Fenix ARB-L21-5000U Rechargeable Battery

(68 customer reviews)

$34.00 $24.95

SKU: ARB-L21-5000U Category:

ARB-L21-5000U is a high capacity 21700 Li-ion USB rechargeable battery built for more power and longer runtimes. This battery has its own USB-C charging port for quick/easy charging without the need for a separate charger. Additional features include a protection circuit in the anode to help prevent short circuits, over charge/discharge and over heating. Pressure relief vents which expel waste gas in the rare case of an internal short circuit preventing an explosion. Battery capacity up to 5000mAh. 500 charging cycles. This product will only work in those models supporting 21700 batteries.  A USB-C charging cord is NOT included. Important Note: THIS BATTERY IS NOT COMPATIBLE WITH 18650 FLASHLIGHTS OR OLDER STYLE CHARGERS. COMPATIBLE CHARGERS ARE THE ARE-A2ARE-A4ARE-D1 OR ARE-D2.

For commercial orders and large purchases, contact us at (888) 775-9996 x6, or
WARNING. Be aware of counterfeit Fenix merchandise in the U.S. marketplace.


Specifications of the ARB-L21-5000U Rechargeable Battery

  • 5000mAh high capacity
  • USB Type-C rechargeable battery
  • Protection circuitry to prevent short circuits
  • Pressure vents to prevent explosions
  • 500 charge cycles
  • Indicator light on battery is red while charging, blue when charged
  • Currently compatible with the HT18, LR35R, PD36R, PD40R V2.0, TK22 V2.0, TK22 UE, and TK30.

Capacity: 5000mAh
Voltage: 3.6V
Charging Current: Recommended 1A, maximum 5A
Weight: 2.6 ounces (72.5g)
Size: Length: 2.99″ (76mm) Diameter: 0.85″ (21.5mm)
Warranty Period: 12 month from date of purchase

68 reviews for Fenix ARB-L21-5000U Rechargeable Battery

  1. robert m. (verified owner)

    If you ask me this is the rechargeable battery design flashlights have been waiting for. With one in the PD40R and one fully charged I should be in good shape next time power goes out.

  2. Corey L. (verified owner)

    Excellent batteries. Have purchased at least ten or more in the past few months. Will order more as needed! Thanks again.

  3. Clint Bennetsen (verified owner)

    These are great maximum amp batteries. I ordered two of them as spares for my Fenix lights.

  4. Brandon Tysinger (verified owner)

    These rechargeable batteries last hours upon hours. I have 2 for my flashlight and never can run either completely dead.

  5. Michael S. (verified owner)

    Wonderful battery. Great power from it. The usb-c connection is very handy.

  6. Buddy G. (verified owner)

    Good quality.

  7. Howard A. (verified owner)

    Quality battery

  8. thai tran (verified owner)

    Good! Do we sale the battery holder

  9. Anonymous (verified owner)

    Fenix always make quality and reliable batteries

  10. Jeff Eikenberry (verified owner)

    I own three of these batteries, and absolutely love them. This newer 21700 format allows for the perfect combination of size, output, and runtime. It actually turned out to be MUCH more convenient than I’d even planned to have the built-in USB-C charging capability! There are almost always USB-C charging cables available to me….multiple rooms in the house, in my car, at my office, and even at the homes of family members….all of which makes it very convenient to be able to charge these without trying to plan on when and where I’ll need to have my battery charger. These batteries charge quickly at 2-amps via their built-in USB-C, and have rock-solid consistency during use and seem like they just keep on running! These batteries make me want to keep buying more 21700 flashlights 😀

  11. Andrew (verified owner)


  12. Ricardo delprado (verified owner)

    Backup power

  13. Dmitri (verified owner)

    Great spare battery to the existing one. It is always helpful to carry a charged backup.

  14. Kris K. (verified owner)

    Good life. Bought one as a backup for my TK22. Have used it quite a bit without needing a recharge so far. Surprised with performance at the moment.

  15. Alan Johnson (verified owner)

    21700 batteries endure elongated episodes.

  16. Nick (verified owner)


  17. David Norton (verified owner)

    Easy to recharge.

  18. Anthony Bautista (verified owner)

    Good rechargable battery

  19. Jessten Hower (verified owner)

    This battery works great

  20. Alden F. (verified owner)

    Great spare to have and can re-charge anywhere using the batteries own port.

  21. Casey (verified owner)

    Battery is incredibly long lasting, for the price they should include a case….

  22. Tommy R. (verified owner)

    Love it!

  23. James M. (verified owner)

    Quality cell, but we will see after more time, say a year

  24. David B. (verified owner)

    I carry this light/battery (PD36R) daily, and while it doesn’t get heavy use…it gets used every day. I’ve had it for about a month and have only had the charge the battery the first time out of the box. Excellent!

  25. joe g. (verified owner)

    Great battery life and built in charging port is a plus!

  26. Richard K. (verified owner)

    So far so good

  27. Daryl T. (verified owner)

    simple charging.

  28. Robert (verified owner)

    Biggest battery I brought besides a car battery.

  29. CATALIN C. (verified owner)

    Good quality product. Best.

  30. Kennard Y. (verified owner)

    What an amazing battery. Loooong life, rechargeable and does not have a proprietary design. Five stars all the way!!!

  31. Chad (verified owner)

    Perfect backup battery

  32. Carlos R. (verified owner)

    holds charge well

  33. Brian O. (verified owner)

    Excellent battery with good battery life and rechargeable

  34. dante (verified owner)

    They are batteries with a built-in recharging port and a cool led indicator incorporated into the anode. No complaints.

  35. Corey L. (verified owner)

    Great batteries. Just like the rest of their products.

  36. Jason Rocco (verified owner)

    Good overpriced battery

  37. Benjamin Aragon (verified owner)

    Wrong battery

  38. Anonymous (verified owner)

    This is a powerful long lasting easy to charge battery.

  39. Paul M. (verified owner)


  40. Jaron (verified owner)

    Great replacement battery! Really like that it includes USB-C charging right on the battery.

  41. Guillermo Parga (verified owner)

    Battery good but flashlight doesn’t turn on anymore.

    • Dianne

      Warranty has contacted you to help troubleshoot any issues on the flashlight

  42. Tyler B. (verified owner)

    Great battery! Awesome design!

  43. Andrew G. (verified owner)

    Works great and holds a good charge.

  44. Ron K. (verified owner)

    Excellent battery. I like the charge port on the battery.

  45. Richard N. (verified owner)

    love the little led charge indicator on the batery

  46. Dino C. (verified owner)

    Long lasting, quick charging!

  47. Darren H. (verified owner)

    So far so good but charges slowly.

  48. Tim Bender (verified owner)

    Works great

  49. Kevin E. (verified owner)

    Tons of juice. Minus one solely due to the lack of onboard charge port combined with the inability to charge in my nightcore charger. I have been forced to charge it inside the PD-36, which is inconvenient when I’d rather swap it out and charge separately. This is a trivial issue though, when seeing the power and capability this battery provides.

  50. Chris B. (verified owner)


  51. Nickolas F. (verified owner)

    I have been using this battery with the PD36R for a few weeks now. I use it nearly every evening when I take the dog for a walk as I live in the woods, probably for 15 to 20 minutes at a time at a lower setting. I fully charged the battery when it first arrived, and I haven’t needed to plug it in again since. By contrast, my old Mag light would go through D cells at the rate of 2 every couple weeks on the same walking path, and those were not rechargeable!

  52. Alan Horne (verified owner)

    I am still (2 weeks) on the 1st battery!
    Incredible staying power.

  53. Tracy A. (verified owner)

    Love it

  54. Jon Cortez (verified owner)

    Great product so far!

  55. John Poggi (verified owner)

    once again, batteries are awesome

  56. Jay (verified owner)

    so sick. battery lasts forever

  57. Creed S. (verified owner)

    Last long….a little expensive

  58. arthur (verified owner)


  59. Anonymous (verified owner)


  60. Rafael (verified owner)

    Excellent service very fast process and the product is of excellent quality. I highly recommend these products

  61. Jerry Robbins (verified owner)

    Great battery.

  62. Bruce Baumel (verified owner)

    Excellent Fenix product

  63. Mitchell (verified owner)

    I’m generally not for rechargeable batteries, but in this instance I took a chance and am not disappointed.

  64. John Petersen (verified owner)

    Fantastic battery that offers long run times and tells you when it’s fully charged.

  65. Kenneth (verified owner)

    Wonderful batteries!

  66. Anonymous (verified owner)

    Perfect battery replacement.

  67. Rod F. (verified owner)

    Great life

  68. George Robinson (verified owner)

    Love it!

Add a review

Your email address will not be published. Required fields are marked *

You may also like…