FENIX ARB-L21-5000U BATTERY

The Fenix ARB-L21-5000U is a 5000 mAh 21700 lithium-ion battery for a compatible flashlight or headlamp. The battery has its own USB-C charging port, so you can charge the spare battery while the light runs on another battery. An indicator shows when charging is complete.

Suitable for

• Use as a USB-C rechargeable spare battery for hiking or travel

• Use as a replacement battery for the Fenix TK20R V2.0 flashlight

• Use in a compatible light powered by a 21700 battery during extended outdoor work

Why choose the Fenix ARB-L21-5000U?

• 5000 mAh capacity for a compatible 21700-powered light

• Can be charged directly via the USB-C port or in a suitable battery charger

• Protection circuit helps protect the battery against short circuits, overcharging and over-discharging

• Pressure relief vents help reduce internal battery pressure

Technical specifications

• Manufacturer: Fenix

• Model: ARB-L21-5000U

• Battery type: protected 21700 lithium-ion battery

• Capacity: 5000 mAh

• Nominal voltage: 3.6 V

• Charging port: USB-C

• Charging current via USB-C: up to 2 A

• Charging current in a separate charger: 1 A recommended, 5 A maximum

• Charging indicator: red while charging, blue when fully charged

• Charging cycles: 500 according to the manufacturer

• Length: 76 mm

• Diameter: 21.5 mm

• Weight: 72.5 g

Included

• 1 × Fenix ARB-L21-5000U battery

Frequently asked questions

What cable is needed to charge the Fenix ARB-L21-5000U?

You will need a USB-C charging cable compatible with the battery's port and a USB power source. The cable must be selected separately.

Which Fenix battery chargers are compatible with the 5000U battery?

Fenix Lighting lists the ARE-A2, ARE-A4, ARE-D1, ARE-D2 and ARE-X1 V2.0 as compatible chargers.

Is the Fenix ARB-L21-5000U compatible with the TK20R V2.0 flashlight?

Yes. Fenix confirms that this battery is compatible with the TK20R V2.0. For other lights, check the manual for the permitted battery type and dimensions.

When is the Fenix ARB-L21-5000U the right choice?

The 5000U is a good choice if you want to charge the battery separately from the light and already carry USB-C charging equipment. If you usually charge a compatible battery in the light or in a separate battery charger, the ARB-L21-5000 V2.0 offers the same nominal capacity.

Our recommendation

Before ordering, check the exact model of your light and the designation on your current battery. Check the manual to see whether the light supports a protected 21700 battery measuring 76 mm in length and 21.5 mm in diameter. Even within the same size class, batteries can differ in external dimensions and contact shape. If you plan to charge the battery while hiking or travelling, test it at home with the cable and power source you intend to take with you.

On a longer trip, keep a charged spare battery in a suitable battery case, with its terminals separated from metal objects. If you need the light for several evenings in a row, estimate the runtime based on the light mode you actually use. This will help you decide whether one spare battery is enough or whether you also need a way to charge it.

21700 spare battery with USB-C charging

The Fenix ARB-L21-5000U is suitable for users of 21700-powered lights who want to charge the battery directly via a cable. Find the right model using product code FX-ARB-L21-5000U.