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SOH now what is this???---->storage... i have more questions than answers
#1
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 or LiMnO2?
Are they going to decline also like this?

Here is the catch:
I am willing to buy a (some) Nissan leaf battery pack(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
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#2
So this is a quick answer Tongue

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 Wink
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#3
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)
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#4
@ 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 Big Grin 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
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#5
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 Wink

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.
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#6
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 :-)
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#7
(10-01-2020, 10:48 AM)Redpacket Wrote: If I understand correctly, LG are the Leaf cell manufacturer?

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

https://en.wikipedia.org/wiki/Automotive...orporation
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https://secondlifestorage.com/showthread.php?tid=6458
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#8
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?
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#9
(10-01-2020, 11:06 PM)Redpacket Wrote: 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?

I think so, too.  As long as you get a batch in good condition that has not been roasted by repeated use of fast charging in hot climates.
And the lithium-manganese oxide chemistry is reportedly much safer, which explains the absence of cell level fusing on most systems.
I'm considering using leaf cells, but for me it's easier (though more work) to use 18650s.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#10
(10-02-2020, 12:01 AM)ajw22 Wrote:
(10-01-2020, 11:06 PM)Redpacket Wrote: 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?

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

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.
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