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

Discussion in 'Batteries and Chargers' started by Mooch, Jul 15, 2015.

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  1. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    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.
     
    • Like Like x 9
  2. Mike89

    Mike89 Full Member

    Apr 25, 2015
    Have you tested the Efest 35A 2800mah battery yet? I'm curious on this one. Have heard good things about it.
     
  3. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    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).
     
    • Like Like x 1
  4. Morandir835

    Morandir835 Idiot Guru ECF Veteran

    Jan 2, 2011
    Outside DC
    Got to love all these high amperage claims sir. Thank you for all the work you do. Have a great day.
     
    • Like Like x 1
  5. Ubervillin

    Ubervillin Full Member

    Aug 30, 2015
    Just wondering what the safe amp draw for 2 of these in parallel might be? From what I understand a conservative estimate is about 1.5x the CDR of a given cell. If that is so, these would be safest in parallel at 30A and below. If not, is there a formula you know that would give me a more accurate result? Thankee in advance and keep up the good work, it is always nice to see testers use the scientific method rather than jumping to conclusions after a handful of tests when it's nice and fresh and new.
     
  6. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    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.
     
    • Like Like x 2
  7. sonicbomb

    sonicbomb Vaping Master Verified Member ECF Veteran

    Feb 17, 2015
    1187 Hunterwasser
  8. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Arrgghhhh...nvm.
     
    • Like Like x 1
  9. Ubervillin

    Ubervillin Full Member

    Aug 30, 2015
    Thankee very much for the info, quitting smoking is the excuse I apparently needed to brush up on my electrical theory some more. I'm not trying to get to below .1 or anything like that I just like the hookah-like hit that comes from the .175-.15 range in my Subtank but at the same time, its good to know that I can go a little lower while still not endangering my co-workers and family.
     
    • Like Like x 1
  10. BackDoc

    BackDoc Ultra Member Verified Member ECF Veteran

    Nov 24, 2010
    Galts Gulch
    Got to love the Amp ratings these battery "brands" claim............if they have the $ to either manufacture or even re brand are we so gullible as to think they are not aware of the Actual ratings vs their claimed rating ?
     
    • Like Like x 1
  11. State O' Flux

    State O' Flux Vaping Master Verified Member ECF Veteran

    Jul 17, 2013
    Seattle
    This "phenomena" seems to have only shown it's ugly face in the past 12-16 months. All the advertised ratings are attainable... but not as continuous (that key descriptive frequently dropped from the rating) and certainly not as safe... and this is where the purposely and knowingly promoted BS claims tend to self-destruct.
    This last bit is what really burns... as you can guarantee that most of the retail vendors knew (and even now, still know)... something dishonest was afoot.

    There have been unbiased tests done prior to these, on most of the cells Mooch has run through the test series... but none prior to this (save for an initial, perhaps false start by Jon Kuro) have been tested under vaping conditions, and none using the all critical element of temperature, and it's effects on cell longevity, durability and safety.

    This is one of those rare and wonderful occasions, where someone has dedicated their time, knowledge, technical and scientific expertise toward the betterment of the vaping community... with no "pay off" other that the occasional "atta' boy" Moochy. Not even the batteries donated are payment, as they are mostly run to destruction.

    Atta' boy... Watt-meister Mooch. :blush:
     
    • Like Like x 1
  12. BackDoc

    BackDoc Ultra Member Verified Member ECF Veteran

    Nov 24, 2010
    Galts Gulch
    Great synopsis Flux!
     
  13. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    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.
     
  14. State O' Flux

    State O' Flux Vaping Master Verified Member ECF Veteran

    Jul 17, 2013
    Seattle
    Yeah, yeah, yeah... don't let it go to your head. Back to work! ;)
     
  15. SUPER K

    SUPER K Super Member Verified Member ECF Veteran

    Jun 3, 2015
    So Mooch, what's your battery of choice?
     
  16. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    One that isn't rewrapped. :D

    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
     
    • Like Like x 2
  17. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Charging an Efest now, sir! :p
     
    • Like Like x 1
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