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  1. #1
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    Tail light brightness question: How much is too much?

    Just out of curiosity, supposing a public road use only during daylight hours for obvious reasons, would this be a good solution? What diffuser optic would you install on it? Would a 12v battery in the bottle carrier suffice to feed it for a few hours? Thanks for the feedback

  2. #2
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    Your issue biggest will be lugging a battery big enough to power it. According to the specs, it is 100W & needs 18-22 volts, ie ~5.5A. Common bike light batteries use 4 x 18650. To run this light you would need 5 x 18650 in series to get enough voltage & 4 in parallel to run it for ~2.5 hours - ie 20 cells. That is a huge battery & will be expensive to boot.

  3. #3
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    Considering a 1.5 per 18650 if bought in a 20 pack it would be 30 total, not too bad, but would I be able to power it directly or would I need a circuit driver?
    Or, more advanced solution, I could configure it like this: 5 watt fixed and 25 watt when I brake at night, 25 watt fixed and 100 watt when I brake during the day...


    Edit: how about something like this? Lipo Li-Po LiPoly Lithium-Polymer 22,2v 2800mah 25C 6S Lion Akku Batterie Power | eBay

  4. #4
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    That battery will power it for 30 minutes @ 5.5A. I think you will find that 1.5 per 18650 will not be the 3400mAh I used in the above calcs, but more like about 2000 mAh, ie you would need 35 x 2000mAh 18650s to run the light for 2.5 hours.

    As for whether you can power it directly the fleabay ad states "LED DRIVER and HEAT SINK must be used in order to work or test !"

  5. #5
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    I think I'll rely on my electronics' expert friend to build a driver then, with dimming modes too eheeheh
    What about cooling, do you think a stock Intel i7 920 heathsink would suffice (even with the fan turned off?)?

  6. #6
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    Re: Tail light brightness question: How much is too much?

    That thing would be seriously dangerous with 5000 lumens even during the daytime. Why waste your time lugging the weight of that thing around when you can achieve awesome visibility in daylight with 3 x XP-E2's ?

    Description says 3kg heatsink required.

  7. #7
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    I wired two of the magic shine tail light together and use just one dual cell litho pack. That two 3 watt led bulbs so yeah it's one the to bright side of things for down town city use but its great for the country roads I ride. I keep on bulb on solid and the other on flashing. My family and freinds who have come across me while I'm riding at random times said they thought I was an emergency vehicle till they within a hundred feet or so. People would pass right next to me with the old standard tail light, now they cross the yellow line with both tires because they have no idea WTF that is flashing in front of them.

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