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Power supply for bike

Discussion in 'Home Power and Microgeneration' started by [email protected], Mar 27, 2006.

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  1. Guest

    Thought of asking this in this forum because I know alot in here have
    a decent electrical background.

    I have an exercise bike that uses 4 "D" alkaline batteries for its
    desplay unit and to drive a motor inside for adjusting the drag of the
    bike. The unit also looks to have a external power supply jack.

    However the manufacturer supplies no such external power pack. There
    is no rating as to what the input would be.

    I can assume because there are 4 D cells that the voltage is max @ 6V.
    How would I figure out what the mah rating should be on a power pack?
    I would like to use one of those plug in step down type packs. IE:
    120v to about 6v .

    I've taken a reading at the jack I think is for an external source and
    it reads about 5 volts with used batteries.

    Can anyone supply info in this area or direct me to a good website
    with such info?



    PS: This bike uses batteries quite quickly thats why I wish to
  2. Guest

    Heres the funny part about an external for this bike.
    The original manual lists no such power adapter. The main website
    doesnt list one as standard either.

    However I did find a third party part suplier that list a external for
    this bike. picture is given and no specs on said device. I have
    emailed the third party supplier with no feedback yet. I am leary
    about buying from this vendor without more info.

    As for making or adapting one myself I fairly confident about getting
    polarity right...its the millampres that confuses me.

  3. Guest

    Maybe what I should be asking is what do 4 d batteries deliver as far
    as milliampres. Should I exceed this in an external power source.

    I would think that the external should be at least rated the same as 4
    d cells or more....Is this right?

  4. 4 D cells can supply a couple of full amps, though not for long.
    What you can do is this...
    Take a slip of plastic or paper and stick a couple of patches
    of copper foil, tin, or anything conductive, to each side with
    bits of wire attached. Slide this between the contacts of two
    of the D cells. Hook the wires to your favorite multimeter when
    it's set to read Amps. Use the various features of the bike and
    read the meter to see how much power it draws. You may note that
    it takes more power to say, move the motors, than at other times.

    You might also try measuring the resistance between one contact
    in the battery compartment (without the batteries in there) and
    one contact of the external power jack. You may find the external
    jack is, more or less, wired in parallel with the batteries.

  5. You are on the right track, but without an ammeter it's going to be
    hard to tell. You can get (lessee) 4 amps out of a lightly-used
    Duracell D battery...
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