Entry level hub dynamo questions



lectraplayer

Member
May 11, 2014
290
12
18
41
I've recently completed a wheel teardown, though I have yet to build (Wobblenator 5000, need a new hoop), but while I'm looking, I would also like to start looking at hub dynamos. I gather that there is more more drag with them. How much can I expect? I'm ultimately looking for 12 volt 1 amp dynamos but will make adjustments later. Running lights (for night riding) right now are 12 volt, 6 watts incandescent (but I will go LED later on). My ultimate goal is to generate power for running lights, and to have some power to charge a battery for a headlight to be used intermittently. While I remember seeing a dynamo for $65 USD (Shimano, I think it was) what should I expect to pay for a halfway decent dynamo? I want to price for both my front, and my rear with Shimano SIS drive.
 

maydog

Well-Known Member
Feb 5, 2010
1,333
174
48
You are unlikely to notice a few watts of parasitic power loss on a commuting rig.

Buy the LED lights now. LED lights are very bright on just a few watts of power and can be had cheaply. Incandescent bulbs are dinosaurs and zero advantages over LEDs for bicycling.

Of course, with a LED setup a generator may be unnecessary, I have a 1K lumen CREE rig with a 4 cell rechargeable lithium battery. I have yet to run it down fully in 2+ hours of riding at full brightness. I paid ~30 for it on ebay.
 

retrogrinch

New Member
Jan 1, 2015
64
4
8
Originally Posted by maydog
You are unlikely to notice a few watts of parasitic power loss on a commuting rig.

Buy the LED lights now. LED lights are very bright on just a few watts of power and can be had cheaply. Incandescent bulbs are dinosaurs and zero advantages over LEDs for bicycling.

Of course, with a LED setup a generator may be unnecessary, I have a 1K lumen CREE rig with a 4 cell rechargeable lithium battery. I have yet to run it down fully in 2+ hours of riding at full brightness. I paid ~30 for it on ebay.
+1 for what maydog posted... Get the LED light now. They are sooooo much brighter and durable! With the extra power that won't be used by the LED headlight, get a super bright flashing taillight. There's no substitute for safety!

For more info on generators and headlights check out Peter White's site. A great source of information!
http://www.peterwhitecycles.com/lightingsystems.htm

Once upon a time I thot I needed a dyno setup but with the new LED lights coming down in price so quickly I've since gone with a battery powered setup. All of my lights (3 in front, 3 in rear) are USB charged and last for many-many hours in flash mode.
 

lectraplayer

Member
May 11, 2014
290
12
18
41
While I'm hunting for a dyno, I may as well also look at lights. Again, I'm not wanting to part with Benjamin (whom is featured on a USD $100), I'm wanting a "truck headlight" beam pattern that lights the width of an average two lane country road at about 50 meters or so. I figure I should have enough "spray" at 10 meters to handle up close, especially since I have grown used to and love my 18 watt sealed beam (30x10 degree beam) I had on my other bike. What headlight will do this on a dyno? Also, are LED dyno tail lights now somewhere around US-DOT (marker) brightness? I want a solid around that brightness.
 

maydog

Well-Known Member
Feb 5, 2010
1,333
174
48
If that 18W light runs on a nominal 12 volts, then it wont do much on 6 from a hub dynamo. Even a 12 V dynamo will struggle to power it. No hub will drive the full 18 watts. If you are wanting cost effective, bright lighting a battery powered LED unit is the way to go. Hub dynamos are cool but cost just as much or more than a good battery and light combination.

I'd consider using a dynamo if I was on a long haul, far from civilization or outlets multi-day type trek, but I would still go with LED lights.
 

retrogrinch

New Member
Jan 1, 2015
64
4
8
Originally Posted by lectraplayer

While I'm hunting for a dyno, I may as well also look at lights. Again, I'm not wanting to part with Benjamin (whom is featured on a USD $100), I'm wanting a "truck headlight" beam pattern that lights the width of an average two lane country road at about 50 meters or so. I figure I should have enough "spray" at 10 meters to handle up close, especially since I have grown used to and love my 18 watt sealed beam (30x10 degree beam) I had on my other bike. What headlight will do this on a dyno?

Also, are LED dyno tail lights now somewhere around US-DOT (marker) brightness? I want a solid around that brightness.
I've done A LOT of checking on lights, both front and back, and have never seen comparison to US-DOT. Taillights typically are compared on overall brightness and dispersion (ie. directional or not). The brightest battery driven LED taillights are 1 to 2 watts. For the longest time, Dinotte has been the brightest taillight. But they do not make Dyno powered lights. For the best selection and info on Dyno lighting I've found has been on Peter White's site (see above post for link). Peter does have beam pattern photo's of several lights, but I'm not sure he has the latest/greatest lights. IMO there is absolutely no comparison in light output between halogen and LED lights. The question is if one wants/needs a far reaching beam or something with a wide spread. I have a wide spread beam on the handlebars and a narrow spot on my helmet. Just a personal preference that seems to work well for me.

MTBR has an annual "Bike Light Shootout" with lots of info including pic's of the beam pattern. Here's a link to the 2014 shootout. http://reviews.mtbr.com/2014-mtbr-bike-lights-shootout

I've only seen steady-on Dyno lighting. Flashing lights draw more attention. Steady on lights provide visibility in front. A steady on taillight helps approaching traffic judge distance. It is much more difficult to judge distance to a flashing light.

Also note that red LED lights need more watts for the same light output. This is why many of the new taillights mix white and red LED's - greater visibility per watt.

Cheers,
Greg
 

lectraplayer

Member
May 11, 2014
290
12
18
41
I figured I wouldn't find a headlight equivalent to a 55 watt halogen truck headlight. However, I'm finding a lot of flashlights that run for hours on AAAs and are pushing a lot of light out, and I can see the distances I'm asking for. That's a inefficient beam for us cyclists though. I'm not asking for a 4500 lumen light. (I think a truck headlight is only 500 lumens) I figure a 10 or 15 degree by 5 degree beam from a 1 watt may do me with decent optics. For the rear, those markers I mentioned are usually 12 volt 3 watt incandescent, and you know what kind of brightness we have here. 5 or 6 LEDs viewed directly should do that. Most LED DOT markers have two LEDs direct viewed, which should be about 30 mA or so. Maybe 100 mA if we go agressive. If I was to go the DIY route, whers can I find optics that will give ms similar to the 15x5 degree beam I was referring to?
 

lectraplayer

Member
May 11, 2014
290
12
18
41
Upon digging through Amazon, I'm seeing quite a few 12 volt dynamos, and that would play right into my current system. Again, after upgrading my lights, I would have no trouble charging the battery and lighting the markers. Would it be more worth my time to do that or use a 6 volt system?
 

retrogrinch

New Member
Jan 1, 2015
64
4
8
Here's a site I stumbled across a while back... It seems to be more in line with what you're trying to accomplish:
http://nordicgroup.us/s78/mr16LED.htm#Introduction_

If I were building a dyno system from scratch I would:

1. Pick the light(s) - this will determine the voltage and power requirements. Light are my top priority - yours may be different
2. Pick the dyno hub which will have ample power and the proper voltage for the lights & to charge accessories (iPhone, etc)
3. Find the USB adapter to charge my "stuff" - it too would have to be the same voltage as the lights and dyno.
4. Check the system cost.
3. Is the system still in my price range? If not go back to #1. Repeat as necessary...

From what I found on various sites, the Shimano and Sanyo dyno's are both well made and reliable.

The Shimano dyno is nearly as low resistance as the Son, but A LOT less expensive.

Some of the dyno reviewers mention vibration. "Better" dyno's produce less vibration. The larger, and most expensive, Son supposedly is the smoothest dyno. The amount of vibration is reported to be a function of the light. In other words, changing the light may affect the amount of vibration observed.

Few (none?) of the lights designed for use with dyno's offer a flash mode. I've read that this is due to European regulation which prohibits flashing lights.

But that's me... If cost is the most important aspect of the project, then go with the least expensive dyno and build the project from that point. From an engineering perspective, there is no compelling advantage to 6V versus 12V. There may be more lights and accessories available with one voltage or the other. You may also find that the budget gear is available in only one voltage.

Other criteria which may drive the decision process:
- Total power need (ie. how many watts are required)
- Lighting at slow speeds such as when mountain biking.
- Disc brakes will limit hub selection
- Spoke count will also limit the selection of dyno hubs.

Cheers,
Greg
 

Froze

Well-Known Member
Jul 13, 2004
4,711
756
113
NE Indiana
I don't see the importance of a dynohub lighting approach unless you plan on long night time rides in exces of 2 hours, like a all night ride. Today batteries in LED lights are all rechargeable so the inconvenience of constantly buying batteries is a thing of the past. Though I would look for lights that use user replaceable batterys so you don't run into a situation when the rechargeables die, and they will eventually die, that it will cost an arm and a leg to send the thing back for the service departement to replace. Of course you could always get those reall cheap generic lights on Amazon for $35 and when the battery fails just buy another complete light again, but keep in mind that those generic lights are at least 50% over rated in their lumens output ratings.
 

lectraplayer

Member
May 11, 2014
290
12
18
41
I have noticed that many of the battery powered lights I have looked at look like a Dorcy or Redline flashlight bubber-randed to my handlebar would be a brighter, cheaper, and better solution. I also saw a bicycle head/tail light at Wally-World that looked like much the same theory (though the tail light looked decent.) As mentioned, I would like a rectangular/oval "truck headlight" beam if I can find it. However, I've had some good rides with a 3 watt 30 degree flood light.
 

retrogrinch

New Member
Jan 1, 2015
64
4
8
In case you have't already been here, check out the reviews on MTBR Reviews
http://reviews.mtbr.com/2014-mtbr-bike-lights-shootout

MTBR provides a lot of info including photo's of beam patterns, light out measurements, runtime, etc. FWIW, I'm using three LED's for my commuter - narrow beam Cygolite, wide beam Light & Motion, helmet mounted Light & Motion. I've got redundancy, able to illuminate where ever I'm looking, and have plenty of light when I'm moving fast. Mountain bikers need good lighting to ride technical trails with any kind of speed. MTBR still has older reviews (2012, 2013) online and the 2015 reviews are just starting so you should be able to find a wide variety of lights from low cost "I just want to be seen" lights, to high performance trail specific LED's which would blind the drivers of oncoming vehicles. My preference is for the USB rechargeable lights as I always have a USB power source handy (laptop, cell phone, tablet, Garmin charger, light charger, etc etc).

Happy shopping!
Greg