The Weltool INR21-40P 4000mAh high drain 21700 Li-ion battery is a powerhouse designed for users who demand high performance, reliability, and efficiency from their power sources. Built with original cells and no additional protection circuits, the INR series is intended for experienced users who understand the importance of proper battery management. This design choice allows for the highest possible discharge rates and efficiency but requires careful attention to charging and discharging practices to prevent damage and ensure long-term performance. Users must avoid overcharging or over-discharging to maintain the integrity of the battery and maximize its lifespan.

The INR21-40P is specifically engineered as a high drain battery, capable of delivering a maximum continuous discharge current of 40A at 25 degrees Celsius. This capability makes it an ideal choice for high-drain devices such as powerful flashlights, electric tools, and other equipment that requires substantial and sustained energy output. With a nominal voltage of 3.6V and a robust capacity of 4000mAh, with a minimum guaranteed capacity of 3950mAh, the INR21-40P strikes an excellent balance between power and runtime, ensuring that your device operates at peak performance for extended periods.

Internal resistance is kept exceptionally low, at less than or equal to 12 milliohms, contributing to high efficiency and reduced heat generation during heavy use. The battery supports a maximum charging current of 6A, although a standard charging current of 2A at approximately 25 degrees Celsius is recommended for optimal longevity. The overcharge protection voltage is set at 4.2V with a tolerance of ±0.05V, while the over-discharge protection voltage is set at 2.5V with a tolerance of ±0.1V. These specifications ensure that, when used with a professional charger that includes proper safety features, the battery remains within safe operational limits throughout its charge and discharge cycles.

In terms of durability, the INR21-40P is rated for approximately 250 full charge and discharge cycles, after which it retains about 60% of its original capacity. This high cycle life ensures that the battery remains a reliable source of power for an extended period, making it a smart investment for users who require consistent, dependable performance. The battery is also designed to function across a wide range of temperatures, with a charging temperature range between 0 and 45 degrees Celsius, and a discharge temperature range from -20 to 75 degrees Celsius. For storage, it can safely be kept at temperatures between -20 and 45 degrees Celsius for up to three months without degradation.

Physically, the Weltool INR21-40P maintains a compact profile with a diameter of up to 21.3mm and a length of up to 70.3mm, making it compatible with a wide range of devices designed to accept 21700-size cells. The battery’s weight is kept to a maximum of 70 grams, ensuring that it adds minimal bulk to handheld devices while delivering substantial power output.

Given the absence of built-in protection circuits, it is crucial to follow specific safety guidelines when using the INR21-40P. Users must never immerse the battery in water or expose it to heat sources such as open flames or heaters. Over-discharge must be strictly avoided to prevent irreversible damage to the cell. When charging, it is mandatory to use a professional charger equipped with overcharge protection to prevent excessive voltage accumulation, which could lead to dangerous conditions. Care must be taken to ensure correct polarity during installation, as reversing the positive and negative poles can cause short circuits or battery failure. The positive and negative terminals must not be connected directly to any metal objects, and the battery should never be pierced with nails or sharp objects, nor should it be disassembled or modified under any circumstances.

The Weltool INR21-40P 4000mAh high drain 21700 Li-ion battery offers outstanding performance for users who require the highest levels of output and efficiency from their devices. With its robust construction, high discharge capability, and careful engineering, it delivers dependable energy for demanding applications, while its compact size and lightweight design ensure convenience and ease of integration. When handled properly and paired with appropriate charging equipment, the INR21-40P stands as a leading choice for powering high-performance flashlights and other heavy-drain electronic tools, providing exceptional reliability and endurance across a wide range of operational conditions.

Model: INR21-40P
Capacity: 4000mAh（Minimum capacity 3950mAh）
Internal resistance: ≤12mΩ
Voltage: 3.6V
Continuous discharge current : 40A（25 ℃）
Max. charger charging current:  6A (25℃)
Standard charging current:2A（25℃ ± 2℃）
Overcharge protection voltage: 4.2±0.05V
Over-discharge protection voltage: 2.5±0.1V
Charge and discharge times: 250 times, the battery has 60% capacity
Charging temperature: +0~+45 ℃
Discharge temperature: -20~+75℃
Storage temperature: -20~+45℃ (Less than 3 months)
Dimensions: ≤21.3 mm (diameter), ≤70.3 mm (length)
Weight: ≤70g

Warnings:
Do not immerse the battery in water.
Do not place it near a heat source such as a fire source or heater.
Do not use over-discharge.
When charging, use a professional charger with overcharge protection.
Do not reverse the positive and negative poles.
Do not connect the positive and negative terminals directly to metal objects.
Do not pierce the battery with nails or other sharp objects.
Do not disassemble or modify the battery

SHIPPING
The final shipping cost and estimated delivery timeframe will be available to you during checkout. Currently, we offer 3 International shipping methods which are steady and easy to track. Priority worldwide shipping, Premium ( Partial countries) and a faster Express shipping. The estimated times stated below are not guaranteed. An international package could experience delays like postal strikes or severe weather or Cov-19 situation. All shipping ways, PO Box address is not acceptable.

For some flashlights, there's a pure battery inside（phone charging）,If We can not ship your packages via USPS or DHL,we'll ship your package in another way.

Note:
When you place an order for just the batteries, for easy shipping, faster and safe delivery, the batteries are placed in the flashlights.

If you don’t receive your order within the estimated time frame provided below and suspect that it might be lost in transit, please contact Flashlightgo Support ( support@flashlightgo.com ) and we can look into the order with the courier. Lost-in-transit requests must be submitted to Flashlightgo Support within 3 months of the date of shipping or before the courier archives the tracking information.

Option 1.
Express by DHL/UPS/Fedex/Aramax/SF etc ( there may be tax need to pay in this way),
The estimated time of delivery is usually 3-7 work days depending on the country. Includes detailed tracking and confirmation of delivery.

Option 2.
Premium ( 6-10days, All tax and Duty Paid),
All tax and duty are prepaid to carrier by Flashlightgo before shipping, so you dont need to pay any tax or duty when you get it.

Option 3.
Priority shipping(1-2 Weeks, average 10 days)
If we marked it is with all tax and duty paid, all tax and duty are prepaid to carrier by Flashlightgo before shipping, so you dont need to pay any tax or duty when you get it.

Learn more,Please click on Here.

To ensure that you get the desirable product, we allow a seven-day product return period. Any product return application outside this period will not be entertained.
All returned product must be unused and the original package should be kept.

Return：
We do not offer return for personal products like socks and hats or food, magazine and fragile or dangerous products The original receipt must be available for application of return.

Discount products：
No product return for discount products

Gifts products：
If the item is marked as a gift when purchased and shipped directly to you, it cannot be exchanged , refunded or warranty.

Exchange：
We only replace items if they are defective or damaged.
Exchange service are offered only to wrong deliveries or product damage not caused by client. If needed, please email to info@flashlightgo.com.

Warranty
How long is the warranty period?
Flashlightgo warrants to the original purchaser that the Product(s) shall be free of any defect in material or workmanship for a period of one year for labor and one year for parts from the date of the original order except the items listed below:
Chargers,Batteries and Other Accessories: 3 months warranty

Should the Product(s) supplied by Flashlightgo prove defective because of improper workmanship or material as reasonably determined by us, Flashlightgo agrees, at its option, to either repair or replace the Product free of charge, excluding any shipping or handling charges.

Learn more,Please click here.