Tested: Capacity vs Internal Resistance

[Doctorbass]

I used my Li-ion Konion cells (60 of them) to evaluate the parallel between the their Capacity and their Internal Resistor.

We can see that as the capacity decrease, the internal resistor increase.
All X value correspond to 2 cells in (2p) config.

i tested all cell in order, so many of the cells come from 4s pack that was used together so their life cycle are the same and that is the reason why you see some flat with 4 following point.

 

[Toorbough ULL-Zeveigh]

I've always considered Peukert while interesting to be rather useless for any practical calculation.
While there are a number of factors that comprise the Peukert effect it seems that internal resistance is the single largest & most significant factor.
With Ri at least you can use it to do caculations that while not perfect come close in making useful capacity predictions.

What if you inverted the resistance figures & plotted conductance instead, perhaps the correlation might become even more plainly visible.
Just 1-drin about how to pronounce Konion, does it rhyme with onion?

 

[Doctorbass]

:wink:

About Konion and onion, i ovserved that when i search on google about konion. it suggest me to search with onion...

Doc

 

[Toorbough ULL-Zeveigh]

damn, that was fast!

Yes it tracks pretty close.
A few cells like 42 & 50 & a few others seem to be exceptions but not by much, within measurement tolerance anyway.
Thanx for all the ongoing testing & leg work, it's very much appreciated.

 

[tailwind]

Hi Doc,

Another way to view the data.
If you squint your eyes the graph seems to show four different populations.

Greg

 

[Doctorbass]

Good representation too!

What i can conclude also is that:

-as the measured capacity is close to the 1C rated (in this case 1500mAh x2)=3000mAh,like brand new cells, we observe LESS variation of the internal resistor and valur are closer to the rated Ri.

- As the capacity decrease, we observe more variation of the internal resistor, and that phenomenum seems to increase as the capacity decrease. and the Ri increase


Ex: with cell of rated capacity of 3000mAh,

Case 1
cell 1 C= 3000
cell 2 C= 2950
(delta C=50mAh)
In this case, Ri would vary only of 1 or 2 mohm
Ri around 32mohm


Case 2
cell A C= 2750
cell B C= 2800
(delta C=50mAh)
In this case, Ri would will vary of 5 to 15 mohm
Ri around 40mohm

Doc