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Thread: Blue Shark design questions

  1. #1
    Enlightened krutzbeuazen's Avatar
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    Question Blue Shark design questions

    Hello Wayne et al,

    I have a Blue Shark (and Remora), those were shipped on 06/Jul/2009.
    General questions:

    1) Is the copper "c" electrically neutral? I wish to connect it to the flashlight body (connected to negative). Is it okay to have it electrically conencted as well (by touching or conductive epoxy etc)?

    2) Which changes happened since then to the Blue Shark and Remora? I may have a "SOS version" of the Remora and have thermal runaway with the installed diode on the Blue Shark. Anything else I missed?

    I wish to mod a 18650 flashlight (JetBeam RRT-21, a lot of heatsinking mass), I have AW 2600 cells here (Vmin 2.8v?).
    If in any way possible, I wish to use a Nichia NC4U133A UV LED. Vf 14.9 (17.3v max!). Imax 700mA, I would mostly use the "low" and "middle" mode of the Remora.

    3) Is such a configuration (Single LiIon, 14.9v, 700mA) possible at all? I understand I am right at the border of the specs, and beyond the advertised/guaranteed limits.

    4) Would I get around swapping the diode?

    5) Alternatively, 500mA Imax?

    6) Alternatively, 2x RCR123a input and 700mA Imax?


    I read a lot on this topic, but still am feeling unsure. A definite answer would help me a lot.

    Thank you for your help and patience, much appreciated!

    Manuel

  2. #2

    Default Re: Blue Shark design questions

    1) Is the copper "c" electrically neutral? I wish to connect it to the flashlight body (connected to negative). Is it okay to have it electrically conencted as well (by touching or conductive epoxy etc)?

    The copper C is attached to the converter GND. If the body of the flashlight is the battery minus this should be ok.


    2) Which changes happened since then to the Blue Shark and Remora? I may have a "SOS version" of the Remora and have thermal runaway with the installed diode on the Blue Shark. Anything else I missed?

    Offhand, I believe the only major change was the diode to help prevent thermal runaway.


    3) Is such a configuration (Single LiIon, 14.9v, 700mA) possible at all? I understand I am right at the border of the specs, and beyond the advertised/guaranteed limits.

    Yes, that is pushing it. Also, the converter really should have the input voltage over 4V all the time. A single Li-ion battery is not recommended at all for this converter. 3.8V is the absolute minimum and I would derate the driver by 50% under these conditions. So, assuming minimum (near dead state) of the battery is 3.8V I would put the max input current at 1/2 or 2A max. But, a li-ion battery will drop below 3.8V quickly which is why I would not recommend a single cell configuration of any type with a Blue Shark.


    4) Would I get around swapping the diode?

    Changing the one diode with the two smaller ones is possible for anyone who works with SMT components.



    5) Alternatively, 500mA Imax?
    That is possible, but, still for a single cell configuration not ever recommended.

    6) Alternatively, 2x RCR123a input and 700mA Imax?
    This is a better solution over the single cell configuration. Ideally, for a boost configuration the closer your input voltage is to the output the driver has less work to do and runs more efficient.

    Wayne

  3. #3
    Enlightened krutzbeuazen's Avatar
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    Default Re: Blue Shark design questions

    Thank you very much for the clear and detailed answer!
    Although it means I have to redesign my project, I now know it with certainity! :-)
    (Which just means I will have to build something much bigger with the Blue Shark! Harr Harr)

    Cheers,

    Manuel

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