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Thread: Can I sub a 18650 for two 16340's

  1. #1
    Flashaholic doctordun's Avatar
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    Default Can I sub a 18650 for two 16340's

    I got a laser from china that came with two rechargeable 16340 3.7 volt batteries.
    Can I use one of my 18650 batteries if it fits in the tube?
    And visa versa, can I use two 16340's for a 18650 battery?

  2. #2

    Default Re: Can I sub a 18650 for two 16340's

    It depends.

    2x16340 -> 1x18650 is a "probably." If the circuit needs 5 volts to operate then no. If it has LVP that cuts out at 5.6V then no. But you can just try it. The 18650 shouldn't break anything.

    1x18650 -> 2x16340 is a "probably not." Too much voltage can fry circuits and for many electronics 6 volts is where stuff burns out. It needs to be specially designed to support higher voltages. Check the manual. Don't just try it to see what happens.
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  3. #3
    HKJ's Avatar
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    Default Re: Can I sub a 18650 for two 16340's

    Quote Originally Posted by doctordun View Post
    I got a laser from china that came with two rechargeable 16340 3.7 volt batteries.
    Can I use one of my 18650 batteries if it fits in the tube?
    And visa versa, can I use two 16340's for a 18650 battery?
    It is about the same as asking. Can a 230V device be used on 120VAC.

    And the answer is the same: Maybe, read the specifications.
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  4. #4

    Default Re: Can I sub a 18650 for two 16340's

    Most likely not I would think. 1x18650 is 4.2v while 2x16340 is 8.4v, so unless you are specified a voltage range something like 3-9v you probably can't swap. Trying 4.2v in something designed for 8.4v would be fine, it just might not work. Trying 8.4v in something designed for 4.2v could cause permanent damage. Also an 18650 being larger diameter might not physically fit.
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  5. #5
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    Default Re: Can I sub a 18650 for two 16340's

    Quote Originally Posted by Random Dan View Post
    [...] Trying 8.4v in something designed for 4.2v could cause permanent damage
    including possibly serious user damage, since if some component fails shorted the cells could go into thermal runaway.

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