Test/review of Samsung INR18650-25R 2500mAh (Green) Ebay

Batteries and Chargers Rechargeable Batteries
1

Samsung INR18650-25R 2500mAh (Green) Ebay







Official specifications:

  • Type: Lithium-ion

  • Composition: LiMn Hybrid (IMR)

  • Rechargeable: Yes

  • Positive terminal style: Flat top

  • Protection: Unprotected

  • Capacity: 2500mAh

  • Max continuous discharge: 20A

  • Nominal voltage: 3.7V



Batteries marked Samsung from ebay.










The two cells matches fairy well, i.e. it is probably new cells, but they cannot deliver more than about 10A and they are strained to do that.























Conclusion

This is definitely not a Samsung INR18650-25R battery, it is some, probably old, low capacity cell and not designed for high current.

The cell works and would have been a acceptable cell about 10 years ago.



Notes and links

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
2

This is my most common 18650 battery. Discharge tests on a genuine version have always been near the 2,500mah spec.

3

Thanks HKJ! Much appreciated.

4

Can you please show how to read the graphs to conclude that the cells are fake? Thanks

5

What stands out is the discharge/capacity test in the first graph, less than 2,000mah. You would expect closer to 2,500mah with a genuine Samsung.

6

With this cell it is easy, there are two obvious points:

  1. The capacity, all voltage curves drops below the chart before the 2Ah (2000mAh) mark.
  2. The 20A curve is non-existing, for a real 25R it will go beyond the 2A mark.

The usual way is to use the comparator and compare the curves to the correct battery, they must nearly match.
Comparator: Battery test-review 18650 comparator

7

Thanks gentlemen for the explanation. In the “”Discharge, power”:https://lygte-info.dk/pic/Batteries2012/Samsung%20INR18650-25R%202500mAh%20(Green)%20Ebay/Samsung%20INR18650-25R%202500mAh%20(Green)%20Ebay-PowerLoadTime.png” plot

!https://lygte-info.dk/pic/Batteries2012/Samsung%20INR18650-25R%202500mAh%20(Green)%20Ebay/Samsung%20INR18650-25R%202500mAh%20(Green)%20Ebay-PowerLoadTime.png!

How come the last 5 minutes (X axis 35 to 40). The current is increasing while the voltage is dropping? What kind of physical process which could allow to boost the current like that? This is kind of anti-intuitive.

8

My other curves are with constant current, this curve is with constant power, this means when the voltage drops the current must be increase to draw the same power.

This is similar to how many boost/buck drivers draws power.

9

Be curious to see what's under the wrapper?

10

Let me also add that the most current tests for Samsung 25R cells done by HKJ are found in some nice brand rewraps. For example, see tests of Vapcell INR18650 2500mAh (Purple) 2018 and Ampsplus INR18650 2500mAh (Black). His tests of genuine Samsung brand 25R cells are quite old, and done on a station with 2-wire battery holder, so they don't quite reflect the performance of modern 25Rs.

The performance difference versus this fake cell is, nonetheless, outrageous. Looking at the shape of its top, it looks like some sort of cell from Lishen.