Sofirn 21700 4000mAh (Black)
/DSC_5281.jpg)
Official specifications:
- Battery Minimum Capacity: 4000-3900mAh
- Battery Discharge Current: 40A
- Battery Capacity: 4000mAh
- Battery Voltage: 3.7V
/Sofirm%2021700%204000mAh%20(Black)-info.png)
This is a high current 21700 cell with good capacity.
/DSC_5282.jpg)
/DSC_5283.jpg)
/DSC_5284.jpg)
/DSC_5285.jpg)
/DSC_5286.jpg)
/Sofirm%2021700%204000mAh%20(Black)-Capacity.png)
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.
/Sofirm%2021700%204000mAh%20(Black)-Temp-10.0.png)
/Sofirm%2021700%204000mAh%20(Black)-Temp-15.0.png)
/Sofirm%2021700%204000mAh%20(Black)-Temp-20.0.png)
/Sofirm%2021700%204000mAh%20(Black)-CapacityTimeHours.png)
/Sofirm%2021700%204000mAh%20(Black)-CapacityTime.png)
/Sofirm%2021700%204000mAh%20(Black)-Energy.png)
/Sofirm%2021700%204000mAh%20(Black)-PowerLoadTime.png)
/Sofirm%2021700%204000mAh%20(Black)-TripCurrent.png)
/Sofirm%2021700%204000mAh%20(Black)-Charge.png)
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