FENIX FX-ARB-L21-4000P BATTERY PLASTIC BOX

The Fenix ARB-L21-4000P is a 4000 mAh 21700 lithium-ion battery for higher-draw flashlights whose manufacturer has approved this model. The battery has a continuous output current of 10 A and a short-term peak current of up to 18 A. This version comes in a plastic case.

Suitable for

• Powering a higher-draw 21700 flashlight

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

• Use in a flashlight for outdoor work whose manual permits the ARB-L21-4000P

• Charging in a compatible 21700 lithium-ion battery charger

Why choose the Fenix ARB-L21-4000P?

• The 10 A continuous current is suitable for compatible higher-draw flashlights.

• The protection circuit helps protect the battery against short circuits, overcharging and deep discharge.

• The steel casing protects the battery cell against mechanical impacts.

• Pressure relief vents help reduce internal battery pressure.

Technical specifications

• Manufacturer: Fenix

• Model: ARB-L21-4000P

• Battery type: protected 21700 lithium-ion battery

• Nominal capacity: 4000 mAh

• Nominal voltage: 3.6 V

• Maximum continuous output current: 10 A

• Maximum short-term output current: 18 A

• Charging current in a separate charger: 1 A recommended, 4 A maximum

• Length: 76 mm

• Diameter: 21.5 mm

• Weight: 70 g

• Packaging: plastic case

Included

• 1 × Fenix ARB-L21-4000P battery in a plastic case

Frequently asked questions

What do 10 A and 18 A mean in the battery specifications?

10 A is the battery's maximum continuous output current. Up to 18 A is the short-term peak current. When choosing a battery for your flashlight, refer to the battery models permitted in its manual.

Is the ARB-L21-4000P compatible with the Fenix TK20R V2.0 flashlight?

Yes. Fenix lists the ARB-L21-4000P among the compatible batteries for this flashlight.

Can the battery be charged in the Fenix ARE-A4 charger?

Yes. The Fenix ARE-A4 supports this 21700 lithium-ion battery. The recommended charging current for the battery in a separate charger is 1 A.

When is the Fenix ARB-L21-4000P the right choice?

Choose the 4000P if your flashlight supports this model and you need a battery with a high current rating. If the same flashlight also supports the ARB-L21-5000U and a higher nominal capacity and USB-C charging directly on the battery are more important to you, it is worth comparing the 5000U.

Our recommendation

Before ordering, check the list of permitted batteries in your flashlight's manual. If the flashlight has been sold in several generations, also check its exact model designation. In addition to the 21700 designation, the battery's external dimensions and current rating matter. If you charge the battery separately, check that the charger supports lithium-ion batteries and accommodates a 76 mm long cell.

Before extended outdoor work, test the spare battery in the flashlight and at the brightness level you actually use. Flashlight runtime also depends on the light mode and temperature. If you use several interchangeable batteries, label their storage cases to keep charged and used batteries separate. During transport, keep the battery terminals isolated from metal objects.

High-current 21700 replacement battery

The ARB-L21-4000P is suitable for a compatible flashlight that requires a continuous battery output current of up to 10 A. The product code for the version in a plastic case is FX-ARB-L21-4000P.