Brand new EVE cells catching fire

[Adrian R]

Hi everyone,

I have been into solar since 2012 and assembled many off-grid/hybrid systems
Recently I bought 48 EVE lf280k cells manufacturing date June 2024 according to qr codes, from an Alibaba supplier I trust, from EU warehouse
two days ago I assembled the first 48v pack made of 16 cells in series, 2 parallel rows of 8 cells. Charge from the factory is usually 30%, I was planning on discharging them to 3,000v with an inverter and a load and after that to perform bottom balance on each individual cell with ebc-a20 and ebc-a40-l to 2.900v.

So I do compression as I always do, 6 threaded bars of 10mm diameter and 2 metal plates
I install bms wires on each cell
I install busbars between cells
I start tightening the nuts on the busbars. At this point there is no bms and inverter attached, no load.
I am tightening last nut on the cell number 16, the general positive pole of the battery bank.

I hear a noise, like electrical sparks and I see cell 8 and cell 16 catching fire around the plus pole. I managed to put out the fire quite rapidly, the black plastic sheet on top of those cells was burning.

Initially I thought it was a short caused by one of the bms cables but all bms cables were fine, except the lug from cable 8 which had burnt from the fire on a length of about 1cm. The fire on top of cell 16 had been much less than what happened with cell 8. Cell 8, if I was trying to dettach the busbar that connected it to cell 9 and re-asttach it and tighten it, would generate more sparks under the black plastic cover, therefore I decided to loosen compression on all cells and remove it from the pack. It is indeed very badly burnt and when I put it in horizontal position there was electrolyte spilling out of it.

Cell 16 remained on the pack for the duration of the discharge process and the duration of the bottom balance, it maintains same voltage as all other good cells. My intention is to replace cell 16 with a good cell for the duration of the charging process up to 3.600v because I see a potential safety hazard in keeping it inside the pack.

Cell 8 was replaced altogether by a good cell for the duration of the discharge process and bottom balance, even though right after the fire it still maintained correct voltage as in the photo attached.

I am working with the seller towards finding a solution, maybe replacing the 2 burnt cells

another solar installer, a friend of mine, told me these blue cells are low quality and the threaded terminals have no solid connection to the interior of the cell and they can get damaged when one tightens the nut on the busbar. I did apply a reaonable amount of torque on those nuts as I have always done.

Before assembly of the pack all cells had 3.287v and internal resistance around 0.50mohm

if there was a short caused by one of the bms cables, at the current generated by these cells the bms wire would be instantly vaporised so the short is out of the question

any thoughts?

anyone faced a similar issue so far?

thank you.

 

[kommando]

I did apply a reaonable amount of torque on those nuts as I have always done.

Define reasonable, I always use a torque wrench set to 4nm for m6 aluminium studs as an example.

 

[ScrotpusGobbleBottom]

I didnt see any mention of insulators between the cells.
Cell 8 and 16 in my opinion would indicate a short between the clamping mech to the outer case of the cells but in that situation I would doubt the fire would be at the poles. Or perhaps it was such a large short that the poles became the weakest point because of over torque of the nuts.

I am requesting as many pics as you can of your setup. Whole battery, sides of burnt cells ext clamping mech..

 

[42OhmsPA]

I am requesting as many pics as you can of your setup. Whole battery, sides of burnt cells ext clamping mech..

Please.
Make a 2nd post when you run out of space in the 1st.

Glad it wasn't worse.

 

[Brucey]

I did apply a reaonable amount of torque on those nuts as I have always done.

No torque wrench? Applying too much force could cause the terminal to fail. Going by feel doesn't seem sound. This batch may have been a little less forgiving than your previous ones (while still being in spec)?

 

[AshleyL]

.........I got a old story about a re-wrapped EVE cell.....with the positive and negative being mislabelled by the seller of "Grade A" cell......

Can you determine* the cell polarity? Using a LED will do I guess?

 

[ScrotpusGobbleBottom]

Using a LED will do I guess?

I am assuming a person that spent $5000 on batteries has a multi-meter. I have been surprised before tho!
edit: multi-meter is in photo.

 

[Adrian R]

Cells were measured with the voltmeter and internal resistance meter YR1030+. There are insulators between the cells and the metal plates, of course. The sides of the damaged cells are intact. Reasonable torque means stopping tightening when feeling resistance from the nut. Yes, a torque wrench is needed and I used one. I have had it for years.

 

[Adrian R]

It is exactly same setup I am always using. I only disconnect bms and inverter, remove old cells that are going to the present project and put in the new cells that are going to be tested. Same insulators, same cables, same bms, same everything

 

[hwy17]

You say the BMS wires were fine but also that a BMS wire was burnt?

It sounds like a short to me.

Also is your BMS really capable of and configured to maintain a bottom balanced battery? Some BMS can do it, but it's unusual nowadays. A battery can't be top and bottom balanced.

 

[robbob2112]

Cells were measured with the voltmeter and internal resistance meter YR1030+. There are insulators between the cells and the metal plates, of course. The sides of the damaged cells are intact. Reasonable torque means stopping tightening when feeling resistance from the nut. Yes, a torque wrench is needed and I used one. I have had it for years.

So at this point the nuts were not torqued on, just finger tight? Or had you used the torque wrench already? If so what setting?

 

[kommando]

Ever calibrated that Torque wrench, you don't need to take it to a lab just use a known datum. Beam wrenches stay calibrated for decades and make good benchmarks for more modern torque wrenches.

 

[TomC4306]

My opinion:
Physical damage caused during assembly by over torque.
A reasonable amount of torque is not a measured value of torque. Quite easy for Big Man hands to over torque what should be 4 or 5 newton meters.
The internal attachment over torque value of the terminals is 8 Newton meters.
Over 8 and the guts of the cell start to spin.

 

[TomC4306]

It is exactly same setup I am always using. I only disconnect bms and inverter, remove old cells that are going to the present project and put in the new cells that are going to be tested. Same insulators, same cables, same bms, same everything

Familiarity breeds complacency.

No matter how many times you've performed a process, you can always f it up.

 

[dayfly]

Isnt that a bit low ? i thought it was 7nm

 

[Adrian R]

Only cable 8 of the bms was burnt obviously on a length of 1-2 cm because cell 8 caught fire right where the cable was attached. Bottom balance means discharging the cells in series until 3v per cell. Afterwards I use ebc a40l and ebc a20 on each individual cell down to 2,900v, afterwards I charge all in series until 3,600v by solar with the inverter. The cells are not disconnected during bottom balance. Torque wrench had been used on all cells with the 4Nm setting by the time it happened. I was on the last nut, the plus of cell 16.

Thank you for all your replies.

So far I know exactly what I knew when I started the topic.

 

[Hedges]

Isnt that a bit low ? i thought it was 7nm

More like 7nm is the limit before terminal breaks loose from plastic.
I don't think I trust any (or at least most) of the aftermarket terminals welded on these cells that were designed for welded busbars.

When torqueing a nut or bolt on this terminals, I think the terminal ought to be restrained with a second wrench (if possible) and torque applied between the two wrenches. For instance, open-end on rectangular base of some terminal styles, or Allen wrench in grub screw hex socket while torque wrench applied with crows foot.

So I do compression as I always do, 6 threaded bars of 10mm diameter and 2 metal plates
I install bms wires on each cell
I install busbars between cells
I start tightening the nuts on the busbars. At this point there is no bms and inverter attached, no load.
I am tightening last nut on the cell number 16, the general positive pole of the battery bank.

I hear a noise, like electrical sparks and I see cell 8 and cell 16 catching fire around the plus pole. I managed to put out the fire quite rapidly, the black plastic sheet on top of those cells was burning.

(commenting as a lurker and EE, not one who has ever wrenched on these cells)

At first I thought you meant during compression. Cells (of other types at least) with defects or shards of metal have punctured their separators, or had creases that caused failure.

So failure occurred while turning nut on busbar. Last one, so not restrained from rotation by slipping over studs of two cells.
I'm thinking rotation of terminal caused an internal short?
But no report of outgassing or swelling.
Cells 8 and 16? When wrenching on 16?
Sounds like either external contact or internal contact.

I think construction is a jelly roll inside a can, with fluid between them. I would expect electrical contact with can to cause some minor current flow, maybe etch through can and cause leak.

"Insulators", is that between [1,2] maybe same sheet between [9,10]?
How about between [1,9] and between [8,16]?

If cans of cell 8 and 16 can short, rotation of terminal maybe could make contact inside between tabs from electrode and can.

Not sure if fire "around pole" is outgassing or electrical contact arcing.

 

[Adrian R]

No swelling, no gassing. Insulators are between front (first) compression plate and number 1, between 1 and 2, etc. Last insulator is between 8 and back (second) compression plate, then another separate insulator between second compression plate and number 9, between number 9 and 10, etc, last insulator between 16 and first compression plate.

While tightening the nuts on the cells I sensed no breaking at all, no noise, nothing out of the ordinary.

Between row one and row 2 of cells there is empty space of about 25mm for the 2 middle threaded bars.

Only outside contact between all cells was the busbars of course.

Thank you.

 

[Adrian R]

Fire was like electrical arcing inside the cell in the upper part close to the positive pole and immediately the black upper plastic sheet in flames

 

[Adrian R]

From everything discussed so far, I suspect the 2 cells were faulty from the factory and damage occured inside even with a smaller torque than max accepted value, however the sparks and ignition took place with a short delay and what is somewhat eery is the fact that 8 and 16 caught fire about the same time (coincidence?)

 

[ScrotpusGobbleBottom]

coincidence?

i dont think so.

 

[Suijkerbuijk]

I think it come from the outside of the alluminium case.
If you set compression on it.
You have to set somting between the cells.
The outside of the case can set arc sparks.
Well that is somting i have read about it.
But than again.
In this YouTube the person tell it to.

And the reaction from somebody see attach files.

 

[Adrian R]

that is good to know. there are isolators between the cells and between the cells and the compression plates
thank you

 

[Daddy Tanuki]

those are the laser welded studs... with the "new" plastic cover on the top cutout to see the "QR" codes i see several red flags about the provenance of those cells. and I am going to leave it at that.

 

[Adrian R]

Can you please explain? How should the top of a good cell look like? The qr codes can be verified with the app, production date June 2024 all 48 cells