| Archive for Downsizer For an ethical approach to consumption |
| Grimnir |
Batteryless bike lights - product, questions etc...Been looking for a dynamo system for my bike and stumbled upon this - http://www.freelights.co.uk/index.htmlLooks like a great system if you just want to have emergency lights always on the bike. But I want more  I want to use this system to charge some batteries. There's a model that uses a capacitor to hold a charge for 2 mins while you're stopped at lights. I asked the makers and this is what they said -
So, does anyone know how I can do this? Would adding more magnets give me a higher charge rate? (matched pairs to keep the wheel balanced of course). What do you think? I like the Heath Robinson look of this device and the DIY kit looks like it could be very useful to me, but I just don't know enough about this type of system to gauge the possibilities.
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| RichardW |
I have a comment
they say this
BUT any magnet that passes a metal object does create resistance. The more magnets & metal (the wires in the fixed bit plus the bike frame) the more resistance. Oh & yes more magnets will produce more charge / current. But move the coils & magnets to the outside rim of the wheel so that you can get more magnets in but still leave a gap between each magnet. I assume that it comes with more than one magnet as standard (the pic shows two) ? Richard |
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| Grimnir |
Yes, you do get 2 as standard. I think the 'no resistance' thing is in comparison to a bottle or roller dynamo, at least that's how I'd read it.
Any iea how I'd set up the wiring to charge batteries? |
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| RichardW |
Follow the makers advice. Cut out the capacitor & wire in a bat. Or you could try just wiring it into the light wires but I think then you will have the LED's on all the time (once bat is charged) & not flashing & the battery will be getting pulse charged (not a bad thing just not efficient) Will depend on if the flashing is controled or a result of the two magnets only creating two pulses per wheel rotation. More magnets will increase the flash rate & the charge output.
Richard |
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| RichardW |
having looked at the diff versions you must have the standby version which gives solid light when stopped if the break is held. This is using the cap to store power. The cap could be replaced by a bat but you wont get flashing lights at stand still (they only flash due to the magnets creating pulses) just longer with the break held on at stand still with constant lit LED's. Cant see why you would want that. The lights will always work (flashing) whilst moving & you wont be stood still for long. A 20 min ride gives up to 2 mins stood still. having a bat wont increase the ratio of ride to stand still in fact due to bat charging losses you will have to ride for about 30 mins to get the same 2 mins you get from a capacitor as that has much less charge losses. I just cant see why you would want a battery in the system.
Richard |
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| Grimnir |
So I'm better of sticking with the SPL capacitor system then? That's cool, makes it easier on me I guess 
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| Tavascarow |
I think you are still going to need a normal front lamp for night riding by law.
I use led lights front & back with rechargable AAA batteries. A lot cheaper than this kit. But I also have a 6v rechargable twin spot for night riding cause there aren't many street lights around here & leds are great for being seen but bl**dy useless for seeing with.
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| Grimnir |
I do have a set of lights on the bike now, LED front and rear battery jobs. The front light is perfectly capable of lighting my way - I mainly use it in town anyway and the LEDs cast as good a light as I've had from many a bulb lamp in the past!
What I would like to do is be able to run the others as secondaries to aid being seen. I had hoped to be able to provide enough power to keep a charge on a main light as well but if the output is not going to be enough then I'll stick with my current setup and get the batteryless set as secondaries |
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| Tavascarow |
Maybe where you are but I nearly hit a badger last winter when I was going full tilt down hill & the thought of me in a heap in the road with a disgruntled badger made me go out & buy these.
http://www.amazon.co.uk/Torch-Highbeamer-Rechargable-lighting-system/dp/B0011W89FO 
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| RichardW |
Ah now to run a second set of batteries, now thats different. Whats is the power needs of the second set? Richard |
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| James |
I've got a friend who has this set-up.
He swares by it as a secondary light source. The power output (intensity of the light) wouldnt increase with an increase in the number of magnets. This would just change the rate of flashing. The amount of power is dictated by the strength of the magnet, the proximity of the magnet to the coil, the guage of the wire in the coil (I think..) and the number of winds on the coil. So in theory you could alter all (or some..) of the above to increase the power output, but you'd basically be re-building from scrath. But without alteration, as an off the shelf system, my friend would not be without them. |
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| RichardW |
My take was not quite the same. Ok so the 7v 7 25ma (peak) wont change but as its pulsed by each magnet increasing the number of magnets will increase the pulses so increasing the % of the time a charge / current is produced (so turning 7v 25ma peak to 7v 25ma constant ish). Lets say that the two magnets produce two pulses for each turn of the wheel & the wheel is turning 120 times per min. So getting 240 pulses per min. Each pulse would be very short & the gap very long (in comparison) but if you added 10 magnets you would get 12 pulses per revolution. So getting 1440 pulses. At that rate the LED's will look like they are on constant ish & the spare current could charge a battery. Failing that buy two one for flashing LED's & one to charge the other battery. Fit enough magnets to the LED one to create a good flash rate & loads to the battery charging one. Richard |