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Tested: No! And I have no plans to do so. See further for why.
This dynamo is of no interest, see the end of this section for the reason and for the final bit of explanation about what Schmidt did with the SON-20R. The impression Schmidt created when they launched this dynamo, was that this was previously named the SON20R. This dynamo hub has 26 poles just like the SON28, but supplies less power. The consequence of that should be less vibrations than with the SON28 (just like the SP SD-8 is vibration free for me, unlike the SP PD-8) but I later heard from 2 people who have issues vibrations with the SONdelux in small wheeled bikes. 1st report is in use in a Moulton APB, which has front suspension which makes the fork heavier and should make vibrations a bit less noticeable, but the vibrations can be noticed by the rattle of the front fender... The 2nd report was from someone else using it in another Moulton. So I thought a comparison against the SP SD-8 would be in order. I didn't get round to that before it became clear that the SONdelux is a neither-nor product. Let me first say this:
The consequence of less power output is less loss, also with lights off, but that less power is supplied could be a disadvantage with the use of multiple LEDs and/or systems that extract power from the dynamo hub for USB devices, GPS systems, etc. See my experiences with the SP SD-8, and this section about vibrations and other issues with dynamo hubs for more on the lower power output of 1.8W hubs (3.0W in a small wheel) in a 622mm rim.
The SONdelux is fairly expensive (ca. € 190,- to 240,- depending on colour and rim- or disc brake version).
Now we come to an interesting section. In 2011 when I looked at Schmidt's website for their claims on efficiency on the SONdelux (to compare with SP) I read this:
Der SONdelux ist der erste Nabendynamo, dessen Generator speziell für moderne LED-Scheinwerfer (wie Edelux und B&M Cyo) ausgelegt ist.
Translated (note: auslegen für = to design for (in capacity/ability)): The SONdelux is the first hub dynamo, whose generator is specially designed for modern LED lamps (such as the Edelux and B&M Cyo).
At the time in 2011 my response was: This is nothing more than a lie. They never designed the SONdelux for LED lamps, it's a 20 inch generator, which gives enough light with current LED lamps at low speeds so that it's now used in 622mm wheels for which it has a special StVZO approval in combination with the Edelux (and not in combination with any other headlamp!) since end of 2009. Note that the rename of the SON20R to SONdelux came after the approval, and that a rename does not make it a dynamo that's specially designed for LED lighting! It's just unbelievable that Schmidt dares to claim the SONdelux was specially designed for LED lamps!
This response was based on what Schmidt themselves wrote on their website, as you can read further on. End of 2012 some things got clear when I contacted Fahrradzukunft about their latest article on dynamos. The updates 2-5 I placed here after that. I had put update 1 here earlier already as I had seen some comments that the SONdelux has a higher power output than the SON20R:
Update 1 Perhaps I have to be more nuanced about this, as the SONdelux, at least current versions, put out more power it seems than the SON20R. But anyway, if that was so since the start, then I still feel you can't talk of generator that was designed for LED lighting, it was just slightly altered at best.
Update 2: Someone working in the field of bicycle dynamos told me that this behaviour of fairly high power at higher speeds was typical of the tradeoffs in dynamos (using less coils), however, I assume this is only for resistive loads, with which dynamos are tested for StVZO, as with the SD-8 this is not the case when I measured with the special dynamo driver... Note that LED headlamps and that driver are NOT resistive loads and with the special dynamo driver using an SD-8 I could not get anywhere near the PD-8's power output. So if this is correct (I never got round to measurements using a 12 Ohm resistor, though I wanted to as I wrote on my dynamo measurement page..., so I'm just mentioning this all to keep everyone informed of what I was told) this means that in reviews other than mine, more tests must be done to show what power output is possible (I already do that of course). And actually, this is already taken into account though not very accurately, by watching the power output at low speeds. From the info from this dynamo designer, the SONdelux was indeed no different from the SON20R in output. Anyway, that's the information I have, my own measurements to come when I have time.
Update 3 (2012-12-27): I wrote to Fahrradzukunft about their test, or rather, the writeup by Oehler. I will dedicate a special page to this issue, in German and in English, and move the SONdelux stuff to there soon. Oehler (from Schmidt) wanted me to apologize for saying that I said that it's a lie that the SONdelux is specially designed for LED lighting, because the SONdelux apparantly is not the same as the SON-20R. I declined. Let's go back to what happened: People had been using the SON-20R (meant for small wheels) in standard sized wheels to give minimal drag and this works for e.g. road bikes. Also, someone I know had suggested to Schmidt to make a dynamo specially for LED lighting. Schmidt probably thought then that they should (try to) get the SON-20R (standard or modified) approved for use with the Edelux. Then this happened: Schmidt themselves, on their website nabendynamo.de wrote that the SON-20R in combination with the Edelux was StVZO approved and they thanked the approving authorities for allowing this technical progress to be used (on the road)... They then renamed the SON-20R to SONdelux. You will find the same 'fact' that the SONdelux is a renamed SON-20R mentioned on lots of websites, even those of distributors of Schmidt products... So the cause of thinking "It's a lie that it was designed for LED lighting" is what Schmidt themselves wrote. I'm not going to apologize for their mistake! (or perhaps it was even disinformation, see below). Then we come to the fact that the SON-20R is no longer made. What are you to do then for a small wheeled bike? Use a SONdelux? This makes clear why people using the SONdelux in small wheels have issues with vibrations! In small wheels it provides a lot more power than the SON-20R at moderate speeds, which gets mostly wasted in power limiters in the headlamps, unless you are using a USB application. So, it seems to me that Schmidt made it look like the SON-20R was StVZO approved which was then named 'SONdelux' as people want a very light running hub. But if you look at power production, the SONdelux gets above the SON28-new at higher speeds and as I said this power will mostly be wasted with a small wheeled bike. In a small wheeled bike this higher speed range is where you will quickly come as the wheel rotates faster for the same bike speed. So why did Schmidt stop making the SON-20R? I think this is answered by the 'disinformation' of the name changing. They imply the SONdelux is just as good for small wheeled bikes as the SON-20R with this rename and the StVZO approval for the SONdelux can be used as advertising for people using it in bigger wheels whereas using the SON-20R in a standard wheel could make people think "Is it OK to do this?". So by removing the SON-20R from the lineup they need to keep 1 less model in production. Whatever the reasons, assuming the power curves as measured by Schultz are correct, and I don't doubt them, then the conclusion is clear: The SONdelux is a pointless product, as it's not optimal for small wheeled bikes (wasted power, though this could be of use when using USB power), and for standard size wheels (559mm or 622mm rims) it provides less power than the SON28-new at speeds less than 30 km/h, so it doesn't provide much power at the average speed people ride at (i.e. ca.15-25 km/h) which means less light but more crucially means less power for USB applications, and finally for those who want the least power used on lights (esp. road bikes, riding at fairly high speeds), the SONdelux uses more power than the SON-20R would.
Update 4 (2012-12-28): I haven't found my own saved webpages on my PC yet (from Schmidt's website, esp. the pages of the SON20R and SONdelux), but Schmidt's statement of the SONdelux approval says exactly what I wrote above: http://www.nabendynamo.de/news/2008-2011.html and go to 1.1.2010:
SONdelux jetzt mit StVZO-Zulassung
Endlich ist es amtlich: Schmidts kleiner Nabendynamo SONdelux (früher SON 20 R) passt hervorragend zum LED-Scheinwerfer Edelux. Darum hat das Kraftfahrt-Bundesamt im Dezember dieser Kombination den amtlichen Segen gegeben, für alle Laufradgrößen von 16" bis 28". Wir bedanken uns für die Legalisierung des technischen Fortschritts!
Linkhinweis Zur SONdelux Produktseite.
(Btw., I already quoted this on my StVZO page long ago, to point to the fact that special StVZO approvals are possible)
So it says: "Schmidt's small dynamo hub SONdelux (previously SON 20 R) goes magnificently together with the LED headlamp Edelux". If they wanted to say the SONdelux was based on the SON-20R (so with some essential changes), they would have said "basiert auf" or "eine Weiterentwicklung von". This way of stating it, along with the removal of the SON-20R from the product line-up (logical if the SONdelux is just a new name for the same dynamo, not logical otherwise), I think confirms my view that Schmidt wanted to cash in on the desire for people to have the lightest running dynamo hub, for which road bike users had been using the SON-20R, and to use the StVZO approval as marketing, by making it look as if the SONdelux was a SON-20R with approval.
Update 5 (2012-12-29): Summary: What Schmidt wrote with the approval notice of the SONdelux contradicts that the SONdelux was specially designed for LED lighting. Either it was 'previously the SON20R', or it is quite different and was 'specially designed for LED lighting'.
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Last modified: Fri Dec 14 08:14:26 CET 2012