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  • flashlight batteries

    Ok so i have a fenix tk11 with the r2 led. according to fenix it will use either a 18650 or a 2 cr123a. i guess the 18650 is li-ion and the cr's are not. it appears as though the 18650 give you more lumens out put and longer run time. Are these batteries rechargeable, or are there one available that are. Have any of you used these batteries what do you suggest, as far as size brand, rechargeable v primary etc.

  • #2
    18650's are rechargeable. They do give you more lumens and a longer runtime. I recommend these:

    http://www.batteryjunction.com/ultrafire-brc-18650.html
    http://www.batteryjunction.com/wf-139-.html

    Here are primary batteries as well:

    http://www.batteryjunction.com/titan...3a-double.html

    Pretty much the only differences between using primary and rechargeable are with primaries you will have constant regulation (meaning the light will stay the same brightness level for the duration of the battery. Shorter runtime, less ouput) and the rechargeables are only mostly regulated, so light output will drop (but you shouldn't really notice a difference in loss of output with this light. Plus longer runtimes). Primaries you can keep and not worry about charging. I use both.

    I use the rechargeables until I need to change batteries and then put in primaries, until I can get home to recharge or unless I have spare rechargeable around. I always carry spare batteries.

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    • #3
      thanx i'll check em out....

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      • #4
        Originally posted by Brightlight View Post
        Pretty much the only differences between using primary and rechargeable are ...
        Good information, but I found this slightly misleading. Your points may only be apparent in this one particular flashlight.

        Rechargeable Li-Ion batteries come in many shapes and sizes. In this particular case, the 18650 size is roughly equivalent to the size of two CR123A primary batteries stacked on top of each other. The 18650's diameter is slightly larger, so it may not fit in some lights designed for 2xCR123 (not applicable to TK11). Also, the nominal voltage of a CR123 cell is 3 volts. So two stacked in series produces 6 volts. A 18650 cell's nomnal voltage is 3.7 volts. A single 18650 does not have sufficient voltage to drive the LED's circuit in regulated mode and instead reverts to direct drive. That is why the light will dim over use as the 18650 cell drains. When 2 CR123 cells are used, they produce 6 volts, enough to power the regulation circuit. As the CR123 cells drain, the voltage drops until the light can no longer maintain regulation and then the light reverts to direct drive.

        If you decide to use rechargeable Li-Ion cells, make sure you get protected batteries (prevents discharging the battery too far) and a good charger. Over-charging or discharging the battery will cause damage and possibly explosion or fire. If you drain an unprotected battery too far, the cell will "die" and will no longer retain energy.

        Buy GOOD quality batteries! AW brand for rechargeable and Surefire, Energizer, or Duracell for CR123As. There have been multiple reports of citizens and officers using cheap batteries in their lights and resulting in the batteries venting or catching fire. There is one report of an officer's weaponlight catching fire, destroying his weaponlight, handgun, holster, and a bruised ego.

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        • #5
          Hey Beavo, since you seem pretty knowledgeable about batteries, I have a question. I received an email showing where an officers M6X light exploded. Or actually the batteries in the light exploded burning his Glock and leg. I can see them exploding in a charger, or tossing them into a fire. What would cause them to explode in the light when not in use?

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          • #6
            Originally posted by GGG View Post
            Hey Beavo, since you seem pretty knowledgeable about batteries, I have a question. I received an email showing where an officers M6X light exploded. Or actually the batteries in the light exploded burning his Glock and leg. I can see them exploding in a charger, or tossing them into a fire. What would cause them to explode in the light when not in use?

            Those should have been CR123A primary cells (non-rechargeable). Lithium batteries have a very high energy density and contain rather hazardous materials. Poor quality batteries can have interior containments fail and create uncontrolled reactions. This usally results in "venting" where the gases build up and cause the battery to explode. Quality batteries have built in safeguards that release the gas before the battery explodes. However, this gas is highly flammable. A spark created by a short circuit or heat created by the battery itself can result in fire.

            Using two cells with varying levels of depletion result in similar, spectacular results. Because the charge levels are different, one cell attempts to "charge" the other cell. If one cell is nearly depleted and the other is "full", this results in a very rapid discharge of energy. This fast discharge creates alot of heat and could cause the batteries to explode.

            Do not attempt to recharge lithium batteries (primary cells)!

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            • #7
              Thanks, I guess that would explain it.

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              • #8
                Originally posted by beavo451 View Post
                Good information, but I found this slightly misleading. Your points may only be apparent in this one particular flashlight.
                Yes, I guess I should have stated that. Perfect example: My Olight M20 and EagleTac T20C2 brightness level drops rapidly when using 18650's while my M30 is fairly regulated.

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