Efest 38A 2100mAh 18650 Bench Test Results...an ok 20A cell, no higher

Tested at 10A-38A constant current. Cells were graciously donated for testing by Liion Wholesale (Liion Wholesale Batteries). To prevent any confusion with the eGo-type "batteries", I use the term "cell" here to refer to a single 18650, 26650, etc.

Dropbox - efest 38a 2100mah 18650 wrap.jpeg

Dropbox - efest 38a 2100mah 18650 can.jpeg

Dropbox - efest 38a 2100mah 18650 top.jpeg

Dropbox - efest 38a 2100mah 18650 bottom.jpeg


Disclaimer
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. My safety precautions are the ones I have selected to take and you should not assume they will protect you if you attempt to do any testing. Do the research and create your own testing methods and safety precautions.


Bottom Line
This is only a 20A continuous discharge current (CDR) cell. At above 20A its voltage sags very low. At 30A or higher the cell is damaged by each discharge.


Test Results
Dropbox - efest 38a 2100mah 18650 constant-current tests.bmp


Comments

• Discharges at 10A and 15A showed OK capacity.
• At 20A, down to 3.2V, this cell has only 70% of the capacity of the Samsung 25R. The temperature at 20A was moderate.
• At 25A and 30A the voltage sagged considerably and the temperature rose to 85°C and 98°C, respectively. This is clearly a 20A cell.
• At 35A and 38A the voltage is so low that the cell is essentially useless.
• Five additional cycles at 30A started showing signs of damage caused by the high temperature, further emphasizing that the cell has a rating considerably lower than 30A.
• While operating any cell at its rated maximum current causes damage to the cell, I would expect decent cycle life from the Efest 38A 2100mAh cell at 20A due to the moderate temperature at that current level.
• See my blog for more information on the testing procedures, equipment used, and links to all my test results.

 

Not yet. Not sure I'll be getting to this one though as it all depends on donations. I'm happy to spend the time to test each of these cells (up to 2 days each) as it can be fit in between work stuff (I have a home office). But I just don't have the money to purchase all these cells (and the 26650's, 18500's, and 18350's I'd like to test too).

 

Two of these batteries at 30A total is safe in my opinion.

You can check my safety grades table (link in my signature) to get an idea of how hard you can run any battery I have tested. Multiplying the single battery current by 1.5 is safe, but it's quite conservative in my opinion. If are using two of the same model battery, of the same age and number of cycles, and not stressing them so hard that they're running at the ragged edge of venting, you can multiply the single battery current by 1.8 when using two in parallel.

[edit] 30A total should be safe but in my opinion you can run two of these at more than 30A. Assuming you want to stay within my green Pass safety grade zone, that means 20A per battery. The total would then be 36A, echoing @sonicbomb's recommendation.

 

Arrgghhhh...nvm.

 

Thanks Flux!
I don't even get free destroyed batteries. :-(
The wonderful donations that were made have run out. The tests are now being done with cells I have purchased.

 

One that isn't rewrapped.

Up to 10A = NCR18650GA (though the HG2 is great here too)
Up to 20A = HG2
Up to 30A = VTC4 or HD2
Up to 40A = HB6

 

Charging an Efest now, sir!