Dynamo light + dynamo GPS (or phone) charging. Bye-bye batteries?- Mtbr.com
Results 1 to 9 of 9
  1. #1
    www.bigrobracing.co.uk
    Reputation: robdeanhove's Avatar
    Join Date
    Dec 2005
    Posts
    312

    Dynamo light + dynamo GPS (or phone) charging. Bye-bye batteries?

    earlier in the year I got a proper, off road capable dynamo up and running, and was chuffed enough with it I posted it on this forum. I've finally got my bike set up with an updated dynamo powered LED light and charger and I'm super chuffed with it. Now I've been riding it a while and am happy it's all working reliably, I thought it best to share:

    The power from the SP PD-8 hub can be switched, via a little switch on the bars, from the front light to a USB carger, that happily charges my GPS or my smart phone, while they're on and working and faster than they use power.

    The cockpit setup:



    The USB cable can also be used to charge my joystick head torch if needed for multi-day rides involving camping.

    Power is provided by a tiny, light weight dynamo hub from Shutter Precision:



    The light is a pre-production (available soon) Exposure dynamo light, with off-road-capable standlight. The standlight also powers the rear light, which is the standard, and well proven, exposure redeye should you want one for the on-road sections:

    FRONT LIGHT


    REAR LIGHT


    The charging can then be done by one of the many dynamo chargers available on the market, which just attach to the main power cable from the hub. Most of them come with selectable outputs either to the light or USB plug, to keep the intervention required to install it all minimal.

    Forseeing the nay-sayers, here's a couple of FAQs I answered earlier:

    1) So, dynamos are heavy, right? No! The Exposure light comes in at a flyweight 112g, with the SP hub another 390g, A total weight of 502g. Yes, a MaXx-D is only 337g, but you still need a front hub, and with a Hope Pro 2 coming in at 190g, that's a total weight of 527g, 25g heavier. And that's without factoring in having to run my battery light on a low light setting or the weight of carrying alkaline batteries as spares for the GPS or some form of battery charger.

    2) Isn't a dynamo draggy? Well, Please excuse the maths, but if you rode at 20mph for an hour the light would pull about 6W from your legs during this time, this is equivalent to approximately 5.2kcal. There are approximately 72kcal in a McVites Digestive biscuit, enough to power your light for just under 14hrs and that's assuming you pedal down the hills and around every corner! So yes, it does draw a tiny bit of power, but I certainly can't tell the difference and it's a damn good excuse to eat an extra biscuit every few rides ;-)

    There's a bit more detail on the details of my setup, and some pretty pictures of my bike and the rather special wheels Reynolds helped me out with ON MY BLOG HERE (CLICKY).

    Enjoy..... Dynamo power FTW!
    Last edited by robdeanhove; 07-06-2012 at 11:30 PM.

  2. #2
    Nightriding rules SuperModerator
    Reputation: crisillo's Avatar
    Join Date
    Jul 2004
    Posts
    20,787
    Sweet setup!

  3. #3
    mtbr member
    Reputation:
    Join Date
    May 2005
    Posts
    3,876
    2) Isn't a dynamo draggy? Well, Please excuse the maths, but if you rode at 20mph for an hour the light would pull about 6W from your legs during this time, this is equivalent to approximately 5.2kcal. There are approximately 72kcal in a McVites Digestive biscuit, enough to power your light for just under 14hrs and that's assuming you pedal down the hills and around every corner! So yes, it does draw a tiny bit of power, but I certainly can't tell the difference and it's a damn good excuse to eat an extra biscuit every few rides ;-)
    I suspect that as moderately fit person I can only produce about 100W/hr. An additional 6% seems like it would be pretty noticeable. For my preferences and current uses, I'll continue to go with batteries.

  4. #4
    Rep Power Infinity +2
    Reputation: brad72's Avatar
    Join Date
    Jun 2009
    Posts
    1,539
    You have an excellent setup Robdeanhove. I would love to run a dynamo hub but unfortunately I cannot find one to suit a 20mm thru axle. Maybe one day someone will build one.

  5. #5
    www.bigrobracing.co.uk
    Reputation: robdeanhove's Avatar
    Join Date
    Dec 2005
    Posts
    312
    Quote Originally Posted by crisillo View Post
    Sweet setup!
    Cheers!

  6. #6
    mtbr member
    Reputation:
    Join Date
    Dec 2011
    Posts
    45
    Quote Originally Posted by Vancbiker View Post
    I suspect that as moderately fit person I can only produce about 100W/hr. An additional 6% seems like it would be pretty noticeable. For my preferences and current uses, I'll continue to go with batteries.
    I've always thought it was around the 200W range. My dynamo setup probably draws about 7W at the lights, assuming 60% efficiency that comes out to 11-12W at the hub. I've tried disconnecting it on hot daytime rides and can't say there's an appreciable difference, except that I'm less visible to drivers.

  7. #7
    www.bigrobracing.co.uk
    Reputation: robdeanhove's Avatar
    Join Date
    Dec 2005
    Posts
    312
    Quote Originally Posted by Vancbiker View Post
    I suspect that as moderately fit person I can only produce about 100W/hr. An additional 6% seems like it would be pretty noticeable. For my preferences and current uses, I'll continue to go with batteries.
    I suspect that it's nearer to 150W-200W if you're reasonably fit, and that's assuming you're pedalling near the top of zone 2 or creeping into zone 3 on an extended ride, nowhere near your aerobic threshold power.

    Also you're ignoring the fact that you're assuming you're pedalling the full time and that the bike is moving fast, you're getting "free" light on any downhill gradient or time when you're freewheeling or braking, reducing the percentage even further, before you take into account that the light is (fractionally) lighter.

    I've been riding with one for a couple of years now and don't notice it. If you're desparately worried about 6W, you can get 10W from an aero TT helmet and swapping baggy shorts or a lycra skinsuit is also worth >>10W, yet I don't see many people doing this, let alone worrying about losses.

    There is an additional benefit too, assuming your night rides last longer than 1-2hrs: For me, having a light that is running at full power for the full duration of a ride, rather than turning down the brightness to conserve battery power is worth more speed than 6W "drag" at full speed.

    And that's without worrying about the environmental impact of producing and disposing of batteries.

    However, I will concede that no product is the best solution for everyone, and choice is a good thing, so we're all entitled to our own opinion and to choose the product that best suits our needs. I'm sticking to my baggy shorts and "bright all night" dynamo light ;-)

  8. #8
    www.bigrobracing.co.uk
    Reputation: robdeanhove's Avatar
    Join Date
    Dec 2005
    Posts
    312
    Quote Originally Posted by brad72 View Post
    You have an excellent setup Robdeanhove. I would love to run a dynamo hub but unfortunately I cannot find one to suit a 20mm thru axle. Maybe one day someone will build one.
    I have been asked the same question by the fat bike guys with 135mm hubs. No-one makes a 135mm dynamo hub, or 15mm or 20mm thru-axle hub, yet (that I know of), but you can purchase a bolt on solution, designed for the non-drive side of your rear wheel. This may be able to be made to work with the non-disc side of your front wheel. It may require a little work with a file to fit a 20mm axle through it though. I know of one guy who is using it happily on a Moonlander (QR axle though) and Kerry at K-Lite has tested one on the right side of a front wheel on his test rig too and declared it a success.

    It's called the Sunup Eco DS-1R Spoke Dynamo, you can buy it from IDC on eBay, the link is HERE

    It looks like this:

  9. #9
    www.bigrobracing.co.uk
    Reputation: robdeanhove's Avatar
    Join Date
    Dec 2005
    Posts
    312
    Quote Originally Posted by brad72 View Post
    You have an excellent setup Robdeanhove. I would love to run a dynamo hub but unfortunately I cannot find one to suit a 20mm thru axle. Maybe one day someone will build one.
    SON just announced a QR15 disc brake compatible dynamo. SEE HERE

    Me, I'm waiting in hope for Shutter Precision to follow suit and make a a QR15 version of the SP PD-8 dynamo hub.

    SON's hub:

Members who have read this thread: 0

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.