Why calling it 'impedance' ?

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Greetings.
The cells forming a battery pack, and their internal characteristics, referred as 'impedance' instead of resistance. On day one I learned impedance is tightly tied to a frequency. Where is frequency present on direct current in order to use that term ? Seen used in several tutorials. Why ? Since when is that a proper way to refer to internal resistance ?

Pages 2-2 and 2-3 at
----> https://www.ti.com/download/trng/do... Cell Balancing - What to Balance and How.pdf
 

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Battery internal resistance is in fact frequency and state-of-charge dependent. It's usually referred as impedance.
 

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impedance is the combination of resistance and reactance(frequency-dependent part). It is not incorrect to refer to a wholly resistive parameter as impedance.
 

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"Impedance" because something "impedes" the flow of current.
You could have said "resists" but that one's taken. So "resistance"
has its explicit dV/dI meaning, while "impedance" also includes
derivative and integral (inductor, capacitor) modes of "impeding".
 

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Impedence is where you get to use the pythagorean theorem from math class. Impedence is eqial to the hypotenuse of a right triangle with one leg equal to resistance and the other leg the reactance, either capacitive reactance or inductive reactance to alternating current. If the reactance is 0 then the impdance equals the resistance.
 

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Thanks.
And... this internal 'impedance-named' for direct current cells in batteries; is when charging, standing-by, or discharging ?
 

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Impedance can be measured in all battery operation states. We built battery testers that are able to superimpose AC current during charge, discharge and idle state performing impedance spectroscopy.
 

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