Resistance V Capacity

miwall

New member
Joined
Oct 26, 2016
Messages
18
Hi I have just started building Mi powerwall! Have to say great job with the 'youtube' Mr HB Powerwall, have been inspired with your enthusiasm, great job and now... I have a thought that I would like to throw out there.
'Charging and discharging and internal resistance'...I think I have noticed a corrleation 'probably no surprise' with internal battery resistance and capacity anything above about 170/200 m Ohm's seems to have a low Capacity below 2000mA ???? So with that why not check the resistance first and discard from there. I also ran a test to see the difference in resistance from part charged to fully charged 3.4V ish to 4.17V isn and there was maybe a 10 to 30 m Ohm difference!!.......and now a Question:what size copper sheet are you using for the bus bar that you solder the batteries to?
Keep the great work up Thanks Mi powerWall. :mrgreen:
 
I tried that on mine and cells below 3v, which were almost all of mine, read really high on resistance. I don't even test resistance any more until a battery is fully charged.
 
Ok noted will try the same with some of my lower voltage cells and post the results :mrgreen:
 
HI Paul i have watched quite a few of your youtubes, But if i did as you say and discarded any thing over 120 M Ohm's i would have very few Cells for me i am using the OPUS-BT-C-3100-V2-2-18650-26650-Li-Ion-Ni-Mh-AA-CHARGER-TESTER-ANALYZER and anything round about the 150mA I am using, the test is being preformed when being fully charged. Not sure you would have moved back home when i send this.
Cheers Battman :mrgreen:
 
OH - and I just realised - you're probably doing single cells? My resistance measurements are for pairs.

I arrived at my 120 mOhm threshold by measuring resistance and capacity on a bunch of cells and then plotting resistance vs capacity to find the extremes. Then I just picked a threshold value at about the 80% mark. So I'm discarding the worst cells (which I'll use for something less important).

Hope that helps.

Cheers, Paul
 
Back
Top