My setup for battery research / development

[batteryGOLD]

Hi all, I'm new to this forum, as presentation I have something to show you all.
See pictures from my battery research setup.

https://ibb.co/8bfRtJk

https://ibb.co/VDNTZyW

https://ibb.co/zVsD0mf

https://ibb.co/LJrZSMZ

I have also a video about battery cells worst problem Dendrites here is lecture video : https://streamable.com/rksrw

Peace

 

[spinningmagnets]

Welcome to ES, and thanks for posting.

 

[john61ct]

https://phys.org/news/2019-10-scientists-dendrites-whiskers-lithium-batteries.amp

 

[batteryGOLD]

I have some experiment that maybe be of your interest

For those that want to learn something today here is today class experiment :

-pick up 1 old 18650 cell with many use and low capacity results, not useful ,considered sh*t but still working
-pick up 1 new generic or brand genuine cell

-test old cell @ 1A discharge and measure mAh from 4,1V to 3,6V useful window and write those crappy results
-test new genuine 18650 cell @ same 1A discharge from 4,1V to 3,6V & write results (do not worry to get only about 1/3 capacity or less, cells label say example 2500mAh for a window 4,2V to 2,5V discharge at ideal case 0,2C discharge ).

-Now make sure two cells old and new are at same voltage and parallel those 2 (one new and one used with good contacts for pair)
-Charge this parallel mix paired block to 4,1V

-Do again discharge test 4,1V to 3,6V for this paired 2P block @ 1A

-Sayy woww

-You can still continue capacity test until cutoff voltage 3,0V for crazy results.

 

[batteryGOLD]

- Now add a second sh*t used cell to this 2P block, will be a final 3P block . One new and two crappy old cells mixed parallel. Do test discharge from 4,2V to 3,0V @ 1A for this 3parallel cells and write results.

-Get amazed with results

 

[batteryGOLD]

- If you want for contribution post some pictures photos of results & setup used, plus new cell details and old cell reference age /year for all knowledge and building database

Thanks

 

[john61ct]

So you're saying the (Ah capacity of the) whole is greater than the sum of its parts?

 

[batteryGOLD]

YES Sir, some cases a lot MORE

 

[john61ct]

Interesting.

Can you explain why?

Peukert coefficient for most LI chemistries is rarely much over 1.06

 

[batteryGOLD]

According to study & experiments the old tired cells are limited by natural aging processes and dendrites inside, blocking current flow inside cell due to high internal resistance. When U apply load to tired cell, voltage drop is large, soo cell quick reaches cut off point of 3,6V or 3,3V (direct to low useful capacity results obtained)

When you pair old and new cells, the new cell will be dominant & lock same voltage at both cells parallel. The new one cell will get most of the current while being dominant at voltage for this 2P system.

Soo this paired system will have much less voltage drop, increasing significantly the final capacity. and lowering a lot the internal resistance of the system. "(Ah capacity of the) whole is greater than the sum of its parts"

At some cases, one new cell plus one used tired cell paired parallel is almost same has having two new cells depending at load.

 

[batteryGOLD]

wikipedia source:

"Peukert’s law is a valuable tool for estimation. However, it has limitations.
Battery age is not considered. The Peukert exponent increases with battery age.."

Soo I guess that law does not apply when doing parallel of mixed new and old cells Also estimation is different than real world true results.

But the "exponent increases" could be turned into near "exponent decreases"
Try to mix parallel 10P tired old cells, pair them with good quality LiPolymer 5mOhm cell (VERY CAREFUL WHEN PAIRING ALL CELLS MUST BE ALL SAME VOLTAGE minimal difference allowed)

Say woww to total final Ah available capacity results

 

[john61ct]

Soo I guess that law does not apply when doing parallel of mixed new and old cells

Actually applies more, but yes the exponent is indeed very variable over different conditions, takes precision to measure.

But yes can see how the good cell keeping voltage high will allow more to be extracted from the old.

Lifetime of the new cells will be much lower though,

and pushing the old ones far past EoL does get a lot riskier, especially with chemistries and use cases where thermal runaway is already a high risk

Generally it is best to retire worn out cells and replace the whole pack with new.

Boom bad.

 

[Hillhater]

See pictures from my battery research setup.
https://ibb.co/LJrZSMZ
Peace

Hi, and welcome to the forum,
its always good to have fresh ideas to contemplate.
But, be prepared for some debate and critical comments as your suggestions are controversial compared to prevailing wisdom of coupling cells of differing capacity and age .
A question...
What is the function of those two big speakers ?
..are you using them as a battery discharge load ?
...or just entertainment !

 

[Hillhater]

Generally it is best to retire worn out cells and replace the whole pack with new.

John, ....unlike a toothbrush with no bristles,... identifying when a cell is “worn out”. Is not so simple.
There is no written or agreed set of parameters to define when a cell is at “EOL”.
It varies depending on chemistry, application and intended use, etc.
In extreme cases , people have even been known to revive cells at “0.0 voltage” and reuse them !

 

[john61ct]

Personally I use 80% SoH for mission critical use cases, especially when traveling in primitive locations where suitable replacements are hard to come by.

Will stretch to 70% otherwise, but only if money is scarce,

 

[billvon]

According to study & experiments the old tired cells are limited by natural aging processes and dendrites inside, blocking current flow inside cell due to high internal resistance.

Dendrites can actually decrease internal resistance by providing more surface area. Most often there's no visible effect since they are so small. But once they grow long enough they short across the electrodes and you get a short (at best) or a fire (at worst.) That's why they are bad.

Soo this paired system will have much less voltage drop, increasing significantly the final capacity. and lowering a lot the internal resistance of the system. "(Ah capacity of the) whole is greater than the sum of its parts"

That's true. But you'd get the same benefit by simply discharging the older cell at a lower rate - or paralleling many old cells so the rate per cell goes down.

At some cases, one new cell plus one used tired cell paired parallel is almost same has having two new cells depending at load.

It's more like having an old cell at a lower discharge rate.

 

[docware]

- Now add a second sh*t used cell to this 2P block, will be a final 3P block . One new and two crappy old cells mixed parallel. Do test discharge from 4,2V to 3,0V @ 1A for this 3parallel cells and write results.

-Get amazed with results
Sayy woww

batteryGOLD, if you look at any discharge chart, you will find out that all cells have higher capacity when discharged with smaller current. For example LG MJ1 has roughly 1750 mAh at 3 A discharge, 2 000 mAh at 2A and 2 260 mAh at 1 A, all at 3,5 V end-voltage. You are doing exactly the same when parallely connecting the cells, old or new. In other words, it is normal that we can extract more capacity from the cell at lower discharge rate. And of course, internal resistance go down proportionaly to the number of parallel cells.

Woww not required

View attachment 2
View attachment 1

 

[john61ct]

all cells have higher capacity when discharged with smaller current.
…
You are doing exactly the same when parallely connecting the cells, old or new. In other words, it is normal that we can extract more capacity from the cell at lower discharge rate

AKA the already mentioned Peukert effect.

My impression was he'd exceeded the usual impact from that.

 

[batteryGOLD]

The end of life of cell is unknown,a cell can last more than ten years with great amount of energy.
The only limiting factor value is internal resistance and self discharge rate, but this can be compensated.

So for example you have a pack of six cells ( six pack?! ) from old many years laptop. 3S2P 12V (3serial 2 paralel)
Those cells sure are dead tired. For test capacity the usefull cap sure is less than 50% or much less, some at zero volts, but most easy to recover from zero to life again.

So there are few options and you can choose one:
1st case - Send cells to trash (most do this , worst case scenario..)
2nd case- Put cells at storage and never use them anymore..
3rd case -Use those cells for power 0,25W LED or low drain apps with very low performance
4rd case -Pick up 3x new good quality brand cells to pair with every 2P (Your final battery will be 3P3S - MAKE sure all cells same voltage at join moment) --> 12V more than +5Ah (4,2V to 3,6V voltage window ) battery for any medium demand current app (reuse concept) Test you new 3P3S pack @ 2,5A discharge rate. post results if you want..

Sony speakers are kind of load but to play very loud sound & bass with class D 200W RMS amp

docware user contributor:
Thanks for your great graphs , really easy to understand cells limitations and performance.
Could you or anyone do a great graph using 2 old cells paralleling one new good quality to show US tha great results.
Compare old cell#1 solo, old cell#2 solo , (cell #1,#2,new#3) parallel combined at 2,5A discharge

That data should be great for all community to see reuse concept. Thanks

 

[john61ct]

Just remember, with many LI chemistries, the critical factor driving cell / pack retirement is fire risk.

Climbs geometrically with SoH once below 70-80%.

And yes, gentler C-rates or added protective circuitry reduces the risk, but certainly does not eliminate it.

 

[goatman]

I bricked 52 or 56- 25r down to 0.0v I was able to save 28 cells that I thought I could trust. I use them in a 14s4p that are paralleled at the battery pos and neg. it works but I don't trust it and it stays outside. if its on my bike, its a spare that I can toss off quick. bottom line is im getting rid of the cells I saved. I don't trust them.

heres my problem with what you are doing, if you are selling these batteries are you telling people in big bold type face what these batteries are? or is it in a fine print disclaimer. when you pull nickel strip off the 18650 you take a piece of the shell with it.

I could see selling used 18650 batteries as singles to people who know. this almost sounds like counterfitting 18650 cells but instead selling packs that are half new cells and half used unknown cells and calling it refurbished.

 

[batteryGOLD]

I bricked 52 or 56- 25r down to 0.0v I was able to save 28 cells that I thought I could trust. I use them in a 14s4p that are paralleled at the battery pos and neg. it works but I don't trust it and it stays outside. if its on my bike, its a spare that I can toss off quick. bottom line is im getting rid of the cells I saved. I don't trust them.

heres my problem with what you are doing, if you are selling these batteries are you telling people in big bold type face what these batteries are? or is it in a fine print disclaimer. when you pull nickel strip off the 18650 you take a piece of the shell with it.

I could see selling used 18650 batteries as singles to people who know. this almost sounds like counterfitting 18650 cells but instead selling packs that are half new cells and half used unknown cells and calling it refurbished.

Hi Sir,

I DON'T sell any cells/batteries , I just do development and build batteries to company customers with new genuine cells branded from EU certified warehouse at company LAB. Reused concept is under development and testing. but never recommended. Just for scientific experiments USE allways new cells when building any kind of battery.

For 0V cell recovery (check voltmeter and see cell voltage increment if it blocks at 0,8-1V U got a shunt cell, but some go alive keep tryin)
MOST 0volts cells are ready to recover, but give those small current until 2,5V cell voltage , maybe some heat, then give a break some time than if U want give fast charging until 4V than gentle finish until 4,1V let it rest, check voltage, go quarantine 1week than check voltage again. If low loss ready for reuse.
0V cells maybe some lost 10% capacity, and other dont't . 18650 are crazy and some after some recover cycles go OK

There is some solutions for perfect bat pack. But U need to know all cells capacity and use web site repackr.com
That will balance cells capacity to build packs.

Measure all your cells capacity and match those. Than use a new cell per each 4Pcells This means u need to buy 14new good quality branded cells , advice Sony VTC5A pair new with those U have, now U get a massive POWER PACK 14S5P
Gold advice-> Use double nickels!

Go POWER