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Possible to Connect Magicshine 900 to Hub Generator?

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Possible to Connect Magicshine 900 to Hub Generator?

Old 12-11-09, 05:32 AM
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Possible to Connect Magicshine 900 to Hub Generator?

Has anyone tried this? Rather than running the light off of the battery pack, could the lamp be run directly from a 6V 3W hub generator? Or better, is there a way to feed the hub generator output in parallel to the battery pack? Would that increase the time between off-bike battery recharges?

Thanks in advance for your advice.
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Old 12-11-09, 09:18 AM
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I doubt it. The light has a digital controller in the head which is cheap, so it's only barely as sophisticated as it needs to be, and as such it's probably going to go haywire with a non-constant power source.

Also, 6v at 3 watts is 0.5 amps, and my measurements indicated that on its lowest setting, the MS light draws 0.49 amps at 7.4 volts, or about 3.626 watts. Since the light starts on high when you turn it on or apply power, the first thing it's going to do is to try to draw 1.5 amps (about 10 watts) to kick into high mode, and it'll just immediately shut down. You might be able to get it to run on low mode if you were going full out all the time, but you can't ever get it to switch into low mode in the first place.

You might be able to use a proper up-converting voltage regulator to kick your generator's output up to 9v or so and use it to charge the MS battery, but you'd also need LiIon charging circuitry involved there. Or you could try using a 6 cell NiMH pack and an upconverting power supply, that gives you 7.2 volts and wouldn't need much charging circuitry, but you definitely need the generator to put out more than 7.2 volts to charge a 7.2 volt pack.

I'm not even sure about that, since 6 NiMH cells will be putting out more than 7.2 volts on full charge. It's at least feasible though. Directly connecting the light to the generator isn't. Pick up an IQ Fly for that, it's what it was designed for.
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Old 12-11-09, 01:29 PM
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It's much harder to design a proper charger for NiMH than for Li-Ion. Li-ion you just use a cc-cv charge cycle and it works fine.

With NiMH if you don't want to cook your cells you have to mess around with temperature sensors and look for the voltage drop at the end of cycle and they are more efficient on a fast charge cycle which you won't have the current for...
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Old 12-11-09, 08:21 PM
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From the output characteristic curves I have seen posted hub dynamos can put out far above 6V at higher speeds with the correct load attached. They will not go above about .6 amps though due to internal impedance. To get maximum power out of a hub dynamo you need a koad with higher than normal dynamo light resistance which is why most homebrew multiple LED dynamo headlight circuits have the LEDs hooked in series. I believe that the Magicshine has the 4 LEDs on the chip connected in parallel. Not dynamo compatible unfortunately.

The more you are trying to get out of a hub dynamo the higher the speed at which the light will reach full luminosity too. Street legal German dynamo lights reach rated light output at about 6 MPH while the Supernova E3 Triple, not German street legal, reaches maximum output at 25 MPH per the manufacturer. Lots more light total but it is using the dynamo to near maximum capability.
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