Complete bicycle electric system: dynamo, batteries, lights, accessories

Calina

Enlightened
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Jul 26, 2006
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955
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Longueuil, Québec
A couple with the same requirements as yours was touring Europe last year with the TuneCharger. Jean-Michel (the inventor) can probably get you in touch with them.
 

alexlockhart

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Jun 27, 2007
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60
OK, I've had a lot of good responses from people on the 3 forums where I posted this, and have changed my design ideas somewhat, so I'll try to synthesize the good suggestions and update my design here for everyone.

bikecurrent_b_barry said:
For the LI packs, three by three in series parallel, is a maximum charging rule to follow. I'll charge a single pack of four in series ok, but more than that will result in voltage variations between cells that will lead to overcharging of one or more cells as other cells diminish, not a safe occurrence to have a cell charging to 4.5V to make up for three others which are maxing out at 4.1 repeatedly while the total charge voltage of 16.8 makes it look like the whole pack is charging as normal. . . was thinking later why do you want such high voltage to begin with, and rereade tha tyou are putting the LEDs in series. You'll get much better efficiency through the regulators wiring the LEDs 2x2, so ~9.9 volts will be your minimum required to feed to the regulators. this will greatly simplify the power and charging requirements.
Then you can use a three or four LI in series battery, without the risk of the higher voltage. If you haven't worked with the 19.8 (nominal, 25.2 max) voltages, they arc and spark much easier, and if you get a momentary short, melt wires much quicker.
Based on my measurements of current and voltage to the LEDs and from the battery, so pre and post regulator, BuckPucks are ~90-95% efficient in the 9 to 12.6 range, but down to 85% above 16V. Haven't used the TaskLED circuits yet, but by their specs they are less efficient than that.
The idea of wiring my Crees in 2S2P had occurred to me, but I had dismissed it since then they would each see half of the current the driver gives, meaning my maximum drive current would be 500mA per LED. However, I knew I wasn't going to need or want them to be run at 1000mA each, and figured that I'd experiment with setting the max level at 500mA or 750mA and see how I liked it. 500mA per Cree would mean about 120 lumens each (before optics losses). As a comparison, I currently have a DiNotte Ultra5, which produces 120 bulb lumens with a 20 degree collimator, and a Seoul flashlight as a helmet light whose maximum drive level is about 500mA, meaning it's also producing around 120 bulb lumens, but it's fairly tightly focussed. Imagining the amount of light from 4 Crees producing 120 lumens each, with the beam pattern I'll have, I think that will be more than enough light for a screaming descent. So now I plan to run the Crees in 2S2P, as suggested, and power them with a battery pack of 3 cells in series (3S4P for 12 cells). Several people said that wiring the two 3-cell chargers in series for the 6-series setup would not work due to the chargers being unable to sense the voltage regulation, so that idea was abandoned, which is just as well, since I've also been pointed to the safety concerns of overcharging a cell in a 6-series pack due to imbalances. So using a 3S4P configuration turns out to have many benefits. Another advantage of that setup is that my nominal battery pack voltage will be 11.1V, so I won't need any regulation between the batteries and my various battery chargers designed to run on 12V.

cpf_wmaurer said:
Alex, I'm very interested in your solution to this problem, as I will be embarking on a pan-Americas cycle tour next year, and, like you, want to charge all my gadgets from a Schmidt SON hub. I think your knowledge of electronics is much greater than mine, and it sounds like you're making great progress towards a design.

I have spent some time searching for an off-the-shelf product that satisfies this purpose, and have found something called the TuneCharger which claims to collect as much power as possible from inherently unstable sources (dynohub, solar panel) in order to charge batteries in a 'smart' manner, i.e. not overcharge:
http://www.tunecharger.com/documents_088.htm
I believe that the latest version of the TuneCharger is will be ready for sale in the next few weeks, which has been sized for the dynohub, including rectifier and overvoltage protector.
I was so excited to find this that I spent the next several hours reading the webpage and many of the posts on the Yahoo discussion group for it, repeatedly exclaiming "This is SO COOL!!"

The older versions could only charge lead acid and nickel batteries (using a pulse-charging method, very efficient), but the new one (just now in production) has an end of charge sensor which can measure the instantaneous pack voltage in between charge pulses, so it can charge Li-Ions safely with a user-settable cutoff voltage. It also can charge batteries which are being used simultaneously, which is a necessary part of my design that I was unsure about with the other cheap charger I was going to use. I need to read more about this and get info from Jean-Michel (the inventor) before planning for exactly how to use this, but it looks like exactly what it says: the missing link.

One of its best features for making use of dynamo power is its maximum power point tracking (MPPT), which adjusts the load given to an ohmic device to continuously find the sweet spot for power production. This will ensure that the dynamo produces at least 3W at 8km/h (its design spec) and at least 9W at 24km/h (my average touring speed), meaning I'll have 43-58Wh of useful power after 6-8 hours on the bike (assuming 20% loss in the electronics).

cpf_Steve_K said:
There's not a lot of info at the website (that I can read), but I did notice a mention of a maximum input voltage of 20v. Wayne mentions an overvoltage protector. Is this something added on to clamp the dynamo output to 20v? If so, it should be sized so that it can dissipate 10 watts or so.
Yes, it does mention 20V max, and 8W max power processed before it starts limiting the supply (from the dynamo). I'll have to find out if that means I have to protect it from higher voltages (with a shunt regulator, as you suggest) and if I may want to wire 2 in parallel (which is possible) to make use of the available power all the way up to 26mph.

So, assuming the TuneCharger is what I think, here's my updated, simplified, safer, design: Dynamo connected to input of TuneCharger, which is connected to 3S4P battery pack (9V-12.6V range), which is connected to the bFlex, which drives my 4 Cree headlight in 2S2P, and also acts as a 12VDC source for connecting chargers for various batteries, including my laptop. A bonus is that when I have AC power, I expect I can plug my laptop power pack into the TuneCharger, and it will charge the batteries using that input just like it would with the dynamo input, only much faster since it has 65W to work with.

My next step, and perhaps the only remaining questions, is to find out from Jean-Michel if the TuneCharger will do what I want, and what I'll need to consider to make it work. Anyone see any problems, or have any concerns? I won't be able to start building and experimenting until everything arrives, so I want to be ready to go with a solid design, to minimize my time and expense in experimentation and making mistakes. So far I've had excellent responses and suggestions, thanks to all!

Alex
 

PeLu

Flashlight Enthusiast
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Jul 26, 2001
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Linz, Austria
..seem to recall reading something about the TuneCharger working with Li-Ion batteries somewhere on the yahoo e-group.
Thanks all the people here bringing the TuneCharger back into my mind. I watched it some time ago (and was in contact with Jean Michel about uring it from a bicycle dynamo), but had the impression that there is only little progress. It looks much better now. And I'm shure it could be combined with Martin's circuit of switching in between different series capacities to get out the possible maximum (if it turns out it is not enough).

Alex: don't worry about how the 'built in current limiter' works, the only influence it has, is that you can overcome a reactance but not saturation.
 

wmaurer

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Joined
Sep 14, 2007
Messages
5
Alex, the solution I wish to build is similar to yours, possibly a little simpler. I will most likely be using an off-the-shelf light such as the Lumotec Fly. I'll just switch dynohub output between headlight and battery charger.

I plan to use a bank of NiMH rather than Li-Ion batteries. I want to be able to swap out AA/AAA NiMH batteries from the bank for use in head torch, LED lantern, SW radio, bluetooth keyboard and Cateye LED blinkies. From the battery bank I will need to output 5VDC or 12VDC for charging my GPS-Phone-PDA (HTC P3300), e-Book reader (Bookeen Cybook), and camera Li-Ion BLM-1 battery charger.

You might be interested in the on-the-bike multicharger that this guy built for the round-the-world bicycle trip he and his wife did a few years back:
http://www.mark-ju.net/bike_ride/equipment/charger.htm

I think that using the TuneCharger we'll have a smarter (in terms of battery charging) and simpler (in terms of how much we have to build ourselves) system.

Wayne
 

PeLu

Flashlight Enthusiast
Joined
Jul 26, 2001
Messages
1,712
Location
Linz, Austria
You might be interested in the on-the-bike multicharger that this guy built for the round-the-world bicycle trip he and his wife did a few years back:
Mark's charger is a little bit more complicated, but a proven design.

There are a few devices readily available, but most of the documentation is in German.
This one is sold in small quantities:
http://www.shop.isdn-stollberg.de/xtcommerce/product_info.php?products_id=31
Busch&Mueller offers a charger (sorry, I could not find the English version, maybe somebody else can?):
http://www.bumm.de/index.html?docu/492rk.htm

And there is a charger with several different versions (6V and 12V for example) desgined by several memebrs of the German bicycle touing forum. Their design is simpler, they charge NiMH cells with constant voltage. Funny enough it works well and the cells live long.
http://www.t3productions.de/rad-forum-lader/

Just for people who look for a simpler design.
 
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