More Charger/Tester fun

Give a man a fish and he will eat for a day.
Give a man Excel and he will analyze data to death.

So anyway I came across the good fortune of 1600 LGGBM261865/LGEBM261865 cells.
All have great IR numbers so far with 41.9 mΩ the highest and 35.23mΩ the lowest.
Testing with a capacity of Max 2885mAh and Min 2512mAh
So far I have tested 333 of them with my combination of testers and started to find a peculiar consistency with each tester and its slots.
My testers are:
4 Foxnovo with 1 that has 2 slots down.
3 OPUS
1 SKYRC
1 XTAR

Now granted the cells are slightly used 2600mAh cells and I am using that number as a baseline decided to play around with data for a bit and came to some interesting findings.
The OPUS averages 106%_________________ and4.1460 Volts after charge
The XTAR averages 102%_________________ and 4.1654Volts after charge
The SKYRC averages 100% (no surprise there)__ and4.1913Volts after charge
The Foxnovo averages 103% __________________ and4.2023Volts after charge

The OPUS final charge Voltage has me somewhat worried as it is close to the SD Voltage we all go by after a month of sitting.
Makes me scratch my head of how many I tossed of those. So in my spreadsheet I now record the Voltage as it comes out of the Tester.
Also this is my experience with my testers and by no means indicates your testers are the same.
Now on to the slots.
So I decided to label each individual slot on each tester and recorded the results.
These are the initial results after 333 cells. After 1600 we will see if anything changes, but there definitely is a pattern.
( I know, I can hear it now "This guy must have too much time on his hands")
Needless to say here are the results:

Wolf

Very useful for anyone needing high accuracy.

Have you tried data logging every cell and integrating current between 3.9 and 3.0v (zero current pulse off) , discharge must be > 240 seconds deep too. Use that as your nominal range... just a thought.

Initial voltage makes a huge difference. 4.05 to 4.18 is some 20% ..

Using my custom box of tricks (charger and discharges) my cell population looks like




And by cell types

I have not done any data logging as the off the shelf charger/testers do not have an interface to accomplish that.
The SKYRC does and if I so desire I could do that.

The purpose of this exercise was just to see if individual slots of individual (Off the shelf)charger/testers had a correlation to mAh results and the final voltage a cell was left with at the end of the "canned" program.
Again the SKYRC allows almost infinite selections but was set to a "canned" program to make it fair. The only thing that was different was the discharge V was set to 3.0V rater than ~2.8V (which is evident by the mAh results) as all the other charger/testers arenot adjustable.
The averaging of all the results clearly shows that each slot on each charger/tester has a predictable outcome. It is probably due to tolerances within the parts that measure the results of each slot.
Now mind you we are talking <10% and in the whole scheme of things is really not that critical.
That's why I called it fun.
Snippet of the sheet of testing data collected.





For some more serious studies regarding cell interaction etc. see my threads on:

High and low drain cells mixedhttps://secondlifestorage.com/showthread.php?tid=7873
Behaviour of cells in parallelhttps://secondlifestorage.com/showthread.php?tid=7846


Wolf

Hells Bells.. I found it hard enough to compare result data from different slots of the same discharge setup, let alone different discharges using different cut off times all with independent clocks..

All may read 1A but not all will real 1000mAh after exactly 60 minutes.

Then throw in the different start SoC due to charger end voltage and current cut-offs..

Have you tried using a bench-top power supply to regulate exactly 1A into into slot for one hour? Validate its voltage, current and timebase accuracy? That may tell you a lot about its measurement capability.

I've also seen that some batteries read good capacity but have higher IR at low SoC than other cells. I wonder if this could be a good predictor for binning versus using certain cells in your packs?

FWIW, for my set of batteries (1.6Ah to 2.5Ah), when using a 1.6A discharge current, the 3.0->2.7v component makes up 2-6.5% , 3% avg. bugger all really.. but that variation will throw off your numbers if you're comparing brand to brand..

Araknid said:

...............Have you tried using a bench-top power supply to regulate exactly 1A into into slot for one hour? Validate its voltage, current and timebase accuracy? That may tell you a lot about its measurement capability........................

Click to expand...

If time allows I may do that.

I've also seen that some batteries read good capacity but have higher IR at low SoC than other cells. I wonder if this could be a good predictor for binning versus using certain cells in your packs

Click to expand...

He hehe wow are you late to the IR party. I have a whole study of ~6500 cells dedicated to the study of how IR affects a cells SOH and that different chemistries have different IR results etc.............

Search the forum for does internal resistance matter, a never mind here is the link https://secondlifestorage.com/showthread.php?tid=6575&highlight=ir+matter
There are many more posts on IR by me............................

In my PowIRwall build I used a variety of cells with a narrow window of IR from 45m? to 65m? and mAh of 2250 to 2650.
https://secondlifestorage.com/showthread.php?tid=7804

I also have an IR cheat sheet that gives you a guideline of what an acceptable IR is for common cells we see.
https://drive.google.com/file/d/169QnjLDBmFyfOY6RybH0VGBR4bV2NJDT/view?usp=sharing

And last but not least behavior of cells in parralell.https://secondlifestorage.com/showthread.php?tid=7846

Wolf

Wolf said:

Araknid said:

...............Have you tried using a bench-top power supply to regulate exactly 1A into into slot for one hour? Validate its voltage, current and timebase accuracy? That may tell you a lot about its measurement capability........................

Click to expand...

If time allows I may do that.

I've also seen that some batteries read good capacity but have higher IR at low SoC than other cells. I wonder if this could be a good predictor for binning versus using certain cells in your packs

Click to expand...

He hehe wow are you late to the IR party. I have a whole study of ~6500 cells dedicated to the study of how IR affects a cells SOH and that different chemistries have different IR results etc.............

Search the forum for does internal resistance matter, a never mind here is the link https://secondlifestorage.com/showthread.php?tid=6575&highlight=ir+matter
There are many more posts on IR by me............................

In my PowIRwall build I used a variety of cells with a narrow window of IR from 45m? to 65m? and mAh of 2250 to 2650.
https://secondlifestorage.com/showthread.php?tid=7804

I also have an IR cheat sheet that gives you a guideline of what an acceptable IR is for common cells we see.
https://drive.google.com/file/d/169QnjLDBmFyfOY6RybH0VGBR4bV2NJDT/view?usp=sharing

And last but not least behavior of cells in parralell.https://secondlifestorage.com/showthread.php?tid=7846

Wolf

Click to expand...

hell ye I'm total noob only been going off research papers and alike

I'll pop some ideas in another thread after reading the rest of those threads. skim reading agrees with two studies i've read from early this year and late 2019.