Tesiyi 40A 2600mAh 18650 Bench Retest Results...changed cells, a very good 25A/2500mAh

[Mooch]

These cells were donated by Tesiyi for the purposes of testing. Thank you! To prevent any confusion with the eGo-type "batteries", I use the term "cell" here to refer to a single 18350, 18650, 26650, etc.

While the test results are hard data, the conclusions and recommendations I make based on these tests are only my personal opinion based on my criteria for setting a rating. Carefully research any cell you are considering using before purchasing.

Testing cells at their limits is dangerous and should never, ever, be attempted by anyone who has not thoroughly studied the dangers involved and how to minimize them.

If the cell has only one current rating number on it, or if it says "max discharging current" then I have to assume that the company is stating that the cell can be discharged at that current level in any way, including continuously.




Bottom Line
In my previous tests I rated this ICR Tesiyi cell as decent, but very overrated at 25A/2300mAh. They've changed cells but it is still overrated. It's now a 25A/2500mAh ICR cell but the wrap has not been changed in any way to indicate that the cell was changed. They have also switched from a double-layer wrap to a single one. In addition, Tesiyi has still not updated the wraps to indicate continuous/pulse ratings as they said they would months ago. If Efest can start doing this, with accurate ratings, then I would fully expect the other companies to be able to do so too.

All this aside, this is a good 25A ICR cell with good capacity and the classic flatter discharge curve that provides a more consistent vaping experience when using a mechanical/unregulated mod. It delivers more capacity down to 3.2V than the Samsung 25R and hits harder than the VTC4 at higher current levels.


Continuous-Current Test Results



Pulsed-Current Test Results



Comments

• At 10A continuous it reached a bit more than 2300mAh. This is average performance for a 2500mAh cell at 10A so I am rating this cell at 2500mAh.
• At 15A continuous the temperature rose to 55°C. This is significantly below the average temperature of a cell running at its continuous discharge rating (CDR).
• At 20A continuous the temperature rose to 69°C. This is a below the average temperature of a cell running at its CDR.
• At 25A continuous the temperature rose to 79°C. This is the average temperature of a cell running at its CDR and is an indication that this is the cell's true rating. There's no sign of extra sag in the discharge curve that would indicate that it was being operated at above its rating.
• At 30A continuous the temperature rose to 89°C. This is way above the average temperature of a cell running at its CDR and is an indication that we're above the true rating.
• At 35A continuous the temperature rose to 100°C. This is a ridiculously high temperature and is at my safety limit. The voltage has also started to sag considerably.
• At 40A continuous the temperature rose to 107°C. This is over my 100°C safety limit. This is clearly not a 40A cell!
• I am setting a CDR of 25A for this cell. Operating at that level would bring the temperature up to the average for a cell operating at its CDR. While operating any cell near its rated maximum current level causes damage, I would expect decent cycle life from this cell at 25A continuous.
• I have included pulsed discharges but I haven't set pass/fail standards for pulse testing yet. The discharges were done at 5sec on/30sec off, down to 2.5V. One chart shows the entire discharge at each level. The other chart is zoomed in to show the first 5 minutes to make it easier to see the voltage sag at different current levels.

To see how other cells have tested and how hard you can safely push them, check out these links:
List of Battery Tests | E-Cigarette Forum
18350 Safety Grades and Pulse Performance Data | E-Cigarette Forum
18650 Battery Ratings -- Picking a Safe Battery to Vape With | E-Cigarette Forum
26650 Safety Grades and Pulse Performance Data | E-Cigarette Forum