It was a while back when I bought some cells from Aliexpress, found problems straight away, despite much testing and proof that there was some faulty cells they still refused to admit it.
Not going to go into details about all of it now as I'm done with all that.

I will just show what was going on and why, the cell would show voltage but would not discharge the voltage would drop to zero (open circuit) when connecting the inverter.




I removed the cell and tried to charge it separately from the others, it would take current for a moment then go open circuit, put a lot of weight on the terminal and it would start again.
I only recently got hold of a little endoscope camera so I thought I would check inside the cell

Sorry about the small photos, the camera was only 640X480 and had a agle mirror on the end made it worse.
The square aluminium block is the battery terminal going through the plastic top, photos are upside down.
The little plate should be holding the battery plate to the terminal, not sitting there on holiday.




You can see the plates are barely touching the terminal, any wonder it don't F n work.


Hey there's a washer!!!


Oh look, a NUT FFS.


The terminal at the other end with copper plates, can see some threaded rod.


The rest of the cells are working ever since after replacing 3 that were like this.
Well I learned my lesson, don't buy cells from Ali.
I have these batteries in the shed running most days and sometimes they power the house, so I'm getting use out of them.
They are getting out of balance more often lately so will have to make some changes, more on that later.

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Cheers Aaron
Off The Grid

Wow Aaron, they seem more like garbage fake copies and less like lower grade factory rejects, but as I haven't seen many of this type up close I may be way off the mark.

Thanks for sharing.

They are very heavy cells compared to the new blue metal case cells.
I was trying to work out how they assembled them, the terminals appear to be moulded into the top, the top is welded to the outer case, Perhaps they lowered the plates and the top assembled into the case like it was done with some FLA batteries.

Oh that makes more sense now. I seem to recall seeing a post and a picture on another forum showing a similar problem. Was a few years ago though.

BTW thanks for the Scanner app on my thread, the cells appear to be real EVE cells
.
Edited 2023-12-19 10:17 by KeepIS

Thought it worth an update, just decided to cut the white cell opened below the terminal just to see whats going on, sort of prompted to do this because of the other white cells in the shed.
Ok those vibrating saws are handy sometimes, I cut out the area where the positive terminal bolts are located, already new the nuts  and backing plate had fallen off.
Can see the bolts still in place through the thin aluminium plates, the other side had to be cut opened as well so the bolt heads can be held or removed, I decided to remove them one at a time for inspection, found that they where eaten away for some reason, they were fairly clean SS bolts, retrieved the nut from inside and found it would slide over the bolt threads with out even touching the thread, so it has corroded somehow, perhaps low grade stainless steel as they do stick to a magnet, the other thought it that the batteries might have been stored on there side for some time submerging them in electrolyte and corroding the bolts, these cells are wet with electrolyte so don't tip them over or it will spill out any opened hole...found out.
There was absolutely NO corrosion on the aluminium plates or the copper at the other end, they where as clean as you could ever get.






Anyway just for fun I replaced the bolts tightened them up and glued the plastic case together, checked the voltage and it was just a little lower than last I checked, turns out it was sending some power to parts of the cell that had no contact previously.
Connected the cell to an old charger give it about 40 amps, thats about all I could get from the old charger at low voltage.
So there was almost no resistance at the cell terminals now the voltage barely moved at all, so it would take more.
It looks like it might work now, it might be cheap fix for this cell that was going to be thrown out,  but will leave it sit outside for a while to see if it has any shorts or reaction to being opened.

I wouldn't be surprised if some of the other cells will need new bolts as well, what else is strange is the negative terminal bolts seem to be ok, they bolt through copper plates.

Apologies my writing style,  its getting terrible, I used to be better than this, getting older and spending time on better things than a keyboard.

Hopefully some of this makes sense, it might be good for someone else with the older plastic type cells that can be repaired.
Edited 2024-10-15 18:27 by Revlac

Doesn't bode well for the longevity of the cells if the bolts corrode like that.
I hope that the repaired cell keeps working.
Thanks for the warning
Pete

Looking at it again, this might be electrolysis on those bolts.

Aaron, stainless steel (any grade) and aluminium are a *very* bad combination. I know this because for many years I had a sailboat and If I did not insulate these two from each other they would corrode (electrolysis).

Actually, stainless only stays so in the presence of oxygen. If you place it in a sealed space with some kind of electrolyte it will suffer what's called crevice corrosion. The picture of your bolts & nuts show evidence of that.

The big (200Ah) lithium cell I have do use stainless bolts for the connection but these go into a blind hole, no access to the battery inside.
Negative terminal bolt screws into a copper electrode connection, the positive into an alumunium electrode connection, both are blind holes.

Hi Murph,
I did some years building Boats, Quite often we used stainless steel fittings at the customers request, I remember one fellow brought in some yellow stuff in a squeeze bottle, wanted that stuff under ever nut bolt screw and fitting, oh fun.

  Quote  

The big (200Ah) lithium cell I have do use stainless bolts for the connection but these go into a blind hole, no access to the battery inside.
Negative terminal bolt screws into a copper electrode connection, the positive into an alumunium electrode connection, both are blind holes.

Yes these are the same, 10mm blind holes in the top with SS bolts on the terminals, photo top of page.

I could use an aluminium rod inside the cell and rivet it in tight to hold the plates to the terminals instead of those bolts they had inside, its probably better being the same material.
It wouldn't surprise me if some (other manufactures) of the other plastic case batteries had similar fixings inside the cells.

Hi Aaron, Yes, that yellow stuff was still available last time I went to a ships chandlers but it was horribly expensive. I mostly used plastic washers.

Regarding the terminals, I think it's a really bad design to use *any* type of bolt/nut inside a battery. The big cell I took apart had solid copper & aluminium blocks under the terminal, these finned out into many thin layers which became the active electrodes. No screws were in there at all.

  Murphy's friend said  

Aaron, stainless steel (any grade) and aluminium are a *very* bad combination. I know this because for many years I had a sailboat and If I did not insulate these two from each other they would corrode (electrolysis).

Actually, stainless only stays so in the presence of oxygen. If you place it in a sealed space with some kind of electrolyte it will suffer what's called crevice corrosion. The picture of your bolts & nuts show evidence of that.

The big (200Ah) lithium cell I have do use stainless bolts for the connection but these go into a blind hole, no access to the battery inside.
Negative terminal bolt screws into a copper electrode connection, the positive into an alumunium electrode connection, both are blind holes.

Aluminum with stainless hardware is how ham radio antennas are built... never had a problem with corrosion. Its when you add saltwater and can create a path for electric current to flow...

Whole lot of stainless and aluminum up in the air...

Been charging the cell for a couple of days with a lab power supply to 3.6v, once it got to that stage the charge amperage dropped off fast, all is going well.
Put this cell in the shed battery bank, in place of cell number seven, thought it would be a bit of a hassle changing a cell in an existing setup but NO, it was really very easy.
Been running with that repaired cell and its working well, better than I expected so will see how it holds, its the same age as the others just hasn't done the same amount of cycles.