Samsung ICR18650-28A 2800mAh (Purple)
Official specifications:
- Place of origin : Samsung in Korea
- Capacity: 2800mAh
- Ultra-high capacity and premium built quality
- Unprotected
This battery is not the usual 4.2 volt charging, but needs 4.3 volt charging, i.e. a special charger must be used (Some hobby chargers can be adjusted for it).
The cell has a higher voltage than most other batteries.
Test with 4.2 volt charging
It is possible and perfectly safe to use this battery with 4.2 volt, but it will have less capacity.
When only charging to 4.2 volt the battery looses about 220mAh in capacity.
Conclusion
That is a good cell, but the requirement for a special charger to get the full benefit of the battery, does reduce the usefulness of it. Using it with a 4.2 volt charger negates any benefit of the higher voltage and capacity.
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