Advice on converting Magicshine MJ-808 to run on AA disposables- Mtbr.com
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  1. #1
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    Advice on converting Magicshine MJ-808 to run on AA disposables

    I'm planning on doing some multi-day bike-packing trips/races this year and I'm thinking it would be good to have a bright light that doesn't run on rechargeable batteries, but disposable AA (Lithium or Alkaline), for quick refuels at convenience stores.

    I have a Dinotte 200L AA, which I don't think is bright enough for this purpose.
    I also have a Magicshine (older version), which is plenty bright.
    So my thought is to convert it.

    I'm not all that electrically inclined, so I'm hoping for some help/advice on this.

    I bought a 6x AA holder and have run 6 AA Nimh on the light with success.
    6 fully charged Nimh AA in series have similar unloaded voltage (8.4v) as the Li-ion Pack.
    Run time was a little over an hour on high.
    When running on High with fresh batteries the voltage is 7.15V.
    Which makes the fuel gauge led turn red.

    For Lithium disposables, I'm thinking of running 5 in series which should give starting unloaded voltage of 8.5 (1.7 x 5) volts.

    For Alkalines, I'd like to run 6x, but I'm not sure if the light can handle the 9v starting voltage.
    Running 5 x alkalines seems a bit low at 7.5 volts starting.

    Do this sound reasonable / possible?

    Thanks,
    Kevin

  2. #2
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  3. #3
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    Thanks for the response.

    So if the driver is rated to 10v, how safe is it run it at 9V?
    I assume it good for the driver to some amount of margin over the input voltage.
    I don't plan on doing any modifications to the light head.

  4. #4
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    engineers like to build in margins :-)

  5. #5
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    6 fully charged Nimh AA in series have similar unloaded voltage (8.4v) as the Li-ion Pack.
    6s nimh @ 1.2V per cell =
    problem with AA batteries is voltage sag, they cant supply the current quick enough
    yes, i would try 6 alkalines
    ...Scun.thorpe, UK

  6. #6
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    engineers like to build in margins :-)
    Yes we do, and for good reason...I don't want to be without light at 12,000 ft at 3m in a rocky mtn thunderstorm.

    6s nimh @ 1.2V per cell =
    problem with AA batteries is voltage sag, they cant supply the current quick enough
    yes, i would try 6 alkalines
    Thanks. All my Nimh AA measure 1.4V fully charged, is the 1.2V a nominal value or voltage with some nominal load?
    I'll give the 6 alkalines a try. Thanks.

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