Dynamo hubs

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  • I've been thinking about these since a conversation with Horatio just prior to his touring holiday in La Belle France during the TdF.

    His requirement was for some way of charging the various electronic peripherals which we all carry these days- phone, Garmin, Kindle etc.

    I've been having a look at a couple of different units from a Taiwanese company called Shutter Precision.

    What interests me about them is that they make a clutched Dynamo, the PD-7:


    The advantage being that when not needed you can remove the 5W drag that the Dynamo exerts.

    Of course, the clutch mechanism adds weight and complexity, the question is whether the ~200g weight penalty over the PD-8 is worth the saving in drag:


    I don't have the maths to answer that question sadly- I guess it also depends on whether or not you'd constantly have some gadget charging, also.

    The other thing that occurred to me was that you might want to charge a battery pack in order to run more power hungry gadgets when stopped- laptops and so forth.

    There are products out there that allow you to switch between the dynamo powering lights, or powering a USB connected device:


    I imagine a bit more searching will turn up something that provides a USB hub type arrangement.

    Has anyone got any experiences of doing this that they'd like to share?

    Insights, comments etc.

  • I use a schmidt son dynamo on my touring bike, and you don't notice any drag, lights on or off. I am planning on an accessory charging system some time, but they only really work if you are riding for several hours currently (!)

  • That's interesting. I think that "always on" is winning for me at the moment.

    I believe that the term I was looking for was "cache battery" in my first post- so it would go:

    -Cache Battery
    -USB cable to device

    The idea being that the cache battery would charge constantly, and be available to power devices when stationary.

  • I do use a cache battery, but I charge it at home / bar / hotel. I am pretty sparing with the use of electronic devices when touring, so it has always been enough.
    Sorting out charging when off the bike has never been a problem for me, and I have been to places where you can't buy coca cola, but can still charge an iPhone

  • Which battery do you use?

  • a veho pebble pro

  • Of course there is the Shimano DH-3N80 which is £65 from Rose bikes:


    Appears to be a similar weight to the Shutter precision unit, but some reviews I have read say it vibrates quite a bit- anyone able to comment on that?

  • I've got the shimano xt dynamo hub on the front of my big dummy - feels a bit notchy unbuilt but when built into a wheel it's fine. Also have the sp pd-8 but still waiting for it to be built up into a wheel for the winter bike. This hub also feels notchy prior to being built. I think rob dean as a blog article about the sp hub and charging devices, etc

  • I ordered the Shutter Precision PV-8, 24 hole drilling, looking forward to seeing what it is like.

  • The hub has arrived (really fast delivery), looks very nice but when I rotate the axle it feels like the bearings are shot.

    Is this just the magnets providing drag?

    I had assumed that that would be a constant drag rather than the lurchy feeling of FUBAR bearings, but I have never played with a dynamo hub so don't really know.

  • Yes.

  • Sorry yes as in it is fine.

    They always feel really notchy.

  • Does it feel sort of notchy as you rotate it? That's normal at low speeds, you won't notice as you ride.

    It's not going to be constant drag as the magnetic field has to rise and fall relative to the coil(? or whatever it's called) to induce a current. I have a feeling the hub has a ring of magnets rather than a single ring magnet, so the coil goes through north-south-north-south etc as the wheel turns.

    (This explanation is probably wrong in all details but the right general idea)

  • That conveys your meaning well, thanks.

  • How are you getting on with the hub?

    I'm thinking about getting one of these for a front light + charging Garmin etc.


    Gives me the option to upgrade to discs at a later point.

  • Dammit are you using a dynamo hub for charging usb accessories yet?

  • My plan for future long distance rides (if I go back to Audaxing once MiniGB is a bit older) is to get something like the "B&M Luxos iq2 u" front light as:-

    a) It throws out a metric shitload of light (I used to use Solidlights XB2 before they got nicked) in a nicely shaped beam that won't dazzle other road users
    b) it (the light itself) contains a small cache battery
    c) it also provides a USB port for charging other stuff (I'd have a PortaPow battery pack in a tri bag behind the stem, or use it to power my Edge 705 GPS whilst riding)

    I've used a standard SON dynohub for years for Audaxing and they work great. Never noticed the extra drag.

  • The new and revised Luxos is really excellent - it actually charges everything very well on the move.

  • Very tempted by the Luxos, trying to figure out whether to go for that or get The Plug III as a stand-alone USB charger.

    It's for a touring bike rather, already got a decent dynamo set-up on the audax bike.

  • I'm currently looking into this sort of thing as i start to get kit together, and this was a great read

  • I think I'm going to put a dynamo hub (SP PD-8) on the Time Machine, along with an Exposure Revo/Redeye pair.

  • I was thinking of getting alfine hub and build something like this: http://www.alieneye.info/bike_USB_power/­bike_USB_power.html

    Those commercial usb-thingies seem damn expensive. Do they have some super speshul component wizardy inside or am i missing something here?

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Dynamo hubs

Posted by Avatar for Dammit @Dammit