SOH now what is this???---->storage... i have more questions than answers

100kwh-hunter

100kwh-hunter

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Now what is the big deal about SOH.
When i was harvesting li ion 18650 i toke all the cells out that where below 80% soh.
Because it was safer?
But if i would assemble packs (14s100p)with only ~50 to 70% soh i would have ~1 to 1.3amp left from a 2A cell?
And they would decline faster and faster? right?

Probably i am completely wrong about this.

What about other chemistries, like NMC orLiMnO2?
Are they going to decline also like this?

Here is the catch:
I am willing to buy a (some)Nissan leaf batterypack(s) for 2160E with a SOH of 83%

For those who know me...yes i started to collect laptop and e bike batts again, this virus has no cure......

What are the facts about SOH?

Thanks in advance for your answers on this probably stupid question, but i really like to understand the mysteries around SOH.
With best regards Igor
 
So this is a quick answer :p

SOH is important because it shows how much capacity (Ah not A) is left.
Currently most manufactures dont show how they degrade below 60-80% depending of chemistry.
Some claim it drops fast or that it becomes unstable... Some claim that its linear down to 0%.. But still with higher statistics that it may fail....

There are tests done on the forum that actually shows a linear degradation on standard LiIon cells BUT it also have shown that its not 100% predictable below 80% SOH..

By reading ALOT of scientific papers i do think LiIon is pretty stable atleast down to around 50-60% and LiFePo4 is even better.

And most importantly. Its Ah and not A ;)
 
agreed with damomer.
You don't want to spend a lot of time/money on something that'll last only a year or two, maybe 3, when you could go with slightly higher SOH grade and it last muuuuch longer.
Granted, generally speaking, we use the cells at a fraction of their designed discharge, and voltage range. This extends the life quite a bit. So if you add up all the methods for extending life, you could put a system in place and not have to worry about replacement for 5 - 10years, or longer perhaps. (which is why using some form of power-in/power-out comparison to keep on an eye on SOH over time)
 
@ Daromer,
Yes i read those test with interested, he was testing curtain cell up to 1500! cycles?
Going to reread it when i have more time.
I thought if you drain ~100ma(h) for one hour from a cell that holds 2A then the ah would be 0.100mah and the left over storage would be 1900ma?
If i would drain a 2a cell in 15 minutes than i would have a 10ah discharge.
Apparently it must be: the cell is/was able to give 2a in one hour..2ah.
Got it, i hope i will remember this from now on.(was expecting Sean to jump on this one btw :D :cool:..)

So basically below/around 80% no matter what, a cell would be to costly and degrade to fast, despite the chemistry.

@Korisan,
I don't think that the drain is the most important for me, but more the total storage and the lifespan.
What i already thought is it was not much by comparing them to my li ion endeavors.
100e for a kwh seemed cheap and good...
I think i will go with new LifePo4 cells--> 266e (aliexpress, new and a grade) to 300e (Winston/Thunder-sky)for a kwh, a bit more expensive but it will last 5 times longer, so cheaper in the long run.

Best Igor
 
If your drain a cell with 100mA and that is done for 1 hour you drained 100mAh. If it was only 30 min you end up with a minus of 50mAh ;)

What happens below 80 or 60 or 40 is basically a bit of a mystery due to most manufactures generally go to 60-80% and dont have tests going further down.
 
Like said above, with 18650 cells, what happens below 80% remaining SoH seems to be variable.
I'd suggest that the car manufacturers would be aiming for quality & stability, so they would be more likely to last better.
Leaf cells have large capacity & you would be using them at a fraction of the charge/discharge amps they are rated for - this further suggests they would last better.
If I understand correctly, LG are the Leaf cell manufacturer?
In this thread, LGs are lasting very well:
https://secondlifestorage.com/showthread.php?tid=6868
A perfect comparison? Maybe not ... but if I had the need, I would feel happy buying those packs myself :)
 
Redpacket said:
If I understand correctly, LG are the Leaf cell manufacturer?
Click to expand...

Actually, Leaf cells are produced by the company AESC, which NEC+Nissan+Tokin togetherestablished more or lessspecifically to produce batteries for Nissan. While it started out well, "issues" (general uncompetitiveness due tolow production capacity and mediocre energy density?) lead to it getting sold off to a Chinese company.

https://en.wikipedia.org/wiki/Automotive_Energy_Supply_Corporation
 
Interesting. I'd suggest still very likely to be good cells though.
A number of forum people are using them - anyone how do they seem to be going? Any signs of early decline or seem to be lasting OK?
 
Redpacket said:
Interesting. I'd suggest still very likely to be good cells though.
A number of forum people are using them - anyone how do they seem to be going? Any signs of early decline or seem to be lasting OK?
Click to expand...

I think so, too. As long as you get a batch in good condition that has not been roasted by repeated use offast charging in hot climates.
And thelithium-manganese oxide chemistry is reportedly much safer, which explains the absence of cell levelfusing on most systems.
I'm considering using leaf cells, but for me it's easier(though more work) to use 18650s.
 
ajw22 said:
Redpacket said:
Interesting. I'd suggest still very likely to be good cells though.
A number of forum people are using them - anyone how do they seem to be going? Any signs of early decline or seem to be lasting OK?
Click to expand...

I think so, too. As long as you get a batch in good condition that has not been roasted by repeated use offast charging in hot climates.
And thelithium-manganese oxide chemistry is reportedly much safer, which explains the absence of cell levelfusing on most systems.
I'm considering using leaf cells, but for me it's easier(though more work) to use 18650s.
Click to expand...

If you can find a low mileage leaf car then yes it would be a good deal. A 100k leaf car has a lot of 'miles' through it. Think about it, a tesla car is 4x larger capacity than a leaf car. So a 100k leaf is equivalent to a tesla car at 400k in terms of battery cycles through it. That is why the early gen 1 leaf owners were complaining about battery life after a couple years and they came out with a 80% long life charging plan to try to mitigate the degradation as well as a $2850 battery swap option. The ones sold by batteryhookup are probably from these battery swap programs.
 
Gents, i thank you for your answers.

Yes a bit of a late replay, i wanted to read more.

If I understand it correctly the leaf cells (if not mistreated) could be used up to even 15% soh?
If this is true, than it will be a better deal than with the Winston/Thunder-sky or the ones from BLS both incl the advised bms.

For a total of 20kwh storage:
Second handed leaf: 4700E incl batrium. (toke a swing at the import tax ~500E)
New Winston cells: 12.800E
New BLS cells: 5600E.
Those prices are not including wires fuses cabinet inverter ect, just storage with bms.

But how far can you go with LiFePo4 cells in terms of SOH?
Or with the Leaf cells?
Can anyone shed some light on this or own experience?

Thanks in advance for your answers, best Igor
 
Mnay LiFePo4 have datasheets below 60 or even down to 40. Mine have charts down to 40%. So in current pace the AGE Will degrade faster than cycling for me....
 
At Daromer,
I found a lot of bullshit about age, really a lot, but no facts or stats.
I think i understand yoursituation.
But you sell and gain every day, how does age count for your cells?
Is your problem not more the cycle life????

But Oke

For example:
https://www.abcnissan.com/blog/2018...e, you will see,problems will start to happen.

Especially the part in "cold" conditions.....if reading carefully you will find what they all say:
Cold climates yield a longer battery life, but a shorter driving range.....

But we don't use 85kw in one hour, except in our cars....24kwh would be empty in 45 minutes on the highway not city!
24kwh i would not even use in one day(the ev's and induction cooking is a different story)
I understand the hot and cold climatepart, but aging is new for me.
I am planning to store them in a "basement type like conditions" like my wine ~15 to 20c max whole year around....

So go big or go home hold no ground?
Please tell me more.
ANYinfo is appreciated, thanks in advance, with best regards Igor
 
Age is like everything else
In some tests they state you loose up to 6% of the total capacity per year. This at stored temperature at 20C and i think it was 80% SOC... But dont take me on those numbers 100% since it was some weeks since i read it last time...

For instance i got like 2500 cells that was NEW-old stock. They were 6 years old and testing yielded a loss of around 5--10% in total. They were all stored in less than 15C and where at 40% SOC.... So with those to you can calculate. Higher SOC and higher temp = more loss per year. Easy 6% loss per year in capacity just due to age for many of the users here

I dont think the cycle count is what kill my cells. Note that i cycle roughly 10% of the total capacity per day at most. Lets say you need 60% or more to count as a "cycle" when we talk from the datasheet. That means i cycle roughly 365/6 = 60 Cycles per year. IF we translate that very very roughly to losses in capacity thats like uhm.. Fraction of a % :) Note that at 60% cycle my cells are guaranteed 5000 cycles before they have lost 40% of their capacity. So if we take those number i loose around
83 years before that happen or 0.7% capacity loss per year.
And 0.7% loss per year cycling is less than lost due to age ;)

Note that i dont cycle more than 10 months out from 12. Also note that my average temperature for the cells are around 12-13C if we flatten it all year around :)

Hope that give some input and why i have done as i have and why i reason like i do. I have sat down calculated and looked through how it works.

Go big or atleast big enough is important!
 
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