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Measuring capacity

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  • Measuring capacity

    According to IEC 61960-4:2020
    The cell or battery shall be discharged, in an ambient temperature of 20 °C ± 5 °C, at a "constant current" to the end-of-discharge voltage specified by the manufacturer.

    If I see official specs of lithium 18650 they measure as IEC describes (see atachment)​​​​​​.

    Cheap charger/testers measure capacity by discharging till a certain voltage , eg cut-off @ 2.8v not adjustable.

    Can I assume (tester)tools that not measure till the "end of voltage" specified by the manufacturer, the method of testing capacity is then "invalid" ?

    Attached Files

  • #2
    Correct. Many manufacturers set their "end of voltage" setting differently so that they can achieve the cycle life count and durability that they want. They also can play games with the C rate of the charging and discharging process to inflate their numbers.

    From what I have seen, and I have investigated around a dozen Chinese manufacturers and American "manufacturers", most manufacturers have slight differences in their rating process. So if you use a generic battery tester to measure capacity it may be off of their rating, but both ratings may be correct as tested.


    • #3
      To cope with that situation,
      I try really hard to only buy batteries that have a good following and a good reputation......

      Or...have a good and free return policy.

      If those things are absent I usually abstain.

      Recently I took a chance on a 120Ah battery pack advertised on Amazon.
      The battery tested out to 124Ah using MY testing method which is more stringent and less forgiving than most manufacturers.

      But I made sure it had a return period just in case.