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Bench Test Results: VRK 25A 3750mAh 21700...an average 20A battery

Discussion in 'Batteries and Chargers' started by Mooch, Jun 25, 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.

    D632FCB1-94F9-4008-8AFA-9534F33490BA.jpeg EBD98316-C9A2-48AB-B985-4EB66EF6ED22.jpeg A113E45C-0027-40BE-A6BD-5777B3E78FF9.jpeg 6BD2F04B-E915-449D-8858-6570F40F9495.jpeg


    Bottom Line
    This VRK appears to use the same cell as Basen and CoilArt 21700’s, not a great performer. The Golisi S35 and Efest 3700mAh are better and have higher current ratings. Even the five “leg” top contact 20700’s from iJoy/Efest/EBAT/Ampking and others perform a little better and have higher current ratings too.

    The 40A ”Max Discharge” rating on the wrap is useless as VRK doesn’t define what that means. Some type of “pulse” rating? We can’t use it to compare against any other cell unless we know the pulse width, time between pulses, and what criteria they use to set the rating (Temperature? Voltage sag? Cycle life? A combination of those?). That’s only if all the cell wrapping companies use the same pulses and criteria too.

    The two cells delivered 4118mAh and 4116mAh at 0.5A down to 2.5V. I don’t know why VRK rated this cell at 3750mAh unless perhaps they are expecting to change cells or, for this batch, they switched over to a different one?

    I am estimating this VRK’s ratings at 20A and 3750mAh. I’m not giving them a higher capacity rating due to the risk of the cell being changed.

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


    Continuous Current Discharge Graphs
    FFC92D22-3D77-4163-895A-1B47C8D173DB.jpeg


    Ratings Graphic
    90085F28-AA3B-4A7F-8F01-EA9EEB34D090.jpeg


    Performance Specs
    - DC Internal Resistance = 22.5mOhms (milliohms) average for the two cells.
    - Total energy delivered down to 3.2V at 10A continuous = 11.9Wh (Watt-hours) average
    - Total energy delivered down to 3.2V at 20A continuous = 6.6Wh (Watt-hours) average

    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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