Pedal powered electrical generation?

Discussion in 'The Projects Forum' started by jawnn.geo, Aug 4, 2012.

  1. jawnn.geo

    Thread Starter New Member

    Aug 4, 2012
    I need all the info I can get about how to generate electricity with pedal power. I am going to read this thread, (must take it home on paper, no Internet in my house. I pedal to the library)

    what I have is a generator, I think it is DC, but want to know are there more efficient devices? I presume that an alternator would just wast power being converted to DC for the batteries.

    And that lead acid should be charged slower than Lithium. Not that I can build a fast charger... And I saw a video about how they went directly to the generator from the crank making a relatively slow charge.

    But I am worried about the load of charging and getting the thing spinning fast enough. May need a heavy flywheel to keep a regular RPM.

    And how efficient can one be? what a re the power losses.

    I will be back with more intelligible questions on Monday.

    This wil be just to charge two small 8 amp hour batterys.
  2. Markd77

    Senior Member

    Sep 7, 2009
    Assuming 100% efficiency in everything and fully discharged batteries (not recommended, it's bad for them), and that they are 12V batteries.
    8x12x2=192 Wh (aka 0.192 kWh)
    This means you would have to pedal at 192W for an hour, or more likely 96W for two hours, because 192W is hard work even for a pro cyclist.
  3. jawnn.geo

    Thread Starter New Member

    Aug 4, 2012
    So what about 35% efficiency? or is that for alternators having to convert to DC? So a DC generator would be more efficient?

    Would it be better to use a one stage increase, rather than a two stage with much faster RPM? (But less efficiency)

    My lights stop working at just about 10 volts; or is that almost 11 volts... I use LED's

    I didn't learn anything from that long thread with estimations.
  4. BMorse

    Senior Member

    Sep 26, 2009
    A little more info on the batteries and the "generator" would be great to be able to help you out in any way.....

    You can use a DC motor as a generator, the best ones to use would be high voltage/ low RPM Permanent Magnet DC motors (So a 120 VDC/600 RPM would be better than a 24 VDC 4200 RPM motor).....

    Look here for some insight on how to go about charging batteries from a DC motor generator (same concept as what you are doing, except it is wind powered instead of pedal powered...) >>
  5. wayneh


    Sep 9, 2010
    The design challenge - to optimize power captured into a battery - will be matching the power supply (rider) to the load (DC generator charging a battery). The capability of a human bicycle rider is well documented, although every person is different, but we know almost nothing about the load you are working with.

    Can you gear your system to give high speed at the motor shaft? The DC generator is most likely looking for more speed than typical bicycling machinery provides. At engineering demonstrations, you'll usually see a belt-driven pulley arrangement to get more rpm into the motor.

    A fit rider can produce 100W for extended times (you'll need hours). A lot of this will be lost before it gets to your battery. Battery charging/discharging is about 50% efficient overall. I'll be curious to see what wattage you can deliver to your final load.
  6. vk6zgo

    Active Member

    Jul 21, 2012
    Back in the day,the Flying Doctor service in Australia supplied people on remote cattle stations with "pedal wireless" radios.
    The receive side normally ran off batteries,but when you wanted to transmit you operated the pedals,which supplied HT to the transmitter.
    The generators were purported to be quite efficient & easy to pedal.
  7. wayneh


    Sep 9, 2010
    It was similar in the U.S. My grandmother had a radio with a battery that could be charged by their windmill, which was probably the standard old Aeromotor type.

    As for "efficient and easy to pedal", consider the bicycle generator for lighting. I believe the standard is a 6W generator. Any rider can detect this load, but it's easy to overcome it and keep moving. A 60W load would be like applying the brakes, for most casual riders.