Test/review of Sofirn 21700 4000mAh (Black)

Sofirn 21700 4000mAh (Black)







Official specifications:

  • Battery Minimum Capacity: 4000-3900mAh

  • Battery Discharge Current: 40A

  • Battery Capacity: 4000mAh

  • Battery Voltage: 3.7V



This is a high current 21700 cell with good capacity.









The cells matches very nicely and can deliver a lot of current.
Sorry about the 30A curve, but my battery holder melted at that current and temperature.























Conclusion

This is a good cell that can deliver a lot of current, but using well above 20A will need a thermal cut-out.



Notes and links

The batteries was supplied by Sofirn 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

Thank you HKJ for this info.

Thanks for the test, HKJ! :+1:

I suspect a lot of people will appreciate this review…I know I do having some of these cells shipped with Sofirn torches.

Just a question for my own edification: on your discharge graph, do the data lines in the section I’ve circled indicate some type of rebound after the resistance is removed? (I hope it’s OK to copy pasta this segment from your original. If not, let me know and I’ll delete it.) Thanks, HKJ!!!

Yes it is, but I do not include it on all discharge curves.

Oh good, I was hoping you would eventually have this one to test…big thanks! Using your comparator it seems to exactly mirror the Samsung 40T, so a top contender with that and the Moli P42A and the Lishen. I think I have noticed similar a couple of my lights where I use both this and the 40T. I did notice right away that turbo performance with these “older” 4000mAh was better than with their newer 5000mAh that they include with many lights now.

Much appreciated, HKJ, as always!

On the Sofirn website they wrote Made of Lishen LR2170LA.

Thanks for the review HKJ.