Efest 2600mAh 18650
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 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 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 can be dangerous and should only be attempted by those who have thoroughly studied the associated risks and methods for mitigating them. The safety measures I have implemented are based on my personal decisions, and it would be unwise to assume they will protect you during your own testing efforts. Conduct thorough research and develop your own testing techniques and safety precautions.
Efest Batteries 18650
Key Point: like other best 18650 batteries, this battery 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 can modify the type of cell it employs beneath the outer covering at any given time, as it has 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, battery venting in the event of a malfunction or accidental activation of your mechanical mod's butto,n like the Efest 20700 3100mAh.
Efest 18650 Battery Review
Observations: At a discharge rate of 10A, the cell achieved a capacity just under 2500mAh, demonstrating commendable performance relative to its rated capacity of 2600mAh at 10A. When subjected to a 15A discharge, the temperature increased to 72°C, which is slightly below the average temperature typically observed for cells operating at their continuous discharge rating (CDR). This indicates that the cell remains within a safe operating range relative to its designated current level. At a discharge rate of 20A, the temperature further increased to 83°C.
The observed values are at the upper limit of what is deemed acceptable for a cell operating at its Continuous Discharge Rate (CDR), indicating that the rated current level has been reached. At a current of 25A, the temperature escalated to 95°C, a figure that significantly surpasses the upper threshold for cells functioning within their CDR. Further discharges at 30A and 35A resulted in temperatures of 104°C and 112°C, respectively.
Both of the discharges exceeded my established safety threshold of 100°C. A discharge conducted at a current of 40A resulted in the voltage rapidly declining to the cutoff point of 2.8V, indicating that this is not a legitimate 40A cell. Subsequently, a second discharge at 20A revealed a decrease in cell voltage, which signifies an increase in internal resistance. This deterioration can be attributed to the extremely elevated temperatures experienced during the 30A and 35A discharges.
I am in the process of establishing a Continuous Discharge Rate (CDR) of 20A for this cell. While operating any cell near its maximum rated current can lead to degradation, I anticipate that this cell will demonstrate a favorable cycle life at the 20A threshold. Additionally, I have incorporated pulsed discharge tests; however, I have not yet determined the pass/fail criteria for these pulse evaluations.
The shots were executed using a cycle of 5 seconds on followed by 30 seconds off until a voltage of 2.5V was attained. One chart illustrates the complete discharge at each level, while another provides a closer view of the initial 5 minutes to better observe the voltage sag at different current levels.