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 revolution

Either 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]

On another forum, I learned of two documents on USB chargers that are supplied by hub dynamos.  I thought I would share them.

Thanks for sharing these links.

- DaveS

[Pavel]

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.

I guess we have left the carefree cycling of the 1970's far behind.

[igarocom]

[Edited to remove commercial promotion, since unauthorized advertising is prohibited by Forum member guidelines. -- Dan, Thorn Forum Administrator]

Hello,

[The] reason you can't get more power from Sinewave, e-Werk, USB-Werk etc is because these devices uses chipsets which have a current limit (i.e Sinewave 1A/5W, and E-Werk has a 2.8W limitation at 5V). This is the reason many of the devices level off in the chart.

The "free power" technique is just two electrolytics capacitors back to back and assists to ride out the low frequency generated by the dynamo. What matters is that there is sufficient capacitance on the input side of the circuitry, meaning it can be in two places; 1. across the dynamo (this technique) or 2. after rectification.

So here's the thing, if you're going reasonably quick and have a load attached then the AC across the dynamo might be 6V. A typical Shimano hub resistance is 4.3ohm which gives a backflow of 1.4A when the hub's AC is at 0V. If the load (i.e USB device) is high enough then part of this will go through the circuit.

Consider when you don't have a load attached and you're going downhill at speed. The AC is now 50V and amperage being put back into the dynamo is 11.6A at peak. The capacitors can't sustain that discharge rate cycle and will fail either through wearout or heat, but while they are operational that power is being reversed into the dynamo.

I made an argument on another German website that efficiency at low speed is more important in real-life conditions. I'll now explain:

Riders will rarely see more than 5w from the dynamo (certainly not consistently) and most USB devices that accept high current input will park the current at a determined level. They do this by increasing load and testing the voltage drop on power on to determine what power level can be drawn (i.e USBv1 is 100mA, USBv2 usually 500mA-1A, power adapter 1.5-2A). If I take the Sony M4 Aqua for example (using an Igaro D1) the input current is 0.74A. It doesn't matter if I go 60mph, it will remain 0.74A. If I plug the same phone into a wall charger it'll take 1.5A. Why? because it "asked" for 1.5A and the voltage drop was too low, so it switched to 0.74A and stuck at that level. Most phones and USB powerbanks will do this - it's a requirement of being able to charge from USB sources of different current levels.

This is exactly why the Sinewave Revolution takes 10 seconds to turn on. [Another brand, t]he Igaro D1 also has a similar approach but monitors the dynamo frequency (I don't know if the Revolution does this). Also worth mentioning, if the charger has no voltage cutoff then the device may not charge at all (hence E-Werk doesn't work with iPhone).

In summary I recommend you take [published charger efficiency and output] charts with pinch of salt as you'll probably never be able to charge the internal "cache" battery and a smartphone at the same time, and if you go down the USB Werk route you'll have such low efficiency by way of cache battery losses that you'll not be able to keep your phone charged at all. This is the difference between sticking a dynamo on a motor for a graph and actually getting out there and riding. I'd impress upon you that when I did that (I'm a RTW tourer) and analysed the best means of keeping devices powered I concluded a powerbank works best for convenience (might as well charge something if not the phone/gps), but otherwise get the juice directly into the device. The best means of doing that is through efficient USB circuitry, because 3W of power in real world riding means efficiency is a deal breaker. There is no "free power".

Cheers,

Andrew

[E-wan]

interesting

does anyone know of a USB battery that allows charging pass through and fast USB charging using a higher current

planning on powering a Samsung galaxy S5 and Lezyne Macro Drive 600XL front light Both of which support fast USB charging

Thanks

[John Saxby]

E-wan, a note that my Anker 2600 does not allow pass-through charging. Not a problem for me, as I don't need the latter.  If I need to charge a device at the same time as my battery, I just use the Y-splitter cable.  Recharging then takes longer, of course.

[DAntrim]

I use the power monkey extreme battery to charge my Galaxy S5 which allows pass through charging, which also gives the option of charging the battery from mains, dynamo or solar.

[John Saxby]

plan on using... a Lezyne Macro Drive 600XL front light

Looks like a good piece of equipment, E-wan, and at a good price as well.  Look forward to your reports, both on charging and your battery, and on lighting the way.

[Delatorre]

plan on using... a Lezyne Macro Drive 600XL front light

Looks like a good piece of equipment, E-wan, and at a good price as well.  Look forward to your reports, both on charging and your battery, and on lighting the way.

I'd like to hear an update on this too. I think a 600XL would make a good front light.

[Matt2matt2002]

Anyone know anything about the igaro system?
SJS sell it for £160 approx
Tech info:
The Igaro D1 includes over-voltage, over-heat and short-circuit protection. Power continues no matter how fast the operator rides. Digital frequency monitoring enables power at the lowest possible stable speed and prevents connected USB devices switching on/off rapidly at very low speed, resulting in superb USB device compatibility.

[Danneaux]

Anyone know anything about the igaro system?

http://thorncyclesforum.co.uk/index.php?topic=12300.msg90605#msg90605

I included a link to a custom Google search. The first few entries there provide the most popular reviews.

Best,

Dan.