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Old 12-30-04, 10:02 PM   #1
danhulme
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plug and play

Ok I want to use a stationary bike to set up a generator station to run the TV & computer. I figure I can set up a drive system for an alternator to charge a sealed 12 volt car battery. Have the battery go to a 2000w inverter. Plug and play system. Do any of you know of an affordable system on the market to do this with?
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Old 12-31-04, 12:14 AM   #2
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First off, not to poke any bubbles, but you're hardly gonna be able to push 300 watts. I thought about the same proposal a few times(dad is a power supply designer) and we concluded it would be very tiresome indeed.
1 horsepower is 760 or so watts, as a reference. Last I checked my bf could put out about 350 max when race warmed up. 200 some for any endurance. Kudos If you can work it(harbor frieght tools has good inverter deals), but take into consideration the alternator or generator will both have intrinsic drags as well.
I'm open to new ideas on it, however so shoot away.
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Old 12-31-04, 09:30 PM   #3
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Iím still trying to figure it out but seems that with the right drive ratio you should be able to spin an alternator sufficiently. I really wish I had paid more attention in school. I figure for rider comfort a seated style stationery bike would be the way to go. I donít know weather to run a direct drive to the alternator or use a heavy wheel to drive a pulley on the alternator, the kinetic energy might assist in keeping a nice endurance pace. This would increase the RPMís of the alternator. An automotive alternator maintains an average of 2000 rpmís (guess). So I am thinking I will need to work the ratios out to maintain that on the alternator to get the most efficiency. I guess if it was easy it would have already been done.
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Old 12-31-04, 10:45 PM   #4
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Forget about RPM. The first issue is a simple energy balance. You need to determine the steady state energy requirements of whatever you are planning to power with the system. If the TeeVee requires 150 watts, then you must supply more than 150 watts while the TeeVee is operating or your battery will run down. If the computer draws 200 watts average, then, again, you must supply more than 200 watts to the system.

Keep in mind that you have specified several pieces of equipment between you and the appliance. Each of these, the alternator, the battery, and the inverter, have losses of their own. The alternator is probably the most efficient, but the battery and inverter are probably not very good. I would not be surprised if there were 25% loss in the chain. So a 200 watt appliance would require you to push 250 watts.

However, there is another catch. If the battery starts to discharge because of peak loads or if you cannot keep up with the demand, it will start sucking down power as well adding to your load. This could become a vicious cycle where it gets harder and harder to pedal as the battery become more and more discharged.

Depending on what you want to operate, and how strong you are, it might be feasible.
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Old 01-01-05, 02:19 AM   #5
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I've seen a TV/VCR combo at the Campus Center for Appropriate Technology at Humboldt State University in Arcata, CA, in 1999. I don't remember how it worked, but the pedaling did charge a battery, a car battery I think. The also had a pedal powered washing machine. It was an old school machine and the bike just spun the agitator.
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Old 01-01-05, 09:50 AM   #6
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subcom the tv,vcr,dvd combo claims to use 85 watts. I was worried about the rpms at the alternator because I was thinking of using a Self-Exciting Alternator GM type. This type of alternator requires a certain rpm to activate. Ideally the system would be allowing 30 minutes of steady pedaling (50-70)rpm to operate the appliance and store enough excess energy for an additional 30 minutes of use. Mind you I would like to keep this low dollar.
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Old 01-01-05, 10:02 AM   #7
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Thanks fixed i found site with info....http://www.humboldt.edu/~ccat/pedalp...final_htm..htm
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