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Bench Retest Results: Efest 35A 4200mAh 26650...lousy performer, ridiculous current ratings

Discussion in 'Batteries and Chargers' started by Mooch, Jan 23, 2020.

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  1. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    These tests below only note the ESTIMATED ratings for these batteries at the time I tested them. Any battery that is not a genuine Samsung, Sony, Murata, LG, Panasonic, Molicel, or Sanyo can change at any time! This is one of the hazards of using “rewrapped” or batteries from other manufacturers so carefully research any battery you are considering using before purchasing.

    Misusing or mishandling lithium-ion batteries can pose a SERIOUS RISK of personal injury or property damage. They are not meant to be used outside of a physically and electrically protected battery pack. Never exceed the battery’s current rating and keep the plastic wrap and top insulating ring in perfect condition. Use of any of these batteries is AT YOUR OWN RISK.

    Testing batteries at their limits is dangerous and should never, ever, be attempted by anyone who has not thoroughly studied the dangers involved, understands the risks, has the proper equipment, and takes all appropriate safety precautions.

    If the battery has only one current rating number, or if it only says "max", then I have to assume the battery is rated at that current level for any type of discharge, including continuous.

    2F1A8304-7022-4C86-8377-F6F05068C336.jpeg B0B9E464-4DCD-4FC3-9A0A-56DDA51C9DD3.jpeg 889785D3-7B0C-435C-99BD-BA58EF21DA39.jpeg DD5310AD-604E-417F-8EB1-E44A76493105.jpeg


    Bottom Line
    This cell DOES NOT use the same good performing Yong De Li New Energy Company YDL 26650D cell that other companies also wrap. This Efest is a very poor performer with hugely exaggerated current ratings.

    The authenticity of the cells I tested was checked at Efest’s web site.

    The DC internal resistance of these cells is almost 50% higher than the 26650’s using the YDL cell. This means the voltage sag will be a lot larger with these Efests when above about 10A/30W.

    At 90W the 26650’s using the YDL cell would give you about 125 two second puffs. This Efest would give you about 12 puffs...yes, just 12. At its preposterous claimed 50A “max pulse discharge” rating, about 150W, this Efest wouldn’t even give you one puff. At 50A this cell’s voltage almost instantly dropped to my 2.8V cutoff. I am giving these Efests a 20A rating.

    The capacity for the two Efests I tested was 4518mAh and 4614mAh at 840mA (0.2C) down to 2.5V. This is typically poor consistency for a China manufactured cell but these cells easily meet their 4200mAh rating. I am rating this cell at 4200mAh to prevent confusion but these are clearly higher capacity cells. This would NOT help them perform better than the 26650’s using the YDL cell except at very low power levels, about 20W or lower. There are better choices for lower power levels though.

    Two cells were purchased for testing by me.


    Continuous Current Discharge Graphs
    E14D1F58-3CEF-470E-B52F-03E90897FA71.jpeg


    Ratings Graphic
    E398A493-68A2-4A82-B761-32B2C9331A29.jpeg


    Performance Specs
    • DC Internal Resistance = 22.9mOhms (milliohms) average for the two cells.
    • Watt-hours (energy) delivered at 10A down to 3.2V = 12.9mAh
    • Watt-hours (energy) delivered at 20A down to 3.2V = 7.8Wh
    • Watt-hours (energy) delivered at 30A down to 3.2V = 0.6Wh
    • 2-sec puff count at 30W = 774
    • 2-sec puff count at 60W = 234
    • 2-sec puff count at 90W = 12
    I want to work for the vaping community full time! If you feel what I do is worth a couple dollars a month and you would like early access to battery availability, battery and charger testing and news, and a say in what I test, then please consider becoming a patron and supporting my testing efforts: Battery Mooch is creating battery tests and educating vapers | Patreon.

    To see how other cells have tested check out this link: List of Battery Tests | E-Cigarette Forum

    ***I have switched test jigs, resulting in slightly lower IR readings versus my previous setup. Add 1.6mOhms to this IR value in order to compare these cells to others tested previously.
     
    • Like Like x 2
    • Informative Informative x 2
  2. Oregon Linda

    Oregon Linda Ultra Member Verified Member ECF Veteran

    Jun 1, 2013
    Salem, OR
    Looks like Efest is still up to its old tricks. At this point, I wouldn't buy any of their batteries ever.
     
    • Agree Agree x 1
  3. sonicbomb

    sonicbomb Vaping Master Verified Member ECF Veteran

    Feb 17, 2015
    1187 Hundertwasser
    Efest blow, this we know
     
    • Agree Agree x 2
  4. Northstar6

    Northstar6 Senior Member ECF Veteran

    May 16, 2019
    The only decent cell they make is 10440...and that's basically due so few companies even produce it.
     
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