Can I use this in flashlights other than Nitecore models?

Yes. Any device that accepts 21700 batteries will work with this cell. It's optimized for Nitecore i-series lights but functions in other brands' 21700-compatible flashlights and electronics.

What does 'used' mean for battery capacity?

Lithium-ion cells lose capacity with charge cycles. A used battery may hold less than its original 5000mAh rating depending on how many times it was charged and how it was stored. Check the seller's listing for specifics on remaining capacity or cycle count.

Do I need a separate charger?

Not if your flashlight has a built-in USB charging port, like the Nitecore i4000R. Otherwise, you'll need a standalone 21700-compatible charger such as the Nitecore UI1.

How does 21700 compare to 18650 batteries?

The 21700 format is slightly larger—21mm diameter versus 18mm—which allows for greater capacity and energy density. Many newer flashlights and devices are moving to 21700 for longer runtime without increasing overall size much.

Nitecore NL2150HPI 5000mAh Rechargeable Battery for i Series Flashlights (P20i, P20iX, SRT6i, etc) - Used

stainless steel
rechargeable

The 3-second version

5000mAh capacity in the 21700 format for extended runtime
Nickel-plated stainless steel terminals resist corrosion and impact
Built-in pressure relief valve and overcharge protection
Used condition—capacity may be below new spec
21700 size only; check device compatibility before ordering

Why it's on GiftsFeed

21700 Rechargeable Li-ion Battery with 5000mAh Capacity

Most flashlight owners discover they need a second battery the moment the first one dies on a camping trip or during a power outage. Generic 21700 cells flood the market, but their protection circuits and discharge consistency vary wildly—and a failing cell in a high-output light can mean flickering or unexpected shutdowns.

This Nitecore cell uses nickel-plated terminals and a pressure relief valve, which matters when you're pushing fifteen amps through a compact package. It's engineered to match the draw characteristics of Nitecore's own lights, so you get stable output instead of sagging brightness. Worth it for anyone who relies on their flashlight and doesn't want to gamble on off-brand cells.

Good gift when

Flashlight owners who need a backup cell for overnight or multi-day trips
People running multiple 21700 devices who want interchangeable spares
Users of Nitecore i-series lights seeking a replacement or second battery

Skip it if This is a used battery, so actual capacity and cycle life depend on how the previous owner charged and stored it. If you need guaranteed performance, order new.

Specs

Capacity: 5000mAh
Battery Type: Rechargeable Li-ion
Format: 21700
Terminals: Nickel-plated stainless steel
Protection: Pressure relief valve, overcharge/over-discharge/short-circuit safeguards
Compatible With: Nitecore i4000R, P20i, P20iX, SRT6i, and other 21700-compatible devices
Charging: Standalone charger or USB port in compatible lights
Condition: Used

What's included

Nitecore NL2150HPI 21700 rechargeable battery (used)

If you're giving it

No sizing to guess

A practical spare for flashlight users; ships as a bare battery without gift packaging.

The details

This 21700 lithium-ion cell delivers 5000mAh capacity in a format that fits a growing range of flashlights and electronics. Built to power Nitecore's i-series lights—including the i4000R, P20i, P20iX, and SRT6i—it also works in any device that accepts 21700 batteries, making it a practical spare for multi-device owners.

The cell features nickel-plated stainless steel terminals that resist corrosion and maintain consistent contact over thousands of cycles. A pressure relief valve and thermal protection guard against overcharge, over-discharge, and short circuits. You can recharge it in a standalone charger or directly through the USB port built into compatible Nitecore flashlights.

At 21mm diameter and 70mm length, the 21700 format offers greater energy density than older 18650 cells without demanding a larger housing. That translates to longer runtime between charges in lights designed for this size, and more reserve capacity when you need extended output.

The battery arrives with global product liability insurance and meets multiple electronic safety certifications. Its construction prioritizes stable discharge rates under load, which helps high-output flashlights maintain consistent brightness through the middle of the discharge curve.

This is a used unit inspected and tested by the seller. Rechargeable lithium-ion cells degrade with charge cycles, so capacity and internal resistance may differ from new specifications depending on prior use. Check the seller's notes for details on condition and remaining capacity.

Nitecore

Nitecore NL2150HPI 5000mAh Rechargeable Battery for i Series Flashlights (P20i, P20iX, SRT6i, etc) - Used

High-performance cell engineered for Nitecore i-series flashlights and compatible 21700 devices

$19.96$25.9523% offat nitecorestore.com

Quantity

Buy from Nitecore

Ships and sold by Nitecore. About this merchant

The 3-second version

5000mAh capacity in the 21700 format for extended runtime
Nickel-plated stainless steel terminals resist corrosion and impact
Built-in pressure relief valve and overcharge protection
Used condition—capacity may be below new spec
21700 size only; check device compatibility before ordering

Questions

Can I use this in flashlights other than Nitecore models?: Yes. Any device that accepts 21700 batteries will work with this cell. It's optimized for Nitecore i-series lights but functions in other brands' 21700-compatible flashlights and electronics.
What does 'used' mean for battery capacity?: Lithium-ion cells lose capacity with charge cycles. A used battery may hold less than its original 5000mAh rating depending on how many times it was charged and how it was stored. Check the seller's listing for specifics on remaining capacity or cycle count.
Do I need a separate charger?: Not if your flashlight has a built-in USB charging port, like the Nitecore i4000R. Otherwise, you'll need a standalone 21700-compatible charger such as the Nitecore UI1.
How does 21700 compare to 18650 batteries?: The 21700 format is slightly larger—21mm diameter versus 18mm—which allows for greater capacity and energy density. Many newer flashlights and devices are moving to 21700 for longer runtime without increasing overall size much.