an-oscilloscope – gschenk May 23 '22 at 13:38
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    @ojs I've now added some scope traces at gschenk's linked question – Chris H May 23 '22 at 14:29
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    @gschenk the B&M halogen lamp had a pair of Zener diodes but it still went through bulbs pretty quickly. LED based lamps generally have rectifier, large capacitor and driver circuit to keep the LED healthy. – ojs May 23 '22 at 14:29
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    @ChrisH thank you, that's great information. And unexpectedly smooth curve from SP-PD8. – ojs May 23 '22 at 14:31
  • I know, @ojs. I must have only measured it loaded in the past. I did have an incandescent front light for bench tests, which I think sharpens the spikes on the Shimano - perhaps the resistance of the filament actually changes measurably on this timescale, or perhaps the lower bits aren't very stiff sources. That hub was recovered from an old rental bike with incandescent lamps. – Chris H May 23 '22 at 14:38
  • @ChrisH I think the hypothesis makes sense. The filament's temperature could vary by hundreds of degrees before you can notice it by eye and at that point the resistance change should be significant too. – ojs May 23 '22 at 14:49
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    @ojs I have access to the kit I need to do that experiment in work! I've been doing time resolved FTIR spectroscopy. I think we might need a bit of signal conditioning to use the dynamo output as a trigger. But going to the literature the thermal timescales of small bulbs are of the right order of magnitude to change their resistance appreciably within the period I measured or at slow riding speeds - and they do observably flicker though not down to darkness. – Chris H May 23 '22 at 15:05
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According to the bike's data sheet the bike ships a Supernova E3 Pure 3 front light. It is specced for 6 V (AC) 3 W. This is a datum that indirectly supports JoeK's conjecture the hub provides these specs.

gschenk
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It looks like it is a Kasai FS with branding removed. Kasai FS hub Details can be found on the manufacturers website: https://www.kasai-tech.com/fs-dynacoil-disc---ta.html

Excerpt from data sheet:

6v / 3W

Fits 6-bolt rotor or Centerlock rotor

15mm Thru-axle

OLD: 100mm

Flange-Flange:​​ 50mm

gschenk
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Andy P
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