Today was my first test ride for the new power supply device chain: new dynohub SON 20R, JaWeTec Bikecharger, SwissBatteries PowerTank M, Garmin Oregon GPS without internal batteries, Schmidt Edelux lights playing all together. I did some short slope of probably 45km with some 1300m of elevation. Most of the uphills were too slow to keep the bikecharger charging the Powertanks internal battery, so I switched it off at uphills and let the Powertank drive the GPS on its own. At first image those two Powertank LEDs are visible. A red one indicating charging state and a blue one indicating some device at USB out consuming power.

With such short ride I could not enforce any power outage and I could not determine whether the GPS would empty the Powertank quicker than it could be recharged by the bikecharger. No problems today. The Garmin GPS ran continuously without internal batteries, performing routing, showing maps, trip computer and several other jobs permanently. No power saving mode, but no backlight, though.

Charging of the Powertank starts at less than 10km/h with the SON 20R dynohub. As soon as speed goes further down, one should consider switching off the bikecharger to protect the Powertank from those remaining slow pulses at DC out of the bikecharger no longer being able to provide constant voltage from dynohub out.

There is one more interesting experience: with the SON 20R there is no need to switch on the lights when reaching speed of 50km/h to protect the bikecharger from dynohub overvoltage. Actually the charger would switch off itself automatically for that reason. I had to take care about this when using the stronger SON 28S dynohub.
On the other hand, I found out, as soon as switching on the lights, there is not enough power to charge the powertank, no matter how fast I am riding. With my previous installation it looked as like there was enough power left to charge the GPS even when lights would shine, but there definitely is not. The Powertanks red LED will not even flash slowly with lights switched on. So that was not a very good idea, anyway. Something that I will no longer pay any attention to.

Finally some words on installation and weight: the whole collection of USB devices and cables including GPS but without dynohub and lights makes up 342g. See third image. Installation looks some kind of messy at the moment, but everything will be protected by some small bag mounted at top tube. At final stage there will by two wires from the top tube bag to handlebar and the GPS at the handlebar. Should look quite clean. Need to get appropriate bag.

Finally I received missing Sapim Force spokes of length 254mm in black colour and built the new Big Dummy front wheel with lightweighted SON 20R dynohub and strong Spank Subrosa rim in chocolate colour. This time I took some pictures showing the building process which should pretty much follow Sheldon Browns guidelines with 3 crossings. Leading spokes run at inside at outermost crossing to maintain better tension at trailing spokes when braking hard with disk brakes.
The resulting wheel should be very strong. It has got 1197g of weight (including rim tape, without quickrelease axle). That appears quite ok for a durable disk brake dynohub wheel. The new front wheel will replace my current SON 28 / Spank Subrosa front wheel at the Big Dummy. The latter one will be installed at our winter MTB where it will replace an older Shimano dynohub wheel, making it easier to juggle lighting equipment between those cycles just in case. Also I can finally install my Shimano XT centerlock front disk rotor to the Big Dummy, replacing a cheap noname 6 bolt rotor. And last but not least, it will shave off another 200g of weight without introducing any compromise.

Click to load gallery!

Here it is. Measured 392g of weight without axle. Note there is some protective plastic coating around the hub making it less shiny than it actually is. Plastic will be removed after wheelbuilding.
Unfortunately silver spokes were supplied instead of black, so I will have to wait some more days before being able to build and ride the new wheel.

Within the last days, the brandnew Schmidt dynamo 20R came out as centerlock version.

Check manufacturer Schmidts homepage for details. I hope I will receive this item within the next few weeks. It will replace my SON28 disk hub in the Big Dummy, shaving 200g of weight off the latter. Also, I will finally be able to install my Shimano XT 2008 disk rotor with it. Currently I need to use some 6-bolt replacement rotor instead. Maybe, probably, this could have an impact on the fork oscillation issue mentioned previously. I hope so, but I do not know at all.

Late addendum: In the manufacturers installation document there is a clear statement against using this hub dynamo together with disk brake in tandems or cargo bicycles with front wheel(s) sized bigger than 20″. I have not been aware of that severe restriction until I found the mentioned document to be released, so I would like to point it out.

Today I received the JaWeTec USB charger for dynamo hubs as like SON or Shimano DH-3D71 or Alfine or similar. This is a small box with an ordinary USB type A connector which provides 5V of direct current and 500mA, which should be sufficient to feed any USB charged devices according to USB specification. It is protected against overvoltage up to 50km/h as to manufacturers documentation and may switch off automatically at extreme voltage or heat. The little box has got 50g in weight approximately and can easily be removed from bicycle by unplugging its connector in the dynamo cable. The box unfortunately is not water resistant. I will attach it at downside of my Medion PNA and put the complete unit into some transparent plastic bag.


The chargers power supply cables had to be soldered to the original cables of my edelux headlight. I opened the protective coating around the dynamo connectors, made a soldering joint for each of the two wires and put new shrink hose around each connector. The charger cable runs along the speedo cable up to the handlebar where it can be connected to the box which will be installed together with the navigation device is mounted.

Update: unfortunately the Jawetec charger is no longer available as to my knowledge.

Using some pocket navigation or GPS device for big dummy touring may seem a good idea. For those, using dynamo hubs, JaWeTec in Germany provides some interesting solution for charging USB devices as like PNAs, music players and whatever. A similar device is available at Stollberg Elektrotechnik in Germany. For real outdoor freaks, there even is some 12V solar charging device available (Switzerland), and there is another German supplier with lots of useful navigation equipment and accessories for bicycling usage.

Late addendum: Zzing provide some USB dynohub charger with internal batterie buffering. It works similar to the Jawetec charger but will keep up delivering power even when cycle stops or goes uphill slowly.
Another very flexible solution could be a combination of a small unbuffered dynohub-USB charger (see above) with the SwissBatteries PowerTank which is some sort of mobile power buffer rechargeable in several ways and providing USB out.
Also I would like to mention Pedalpower+, an Australian supplier with several very interesting dynohub solutions, even providing DC hub generators.
And here is another one I recently found: Busch & Müller E-Werk is a brand new universal dynohub charger, apparently without an internal battery buffering, similar to the Jawetec charger.

The new headlight was installed two days ago. It is small and looks cute with its black aluminium jacket. When using the built in twilight sensor, it will be engaged most of the time, since it only switches off when being exposed to sunlight, so this should be slightly adjusted by manufacturer. Nevertheless, it can be switched off manually. There is a yellow-greenish gleam in the LED beam when turned on, which reminds me at unreal tournaments plasma gun. This sort of light colour may improve sight at night, according to manufacturer.