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Thread: Lifepo4 usage for 18650 lights

  1. #1

    Default Lifepo4 usage for 18650 lights

    From the limited reading I've done on LiFepo4, it seems that it's considered a safer alternative to lithium ion but the main drawback is capacity. Have these batteries gotten better lately and is anyone using them in single 18650\2xcr123 lights in place of lithium ion? Would runtime at various outputs be basically cut in half using LiFepo4?

  2. #2
    Flashaholic* Crazyeddiethefirst's Avatar
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    Default Lifepo4 usage for 18650 lights

    I have six 16340 Lifepo4 cells that I run in various Surefire lights. I no longer am out in the field for days at a time, so my usage is in 10-15” increments. Because of that I cannot speak to the length of overall runtime, but I have not seen much difference between the Lithium Phosphate and Lithium ion cells. Perhaps do a CPF search for HKJ & see if he has tested them-from what I have seen he is a very reliable expert on batteries...
    Last edited by Crazyeddiethefirst; 02-12-2018 at 10:55 AM.

  3. #3

    Default Re: Lifepo4 usage for 18650 lights

    Thanks Eddie. What cells are you using?
    Quote Originally Posted by Crazyeddiethefirst View Post
    I have six 16340 Lifepo4 cells that I run in various Surefire lights. I no longer am out in the field for days at a time, so my usage is in 10-15” increments. Because of that I cannot speak to the length of overall runtime, but I have not seen much difference between the Lithium Phosphate and Lithium ion cells. Perhaps do a CPF search for HKJ & see if he has tested them-from what I have seen he is a very reliable expert on batteries...

  4. #4
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    Default Re: Lifepo4 usage for 18650 lights

    For a light meant for a single 18650 a single lifepo4 cell will give a much lower output unless it's a ~300 or less lumen light. Then the cell will be at around the same as the forward voltage of the led and brightness should be the same

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    Flashaholic* Crazyeddiethefirst's Avatar
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    Default Re: Lifepo4 usage for 18650 lights

    Hi Gurdygurds,
    The K2 LifePO4 cells are what I am using-I happen to catch a few really good deals and bought them used but only a few months old. I also use the 16650 & 17650 Lithium ion cells. Both are good options for the Surefire 6px or E1 & E2 with led drop ins.

  6. #6
    Flashaholic*
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    Default Re: Lifepo4 usage for 18650 lights

    LifePO4 = LFP = Lithium Ion.
    I especially use them in headlamps.
    I don't need the extra runtime of the typical LCO. The runtime difference is insignificant for my use.
    If I think I need extra runtime, most likely I really need to take spare batteries with me and expect a battery swap.
    I don't like the LCO cutoff.
    I can achieve relative longer runtimes by keep my batteries freshly charged, instead of using my light for 5 minutes and not charging it.
    LFP can maintain longer runtimes over the lifetime.
    I like the idea my safety isn't dependent on an electronic circuit that might be defective, or fail to work over time, usage, or abuse.
    Wish: 1) Super low beacon; easy find flashlight. 2) Low voltage indicator, so not stranded without light. 3) Simple, one handed control ring mode changer (magnetic control ring). 4) Flood beam for walking/tasks. 5) Pocket carry. 6) LiFePO4.


  7. #7
    Flashaholic* Crazyeddiethefirst's Avatar
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    Default Re: Lifepo4 usage for 18650 lights

    Snakyjake, I thought most rechargeable 16340 & 18650 cells were Lithium Ion(3.6/3.7-4.2) and LifePO4 were Lithium Phosphate(max 3.2v) which is why Surefire sold them-so customers could use the LifePO4 cells(rechargeable), in place of Lithium Primary Cells(3.0v). Please educate me if I am wrong...

  8. #8
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Lifepo4 usage for 18650 lights

    Quote Originally Posted by Crazyeddiethefirst View Post
    Snakyjake, I thought most rechargeable 16340 & 18650 cells were Lithium Ion(3.6/3.7-4.2) and LifePO4 were Lithium Phosphate(max 3.2v) which is why Surefire sold them-so customers could use the LifePO4 cells(rechargeable), in place of Lithium Primary Cells(3.0v). Please educate me if I am wrong...
    You're correct.

    LiFePO4 has a higher 'thermal runaway' point, so it's safer than Li-Co and even Li-Mn, but now we're pretty much in 'hybrid' territory, so good luck figuring out what we're actually using and at what point, or temperature, things start going dwanky on us.

    I can charge up IFR chemistry cells, but I've never felt the need to try them out. I only have one SF light and I've put in a Redilast 4.2v P60 and never use the light, anyhow.

    For devices that use a CR123A where the cost of CR123As is prohibitive, I would try out the Tenergys, or K2s.

    Chris
    Convoy: S2, S2+, M1, M2, Fenix: P1D, PD32, HL30, ET: D25C Ti, SF: 6P, ZL: SC-600, Klarus: P2A, Jetbeam: BA-20, Icon: Rogue 1, L3: L10, Xeno: E03, ShiningBeam: I-Mini, Olight: i3s, SWM: D40A, M11R, V11R, Maglite: 6Ds, MMs, Solitaires, LaCrosse BC-700, Maha C-9000, XTAR VP2, MP1S, XP1, MC1+, WP2 II, NiteCore i4, v2.

  9. #9

    Default Re: Lifepo4 usage for 18650 lights

    I've been checking several of my 1x18650/2xCR123A flashlights and found that most drop out of regulation with an 18650 when the battery voltage gets down to about 3.4 - 3.6 volts which happens when the battery is only partly discharged. Apparently most of them use either a passive regulator or a buck type switching regulator, both of which require the battery voltage to be a bit above the LED forward voltage (typically 3.2 - 3.5 volts or so). I've discovered that at least one type of "high voltage" (safely chargeable to 4.35 V) cell maintains a voltage above the regulation limit for a lot longer than typical cells, so that's what I'm currently using. But a single LiFePO4 cell wouldn't have a high enough voltage to allow regulation and get the maximum output from the flashlights. Some lights would switch to a lower output level and some turn off altogether in a very short time after installing a freshly charged 18650 LiFePO4 cell. They shouldn't have any trouble with two LiFePO4 CR123A type cells, though.

    c_c

  10. #10

    Default Re: Lifepo4 usage for 18650 lights

    Thanks for the responses fellas.

  11. #11
    Flashaholic* Crazyeddiethefirst's Avatar
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    Default Re: Lifepo4 usage for 18650 lights

    Hey Gurdygurds,
    I just picked up 4 Tenergy Life4PO4 16340 cells for $9.95. It will take a while to get some real life experience with them but I will let you know how they compare to the K2 cells....

  12. #12

    Default Re: Lifepo4 usage for 18650 lights

    Right on Eddie. What lights will you be using them in?
    Quote Originally Posted by Crazyeddiethefirst View Post
    Hey Gurdygurds,
    I just picked up 4 Tenergy Life4PO4 16340 cells for $9.95. It will take a while to get some real life experience with them but I will let you know how they compare to the K2 cells....

  13. #13
    Flashaholic* Crazyeddiethefirst's Avatar
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    Default Re: Lifepo4 usage for 18650 lights

    I kinda like the Surefire 6P & have at least 1/2 dozen as well as the 6PX/G2X(another half dozen)...the “users” will get the LiPO4 while those in “ready mode” are stuffed with Surefire & Energizer primaries...

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