Running a bike light on 12V (automotive)- Mtbr.com
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  1. #1
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    Running a bike light on 12V (automotive)

    Hi, im new here and i have a fairly simple question i want to run 2 thorfire bl01 (chinese bike light) i had laying around that i have never used. I want to put it on a snowmobile as auxilary light.

    That battery pack is 3.9V fully charged and the led receive 3.2V on high (mesured on led +/- post) im pretty sure i can not wire them direct with the 14.6/14.8V running voltage of the snowmobile.
    I have ordered a buck converter to lower my voltage to 3.9v.

    The light ThorFire BL01 Bike Headlight Cree XM-L2 LED Bicycle Headlamp Light Set Heavy Rain IPX7 Waterproof with Free 5 LED Taillight 8800mAh Battery Pack for Max 57H Cycling: Amazon.ca: Tools & Home Improvement

    My question is is there a better way to wire this set up?
    Since i dont care about running time can i ''boost'' my voltage a bit to get more lumens or i will burn the pcb ?

    Also i want to bypass the on/off switch on the back to always on(high) when there power to led (on/off switch start in high mode).

    Any help or new idea will be greatly apreciated since im no expert!
    Thanks

  2. #2
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    Reputation: Flamingtaco's Avatar
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    I think you are going to run into an issue providing a controlled voltage/current to the voltage/current controller that drives each light. The drivers in the lights are designed to work with slowly changing voltages from a battery source, but the buck driving is going to make very fast changes that the led drivers might not be able to keep up with, resulting in over and under current conditions . Odd behavior, damaged components, fire maybe (these are cheap Chinese lights).

    What I would suggest to someone in this situation would be to buy 12V LED driver boards to replace those in the lights. Easy Peasy.

    Optionally, buy or build a transformer that can provide the desired current and voltage to the lights, and add a robust smoothing circuit to it's output. The light's drivers will take care of the rest, and you can use other lights rated for the same range.

    You can toss the drivers in the lights entirely and use the buck converter to control them if it can provide constant current control, and if it can handle the difference between the input and output voltages. Better quality linear buck drivers cannot. PWM controllers can be designed for much larger input/output variances. The cheap Chinese variety tend to be noisy, but this shouldn't be an issue in your application.

    Worse case, parts can't be returned, buck and LED driver's can't handle the voltage difference, use a transformer to drop the voltage input for the buck driver.

    Or... give the parts to someone for a bike light project, and pickup an LED light bar designed for 12V systems. You'll get hella more light from a 16 emitter light bar, it's plug and play, and the cheap Chinese versions run about the same as the Thorlights you have.
    I will suffer no butt-hurt fools!

  3. #3
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    Ok thank you for your input, i will try it and see what happen !

  4. #4
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    Also considering something similar to this myself so is there any update on what you did?

  5. #5
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    Quote Originally Posted by Flamingtaco View Post
    ... pickup an LED light bar designed for 12V systems. You'll get hella more light from a 16 emitter light bar, it's plug and play, and the cheap Chinese versions run about the same as the Thorlights you have.
    So this. There have to be 12V off-road vehicle lights that are simple plug & play. You could also get one of those battery operated emergency spot lights that plug into a cigarette lighter. My uncle had one of these, and it hurt to look at. Seriously bright.
    "a hundred travel books isn't worth one real trip"

  6. #6
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    Its still working perfect, i found that my headlight are always at 14.4 V (controled by the ecm) the voltage dosen't go up or down its stay there no matter what so the light is always getting its 4V by the buck converter.

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