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Old 02-13-2010, 12:38 PM
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Earthman Earthman is offline
Motorized Bicycle Senior Member
Join Date: Mar 2009
Location: Pittsburgh, PA
Posts: 82
Default Re: Yet another white wire question

Short answer - no, the white wire will not work with a 20 Watt light. The magneto was designed to only make several Watts of power at 6 volts +/- of AC current, which is enough to run the engine and a low-power (3 Watts max) head & tail light system. You can run low-power LED lighting systems off the white wire, but the light output is relatively low and/or focused into a tight beam. You can run a 20 Watt incandescent lamp (like your photo) if you run it off a battery. You can trickle charge the battery from the white wire. Since the magneto makes alternating current, you will need at least one diode to rectify the current, but a full-wave bridge rectifier (basically 4 diodes) would be better. If you want to charge the battery properly, you should have a voltage regulator as well, but the extra cost may not be worth the trouble - try a single diode or a full-wave bridge rectifier (both available from RadioShack) with a small 6 volt lead-acid battery and see how well the simple system works for you. Otherwise, you can make a 6 or 12 volt electrical system (12 volt automotive components are more readily available and less expensive) that is independent of the white wire and charge it with a wall wart. For my electrical system, I'm going independent of the white wire using two 10-cell, AA nickle-metal hydride battery packs (2 Amp-Hour, 12 volts each where one battery is a backup); a 20 Watt, 12 volt landscape flood light (in a homemade housing); and LED tail light and turn signals based on automotive components. If I do find myself out at night and both battery packs are exhausted, I can stop anywhere and buy 10 AA alkaline batteries and put them into the battery holder to get me home. My main reason for wanting lights is to be seen, but I also want to see the road ahead. I don't plan to commute at night. If I did, I use a 7 AH, 12v SLA gel-cell battery.
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Last edited by Earthman; 02-13-2010 at 12:43 PM.
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