Efest informed me that they would dispatch samples of these products for examination as soon as they become available. However, I am still waiting to receive communication from them. The cells used for testing were generously donated by /u/demoniccow9852 from ECR. Many thanks! To avoid any confusion with eGo-type "batteries," I will utilize the term "cell" to denote a single 18650, 26650, and so on.
Disclaimer
The opinions, deductions, and suggestions I present based on these tests, like the Efest 21700 5000mAh, are solely my subjective viewpoint. Before making a purchase, it is essential to research any battery you are considering thoroughly.
Testing cells to their limits is dangerous and should never be attempted by individuals who have not extensively studied the associated hazards and methods to mitigate them. The safety measures I have taken are my personal choices, and it would be unwise to assume that they will safeguard you during any testing endeavors. Conduct comprehensive research and establish your own testing techniques and safety precautions.
Key Point: Like other IMR batteries, this is a 20A 2600mAh cell. However, subjecting the cells to a single round of continuous discharges at 30A, 35A, and 40A resulted in cell damage. Both cells exhibited similar performance and appearance to the Sony VTC5. It is worth noting that Efest 18650 2600mAh can modify the type of cell they employ beneath the outer covering at any given time, as they have done previously. The authenticity of both cells has been verified.
Results of Pulsed-Current Testing These tests demonstrate the cell's performance under elevated pulsed current levels. If you are operating your mod at these levels, be aware that there is a risk of overheating and, potentially, Lithium Ion Batteries venting in the event of a malfunction or accidental activation of your mechanical mod's button.
Efest 18650 Battery Review
Observations At 10A, it attained a slightly under 2500mAh capacity. This represents commendable performance for a cell with a 2600mAh rating of 10A. At 15A, the temperature rose to 72°C. This figure falls a few degrees below the average for a cell operating at its continuous discharge rating (CDR), indicating that we are still below its rated current level. At 20A, the temperature rose to 83°C. This is precisely at the upper limit of what I consider acceptable for a cell operating at its CDR, and it suggests that we have reached its rated current level. At 25A, the temperature soared to 95°C. This value significantly exceeds the upper limit for a cell operating at its CDR. Discharges at 30A and 35A pushed the temperature to 104°C and 112°C, respectively. Both of these discharges surpassed my safety threshold of 100°C. A shot at 40A resulted in the voltage rapidly dropping to the 2.8V cutoff point. This is not a genuine 40A cell. A second discharge at 20A exhibited a decline in cell voltage, indicating an increase in internal resistance. This damage can be attributed to the extremely high temperatures encountered during the 30A and 35A discharges. I am establishing a CDR of 20A for this cell. Although operating any cell near its maximum rated current level causes damage, I anticipate good cycle life from this cell at 20A. I have included pulsed discharges but have not yet established pass/fail criteria for pulse testing. The shots were conducted with a 5-second on/30-second off cycle until reaching 2.5V. One chart depicts the complete discharge at each level, while the other chart zooms in on the first 5 minutes to facilitate observation of voltage sag at various current levels.
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