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Fenix ​​Li-ion 21700 USB-C rechargeable battery, 5000 mAh

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Fenix ​​Li-ion 21700 USB-C rechargeable battery

Rechargeable battery Fenix ​​21700 5000 mAh (ARB-L21-5000U) with its own charging USB-C connector . It can be charged by connecting the cable to the USB-C connector (e.g. from a computer, power bank or mobile phone charger) or in a classic Li-ion charger.

Rechargeable batteries Fenix ​​21700 5000 mAh (ARB-L21-5000U) with protective electronics (protected) are based on top technology LiNiCoO2, which brings higher safety and also a longer service life .

Fenix ​​battery protection consists of internal safety mechanisms and protective electronics. The added electronic circuits prevent the cell from being overcharged, its excessive discharge, as well as a short circuit or excessively high current consumption . If the battery electronics evaluates reaching the limit values, it safely disconnects the cell.

The internal protection consists of a separator, the most modern protection against overheating (PTC - Positive Temperature Coefficient) and a special anti-explosion valve. If the gas pressure in the cell exceeds a certain limit, the internal separator separates the electrodes inside the battery and thus de-facto interrupts the exothermic reaction, and the anti-explosion valve releases the excess gas pressure outside the battery. Thanks to the combination of electronic and mechanical (temperature and pressure) protection, Fenix ​​batteries are among the safest Li-ion batteries available .

This battery is intended, for example, for use in the Fenix ​​HT18, PD36R, PD36 TAC, PD40R, TK22 V2.0, TK22 UE, E35 V3.0 and C7 LED lights.

However, it cannot be used in 18650 battery lights due to its larger dimensions!

Due to the length of the battery of 76 millimeters (including protective electronics), it can only be charged in chargers that are adapted to this length. Viď. recommended chargers below.

Charging via USB-C connector

Plug the USB cable into the side USB-C connector, during charging the light at the plus pole of the battery lights up red. It lights up blue when fully charged. The charging cable is not included in the package . If necessary, you can buy a basic USB-C cable or a colored USB-C cable, or you can use a reduction from micro-USB to USB-C.

Recommended chargers

The battery can also be charged in chargers for Li-ion batteries type 21700:
  • Charger Fenix ​​ARE-A2
  • Fenix ​​ARE-D1 USB charger
  • Fenix ​​ARE-D2 USB charger
  • Charger Fenix ​​ARE-A4
  • USB charger SC1
  • Eight-channel USB charger VC8


  • If possible, do not discharge the battery below 2.5 V
  • Do not short-circuit the battery (do not connect the poles of the cell with a wire)
  • Do not throw the battery into fire or water
  • Never insert the battery into the charger upside down (opposite polarities)
  • When using the accumulator, pay attention to the safety principles
  • Use only an adequate charger supporting Li-ion batteries

Product features

Protection against overcharging, total discharge and short circuit (>8A). The protective circuit is attached to the plus pole.
Li-ion rechargeable batteries are characterized by a very high capacity, they do not suffer from memory effect or self-discharge
Li-ion in size 21700 are the best choice in terms of stored energy due to the size and weight of the battery, they are gradually gaining ground, for example in the automotive industry

Product details

Capacity 5000 mAh (tested with a discharge current of 0.2 C with termination at a voltage of 2.5 V and a temperature of 25 °C)
Weight 72 g
Nominal voltage 3.6 V
Maximum current consumption 8 A
Maximum charging current 5 A
Charging current of the built-in USB-C connector 2 A
Charging time approx. 3-4 hours
Dimensions 21.5 mm (diameter) x 76 mm (length) (+/- 0.5 mm)
Battery life more than 500 charging cycles
Recommended operating temperature 0-45 °C (charging) / -20 to + 60 °C (discharging)
Package contents 1 pc USB battery Fenix ​​21700 5000 mAh (ARB-L21-5000U)
product ID 131806

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This American brand specializes in the development and manufacture of bike lights and headlamps. Some of their lights have remaining lighting time indicators and light beam control right from handlebars.

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