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Batteryless Flashlights?

Discussion in 'Home Power and Microgeneration' started by Richard P., Dec 4, 2004.

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  1. Richard P.

    Richard P. Guest

    I saw a product at a local mall a few months ago and I saw it again tonight, it's a flashlight that
    doesn't need batteries. You just shake it back and forth for 30 seconds and you get about 20 mins
    of light from it. It has a couple of white LED's and the case is clear allowing you to see the
    magnet that slides back and forth inside a coil of copper wire as you shake it.

    Anyone have any real world experience with these..?
  2. I've played with a few of them. They use a high power magnet sliding
    through a coil as you shake it to generate power. This power gets stored
    in a small capacitor. Often they suggest you turn the switch off when
    shaking it for charging. If you don't turn off the switch you can watch
    the LEDs pulse with the power spikes coming from the coil.

    They take a lot of shaking and they only produce useful light for a
    few times longer than you shake it. You wind up pausing every 20 or
    30 seconds to give it a few more shakes. They're main advantage is
    that they can be stored for long periods of time without worry about
    leaking batteries. Unfortunately, they're only really bright enough
    to light your way to finding a regular flashlight and batteries for

    Personally, I think a better design would be to use this technology to
    update the old squeeze/crank flashlights. Using similar high powered
    magnets, power management circuitry and LED's these old squeeze lights
    could actually be practical.

    One note, they use VERY strong magnets. Do not place them near credit
    cards. On a brighter note, you can usually hang them on your fridge.

  3. I have no experience with the one you describe.

    I have a "no battery" flashlight, with built-in FM radio, no less,
    that was a safety award from work. It has a little fold-out crank, and
    you wind on it for a while, and then you can use the light or play the
    radio. Kind of gimmicky, IMHO, but it does work. I keep it in the
    truck, for emergency use.

    It's not a new idea. Dynamo flashlights have been around since the
    late 1940's at least. I remember my father having one; a small
    Bakelite cae with a handle that you squeezed... Squeezing the handle
    caused a sector gear to move, spinning a tiny pinion gear, which drove
    a PM dynamo. Eventually, continued use would wear the teeth off the
    sector gear.

    Using one of these will give a person an appreciation of just how much
    "work" goes in to making a useful light source.

    Gordon Richmond
  4. Yeah, I've got a small one that a friend gave me, and while it's a
    neat toy, it's not much of a flashlight. I dunno who specified the 30
    seconds gives you 20 minutes, but IME they've got their numbers
  5. wmbjk

    wmbjk Guest

    In other words... if it's midnight and you need ten minutes of light,
    it might be quicker to wait for the sun to come up. :)

  6. Gymy Bob

    Gymy Bob Guest

    The new ones are LEDs and take very little power. The older units were
    incandescent bulbs and make the poor timing truer.

  7. yes they should be water tight. I had a play with one today and even the
    switch was actually a reed switch which did not need a hole in the case. The
    only water point of entry would be where the lens is, but that had a rubber
    grommet around it. It would be good for water sports.
  8. lost soul

    lost soul Guest

    Hey are you the guy that was on slimdogs a couple years ago?

    "Heywood Jablome" <reply to thread> wrote....

  9. Nope. Not me. What's slimdogs?
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