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<p>It is recommended to use a Fenix 21700 Li-ion battery. Other Li-ion batteries are not recommended. As an unmatched battery may cause the flashlight to fail to work normally.</p>

It is recommended to use a Fenix 21700 Li-ion battery. Other Li-ion batteries are not recommended. As an unmatched battery may cause the flashlight to fail to work normally.

What kind of battery can be used in TK21R?

Product Information

Fenix TK21R FAQs

Am I allowed to do modifications to my Fenix flashlight?

Are all Fenix bike light mounts compatible with all Fenix bike lights?

Are all tactical flashlights considered weapon lights?

Are Fenix flashlights waterproof?

Are Fenix headlamps waterproof?

Are Fenix products made in the USA?

Are there any Fenix flashlights for mining, industrial work, or other hazardous environments?

Are there any Fenix flashlights with a TIR lens?

Are there any retailers who carry Fenix flashlights?

Are there instructions on how to take apart my Fenix flashlight?

Batteries leaked or corroded in my Fenix flashlight. What should I do?

Can a 16340 battery be used in place of a CR123A battery?

Can a USB rechargeable battery be charged in a Fenix USB rechargeable flashlight?

Can Fenix AA and AAA flashlights use Energizer lithium batteries?

Can Fenix AA flashlights use Li/FeS2 batteries?

Can Fenix flashlights take extreme temperatures like high 120 degrees?

Can Fenix headlamps attach to a baseball cap?

Can Fenix headlamps work in subzero or freezing temperatures?

Can Fenix USB rechargeable flashlights, headlamps, bike lights, and batteries be charged using a computer USB port?

Can I change the bulb in my Fenix flashlight?

Can I change the color of the headband that comes with a Fenix headlamp?

Can I charge an unprotected battery in a Fenix rechargeabe flashlight, headlamp, or bike light?

Can I leave my Fenix rechargeable flashlight plugged in all the time?

Can I mount my Fenix flashlight onto a shotgun?

Can I order a belt clip for my Fenix flashlight?

Can I order a new tail switch rubber boot cover for my Fenix flashlight?

Can I order a two-way pocket clip for my Fenix flashlight?

Can I power my Fenix flashlight or headlamp with non-rechargeable lithium batteries?

Can I purchase a headband for Fenix headlamp?

Can I purchase a more powerful battery for my Fenix HL40R headlamp than the 2000mAh battery it comes with?

Can I purchase a tail cap or a tail switch for my Fenix flashlight?

Can I purchase o-rings for my Fenix flashlight?

Can I purchase the Fenix BA4C battery case?

Can I recharge my USB rechargeable flashlight using a USB charger for my iPhone or iPad?

Can I register multiple Fenix lights using a single e-mail?

Can I remove the strike bezel on my Fenix flashlight and still use the flashlight?

Can I switch the tail caps of one Fenix flashlight with another?

Can I upgrade any internal components of my older Fenix flashlight with a newer version?

Can I upgrade or trade-in my old or discontinued unit to a current model?

Can I use a Fenix 16340 battery in my older Fenix E15 that was released before 2016?

Can I use a rechargeable lithium-ion battery in my Fenix PD20 flashlight?

Can I use a USB AC adapter with a Fenix USB rechargeable flashlight or Fenix charger?

Can I use any 18650 battery in my Fenix flashlight?

Can I use Duracell batteries in my Fenix flashlight?

Can I use rechargeable RC123A batteries in Fenix lights?

Can I use Samsung batteries in Fenix lights?

Can I use the Fenix E15 on a keychain?

Can I use unprotected 18650 lithium-ion batteries in my Fenix flashlight, headlamp, or bike light?

Can the discharge feature on Fenix chargers power an iPhone?

Can the Fenix HL35 headlamp be tilted up or down or is the headlamp locked in place?

Can the top portion of the headband be removed and re-installed on Fenix headlamps?

Can you explain more about what the APF technology is, how the technology works, and how the technology is different from the hall-effect switches?

Can you upgrade the battery included with a flashlight to a battery with higher milliamps?

Do any Fenix bike lights fit on the vertical bar?

Do Fenix 18650 lithium ion batteries work in other non-Fenix devices?

Do Fenix flashlights come with batteries?

Do Fenix flashlights have glass lenses?

Do Fenix flashlights have parasitic drain?

Do Fenix flashlights have reverse polarity protection?

Do Fenix flashlights that use APF technology require a mechanical tail switch, electronic side switch, or rotary switch?

Do Fenix flashlights use CREE LED bulbs?

Do Fenix flashlights, headlamps, or bike lights work with Nitecore batteries?

Do I have to recharge the batteries in my Fenix rechargeable flashlight or can I use a battery charger?

Do the batteries in my rechargeable flashlight have to be charged through the flashlight or can I use a battery charger?

Do you carry tactical flashlights that feature a red light?

Do you have a Fenix battery charger for the Fenix ARB-L26-4500P battery?

Do you have a Fenix flashlight that is considered intrinsically safe?

Do you have a Fenix flashlight with a single output?

Do you have a Fenix flashlight with an infrared beam?

Do you have a Fenix ultraviolet flashlight?

Do you have a flashing front or back Fenix light for bikes?

Do you have a flashlight that features an adjustable focus, is rechargeable, and has a good LED?

Do you have a headlamp with a single function or output?

Do you have a rubber headband or strap to help keep my Fenix headlamp on my hat?

Do you have a small Fenix flashlight with a red beam?

Do you have a small Fenix pocket flashlight with an output of around 1000 lumens?

Do you have alternate pocket clips for Fenix flashlights?

Do you have any Fenix bike lights that run on AA batteries?

Do you have any Fenix flashlights that run on 10440 batteries?

Do you have any Fenix flashlights with an adjustable focus?

Do you have any open-box, refurbished, or returned Fenix flashlights, headlamps, bike lights, and accessories?

Do you have discounts during Black Friday?

Do you have MSDS sheets for Fenix products?

Do you have upgrades for my Fenix flashlight?

Do you have USB rechargeable AAAA batteries?

Do you offer any package deals?

Do you offer discounts for military or first responders?

Do you sell belt holsters for my Fenix flashlight?

Do you sell bulbs for Fenix flashlights?

Do you sell micro USB charging cables?

Do you sell rechargeable CR123A lithium batteries?

Do you sell replacement brackets for Fenix headlamps?

Do you still sell the ARE-C2 charger?

Does APF allow Fenix lights to be brighter than 2200 lumens?

Does Fenix make a headlamp that has different colored LEDs such as red, green, blue?

Does Fenix make a headlamp with a red LED that has more than one lumen?

Does Fenix make a momentary-on only tail switch for Fenix tactical flashlights like the PD35 TAC?

Does Fenix offer any flashlights for marine or diving use?

Does the APF technology in Fenix lights cause a flicker?

Does the Fenix 26650 battery fit inside a Fenix PD35 (V1), PD35 V2.0, or PD35 TAC flashlight?

General FAQs

Can I buy a replacement holster for my Fenix flashlight?

Can I buy a replacement pocket clip for my Fenix flashlight?

Can I get a battery cable extension for my Fenix headlamp or bike light?

Can I purchase the AC and DC chargers for the Fenix RC40 flashlight?

Can you access strobe on the Fenix TK16 (V1) using the AER-03 remote pressure switch?

Can you purchase extra mounts for Fenix bike lights?

Do you have a gun mount for the Fenix PD25 LED flashlight?

Do you have a protective storage case for 14500 batteries?

Do you have a storage case for 26650 batteries?

Do you have any filters that will fit a flashlight with 28mm head diameter?

Do you have any wands or traffic cones for my Fenix flashlight?

Do you sell diffusers or filters that would fit my Fenix headlamp?

Do you still sell the Fenix NW20 Emergency Whistle?

Does the ALB-10 bike mount work with the Fenix BC21R (V1) bike light?

How can I get a replacement USB port dust cover for my Fenix rechargeable flashlight?

How do the Fenix remote pressure switches function?

I need a new velcro strip for my Fenix pressure switch. Where can I get one?

Is it necessary to screw the lid down of the battery storage container to completely achieve a waterproof seal?

Is the BC21R (V1) compatible with any other Fenix bike mounts?

Is there a remote pressure switch for the Fenix PD32 (V1) and PD32 UE flashlight?

Is there a remote pressure switch that is compatible with the Fenix FD30?

What are the smallest Fenix AA or AAA flashlights that fit with the AD301 red filter?

What does the Limited Lifetime Warranty Cover?

What Fenix flashlights are compatible with the ALF-18 battery holder?

What Fenix headlamps are compatible with the AFH-02 Headband?

What headlamps fit inside the APB-20 storage bag?

What is the difference between the Fenix AER-02 V2 remote pressure switch and the Fenix AER-03 V2 remote pressure switch?

What remote pressure switches work with the Fenix ALG-05 mount?

Which Fenix bike lights are compatible with the Fenix ALD-08 helmet holder?

Which Fenix flashlights does the ALP-MT flashlight holster work with?

Which filter is compatible with the Fenix PD30 flashlight?

Which filters will fit my Fenix flashlight?

Which remote pressure switch is compatible with the Fenix UC35 (V1) or UC35 V2.0 rechargeable flashlight?

Will I get the full output on my Fenix flashlight if I put a filter over the lens?

Fenix Accessory FAQs

Are ARB-L18 and ARB-L2 batteries interchangeable?

Can 14500 lithium-ion batteries be used in most other AA devices?

Can Fenix chargers charge unprotected 18650 cells?

Can I leave my rechargeable flashlight or battery plugged in all the time?

Can I order an extra battery for the Fenix UC40UE?

Can I purchase an extra battery for the TK65R?

Can I safely use the batteries in my Fenix flashlight until they are fully drained?

Can I use a 3500mAh battery with a 3400mAh battery?

Can I use and recharge Fenix ARB-L14-1600U USB Rechargeable Li-ion 14500 Battery in the RC05 Flashlight?

Can I use another brand's battery at the same time as a Fenix battery?

Can I use Energizer batteries in my Fenix light?

Can I use Panasonic li-ion batteries in my Fenix light?

Can I use the ARB-L18-3500U USB rechargeable battery in my Fenix HL60R headlamp?

Can I use UltraFire batteries in my Fenix light?

Can my Fenix 18650 lithium-ion batteries be left in a below zero storage area for days at a time and still function when the light is needed?

Can the 26650 4500mAh battery be used in the Fenix PD35 TAC flashlight?

Can the ARB-L1-2600 work in all Fenix flashlights?

Can the ARB-L18-3400 battery be charged inside the older Fenix UC30 with a USB cable?

Can the Fenix 4800 mAh High Quality 26650 battery be used in the New Fenix HL60R headlamp?

Can the Fenix ARB-L18 3500 mAh battery be charged and used in the Fenix CL25R or the CL30R LED Rechargeable Lanterns?

Can the Fenix ARB-L18-3500U USB batteries be recharged in Fenix chargers?

Can the Fenix RC11 run on the Fenix ARB-L18-3500U USB rechargeable battery?

Can you use a Fenix ARB-L14-1600U 14500 battery with the Fenix E12 (V1) or E12 V2.0 flashlights?

Can you use an ARB-L18-3400 18650 battery in the Fenix TK09 flashlight?

Can you use four CR123A batteries instead of two 18650 batteries in the Fenix TK47 UE?

Do I need to purchase a battery charger for the Fenix PD25's or PD25R's rechargeable battery?

Do Orbtronic batteries work in Fenix flashlights?

Do the Fenix USB rechargeable batteries come with a charging cable?

Do you have 18350 batteries?

Do you have Fenix 18650 batteries with a built-in micro USB charging port?

We do not carry AAAA batteries. We do carry AAA batteries, but they are not USB rechargeable. If you're interested in learning more about batteries, check out our blog where we cover different battery types.  Did this answer your question?   Last up

Do you sell high quality rechargeable AAA and AA batteries?

Do your lithium ion batteries come fully charged?

Do your Ni-MH rechargeable batteries come fully charged?

How big are the Fenix 14500 batteries?

How big are the Fenix 16340 batteries?

How big are the Fenix 18650 batteries?

How big are the Fenix 21700 batteries?

How big are the Fenix 26650 batteries

How can I tell if my battery is fully charged?

How can I tell when my Fenix USB rechargeable battery is fully charged?

How do I know when my battery is finished charging?

How long do Fenix batteries last?

How long do rechargeable lithium ion batteries last?

How long does it take for an ARB-L18-3500U battery to charge via cable?

How long does it take to charge a Fenix battery in a Fenix charger?

How long does it take to fully charge a Fenix ARB-L18-3500U battery using its USB charging function?

How long of a runtime will I see with the Fenix ARB-L18-3500 18650 battery versus the ARB-L18-2600 18650 battery?

How much longer would a Fenix flashlight run if I were to use an 18650 3500mAh battery vs an 18650 2600mAh battery?

How would you compare the performance of the Ni-MH 1.2V battery and the lithium 1.5V battery?

Fenix Battery FAQs

What kind of battery can be used in TK21R?Updated 8 hours ago