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2̶8̶0̶ ̶A̶h̶ 254 Ah cells + smell. Are they damaged / used?

Troubles in Travel

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I ordered 4x 280 Ah cells on Aliexpress. QR codes were OK, terminals bit scratched. But overall there was no cut / puncture / deep scratches on cells. They were all in ok visual shape, no bloated cell either.
I assembled cells into a battery and after a few trials and errors, I think it worked out.
There was 1 think which worried me. During the charging cells I think I smelled some kind of smell. I was a bit afraid so made a few more charging / discharging tests and smell was only appearing in some occasions.

To test are they broken or not, I ordered a battery tester and tested battery twice (9A discharge). It showed 254Ah 3285Wh.
Before test all cells were top balanaced and charger to 3,65V. After discharge, there was quite a big difference in voltage: 1. 2,775 2. 2,829 3. 2,920 4. 2,974 (0,2V diff)
Cells are compressed, but I left minimal gaps to let them expand a bit.
BMS is JBD-SP04S020

My main question is: Are they safe to use? Should i sealed them in a box?

Thank You for all help :)
 
Seal in a box is always a good suggestion.

254Ah is not a bad result to be honest.

Its usually the trash which ends on Aliexpress, so having received actual cells, and not too much damage is a huge bonus.

Off course it's nowhere near the advertised 280Ah, but you opted for buying junk from Aliexpress so it could have been much worse.

Still, dispute it with the seller and see if they can compensate due to the lower capacity.

and next time better buy at a well known seller :)
 
So are they safe to use? They should have 280Ah, but in fact have a lot less. When i watched a lot YT videos, all guys even with grade B cells had 281/282Ah cells
 
So are they safe to use? They should have 280Ah, but in fact have a lot less. When i watched a lot YT videos, all guys even with grade B cells had 281/282Ah cells

Yes, but they bought them at well known sellers, and not at Aliexpress.

Genuine cells are sold in huge quanties directly by EVE and an occasional seller with good sources (with testing rapports and so on), which fully matches the EVE classifications

Bulk cells are sold by many sellers we are using here (Basen, Luyuan, Qishuo, Docan, just to name a few), generally around the 280Ah mark and sufficient for bulk storage

Most underperforming cells, bloated cells, scratched cells, rebranded cells (scratch 230Ah, put new 280Ah label on it) end up on Aliexpress.
And since a lot of people are too lazy to do research and just buy without checking, Aliexpress keeps attracting people.. 99% of the people being scammed (damaged, underperforming, swollen, or no sells at all) have bought them at Aliexpress

As said, the fact you still got 254Ah and got cells is already a bonus, could have been much worse. You opted for Aliexpress, so you opted to take this risk yourself.

And as said by others, you're probably just fine, altought at a slighly lower capacity. Swelling isn't too much, and is pretty common especially at high SOC.
As long as there is no visible other damage, and you secure the cells properly I don't think its going to be a problem.
 
tested battery twice (9A discharge). It showed 254Ah 3285Wh.
If you got 254 AH's output yield with only 9A load they are very used cells. The cell voltage will slump a lot when subjected to higher discharge current.

They are likely safe to use but you may have to limit their maximum load current to keep from early tripping low cell shutdown.

You should check their matching by subjecting series stack to about 20-30 amps and at each cell terminal check the cell voltage after 3 minutes with the load still applied. If their voltage slump difference is more than 100 millivolt delta they are poorly matched, and you will have more trouble keeping them in SOC balance so will have to perform balancing more often. A higher balancing current balancer will help but do not allow balancing below 3.40v cell voltage.
Battery Impedance.png

The below graph is for a typical NEW LF280 cell. The slump can increase 3x to 5x for a well-used cell. Cell is in the 40% to 80% SOC range for measurement.
LF280 overpotiential curve.png
 
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If you got 254 AH's output yield with only 9A load they are very used cells. The cell voltage will slump a lot when subjected to higher discharge current.

They are likely safe to use but you may have to limit their maximum load current to keep from early tripping low cell shutdown.

You should check their matching by subjecting series stack to about 20-30 amps and at each cell terminal check the cell voltage after 3 minutes with the load still applied. If their voltage slump difference is more than 100 millivolt delta they are poorly matched, and you will have more trouble keeping them in SOC balance so will have to perform balancing more often. A higher balancing current balancer will help but do not allow balancing below 3.40v cell voltage.
View attachment 100858

The below graph is for a typical NEW LF280 cell. The slump can increase 3x to 5x for a well-used cell. Cell is in the 40% to 80% SOC range for measurement.
View attachment 100859

Interesting Post. I certainly have used cells. 271 ah CATL cells tested 258 ah with a low C rate.

If I understand the graph, placing a 30% (0.3 C) load of 84 amps on a nearly fully charged (80%) 24 volt bank of eight 271 ah cells should have a voltage drop (slump) of ~60 millivolts at the end of 3 minutes? Anything more would indicate poorly matched cells with degradation? The 271 CATL should be in the same ballpark of the 280 AH cells. Or do I totally misunderstand the post...

In the above post anything over 100 millivolts suggest poorly matched cells with I assume cell degradation. Would that also be the case for the 271 CATL cell battery bank?

Thanks...
 
Interesting Post. I certainly have used cells. 271 ah CATL cells tested 258 ah with a low C rate.

If I understand the graph, placing a 30% (0.3 C) load of 84 amps on a nearly fully charged (80%) 24 volt bank of eight 271 ah cells should have a voltage drop (slump) of ~60 millivolts at the end of 3 minutes? Anything more would indicate poorly matched cells with degradation? The 271 CATL should be in the same ballpark of the 280 AH cells. Or do I totally misunderstand the post...

In the above post anything over 100 millivolts suggest poorly matched cells with I assume cell degradation. Would that also be the case for the 271 CATL cell battery bank?

Thanks...
Voltage slump is per cell.
 
OK, using my example above, if I were to look at each cell reading on the Overkill Solar BMS would that qualify for a voltage slump reading?
Better if you measure across aluminum cell terminals directly. BMS voltages have battery terminal connection resistance and one bus bar resistance.

If you did a good job of cleaning off aluminum oxide and have copper core nickel plated bus bars, each terminal connection is about 0.05 milliohm, and 20mm x 2mm x 72 mm bus bar is about 0.07 milliohms. Total 0.17 milliohms x 80 amps is 14 mV of voltage drop just for bus bar and terminals, so going directly to aluminum cell terminals eliminates that drop.

Measure with DVM directly on cell aluminum terminals, not top of bus bars or terminal bolts or screws.
 
Better if you measure across aluminum cell terminals directly. BMS voltages have battery terminal connection resistance and one bus bar resistance.

If you did a good job of cleaning off aluminum oxide and have copper core nickel plated bus bars, each terminal connection is about 0.05 milliohm, and 20mm x 2mm x 72 mm bus bar is about 0.07 milliohms. Total 0.17 milliohms x 80 amps is 14 mV of voltage drop just for bus bar and terminals, so going directly to aluminum cell terminals eliminates that drop.

Measure with DVM directly on cell aluminum terminals, not top of bus bars or terminal bolts or screws.

OK, I have a decent DVM and will give that a try... Thanks!
 
Thanks for all info. Lesson learned, next time I will just buy new cells on alibaba, since then I will check more often cells voltage and keep them in balance. Thanks again!
 
When the smell is chemical smell, sometimes a whiff...
You're "f*cked".
You are smelling electrolyte.
It should not be vaping outside the cell, so somewhere there is a leak.

Box them in iron or concrete fiber is always a good idea, depending on your C rate usage, it will require some (or none) form of cooling.

You stopped quite early with discharge, 2.9??
And where the cells fully charged?
Really?
Not stopped when it reached 3.65, but kept at 3.65 for several hours? (8-12)
You seem to be missing 10%?

When the cell is fully charged, and fully discharged it will show the total capacity.

That means that the voltage 6 Hours after charge is 3.65, and that the cells will be discharged till they stay at 2.5v.
When they reach 2.5v, and you stop, they will rebound a few times before really reaching 2.5v.

Or even... It should be 2v as that is the lowest level, like 3.75 is the top.

For safety, we like to use 2.5 and 3.65.
Most BMS stop at 2.25 and 3.75, because of the rebound, and reduce of voltage when the charging stops.

So...
What is fully charged?
What is fully discharged?
3.65 to 2.0.
That should bring you quite close to the 280Ah.

254AH sn't bad.
Really acceptable usable capacity (!!)
The electrolyte smell...
That is worse.

You need to find the one that is bad, and probably replace it.
Good thing with lithium, while preference the same age, they don't need to be.
Same goes for capacity.

When you find your bad cell, just be aware that it will degrade more fast.
When the overall capacity is below what you need to use, you can replace the cell at that time.

The Lowest capacity in the set makes the whole capacity.
So if the bad one reduce to 150Ah, the rest still will be capable of doing 254Ah (more or less) but will give just 150, matching the weakest link.

Good to use for now, prepare for replacement of the one (or more) bad cells.

Alibaba or AliExpress...
Doesn't matter much.
Local store they can smell what you smell and act on it.

Online? They will blaim it on the way you packed the cells to send back, or it was your fault for doing something wrong or .. or.. or...
When you payed with credit card, those peeps are usually on your hand can can get some money back.

For online shops.. the only way to do.
(PayPal helped me out a few times also)
 
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