Hub dynamo with disk mount and 12v+ output?
 

I've looked around a little and so far the only 12 volt dynamo I've come across is a unit that rubs the tire:
Dymotech S12.

It seems all of them are 6 volts.

You are probably going to think I'm nuts, which I am (that's another story), but I want to power some 12 volt devices on the road - namely a Ham radio set up (not sure what radio just yet, I have both a KX3 and an FT-857D). Everything runs on 12v.

That having been said, I have a 6 watt solar panel that puts out around 14 volts and it doesn't have much trouble keeping up with the radios for how much I use them in camp when I'm out backpacking, so I have some comparison for power output.

If there aren't any 12v hubs, being they are AC I can step the voltage up. I would have to dig in to some transformer ideas but I should be able to wind one that would give me the output I need. Maybe I could have a switchable version so if I'm going slow I can put more turns on it to make up for the difference in voltage and if I'm going faster I can knock it down. I do have a charge regulator for my solar panel so if I can get up to that 13+ voltage range that would be ideal so I have the juice to drive the charge controller.

The vast, vast majority of dyno hubs are 6V. Older models generally put out around 1.8W, while newer ones are 2.5-3W. So yes, you can do a step-up transformer, but you'll obviously have a corresponding decrease in available current. Also, be sure to remember that 12V is the nominal battery voltage rating - you'll really be wanting 13.8v if you plan on doing any battery charging.

Also, those ratings are when you're going at a minimum speed, which varies based on the dynamo. But you'll need to expect that you'll have to go at a steady 9+MPH, or you're going to get some pretty substantial voltage swings ( and speaking of which, not all genhubs have overvoltage protection, so you'll need to accomodate the possibility of voltage spikes ). All of this is likely to make design of a directly-fed rig more challenging. I suspect you'd be much better off with the dyno charging an intermediate cache battery and then powering the rigs from that.

- Rich, AA2YS

NB: Tire sidewall driven Dymotech S 12.. Now on close out.. Limited to stock on Hand..
$180 down from $300, Now, no longer be imported By Peter to US market.

Use the dynamo to charge batteries/battery pack and then run the radio from that?

Pick a compatible radio?

Maybe, something like this?

http://www.yaesu.com/indexVS.cfm?cmd...35C7E1F02500D9

Best practical voltage regulator would be a set of batteries. Use what you can produce to charge them and then run your toys off the batteries. Think of a small bank of 6 -> 12 Lithium Ion AA batts tucked into a small zip up bag or a water bottle, etc.

20yrs ago I had a Sanyo 12v sidewall dyno that really lit up the road but the resistance was substantial.

Let me rephrase the set up with a picture:

http://i118.photobucket.com/albums/o...ps098f6b96.jpg

It is hard to see, but off on the right side there is a green thing - that is the underside of the circuit board for the charge regulator (Micro M+ kit).

I don't like running any source direct in to a battery because there is no regulation. If I let my solar panel run all day it would pump the battery too high (wherever the internal resistance of the battery would balance out the current going in is where it would stop going up in voltage). That's not good at all for the SLA battery you see there. By having a higher voltage source than the battery voltage it lets you regulate it where you need = the excess voltage goes back in to current (watts = V x C, for the same wattage if you drop one the other goes up, but likewise as already pointed out if you get one up (voltage for example) the other (current) has to drop).

That all having been said, I am surprised the output of the dyno hubs is so low - I can get more power than that out of a solar panel. It wouldn't be convenient to set up on a bike though, maybe when stopped but not when riding. 3 watts all day riding beats 6 watts stuffed in a pannier.

It takes about 50 watts to cruise on a bicycle. How many people do you think would be happy to have 10% be sucked into providing electricity? The design goal of a bicycle hub is to provide "enough" power (to power lights) for a reasonable amount of drag.

A lack of regulation is a deficiency of the charger (not the power source).

If your use of power is short (relatively), charging a battery makes more sense (especially, if your use is when you are stopped).

The idea is to charge a battery and run the devices off the battery, see the picture I attached above. I don't know how much more simple it can be explained than showing. There is no direct powering of anything, just source -> charger -> battery.

The question I pose in this thread is how to do it.

Here is an article I read that talks about the Schmidt SON 28 dyno hub and E-WERK regulator. They claim up to 16 watts.

http://www.cycletourer.co.uk/cycleto...ogadgets.shtml

The E-WERK looks a bit expensive for what it is and what I would use it for (maxed out on v and c). If I can get that kind of wattage out of the Schmidt hub that might be the route to go = double or more what I can get out of a SP or similar.

"Up to 16 watts" doesn't mean you'll get that at normal speeds. The drag is 6 watts at 20 kpm powering a 3 watt light. Google "Schmidt son bicycle quarterly" for more info. How much riding power do you want to direct to not moving?

Check the following too.

http://www.peterwhitecycles.com/pedalpowerplus.asp

It depends on the ride and the road conditions. If I'm going down hill another thought I had was to get some dynos that rub the wheels. With a loaded down bike rolling down hill I wouldn't have to worry about drag, it may even be a good thing. That would give me more electrical output, then switch it out when I'm on level ground/going back up. Just a thought, but if I can get by with low wattage over the course of a day that may prove to be all I need.

Average riding though, I wouldn't want a whole lot of drag. I'd like to have something to experiment with so I have a better gauge. While we're on the resistance topic - loaded panniers are going to be adding a a lot of drag from rolling resistance and, mostly, wind resistance (lack of aerodynamics). I couldn't imagine such low wattage would add a very noticeable amount of drag to the given conditions and other factors.

Then, figure out how to live with the Schmidt son hub (which is the best dynamo available).

The drag is well-known. It's about 10% for road bike cruising speed wattage.

You aren't spending enough time going downhill to consider what power you'd get from from that. Keep it simple: only consider average riding.

If you are on a budget, the shimano dynamo hubs are good too.

reads like the solar panel will do.. the hub dynamo is adequate for its purpose , lighting the dark roadways.

so its hub dynamo with disc brake with 6v3w output,

+ the 12v bottle dynamo with 12v output.. 2 things not one.

Back to the initial question, I think you are going to have to look for a transformer. I have looked for a transformer to boost 6vac up to 12vac but have not found one.

I would like to use such a transformer, a rectifier (about $2) and one of those cheap cigarette lighter USB chargers ($1 at the dollar store) to make a cheap USB charger that connects to a 6vac hub. I really do not want to pay over a hundred bucks for a USB charger that connects to a alternator hub when it should cost so little to build one with these simple parts. I am sure that the commercially made ones are better, but for occasional use I would like to have something like this.

If you find such a transformer, please let me know where to buy it.

Nice...
I think a solar panel and a QRP rig might be the choice FT-817 make a charger to charge the individual AA cells and or you also charge two 6v batteries and make 12v

saw a shimano tech manual for a rear freehub dynamo combination., for a 2 by 6v battery
charge , which as suggested above to be put in series for 12v loads..

Why do you need a transformer? A rectifier and voltage regulator should be all you need to convert from 6VAC to 5VDC.

Well... not entirely. For a 6V nominal input and 5V output, he'd need an LDO regulator as a traditional linear regulator needs at least 2.5V of headspace. And then there's the voltage drop inherent in the rectifier. And there would absolutely need to be some power conditioning for use with a hub dynamo that will have wildly varying output up to the point where it stabilizes at a given minimum speed.

Ah! Someone has already gone to the trouble of a relatively simple design: http://www.ktverkko.fi/~msmakela/ele...namo5v/linear/

pretty easy to find voltage doubler circuits that will easily get the voltage output of a dynohub up to 10+ volts. Transformer is a waste of power in this application. Pilom.com is the place to look

This will work fine to generate lots of electricity. I suggest only riding downhill.

There are radios that can be charged on 5v and there are battery packs that can be charged with 5v and then it'll supply you with 12v or more to charge whatever you need. Only reason to want something to charge in 12v would be to use a cheapo 12v battery charging configuration. Keep in mind that the 12v will cost you efficiency in comparison to the 5v, as will charging a battery vs charging your device directly.

I'm not sure this is universally true, but I think the voltage limiting is in the light. The voltage from the generator varies.

I have the B+M Dymotec 6, and I like it a lot. I'd trust the 12 if I really wanted 12 volts.

This doesn't make any sense. To charge a battery you need higher voltage than what the battery puts out, otherwise no current can flow in to the battery. If you can think of this mechanically - imagine a 1:1 ratio pulley. Hang 120lbs from one side and 50lbs from the other. Which side gets a ride up? You have to give the 50lb side some mechanical advantage to be able to move the 120lb side....Same thing with voltages/currents.

As good as your math skills are only down hill ryding well, that would create too much of an inductive load and cause failure of the generator DymNO to literally de magnetize the coil so you would have to keep some pedaling force on the DymNO which would keep the circuist in equilibrium So I think it's back to the drawing board for ou

OP:

- If you search on ebay for SunUP you will find their bike alternator which has merit, but won't fit on disk brake bikes.

- However the company also sells separately a little e-box for their system that takes the output of a dynohub and outputs it to USB charging ports, etc., and it includes a set of rechargable Lithium Ion batts. Its a nice box that does most of what you are looking for...even if it is mostly marketed to make i-phone users happy (thus it is overpriced for that market).

- As long as you can splice the input wire, it won't care what dyno hub you feed it from. I would also guess you could wire in more sets of batteries to the internal circuit and increase its reserve capacity, etc., subject to your electrical skills.

Hoipe that helps
/K