AA battery pack for Magicshine 808 - Possible?- Mtbr.com
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  1. #1
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    AA battery pack for Magicshine 808 - Possible?

    Hi all,

    Trying to find out if it is possible to set up a battery pack using AA alkalines for my Magicshine MJ-808. For my long distance, unsupported rides there is no way I can consistently recharge batteries. But many times I could swing off route to buy batteries.

    Is this possible? Thanks for the help.

  2. #2
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    Is it not just easier and cost effective to carry a spare magicshine battery that's already charged up?
    The money you'll spend on alkaline AA's will soon add up.
    Or you can of course make your own battery from 18650's, namely Panasonic's. You can buy the magicshine lead from a few places apart from DX. That way you could have a 6200mah battery from 4xpanasonic ncr's.

  3. #3
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    To get close to the nominal voltage (7.2 volts), you need five AAs in series (end-to-end, like in a typical multi-cell flashlight). Using very round numbers of 700mAh per battery, you'd probably want 15 batteries total to get close to an MS power pack. I think they call that 3 parallel, 5 series or 3P5S.

    Have you considered solar recharging? Or running a lesser light?

    edit: oops! I totally botched the 700mAh number... a regular alkaline should be around 2000mAh, so my new and improved suggestion is 10 batteries, 2P5S. Still not featherweight. There's a guy on CPF I've done business with named Cottonpickers that does nice solar panel/recharger combos.
    Last edited by borrower; 01-31-2012 at 09:41 AM.
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  4. #4
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    I have some 10xAA holders that are used for 14.4v, but could be modded to take 2x5AAs.
    If you use lithium primaries they are nice and light at least.

    PM me and I can send you one.

  5. #5
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    Thanks.

    Hoped this would be easier. Now I see why most are using helmet mounted AA flashlights.

    A backup battery would work, but on a multi-day event I would need more than one. I will look into solar recharging. Or get a lower lumen AA flashlight and ride slower.

  6. #6
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    Alkaline batteries' capacity drops off severely when they are subjected to high load. So say an AA battery has a normal capacity of ~2000mah (making up all these numbers) if it's being discharged at up to 200ma, when you have a lamp pulling 800ma the battery only delivers 1.5 hours of light, effectively having only 1200mah capacity (again, all numbers made up, but you can find charts of battery capacity vs discharge rate online). This is why Dinotte lights, though they sell high lumen (~200 lumen) lights with AA packs say to only use rechargeable cells and only use alkaline or disposable lithium cells if you are in a pinch, and not to expect them to last longer than say half an hour.

    I would look into a dynamo hub if I were you. It seems more robust and less complicated than solar charging. Or look for a light that maximizes efficiency (your current light might be fine in this regard) and build up a massive pack for it (or buy a remote controlled airplane/car/helicopter battery pack prebuilt- they come in all sizes and voltages, up to very high capacity).

    I assume if you're on MTBR forum you're riding trails or unpaved paths most likely, so you probably want the extra light. It's a bugger being limited in speed by not having enough light, especially when you're on a tour and not just out for a quick ride.

    Good luck!

  7. #7
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    Quote Originally Posted by Rockin View Post
    Thanks.

    Hoped this would be easier. Now I see why most are using helmet mounted AA flashlights.

    A backup battery would work, but on a multi-day event I would need more than one. I will look into solar recharging. Or get a lower lumen AA flashlight and ride slower.
    I use an L-flex in my lights, configured for multi-mode. With 5 even brightness levels, I can find the ideal brightness for any situation, and it's often not full-on.

    A bit like using gears efficiently, especially as XM-Ls are much more efficient at lower current levels. I get far more run time this way than if I only had 2 brightness levels.

    Lithium AA batteries don't have the same problem with sag under high draw as alkalines.
    I had 2x4 AA pack made up and sealed as a backup for long races, with a shelf life of a decade or more.

  8. #8
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    You may want to look at this post

    AA battery pack for original Magicshine

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