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Bench Test Results: iJoy 40A 3750mAh 21700...hugely overrated but better than NCR20700B

Discussion in 'Batteries and Chargers' started by Mooch, Sep 13, 2017.

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  1. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    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 only says "max" 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.

    Cell photos: https://imgur (dot) com/a/t6nlk
    (Sorry for the split link but direct links to Imgur do not display properly)


    Bottom Line
    This cell has “40A” on the wrap which is far, far above its true rating of 24A. It's capacity is also exaggerated and averages only 3650mAh for the three cells I tested.

    I have spoken to iJoy though and they have agreed to rewrap the cell using more realistic ratings. I will retest when the new wrap is available.

    There was a greater than typical variation in the capacities of the three cells I tested. It almost appears that there is no grading by capacity for the cells coming off the assembly line. It would take several days of testing to determine the true capacity rating of this cell but the 3650mAh rating I am giving it is close to its true rating.

    This cell is outperformed by the 40A 3000mAh iJoy/Ampking/EBAT/Efest 20700 which hits harder and runs just as long at moderate to high power levels. I recommend using this cell at power levels of 50W or less to help prevent voltage sag from giving you early weak/low battery alerts in a regulated mod.

    This iJoy cell does outperform the 15A 4000mAh Sanyo NCR20700B cell though.

    This cell is not a rewrap of any other 21700 that I am aware of. I am rating this iJoy cell at 24A and 3650mAh. Its maximum vaping amps (MVA) limit is 30A, limited by temperature and voltage sag.

    While I am extremely disappointed with the degree of overrating of this cell by iJoy I am glad that they are willing to rewrap it with more realistic ratings.

    The two cells that were tested were purchased for that purpose by me.


    Continuous-Current Test Results
    iJoy 40A 3750mAh 21700 CC NEW BATCH TESTS.jpg iJoy 40A 3750mAh 21700 CC NEW BATCH TESTS CONSISTENCY CHECKS.jpg


    Pulse-Current Test Results
    iJoy 40A 3750mAh 21700 Pulse Tests.jpg iJoy 40A 3750mAh 21700 Pulse Tests ZOOMED.jpg


    Comparisons against Sanyo 20700 cells
    iJoy 40A 4200mAh 26650 Pulse Tests vs 3000mAh 20700.jpg iJoy 40A 3750mAh 21700 CC NEW BATCH TESTS vs ncr20700b.jpg iJoy 40A 3750mAh 21700 CC NEW BATCH TESTS vs iJoy 20700.jpg


    Comments
    • At 0.5A continuous this cell delivered about 3600mAh to 3700mAh, depending on the cell. I am rating it at 3650mAh.
    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
     
  2. Tonee N

    Tonee N Ultra Member Verified Member

    Mar 24, 2017
    Nevada
    Thanks again Mooch.
    I'm really glad that Ijoy responded to you, wish the other companies would fess up and do the same.

    Sent from my SAMSUNG-SM-G891A using Tapatalk
     
    Heartsdelight and Mooch like this.
  3. sonicbomb

    sonicbomb Vaping Master Verified Member ECF Veteran

    Feb 17, 2015
    1187 Hunterwasser
    That your word carry's that kind of weight makes me happy. You tell them.
     
    Heartsdelight and Mooch like this.
  4. Heartsdelight

    Heartsdelight Ultra Member ECF Veteran

    Nov 10, 2015
    Thanks again Mooch!
     
    Mooch likes this.
  5. Barkuti

    Barkuti Senior Member ECF Veteran

    May 3, 2016
    Looks like a great middle ground cell at 24A and 3.6+Ah. From my safety and lifespan standpoint I'd avoid using it above 17A continuous (max current rating × ½√2), halving cell thermal stress. This is about in line with Mooch's conservative 50W recommendation, though I believe it should be good for a lil more in practice (regulated mods shouldn't be cutting off above 2.8 - 3V/cell).

    Cheers :)
     
    Heartsdelight likes this.
  6. Heartsdelight

    Heartsdelight Ultra Member ECF Veteran

    Nov 10, 2015
    But the Sanyo NCR20700B is still good for under 45 watts, .40 - .80ohms right? Single battery use on the Geekvape Aegis mod? Thanks!
     
  7. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Your coil resistance doesn't matter when determining battery current, just the wattage setting.
    45W is pushing it, and your efficiency won't be good, but you can use the NCR20700B at that level.
     
    KenD and Heartsdelight like this.
  8. Heartsdelight

    Heartsdelight Ultra Member ECF Veteran

    Nov 10, 2015
    Huh? Just to clarify, you are saying that the Sanyo NCR20700B's are good to use for 45 watts & under? But it's efficiency won't be good?

    Thanks for all you do & answering :) batteries are all so confusing ;)
     
  9. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Correct.
    There are safety limits, performance limits, and recommended performance levels. They can blur and overlap.

    The B's will survive high wattage vaping, work badly at lower levels, be acceptable at even lower levels, and perform well at even lower levels than that.
     
    Heartsdelight likes this.
  10. Heartsdelight

    Heartsdelight Ultra Member ECF Veteran

    Nov 10, 2015
    Thanks for clarifying :wub:
     

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