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Bench Test Results: Samsung 40T 4000mAh 21700 incredible 25A/30A battery

Discussion in 'Batteries and Chargers' started by Mooch, Jun 9, 2018.

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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, LG, Panasonic, 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 protected battery pack. Never exceed the battery’s current rating and keep the plastic wrap and top insulating ring in perfect condition.

    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.

    6C5D37CD-3DF7-4B26-BA3A-03552856AFA0.jpeg F11B2943-988D-40E3-83C0-113AC423DFE3.jpeg BA94C6C8-F988-4126-8309-E65515CEAE25.jpeg A4E0F79A-C4EF-492F-8D2A-4011C029D959.jpeg

    Bottom Line
    This cell outperforms every 18650 and 20700 in regulated devices at up to about 20A-25A (60W-75W), but in my opinion it is now not a 30A battery.

    The cells I just retested ran a bit hotter than the ones I tested in Dec, 2017, which just made it to a 30A rating. I can’t give the 40T and its rewraps a true 30A continuous rating any longer. But, I will give the 40T a temperature-limited rating of 30A as long at the cell is kept below 80°C.

    When the datasheet becomes available I will adjust the rating if necessary. This can include removing the temperature-limited rating if one is not in the datasheet.

    At above 20A-25A/60W-75W the Samsung 30T is the better performer anyway. The 40T is best at low to mid power levels where it can be the most efficient. At higher power levels its internal resistance, about 25% higher than the 30T’s, causes more voltage sag than the 30T. The 40T is still an amazing 25A/30A battery though!

    If you are running your mod at 60W-75W per battery you will have to try both the 30T and 40T to see which performs better for the way you vape. It’s just not possible to predict.

    Since the 30T and 40T are in the same family of Samsung cells, and without a datasheet being available to confirm the actual rating, I am giving the 40T a rating that brings it to about the same temperature the 30T reaches at its rating. I am estimating this cell’s ratings to be 25A with a temperature-limited rating of 30A (if kept below 80°C) and 4000mAh.

    Two cells were purchased for the purposes of testing by me from IMRBatteries.

    Continuous Current Discharge Graph

    Ratings Graphic

    Performance Specs
    DC Internal Resistance = 15.2mOhms (milliohms) average for the two cells.
    Total energy delivered down to 3.2V at 10A continuous = 11.6Wh (Watt-hours) average
    Total energy delivered down to 3.2V at 20A continuous = 10.1Wh (Watt-hours) averag

    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 and testing 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
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  2. sonicbomb

    sonicbomb Vaping Master Verified Member ECF Veteran

    Feb 17, 2015
    1187 Hunterwasser
    Thank you.
    • Like Like x 2
  3. Heartsdelight

    Heartsdelight Vaping Master ECF Veteran

    Nov 10, 2015
    Thanks for the update!
    • Like Like x 2
  4. Derek Cross

    Derek Cross Senior Member ECF Veteran

    May 16, 2015
    Thanks for this update mooch. I'm now feeling like I made the right decision. I was on the fence on which cell would be better for the way I vape, and clearly the 30t was the way to go. Funny thing is I've been using those Efest 21700 cells and they've been performing right up there with my 30t's and I was surprised. I thought the Samsung cells would outperform the efest by a super wide margin, but they really haven't. They seem to be almost equal IMHO, with the Samsungs only hitting slightly harder. Of course it's being judged, by me and the wattage I'm vaping at so ymmv.

    Mooch, quick question. I've been using the Samsung 20s lately (unregulated tube, pretty low ohms) and notice that they hit very hard up front, but voltage starts to sag very quickly at around 4.0 volts. Is this normal for this cell? With my vtc5a I can go down to 3.8 volts before I "feel" I will need to change batteries after the next redrip. Like I had a little reminder from the vtc5a, telling me (via voltage sag) that "times up"! This was nice. I'm getting that little reminder way too early when using the Sammies (20s)and I'm wondering if this is something that you personally have experienced, or have heard from other vapers in and around the mech "scene" lmao. I understand it has much less mahs then the vtc5a, but would this account for such a sag at such a high voltage? Seems off to me. Also, these are some of theore preferred mech cells, so if other vapers were having these issues, they'd say so in reviews, but im not seeing this. Could it be in my head?

    Anyway once again your info has helped me make a more informed, and safer decision. I know you hear this all too often to the point it sounds like brown nosing, but I just don't know what the community would do without you at this point. Mechs are getting more popular(especially where mechanical squonkers are becoming more readily available) and these posts and your YouTube vids are a means for vapers, new and old to get info that we would otherwise have no access to. I hope you reach your goal to make this a full-time gig man. I really do.
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