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Thread: First time wiring up an 18650 & recharge port

  1. #1

    Default First time wiring up an 18650 & recharge port

    Hi, all.
    I'm hoping someone can verify that I've got the right wiring schematic here.
    All I'm trying to do is replace a busted AAA battery pack with 1, an 18650 and 2, a recharge port.


    Actually, typing out this post makes me realize: I may not have a buckpuck, I may have a resistor, so then do I need to add in a new resistor? I'm doing this on a US saber, and says for the green tri-cree, it has a forward voltage @ 1000mA of 3.7V.

    4x AAA -> 18650 conversion:
    4 AAA in series will be 6V
    18650 is 4.2V

    So then consulting :
    AAA build:
    R = ( 6 - 3.7 ) / 1 = 2.3 ohm
    P = R * I^2 = 2.3 * 1^2 = 2.3 W, so I probably have a 2 ohm, 2 watt resistor already in there.
    What I'll need is:
    R = ( 4.2 - 3.7 ) / 1 = 0.5 ohm
    P = 0.5 * 1^2 = 0.5 W, so I'll need to rip out my current resistor and replace it with a 0.5 ohm, 0.5 watt resistor.

    So then my questions are:
    1, is my wiring diagram at the top correct?
    2, are my calculations correct? I have other sabers I need to repair, so I want to make sure my process is correct for (say) a 3.4V LED.
    3, since the 18650 is 3.7V and the green LED is run at 3.7V, can I skip a resistor entirely, or do I still want a tiny resistor?
    4, someday I want to also convert my 2x 14500s setups into using 18650s as well. My thinking is that I just have to make sure I'm buying 7.4V 18650s, and I just replace them without any other mods (I'm pretty sure my Li-ion sabers have buckpucks). Is that correct?

    Thanks in advance for any help!

  2. #2


    The wiring looks correct. The 2ohm resistor is larger than the 0.5ohm but I doubt if the difference is visible. its good practice to resistor all LEDS for safety/peace of mind.


  3. #3


    Thanks for the confirmation and info! Much appreciated.


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