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  1. #1
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    Default How to do lithium impedance test

    I found this information on lithium. User has to do impedance testing.

    How do you guys do your test?
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    Default Re: How to do lithium impedance test

    Does this come from a specific battery's documentation? If so, which brand/model?

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    Default Re: How to do lithium impedance test

    Quote Originally Posted by jcdup View Post
    Does this come from a specific battery's documentation? If so, which brand/model?
    It comes from a long time seller and installer of PV and tubes solar geysers. It relates to the DIY lithium cells they are selling. I would have look up the brand.

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    Default Re: How to do lithium impedance test

    Surely these cells wouldn't reach 70% of its capacity or 150% of initial internal resistance within a year? I'm clearly missing something

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    Default Re: How to do lithium impedance test

    .
    Last edited by stephenplumb; 2022/06/08 at 08:19 AM.

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    Default Re: How to do lithium impedance test

    Quote Originally Posted by stephenplumb View Post
    Impedance is a term that has no meaning in a DC circuit. It is only used in an AC environment and the maths gets a bit messier.
    Weeeelll, actually -- Impedance is the only thing that has meaning. In a DC circuit it just has zero reactive components, only has resistance.

    ALL circuits have impedance.

    Within the context of this thread, remember that although a battery is a DC device, it most definately IS NOT purely resistive and has very strong reactive components that cause all sorts of funny things for a varying DC Voltage and Current like you get on a battery.

    A Lithium battery most definately has a Impedance and is as far away from a pure resistance DC device as you can get.
    Last edited by Fluffy; 2022/05/23 at 03:28 PM.
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    Default Re: How to do lithium impedance test

    Quote Originally Posted by stephenplumb View Post
    Impedance is a term that has no meaning in a DC circuit. It is only used in an AC environment and the maths gets a bit messier.
    That I know and the more reason to have placed it.

    Still hope someone will give some clues or how such a test is done. Let's then call it resistance testing. It would be easier I presume.

    @Sand - Also my 1st thought when I read it and the effort for a 1 year warranty.

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    Default Re: How to do lithium impedance test

    In my simplistic way I would draw 1A from a new cell and measure voltage, then do the same at 20A (or whatever the cell is rated at), and use the data to calculate the internal resistance.

    Repeat after one year to compare?

    Then to measure impedance drop it from one meter height and measure the bounce... :-)
    Last edited by faniedup; 2022/05/23 at 03:43 PM.

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    Default Re: How to do lithium impedance test

    Quote Originally Posted by faniedup View Post
    In my simplistic way I would draw 1A from a new cell and measure voltage, then do the same at 20A (or whatever the cell is rated at), and use the data to calculate the internal resistance.

    Repeat after one year to compare?

    Then to measure impedance drop it from one meter height and measure the bounce... :-)
    What does it do as you change from 1A to 20A - that's impedance ......
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    Default Re: How to do lithium impedance test

    I know - I know.
    Cheers

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    Default Re: How to do lithium impedance test

    Quote Originally Posted by Fluffy View Post
    Weeeelll, actually -- Impedance is the only thing that has meaning. In a DC circuit it just has zero reactive components, only has resistance.

    ALL circuits have impedance.

    Within the context of this thread, remember that although a battery is a DC device, it most definately IS NOT purely resistive and has very strong reactive components that cause all sorts of funny things for a varying DC Voltage and Current like you get on a battery.

    A Lithium battery most definately has a Impedance and is as far away from a pure resistance DC device as you can get.
    Thanks for this explanation. I was also using the DC = resistance, AC = impedance logic. Just shows matric science is VERY basic and can leave you feeling like an arse.
    Cobus
    Jimny

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    Default Re: How to do lithium impedance test

    Quote Originally Posted by jcdup View Post
    Does this come from a specific battery's documentation? If so, which brand/model?
    I found the link.

    https://shop.thesunpays.co.za/produc...v-lifepo4-cell

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    Default Re: How to do lithium impedance test


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    Default Re: How to do lithium impedance test

    Quote Originally Posted by jab2 View Post
    Thanks for this explanation. I was also using the DC = resistance, AC = impedance logic. Just shows matric science is VERY basic and can leave you feeling like an arse.
    Don't feel like an arse because you are correct.

    R = resistance. ( Resistor,)
    Xl = impedance or resistance of in inducator
    Where Xl = 2πfL. ( Inductive reactance)
    Xc = impedance of and a capacitor
    Where Xc = 1/2πfC ( capacitive reactance)

    All of them summed gives you Z = impedance

    I'm not even going to try and type that out on my phone but you can google it :-)

    Now if you look at the formula for inductive and capacitive reactance you will not the f for frequency.

    In DC circuits the f=0
    Therefore Xl = 0. ( Short circuit no effect zero resistance)
    Xc = 1/0 = infinite ( open circuit - infinite resistance)

    Now as Fluffy said a battery does have reactive components but in order to measure them the Fluke uses an 1000Hz AC signal.

    This type of battery test is really only usefull if you do the test periodically and trend the results but still gives you a good indication of the batteries state

    If a battery didn't have internal resistance it would be able to give you infinite current if short circuit it

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