Looking for Dynamo to charge a battery

I cant believe these things do not exist. Peter white and Nordicbike only talk about dynamos as not producing enough wattage, then they say the typical cyclist can only make 125 watts of power and even a 3w generator would add a noticable amount of lag, and a 20w would be undesirable. http://nordicgroup.us/s78/dynamo.html

First off Lance does 493 watts http://www.tdfblog.com/2005/06/inside_armstron.html

So that means the rest of us are probably going half as fast, so 200-250 watts. 1% is hard to measure subjectively.

Second, who ONLY rides at night. Plus, if you didnt start during daylight hours, you COULD start with a charge battery at half the mAH. If you were to use a 3W efficient generator to charge a battery, you could burn at 6W for twice as long, or use half the battery size. That would make you faster and make up for the weight of the generator.

So why do people try to use complicated dynamo stop circuits. Why not just charge a battery and use the juice to keep things charged on long trips like: http://www.greatdividerace.com/

Seems like burning fat not fossil fuels is the way for us to charge our batteries...am I wrong somehow???

Sorry no deal... :thumbsdow Untrained cyclist is able to generate constantly about 100W of power and about 300W for a very short time - about 1 minutes (it's 40 km/h on flat road) :devil:

A typical bicycle dynamo will charge batteries but it is limited to 500mA. You can get by with limited light output but it is manageable. Just forget about ever running with a 20-watt halogen light driven with a dynamo.
I use a hybrid dynamo/battery electrical system on my touring bike. During hot weather or crossing a desert I will ride all night and sleep during the day. I also need to keep a GPS unit and Cell phone charged. Here is the circuit I use.


The headlight and taillight use 380mA, allowing 120mA as recharging current to compensate for stops or speeds of less than 8 MPH. If I am traveling long distances without stops, hills, or traffic I disengage my dynamo for 15 minutes of every hour to prevent overcharging the Ni-MH batteries. S2 is for use with hub dynamos and prevent slow discharge of the batteries through the diodes in the case of bottle or bottom bracket dynamos when the bike is parked for extended periods. Opening S1 disconnects the LED's allowing a GPS or Cell phone to be connected to a USB port so they can be operated and recharged from the Ni-MH battery pack. Don't forget to disconnect accessories from the USB port when parking the bike for an extended time, as the batteries will be discharged into the accessory. If for some reason the battery pack becomes discharged S1 may be opened, S2 closed, and no accessories connected to the USB port allows 500mA of current to rapid recharge the batteries. Be very careful when rapid recharging the batteries as you can forget your recharging them when using a hub dynamo and overcharge them. I reset my Cyclocomputer trip clock so I can keep up with rapid recharging time.
The 470mF capacitor is not required but I added it to the circuit in the event my batteries were lost or damaged. The capacitor allows driving the LED's directly from the dynamo via the bridge rectifier. The headlight LED will be subjected to full current and a reduced life but it should still provide at least 25,000 hours of use at 500mA of current. The expected life span of the headlight at its rated 350mA of current is 100,000 hours. Using the new Luxeon Rebel LED in the headlight eliminates that problem as it can be driven with up to 700mA and is rated at 80 Lumens at 350mA.

N4ZOU,

That sounds like a slick setup. Yes I have worried about overcharging batteries. Also, fast recharging can be a problem. I figure the easy solution is to use a large enough battery source so that when recharging it takes several hours. Would be cool to have a digital display 'fuel tank' to see the charge directly.

RE: hub dynamos. I am not a serious cyclist, but I can't imagine anyone but a more recreational/adventure type using one of these. Who wants to rebuild a 700 wheel with an inferior hub? Personally, I run a Mavic 729 http://www.mavic.com/mtb/products/EX-729-Disc.995014.aspx based wheel designed for abuse and 20 foot drops (though I dont do those crazy things= http://www.youtube.com/watch?v=54qt6YpZr4Q ). I dont think a Dynamo hub would work.

What I AM looking for is a gear driven (off the inner chainring) dynamo, perhaps one that could be 'disengaged' with the front derailler (since I use it for a chainguide only). All the dynamos I have seen are either hand crank to flashlights or radios, hubs, or run off the tires, which doesnt seem ideal to me at all (except maybe high rotational velocity).

Szemhazai:
I stand corrected. The most I can do sustained is about 1000 kcal/hr (VO2 max 70-72), using this calculator http://joshmadison.com/software/download/dl.php?dl=convertExe4.10 that puts me at 27.78 cal/sec or 116 Watts. I just gained an entirely new appreciation for that animal that is Lance.

I run a bottle type dynamo as I can disengage it so there is no drag when it's not in use. Dynamo hubs are not designed for off road abuse! Your never going to get the amount of light you need for off-road riding from a bicycle dynamo in any case.

I've been considering a Pioneer E-light generator system.
http://www.abs-sports.com/
This system is like a hub dynamo but is not a hub requiring you to build it into a new wheel. It simply slips around the axel and is driven from the spokes. You get the advantages of a hub dynamo without the cost involved and it may be installed and removed easily while still retaining the original wheel.

The dynamo must be driven from a wheel in all cases as your power production would stop any time you stop pedaling if it is connected to the crank. Your lights would go out when you need them most, braking!

n4zou said:

The dynamo must be driven from a wheel in all cases as your power production would stop any time you stop pedaling if it is connected to the crank. Your lights would go out when you need them most, braking!

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No, no, no! A dynamo is for charging, not powering! My trip entails around 60 miles a day on dirt, figure 8-10 hours a day in the saddle. For those 8-10 hours I would want to charge up 'teh batterias' so that when darkness comes, I have power. Each night I would probably discharge the light setting up camp etc.

Regenerative braking would be cool. I have a couple big capacitors, 250,000 uF or something, but I see smoke and flame in my future were I to mess with those (probably from burning flesh, my flesh= not good)

...thats my idea anyway. btw I liked the link to the "e-light generator"

You might find this interesting.

http://www.minesactioncanada.org/competition/2002_2003/PedalGeneratorBatteryCharger_1stPrize.pdf

Something else to think about is using a stepper motor as a dynamo.

http://www.reuk.co.uk/Stepper-Motor-Basics.htm

A few years ago I noticed a stepper motor being used as a dynamo on a bicycle. He had a skateboard wheel attached to the shaft of the stepper motor and was friction driving it on the rear wheel. The stepper motor was mounted on a hinge attached to the bottom of his rear rack with a spring providing pressure to prevent slippage between the skateboard wheel and the rear tire. He passed me and I tried to keep up and look at the setup and even asked if he could stop so I could look closer at it and ask a few questions. He said he did not have time and would be late for work if he did and kept on pedaling. I tried to keep up but he was a "machine" on the order of Lance Armstrong. He smoked me! I was sprinting just to keep up but he was just making his commute. I can just imagine pulling that large stepper motor with something like 20-watts or more drag was nothing to him! It was disengaged at the time I saw it on his rear rack. It was about 8:00 in the morning.

rdhfreethought said:

I cant believe these things do not exist. Peter white and Nordicbike only talk about dynamos as not producing enough wattage, then they say the typical cyclist can only make 125 watts of power and even a 3w generator would add a noticable amount of lag, and a 20w would be undesirable. http://nordicgroup.us/s78/dynamo.html

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Wow, that site is full of great images. :devil:

znomit said:

Wow, that site is full of great images. :devil:

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The information on that page is getting more outdated by the day.
LED's are getting brighter all the time. The Luxeon 1-watt LED and matching Fraen optics in my DIY headlight provides more light with just 350mA of current at 3.7-volts than the standard dynamo headlight it replaced. The new Luxeon Rebel LED has almost doubled light output jumping from 45 Lumens for the standard Luxeon 1-watt emitter to 80 Lumens at the same 350mA for the Rebel emitter. You can force-feed it with up to 700mA with just a slight reduction in life. Luxeon does not have optics for the Rebel on their sales site yet. As soon as a 10 X 20 holder and lens is available I'll be upgrading my light with a rebel emitter and never need worry about pumping a full 500mA of current through it from the dynamo. I am pretty sure in a few more years you'll see dynamos become commonplace with LED headlights equivalent to a 20-watt halogen lamp.

Great info on stepper motors. I was wondering would a DC brushless (like say a computer fan?) driven with a pulley system produce usable current? Would probably need rectifiers. I like the spirit of the white page on the bicycle driven generator. Using spare parts is always cheaper (since they are free) and helps the environment, since reuse is better than recycle.

Plus, its fun!

rdhfreethought said:

Great info on stepper motors. I was wondering would a DC brushless (like say a computer fan?) driven with a pulley system produce usable current? Would probably need rectifiers. I like the spirit of the white page on the bicycle driven generator. Using spare parts is always cheaper (since they are free) and helps the environment, since reuse is better than recycle.

Plus, its fun!

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These might be fun to experiment with but I doubt they would survive very long in the real world. I don't see them to resist dust, humidity and water very well.

Calina said:

These might be fun to experiment with but I doubt they would survive very long in the real world. I don't see them to resist dust, humidity and water very well.

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There sealed better than you might think. They live in harsh conditions found in commercial equipment. Believe it or not the computer case is an exceptionally harsh place. Heat is generated and fans are constantly drawing in unfiltered air filling it with all sorts of crud floating around in the house. Dust, bugs, and cooking grease suspended in smoke can be found coating everything including the stepper motors in your printer and scanner. Stepper motors are commonly used in wind turbine generator systems and are exposed to the elements constantly.


http://www.reuk.co.uk/Electricity-with-Stepper-Motors.htm

I have a stepper motor hooked to a variable capacitor used to remote tune an antenna. It lives in a 50-CAL ammo box at the base of the antenna. It's been out there for about 8 years and has never failed to turn the capacitor. All the aluminum parts are covered in that white corrosion caused from exposure to the elements. Yet it still continues to function properly.

rdhfreethought said:

Peter white and Nordicbike only talk about dynamos as not producing enough wattage, then they say the typical cyclist can only make 125 watts of power and even a 3w generator would add a noticable amount of lag, and a 20w would be undesirable. http://nordicgroup.us/s78/dynamo.html

First off Lance does 493 watts http://www.tdfblog.com/2005/06/inside_armstron.html

So that means the rest of us are probably going half as fast, so 200-250 watts. 1% is hard to measure subjectively.

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Here is a page with a graph of a performance athlete compared to the rest of us. I'd say Peter White is right about the average person.

also factor in cycling is a skill. the more miles one racks up... the more efficient one's body becomes at cycling.

this is on top of fit level. those HPV's are incredible!
my main ride these days is a fully fairing Lightning P-40

back on topic..... have cycled/toured thousands of miles, but have never used a dynamo.
currently using two HID light when riding at night. HID Storm and ARC HID

500 milliamp with today's emitters could put out good bit of light, but no where near amount of lumens to be effective. there's a difference between generating enough light to be seen VS enough light to see.

granted where one rides makes a huge difference in how much light is enough. my requirements riding a fully fairing recumbent at night, is to put off same amount of light as a car.

cy said:

500 milliamp with today's emitters could put out good bit of light, but no where near amount of lumens to be effective. there's a difference between generating enough light to be seen VS enough light to see.

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Are you talking in a relative sense, or are you saying that before high efficiency emitters came along all those incandescent lights just didn't work with dynamos?

To be seen 40 lumens is enough but to see 400 is quite reasonable value .

Go to www.otherpower.com and look up pedalgen. Quite a few post on the subject.

Thurmond

500 ma through two CREE XR-E Q5 bin is nearly 300 lumens. This is what I use for night riding, and it washes out all of my friends' HID systems. With three emitters, 400 lumens would be easy to achieve.

LED dynamo systems have caught up on the DIY end with commercial battery lights, and the runtime is infinite!

As far as drag - a 3W light typically means 6W of drag (50% efficiency for hub dynamos). However, 125W versus 131W is not noticeable to the legs on the flat. Really, you're all making a mountain out of 6W. Until you ride a bike with a hub dynamo running, you're not in a position to make the comparison.

And for a bit more info - a dry chain uses 5% more than a well oiled chain (6W at 125W to pedals). Maybe that might help in the comparison.

Q5 is rated at aprox. 100 lumens @ 350 milliamps, then factor in at least 30-35% transmission losses.

unlikely 300 lumens of usable light from 500 milliamps of juice

how much light needed is relative to ambient lighting conditions and what you are doing anyways...

riding slowly on a pitch black sidewalk has completely different requirements to riding in traffic at night or blasting down trails on a mountain bike. etc..

rideatnight said:

500 ma through two CREE XR-E Q5 bin is nearly 300 lumens. This is what I use for night riding, and it washes out all of my friends' HID systems. With three emitters, 400 lumens would be easy to achieve.

.

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cy said:

unlikely 300 lumens of usable light from 500 milliamps of juice

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I was thinking about that, must have been last night. It's 500mA at 6V, so using an 85% efficient buck supply might give you 700mA at 3.6V. (Am I on the right track there?) Still not 300 lumens, but you could have over 200. That sounds like a very usable amount of light.

cy said:

riding slowly on a pitch black sidewalk has completely different requirements to riding in traffic at night or blasting down trails on a mountain bike. etc..

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Would anyone here actually recommend using a dynamo for mountain biking, though?