Eizfan IMR26650 4200mAh (Gold)



Official specifications:

• Product Name: high power battery
• Model No.: IMR 26650
• Rated capacity: 4200mAh
• Nominal voltage: 3.7V
• Size: Diameter 26.13, height 65.56mm
• Weight: 95g
• Resistance: 23±2 mOhm
• Temperature range: -20~+60 °C
• Monthly Self-discharge rate: <0.5%
• Temperature range: Discharge: -20~+60 °C, Charge: 0~45 °C
• Maximum discharging current: 40A
• Maximum charging current: 6.5A
• Maximum pulse discharging current: 60A

This 26650 cell has good capacity (even more than rated) and is rated for a fairly high current, but I have some problems with the current rating (See below).










When the test was finished one of the cells looked this way. It has probably vented, but it was undramatic (There was no enclosure that could explode or sparks that could ignite the gas). The yellow wrapper is also wrinkled due to heat.
The last test I did on it was the "Protection test" and there it worked fine. Today (3 weeks later) the cell voltage is down to 0.15 volt.
This shows that the venting did not turn off the output voltage (Bad) and that the cell probably worked correctly after the venting, except for high leak current.
The cell that vented was the B cell.



The cell works fine up to 20A, but the voltage sag is rather large at 30A. The 30A trace might be the reason for the venting, but I would have expected that it was visible on the trace.









This curve is made after the 30A trace.



And this is the last traces I made with the cells.





Conclusion

The cell has good performance up to 20A, but I would not run it harder than that.



Notes and links

These cells was run through the testing twice (Due to the 3500mAh cells), the first time there was no problem with venting.

The batteries was supplied by Efan 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
Compare to 18650 and other batteries