Test/review of Vapcell INR21700 4000mAh K40 (Black) 2021

Vapcell INR21700 4000mAh K40 (Black) 2021

Official specifications:

  • Model: K40

  • Size: 21.1*70.6mm

  • Typical Capacity: 4000mAh (0.2C discharge)

  • Min capacity: 3900mAh (0.2C discharge)

  • Nominal voltage: 3.60V

  • Max Continuous Discharge Current: 30A

  • Max Discharge Current: 45A with 80°C cut

  • End-of-charge voltage: 4.20V

  • End-of-discharge Voltage: 2.5V

  • Weight: 68g ( Appr)

  • Internal resistance: 10mOhm ( Appr) AC 1kHz

  • Standard Charge: 2000mA,CCCV 100mA cut-off

  • Quick Charge Current: 6000mA

This is a high current 21700 cell with good capacity.

The two cells tracks nicely and usable capacity do not go down much with higher loads.


These cells are good high current cells with a decent capacity.

Notes and links

The batteries was supplied by Vapcell for review.

How is the test done and how to read the charts
How is a protected LiIon battery constructed
More about button top and flat top batteries
Graphical comparison to 18650 and other batteries
Table with all tested LiIon batteries

Thanks for the review, HKJ!

Genuine Samsung 40T 21700 are expensive and difficult to find in our country (and most foreign stores have difficulty shipping to my country).

I’ve seen a local store carry this Vapcell K40 (I bought a pair), but have not really use these batteries yet.
(btw, the wrapper color does not appear to be “black”, but more like a “dark gold brown” color)

Using your battery comparator, the discharge graphs of the Vapcell K40 appear to track quite similar to the Samsung 40T in almost all discharge currents.

(However, based on my simple visual observation of the Vapcell K40 battery vs a Samsung 40T battery, I think the K40 is not a 40T, because the K40 is slightly lighter in weight and also slightly longer in length compared to a genuine 40T.)

If it is significantly cheaper than a Samsung 40T then it probably can’t be one or it’s used. The battery might be a Lishen LR2170LA rewrap.

You’re probably right… referencing HKJ’s reviews of the LR2170LA, the weight, height & diameter of the Vapcell K40 seems to be a very close match,
although HKJ’s review of the LR2170LA has just slightly less tested capacity than the Vapcell K40 (which in turn has slightly less capacity than 40T), but these 3 batteries’ discharge graph (using the battery comparator) track very closely in almost all discharge currents, other than the slightly less capacity.