Technical > Lighting and Electronics
Some general information on hub dynamos and USB charging.
mickeg:
On another forum, I learned of two documents on USB chargers that are supplied by hub dynamos. I thought I would share them.
I just saw the note from Dan warning us of links in other posts that have malware, I think all of my links below are safe. But Dan, if you find any are problematic, please remove this post. And warn me since I would probably already be infected.
This article is in German, it compares several top USB chargers at different speeds. It also includes a rare one that uses more complex electronics to increase output much more.
http://fahrradzukunft.de/21/steckdose-unterwegs-4/
The link below is the Google Translate version of the above German document. It is not easy reading, as the translation is often unclear or ambiguous. Example, it states: "Will you at standstill of the bicycle enable the USB drive to supply a newly infected consumers, so you have the hub dynamo wheel sat briefly in motion." Thus, it takes careful reading to fully grasp and I will readily admit that I did not grasp all of it.
https://translate.google.com/translate?sl=de&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Ffahrradzukunft.de%2F21%2Fsteckdose-unterwegs-4%2F&edit-text=
And, for those of you that are less technically inclined, the short version of all of this is the graph at the link below that compares the output of several of the chargers at different speeds. (This link is to Figure 13 in the above German document, I listed the link instead of attaching the graph as that might be a copyright violation?)
http://fahrradzukunft.de/bilder/21/steckdose-unterwegs-4/13.png
Of those chargers:
- The Forumslader on the graph is a charger that has complex electronics to force the hub to deliver more power, I had never heard of this before I read the article.
- The B&M Werk is probably the most commonly known one of those compared.
- The Sinewave Revolution is made in USA and sold directly by the manufacturer, thus it may be less well known outside of USA. I considered buying the Sinewave, but instead bought a headlamp/USB charger combination.
- I think some of you are aware of the Plug3 which puts the USB port on the stem cap.
- And, some others including a DIY one that was home fabricated.
I do not own any of the chargers compared, so I will not elaborate further on them. My charger, the AXA Luxx 70 Plus (headlamp/charger combination) was not evaluated and is not included on the graph.
I typically tour at about 20 km/hour, according to this graph all of the USB chargers except the ForumSlader falls in the 2.5 to 3 watt output range at about 20 km/hour. The big difference between the various chargers (other than the Forumslader) appears to be at speeds greater than 20 km/hour where some perform better than others. My measurements of current flow on my AXA Luxx 70 Plus suggest that it peaks at about 2.5 watts and does not increase above that wattage at greater speed, thus mine would slightly underperform the others in power output, especially when riding fast.
Based on this graph, if I was going to go shopping for a new USB charger, I would probably get the Sinewave Revolution if I was looking for a pure USB charger without a headlamp. But if an internal cache battery is important to you, you should look at the others instead as the Sinewave does not have that built in.
My headlamp/charger combination (the AXA Luxx 70 Plus) does not have an internal cache battery either, but with a little bit of experimentation I have found that some of the low cost power banks can be used as a cache battery, as some of them accept power in one USB port while simultaneously delivering power out of another USB port. That certainly could be an option if you got the Sinewave Revolution.
The other document that I recently learned of is at the link below, it discusses how a USB charger can be designed to provide maximum power to the USB port and can effectively get more power out of a hub than the other chargers by varying how the electronics work for different hub speeds. It is more technical than I can understand, all that I really learned from it is that it is possible to boost performance with more complex electronics and that boost can be significant. Maybe some of you will be able to use this information in your travels, which is why I included here. I suspect the concepts here were behind the Forumslader that is discussed in the document described above.
http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm
And to try to make this posting a bit more complete on the topic of dynohubs and USB charging, some links that I have posted before, I am repeating below, as follows.
This link is intended to discuss solar power while bike touring, but it has a lot of good information pertinent to bike touring with a low power USB charger that would be pertinent to a dynohub and USB charger. The Eneloop charger described in this link is out of production, but there are substitutes out there. This also describes a C-USB charger that I bought and have been quite happy with.
https://www.crazyguyonabike.com/doc/?doc_id=9258
And I am quite happy to have a USB current flow meter so I know how much power I am getting out of my USB port. They are cheap and in my opinion, well worth it. The meters at the link below are LED meters, they can be hard to see in outdoor sunlight, the blue ones are harder to see than the clear ones. Shipped from China, expect shipping to take a month. I use one with a LCD display instead of LED, but I do not see the one I used listed on Ebay anymore, the LCD is more readable in sunlight.
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&LH_BIN=1&_nkw=charger+doctor&_sop=15&rmvSB=true
This article is a few years old, I learned a lot about hub dynamos from this article. It has good information on wattage at speed and also on drag.
http://www.ctc.org.uk/file/public/feature-hub-dynamos.pdf
And here I documented my thought process on which USB charger I bought last year.
http://thorncyclesforum.co.uk/index.php?topic=11153.msg81461
If any of you are looking at USB chargers or dynohubs, I hope this helps.
in4:
Thanks for posting, its a great resource for those of us looking a little more closely at the subject. I'm thinking about the best way to run a frontlight and charge a gps, android phone, android tablet (perhaps!) and one of those water sterilising pens. I'd like to keep things as simple as is practical but there are a lot of options out there...which is a good thing.
energyman:
I've had a Busch & Muller Lumotec IQ2 Luxos U Senso Headlight for a couple of years now and it is ideal for seeing your way in the dark and charging ones USB electronics. Simple to fit and it works even when it was used for charging my sat-nav during torrential rain. I have seen other riders with a poly bag over the handlebar switch/USB socket to protect it from rain but I haven't needed to do that. The earlier versions had a jack plug arrangement but mine is the hard wired Switch to Lamp version (Mk 2 ?).
DAntrim:
Some great information there, especially as this is something I'm currently looking at due to the lack of 'SUN' in Scotland last year my power monkey didn't really cope. I had the Shutter Precision 8 (disc version) dynamo built by SJS last September, I've ran this all through winter paired with a B&M Luxos B front and Toplight line plus rear, you read about the drag but have not noticed it (may be due to my snail like pace) and have been impressed with the visibility this has given, so much so I don't even bother to turn the lights off.
The current front runners for a USB charging system are....
* B&M Luxos U - though this had reliability issues with the 1st model since the 2nd iteration I can't seem to find any negative reviews
* Sinewave revolutionEither choice will be paired with an external battery pack which I already have, which will give the ability to charge 2 devices at once.
Carlos
David Simpson:
--- Quote from: mickeg on April 03, 2016, 07:15:26 pm ---On another forum, I learned of two documents on USB chargers that are supplied by hub dynamos. I thought I would share them.
--- End quote ---
Thanks for sharing these links.
- DaveS
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