280Ah Ninthcit cells

[mantonis]

I have just received 16 nos 280Ah Ninthcit cells, at least the cells have Ninthcit labels but the code on the cells refers to EVE.
I actually ordered grade A EVE cells from the supplier BLS Battery through AliExpress. The cells were courier delivered from their warehouse in Germany and they arrived within 10 days of shipment which is pretty quick for shipments from Germany to the Island of Ireland.
They were generally well packed but in a few boxes the terminals had partly penetrated through the cardboard box and punctured the plastic bag. Fortunately no terminals appear to be damaged.
I have measured the cell voltages and they are all within a range of 3.299-3.3020 volt..
There is no VISIBLE external damage and all the cells look clean. The QR codes are all in tact. All good so far. I still have to measure the impedances.

However some of the cells are obviously swollen but I have tried that quantify that by measuring the cells using vernier calipers with long jaws.
I have done that by determining the diameter of the cells across the width as I believe that swelling across the length is usually not an issue (correct me please if I am wrong!)
I first measured the width of the cells on both sides at the top of the cells (close to the terminals). I have found that at those locations the diameter is invariably smallest.
I then slid the vernier calipers to the bottom of the cells, again on both sides and noted the LARGEST dimension.
I put the results of this exercise in a spreadsheet and produced a delta between the smallest diameter and the largest one. I believe that represents the largest "bulge" in the cells.
Please note that I found quite a variation in the smallest width across the top of the cell (range 70.9 to 71.5mm), I assume that is the manufacturing tolerance.
The delta between the largest and smallest width was as follows:
One cell 3mm
One cell 2.8mm
One cell 2.4mm
One cell 2.2mm
One cell 2.1mm
One cell 2mm
Two cells 1.8mm
One cell 1.7mm
Two cells 1.2mm
One cell 1.1mm
Two cells 1mm
The other cells were under 1mm

Whilst bloated cells are obviously a concern I am not sure how much bloating is to be expected and how much would be unacceptable.
Can anybody quantify that? I have not been able to find any standards or specifications for LFP cells that bloating or swelling specifications/standards.
I am planning to put the cells in a pressure frame but I am concerned whether "flattening" the cells would cause internal damage.
As the cells are already charged to a 70% SOC I believe that they should not expand much more.

I would greatly appreciate any recommendations and advice.
Thanks
Mike

 

[time2roll]

They are what they are. Best to assemble and place in service. Mild compression should not be an issue.

 

[mantonis]

I am going to assemble them next week and will then charge the battery to 100% SOC and see what happens.
Hopefully at some time in the future some LFP cell standards will be developed so that us buyers have some sort of guide to work with.
The present situation would not really be acceptable in most industrial sectors.
I am currently involved with a company making precision measuring equipment and it would be easy to equip cell manufacturing lines with equipment to measure the cell case during the charging process and detect and quantify the expansion of the case.
Cheers.
NB It occurred to be that such standards have probably already been established by EV manufacturers. In my experience vehicle manufacturers invariably require measurement of components and assemblies supplied by them, often to high levels of accuracy.
It would frankly be inconceivable that they would allow cell manufacturers to supply without pre-set standards.
The PV industry is obviously seriously lagging!

 

[time2roll]

Yes when purchasing 50,000 cells per month there would be a bit more details in the contract.
DIY gets the scraps that did not pass.

 

[50ShadesOfDirt]

A purchasing department, specifications, tons of research, vendor qualifications, return policies, etc. ...

At our level, all extremely hard to do, but mostly possible even for a one-man show ... you just have to know to do it in advance, or have gone through it with something.

The first generator purchase I ever made was a disaster ... sounded good on paper, but pretty much failed on the ground. The second was a bit better, but I finished discovering all the in's and out's of vendors, generators, location/proximity to service, etc. So, it wasn't until the third that I had it down to a system and a fine art of generator purchasing, operation, automation, and so on, all at low cost.

What a jolt ... oops ...

 

[mantonis]

During most of my career I was involved in the generator industry and in my time I have seen some unbelievably ignorant purchasing specifications drawn up by very expensive consultants employed by companies purchasing the generators.
I therefore fully understand you.
The problem is that large consulting firms mostly employ young inexperienced graduates to do the donkey work but they charge rates based on the cost of their senior staff.
It was always so and it will remain always so.