Bicycle Mechanics - 20 volt 10 watt dynamo??

just seen this item on ebay: http://cgi.ebay.com/U-Stone-Bicycle-Light-w-Generator-Very-Nice_W0QQitemZ7182429786QQcategoryZ22689QQrdZ1QQcmdZViewItem WTF! am i reading this wrong? is this a mistake? i never seen a 20 volt 10 watt generator. most are 6 volt 3 watt. i seen on occasion 12 volt 6 watt dynamos, but even those are hard to come by. if this is legit, i wonder much drag this system must have. it must be miserable....

Is it a Sanyo ? or a Soubitez ? these were killer high power dynamos that mounted right under the bottom bracket on road bikes. it mounted in the kickstand area . The Sanyo was better, it had a built in voltage regulator that kept it from blowing out the bulbs on high speed descents.

I put a voltmeter on these things while they were on bike stands and pedaled them fult tilt on 10 speed bikes. The meter used to read 18 volts or better. and back then, bulb wattages were pretty low in comparison to todays halogens. 10 watts could be realistic, but I think they were more like 2.4 watts or less.

Voltage output changes with RPM and load. So the proper way to specify these generators would be X-volts at Y-rpm. Also the internal-resistance and current-draw will dictate the voltage as well. The higher the current-draw (higher watt bulb) the lower the output voltage will be from any given generator. So that ebay one may be able to generate 20v with no load, but make it supply 1amp of current and it may only be putting out 15v. And with 2amp output, it may only be 10v.

I realise this thread is very old but I wondered if anyone had any links to these high voltage output dynamo's as I want to read about them? Someone said they were Sanyo or Soubitez - any ideas what models? I would very much like to buy something like this to make a generator to trickle charge my laptop battery.

Actual output was probably no better than a hub dynamo or better bottle dynamo as they ran the same 3 watt total light systems as the others did normally.

Minimum output versus speed for dynamo lighting systems is tightly regulated in Europe, at least for street legal systems. Most dynamos can put out well above rated voltage output if the current is kept relatively low. At true high speed I have read of a hub dynamo actually lighting up a 20watt 110VAC fluorescent light. The dynamo was being spun at a speed equivalent to 60+ MPH IIRC though.

Per an email I received some time ago from Supernova their E3 Triple headlight does not reach full light output until about 24 MPH is reached as it draws a lot more than 3W of power from a hub dynamo. They did not say how much power total though.

Sorry but I doubt that you would want to pedal a bike with a 10W or 20W output dynamo that put it out at normal speeds. The drag would be unacceptable I suspect, particularly if using bottle dynamo or bottom bracket dynamo technology. Neither is/was nearly as efficient as current hub dynamos. Per German law the 3W (6V) or 6W (12V) output of a standard bicycle dynamo has to be reached by about 10 KPH I believe.

A European made Union bottom bracket mounted dynamo is still offered by Yellow Jersey last time I checked. I do not remember if it is 6V or 12V. A far eastern copy is also available from a couple of sources.

Thanks for your reply. Do you know anyone who makes a 12v or greater hub dynamo? I understand that most dynamos can output 12v depending on the speed; however as you correctly say dynamos rated for a certain volt are capable of attaining that voltage easily at 10 KPH. I want the highest voltage I can find at relatively low speed, as I am aiming for high voltage and low amp output. I know that Busch & Muller do a 12 volt bottle dynamo, but does anyone know if there were any 12v hub dynamos that were ever made. Even far eastern copies?

I don't think there are any hub dynamos greater that the 6v systems currently available. You can probably increase the voltage but you will have to build the circuits and it won't be at low speeds. You could increase the output by placing something like the SON28 into a smaller wheel but you will increase the drag and of course have something like a bent in order to do this.

Here is an interesting site you've probably already found. http://www.nscl.msu.edu/~daniel/sreg.htm (http://www.nscl.msu.edu/%7Edaniel/sreg.htm)

Thanks for your reply. Do you know if any 12v hub dynamos were ever made in the past, as maybe I can pick up an old one on ebay. Alternatively I was thinking what about replacing the wire in the Dynamo with a slightly thinner wire and increasing the turns, thus giving a higher voltage at low speeds. Of course if I did this the current would be reduced, but that is not a problem.

The original Sturmey Archer hub dynamo from the 1930s was 12V but it was only rated for about .23 amp as I recall for a rated output of about 2.7 watts. It is the only 12V hub dynamo I have read of. No recent 12V hub dynamos have been offered that I am aware of. Here is a link to it on the SA Heritage web site.

http://www.sturmey-archerheritage.com/index.php?page=history-detail&id=51

As has been suggested in another thread you started a high efficiency solar recharger is quite probably a more viable solution as the items needed for a bicycle generator solution with the output that you want have never been made that anyone is aware of.

A better idea would be to ditch your laptop for an iPhone. Then you can use existing technology in a plug and play environment. Are you planning to use the laptop while riding?

A solar charger is anything but practical on a bicycle. You would need a huge solar blanket spread out over the entire duration of the day in optimum conditions to recharge the battery (how would you spread something that large out on a bike?). Most solar chargers only output just a few Watts. Even the very high end solar chargers are still not practical and very expensive. A dynamo is a much better idea, as if you have a hub dynamo it generates electricity continuously. Why waste that energy when you could charge a low powered laptop in 10 - 11 hours.

I think I will open up a dynamo and try and change the wire coil. I plan to do quite a bit of experimentation. if I can't make something work I know of an electrical engineering company who said they would custom build a dynamo speacially for this application.

As for the iphone why would I want to bother with that junk? I am totally against all the Apple hype. Why do I want to pay over inflated prices and then find out I can't even do what I want to do with the hardware once I get it? If you own an iphone it is like being in prison, you don't even have root access or the ability to make your own custom ROMS. I would much rather support the open source community than mess around with hacks on some stupid Apple device.:notamused:

Lots of luck. Hub dynamos have potted windings I believe and at least older ones required a magnet "Keeper" be used if disassembled to keep from damaging the permanent magnets. SRAM indicates that theirs are not serviceable IIRC. Per what I have read the same is true of Shimano.

Hub dynamos have potted windings I believe and at least older ones required a magnet "Keeper" be used if disassembled to keep from damaging the permanent magnets. SRAM indicates that theirs are not serviceable IIRC. Per what I have read the same is true of Shimano.

Do you know any that are serviceable where I would be able to rewind coil. either old or new models?

ok here's another 20 volt 10 watt generator light set: http://cgi.ebay.com/Vintage-Bicycle-Bike-Dynamo-Generator-Lighting-Set-20V-/280666371590?pt=LH_DefaultDomain_0&hash=item415904f606

i knew i had a thread for one of these a while ago. this one's brand new. i currently use a hub generator with a high power b&m led lighting system, & that's hard to beat no matter how many volts these old units put out....

new high power led lighting systems make higher voltage generators obsolete. you get tremendous light from 6 volt systems....

i just thought this unit was interesting as you never hear of such hight power generators. i would love to try this one, but the price is way to high $150.00! just curious how bright it is, but probably doesn't come close to compare to what i have now....