Boxer Black 40A 4500mAh 26650 Bench Test Results...just a 20A battery, but a really good one

[Mooch]

These cells were donated for the purposes of testing by @rice721. Thank you! To prevent any confusion with the eGo-type "batteries", I use the term "cell" here to refer to a single 18650, 26650, etc.


Disclaimer
The statements, conclusions, and recommendations I make based on these tests are only my personal opinion. Carefully research any battery 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.


A note regarding current ratings and my testing
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
This Boxer is a 20A cell with a very exaggerated current rating. The cells I tested had an underrated capacity of 5200mAh though. This cell is one of the top five 26650's I've tested. Its voltage under load and current rating aren't as high as the AWT 4500mAh but it's as good as the Basen and Brillipower 4500's and the Efest 4200's and runs a bit longer. Its length is 65.1mm so it will fit in the VF Stout and other mods that require a shorter cell.


Continuous-Current Test Results



Pulsed-Current Test Results



Comments

• At 10A continuous it reached about 4975mAh. This is significantly higher than what a 4500mAh cell should reach at 10A so I am rating this cell at 5200mAh.
• At 15A continuous the temperature rose to 69°C. This is below the average temperature of a cell running at its continuous discharge rating (CDR).
• At 20A continuous the temperature rose to 79°C. This is the average temperature of a cell running at its continuous discharge rating (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 the cell was being operated at above its rating.
• At 25A continuous the temperature rose to 95°C. This is way above the average temperature of a cell running at its CDR and is an indication that we're above the cell's true rating. There is also some extra sag in the discharge curve and loss of capacity that would indicate that the cell was being operated above its true rating.
• At 30A continuous the temperature rose to 106°C, above my 100°C safety limit.
• At 40A continuous the voltage quickly plunged to the 2.8V cutoff. This is clearly not a 40A cell.
• I am setting a CDR of 20A for this cell. Operating at that level would bring the temperature of this cell up to the average of a cell operating at its CDR. While operating any cell near its rated maximum current level causes damage to the cell, I would expect decent cycle life from this cell at 20A 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

 

[rice721]

Great write up as usual @Mooch and thanks for taking the time to do this