Last fire.. :-(

RCinFLA

Photon Sorcerer
Looks like an example of cascading thermal runaway. Packing a bunch of high AH cells close together has risks.

Thermal barrier board separator between cells helps to confine damage. Should have some thermal insulation, fire resistant, and thin as possible.

I haven't found the idea material and am open for suggestions. My first thought was shower wall 1/2" Durock. Good fire resistance and R value at 0.39 (not fabulous but better then cells tight together)

dug up the old Boeing 787 Lithium Cobalt Oxide battery pict. Highest energy density and highest risk Li-Ion chemistry.

1627155586847.jpeg
 
Last edited:

Supervstech

Administrator
Staff member
Moderator
Wow.
I wonder if fiberglass sheets between each cell would have prevented this… I doubt it.
 

400bird

Solar Enthusiast
Sorry to see that, it's scary to think of what could have happened.

For everyone else working with these cells:
On the EVE cells (and all prismatic cells I've seen), the case if the cell is connected to one of the battery terminals. It can't say that is the causey, but considering that compression happened with the bus bars connected. This could have pushed the terminal into the cell case. As another pointed out, insulation between cells is important to isolate the cases. The thin blue wrapper can't provide reliable electrical isolation between cells. Also, the threaded rod should be insulated between cells so it doesn't short from one cell to another.

But, overall I agree. A manufactured battery should have higher assembly standards than we can build in build in our garages or workshops.
 

RCinFLA

Photon Sorcerer
Maybe something like this:


After reading about the OP experience I'm going back to review what I should do better for fire supression
A bit pricey. Don't really need that high a fire temp rating. More interested in reducing thermal transfer from a runaway cell to next door neighbor.
 

curiouscarbon

Science Penguin
Who is coordinating the group buy on this? I can't spend $900 for a few batteries.

24x100” 1/8” thick 2100 C rated sheet 70 usd

edit: the link seems to go to a smaller size; click on the roll type to see the roll.

  • MATERIAL: Superwool Plus paper, which is flexible, strong, seals well & withstands 2100F. Superwool is an alternative to ceramic fiber with improved health and safety attributes. Superwool products do NOT carry a GHS health hazard warning label.
 

solardad

Solar Addict
@fhorst sorry to hear that this happened a second time to you!
Just wondering if the cell that you think was the issue from the 1st layer was under the cells from the newly placed 2nd layer?

It is hard to tell from the pictures but the space between the layers looks very close. I wonder if the shelf had any bend to it and made contact with the lower level cells?
 

fhorst

making mistakes so you don't have to...
@fhorst sorry to hear that this happened a second time to you!
Just wondering if the cell that you think was the issue from the 1st layer was under the cells from the newly placed 2nd layer?

It is hard to tell from the pictures but the space between the layers looks very close. I wonder if the shelf had any bend to it and made contact with the lower level cells?
The frame of the second layer, is strong enough for me to stand on (80kg) besides this, it had 6 studs that rested on the (almost middle) separator sheet between the 280 and 152Ah cells.
Bending would need several thousand kilos, and even with the heat, it stayed perfect, no bending or twisting.

Space between the 2 layers was about 10 cm, the highest spot, enough to put my hand (in a thick rubber glove) inside if needed, and enough for air.

Each layer is "massive" 50*70cm block of 200Kg.

IMG_20210725_101500_edit_85423254815089.jpg
Red spot is location where it went wrong.

Zoom shows a bit more the space between the layers
IMG_20210725_101935.jpg

Some people might have misread:
Compressing the cells happened, never with the Bus-bars attached.
Total free movement.
If a bus-bar would not nicely fit, it's hole would made a bit wider to fit nicely.

The terminal from the suspected cell was one in "length" not sideways.

As mentioned before, probably cascade of issues during the 18 months, where it's unclear what combination let it fail.

I wish I new.
Not for me, but your sake.

Most of us had several "oepsie" during working.
A tool making a fraction of a second a short between 2 Terminal from same or sevewal cells.
Besides a scorch mark on the tool/busbar, nothing seems to be wrong.

Or having a discharge slightly below 2.0, or charge above 3.75 (both should be fine and within specifications of safety)

Or.. need to make new thread.

List goes on of small and bigger things that can happen.

I had a problem with one 280Ah cell and a screwdriver...
that cell looked OK, internal resistance good, nothing "wrong" , except next day pillow and energy stored.
It was in parallel, not yet mounted at series, so I replaced both.

Probably just went defective and did not selfdischarge, no contact is also no power readings :)

As the other cell had the same (indirect) hit from the screwdriver, 2 new.

That's my normal level of safety I follow.
Absolutely not zero risks, also not taking it to the edge.
Other cell is "fine" but capacity test showed 260Ah, no longer 280.

@RCinFLA Nice boxes!
TJ offers similar
1627184481670.jpg
1627184488302.jpg
8000 THB, $250,-
2 needed per set. (One for each S8, 24v)
40kg stainless steel is actually kind of cheap.

As I already had issues gathering this money..
No financial place for $1500 extra.

This is also the only thing what really will work.

Like the airplane box.
Fire will be contained, and won't spread to other units, if there is enough space and heat insulation between them.
Stacking like I have now....
Won't work.

Trying to stop the problem at one cell...
I doubt that's possible.
Your bus-bar will transport the heat to the next terminal..
Enough to overheat.

Even if that's not happening, the heat resistant sheet will delay, not stop.
And we are talking about hours and hours of heat.

If you can place the sheet on the stove (smallest flame), small pan with water on top.
Come back 6 hours later.
If your water is still cool, you have a winner.
Probably no water left inside and touching the bottom with your finger is a bad, painful idea.

Compression = massive block.
Even with its feet 3/2in water..
The cells in the center won't receive enough cooling.

With no compression, it's possible, but... We know we should.

Alternative is to reinforce each individual cell, put it in steel box and use flexible cables to connect each cell.

That will work.
Not practical, expensive and huge / heavy.
But safe.

As soon as we start compression, having cells close together, they will get infected.

No Social Distancing :)

Best thing to learn here is to realise that we are playing with possible dangerous goods.

Even the professionals do have failures. (look at all the burned wrackages of Electrical vehicles)

We never will reach their level of safety.
So our risks are bigger.

A steel box will get about 500c from selfdischarge LiFePO4 cells.
That's hot enough to turn wood into charcoal (no ignition), and grease turn into vapour that does self ignite.

If someone would use a box like this, it should not have contact with wood, paper, household plastic, or fabric.
Probably forgot 10.000 other things.

I know our household is nothing like yours.
If there is place to put things on top...
In time there will be things on top.
Such a nice shelf :).

I'm not buying those boxes as it would not really help in our situation.
It would not really bring additional safety.

They are inside the house for cooling reason, and stop thefts.
(In the past we stopped a guy trying to get away with one of our 70kg deep cycle lead acid battery on a motorcycle!
I was surprised he could even get the battery on the seat!
The guy was exhausted 🤣

I did think about placing them under ground, just 1.5 - 2 meters.
Receiving natural cooling from the soil, stay 25-30c

When I see our rain season pooring down large buckets at the time, see our 20*40m pond rise 50 cm in a night...
I would just invite a new "enemy" water.

So original planning stays.

Fire protection worked, so did the alarm system.
Nothing really bad happened.
Only what was known to be dangerous did it's dangerous thing. And "lost"

End of the year I'm leaving to Europe for a few months.
Appointments I can no longer delay, and while there, get vaccinated.

Such an ease of mind now with the BYD and the build quality.

No guarantee it won't go wrong, but the chance that it does is so absurd much smaller now.

Now we can focus on more important things.
Like our 250 chicken, cats, dogs, trees flowers and plants.
(Family never left the focus)

Thank you for your replies!
Stay safe, take care and please, be aware of what we are playing with!
 

svetz

Works in theory! Practice? That's something else
Trying to stop the problem at one cell...
Your bus-bar will transport the heat to the next terminal..
That's a good point! For the "water bath" to save the other cells you'd need the bus-bar to "melt" at < 100C. Tesla has those small cells each fused to a busbar, wonder if the fuse goes during the internal short or at high T?

No Social Distancing :)
Perhaps masks for cells? :LOL:


I did think about placing them under ground, just 1.5 - 2 meters. Receiving natural cooling from the soil, stay 25-30c
Interesting idea....

Fire protection worked, so did the alarm system.
Nothing really bad happened.
Good planning and a good example, thanks again for posting all of this (y)
 

Picasso

Solar Addict
Those BYD's look to be the 2nd gen of the ones many of us got shafted by with bigbattery / tech club. Only one out of my 6 I ordered was a 2nd gen. Your pic looks to have the single stud cells, hence 2nd gen.
 

Supervstech

Administrator
Staff member
Moderator
Last week we had a nasty fire.

I worked for months, used only high quality materials, tinned silicone wire that self fuses at 10A, and weeks between each step of construction to be absolutely sure things are safe

The lower layer was good.
Might look a mess with the wires, but absolutely safe, no terminal got more warm than any other, even with +150A charge.
View attachment 57365

How I know for sure it's safe?
Worked like that for over 6 weeks.

Week before started to build the next layer, placing the metal rack, plywood sheets and the repaired tread cells.

All cells where placed and all BMS wires (the pile spaghetti on the picture) was nicely between the cells to the top.
No crushed wires, no damage, all good.
View attachment 57366View attachment 57367View attachment 57368


Top layer received it's compression and that's it.
For days and days.

What happened?
I don't know.
Few days earlier one of my MPPT did not charge, so just one to charge 16* 280 and 16x 152Ah.
That's all that was connected on the lower base.

It went empty that night, my inverter stops at 48v.
Around 07.30 I looked and all was OK, not yet charge, rain outside.
We snugged back to bed :)
Half hour later lights went on again, 49v, restart voltage of the inverter.
08.30-09.00... beep beep beep, smoke detector allarm!

What happened... ??
Top layer of cells where placed like 60 hours before, and no bus-bar yet.

Previous day's we were in the town to visit lung doctors for my COPD, to time or energy to do anything new with the setup.

No high capacity charge, few hundred watts.
This is something that didn't move or got changed in days.

Perhaps a mouse?
Almost can't be.
Even if it did chew the BMS wires, it should self fuse. AWG22

After investigation of the scorching and location most likely is a instant selfdischarge of one of my 152Ah EVE cells.

Those where a trouble from the start. Who is interested.. enough old posts about them.
Use seach.. :)
FIY, the same pouch case is used for 120 and 135Ah cells.
There is a limit hou many sheets you can squeeze in, without getting into trouble.
152Ah was that limit.

Back then, start 2020, the 152's where the best bang for the buck, 280 came just looking and where high priced, compression as we now know is mandatory, wasn't even discussed.

Sure, taping together for ease of handling.. that ain't compression :p

And they bloated, quickly.
Little over a mm.
It did not seem to hurt the functionality. After a year of useage I tested it's capacity, overall 147, top 151, low 144Ah (that's 52 cells)

I did compress them afterwards, slightly.
Strong enough to have 6 cells together and not being able to lift one out from the middle, not so strong that the bloating disappeared.

I did notice that after a month or so, I could easily compress a little bit more, 1/4 threaded rods, tighten with pipe wrench by hand, just the round wrench, nothing extra needed.

That was 8 weeks ago or so since I tightened it for the last time.
And no need, busbars where good, with +4nm torque each on M6, +5Nm on M8
All worked tip top since.
Yes, only 432 of my total 1016Ah, but stable.

View attachment 57372

View attachment 57373
Bloated?? :p
View attachment 57374
Casing fused together.
View attachment 57375
Now they are bloated..

View attachment 57376
And the cell that most likely started the fire.

Instant selfdischarge, at +/- 15% charge
Creating enough heat to infect it's neighbours, who also selfdischarge, chain reaction.

The flames most likely are the Ox-guard, it's grease, and that self combust at 350-450c
Perhaps a light glow of self fusing wire was enough to ignite the grease.
Who will be able to tell.

Flames where calm, heat immense.
I worked at a bakery for several years and know the heat of 275c oven.
This was a lot more.

All lower level cells selfdischarge, bloating like a real pillow.
Top level, all precharged to 100% ...
Some bloated more, most a little or none at all.
They did get really hot feet.
I no longer thrust them for Safety reasons.

I reached out for a loan to my family in Netherlands, and now am the proud owner of 6 X 24v BYD packs with 3* Jikong 2A active balancer BMS.
In other words 3 X S16, 51.2v 260Ah, total 780Ah about 40 kWh.

Funny how life works.
That was my first BMS when all the troubles started.
I was a happy puppy the whole 3 days the Jikong worked.
Total pre-mature launch, where almost all units of first shipment got returned to the seller in a few weeks....
Now it's a grown up product.

View attachment 57378
I'll post some pictures later

What a development there has been in the last 2 years.

This wasn't available, if it was I absolutely would have started with this
Price?
41.500 THB, 1000 THB transport ($ 1.260 + 30)
Under 1300 for 260Ah 51.2v)
Including BMS.

All tax paid, delivery at my doorstep.

Roughly 60kg per pack.
That's 15-20 kg on structural integrity, safety, quality.
280Ah is 5.5kg, *8 is 44kg.
And it shows.

People... What the F are we still doing buying EVE or Lishen and try to do what robotics laser welding does?

Not anymore for the price!!
It's even cheaper then the. 200Ah deep cycle lead Acid we started with!!
(11.000thb / $335 for 12v, 48v 44.000 or $1360)

I'll post a separate thread about the BYD soon.

Take care and stay safe.
My experience is now that any compromised cell is a potential bomb.
Even with 15% charge, results are catastrophic.
In this case only for the cells, due my smoke detector alarm, concrete sheets around the battery and the help of my family.

Releasing the compression, last center nut did not twist smoothly.
A tiny bit of force and it snapped...
The 1/4 threaded rod.
That's how much force there can be on the compression, and even with this, just a few cells the vent bursted...

Know what you are playing with!!

Special thanks to @Just John , sorry the epoxies are used for demonstration, I didn't get the chance to test it with Bus-bars connected...
And won't be using the cells now..
Even with almost perfect repair 😂
I would REALLY like to see some high resolution pictures of the wiring spaghetti you had before the fire.
electricity is alive… voltage leaks and induces, and arcs, and is just searching for a way to equalize as rapidly as possible… “ok because it didn’t burn for 6weeks” I mean… sure, that shows it wasn’t a dead short anywhere, but even a little heat, on a single wire can build up, insulation failing or weakening, then one of the hundreds of wires in that picture shorting out, could cause a BMS or balancer to see a scenario incorrectly, resulting in the fire.
there simply is ZERO reason for all those wires to be crisscrossed like that.
 

Gazoo

Dumb Dumb
I am hoping to integrate per cell temperature monitoring on future battery pack builds. Maybe I can add a feature to the microcontroller firmware to beep loudly if 1) any temperature is rising quickly or 2) any temperature is over a set threshold.
I have thought about this. Monitoring the temp of each cell and if a cell's temp rises beyond the "norm" the whole system will shut down, in addition to an alarm. :)
 

Gazoo

Dumb Dumb
Sorry to see that, it's scary to think of what could have happened.

For everyone else working with these cells:
On the EVE cells (and all prismatic cells I've seen), the case if the cell is connected to one of the battery terminals. It can't say that is the causey, but considering that compression happened with the bus bars connected. This could have pushed the terminal into the cell case. As another pointed out, insulation between cells is important to isolate the cases. The thin blue wrapper can't provide reliable electrical isolation between cells. Also, the threaded rod should be insulated between cells so it doesn't short from one cell to another.

But, overall I agree. A manufactured battery should have higher assembly standards than we can build in build in our garages or workshops.
Glad you brought this up and there was another member who noticed his cells shorting where the PVC wrap was compromised. I can't say that's what happened here either.
 

Gazoo

Dumb Dumb
Glad you brought this up and there was another member who noticed his cells shorting where the PVC wrap was compromised. I can't say that's what happened here either.
I found it. Food for thought.

 

fhorst

making mistakes so you don't have to...
I would REALLY like to see some high resolution pictures of the wiring spaghetti you had before the fire.
electricity is alive… voltage leaks and induces, and arcs, and is just searching for a way to equalize as rapidly as possible… “ok because it didn’t burn for 6weeks” I mean… sure, that shows it wasn’t a dead short anywhere, but even a little heat, on a single wire can build up, insulation failing or weakening, then one of the hundreds of wires in that picture shorting out, could cause a BMS or balancer to see a scenario incorrectly, resulting in the fire.
there simply is ZERO reason for all those wires to be crisscrossed like that.
Here you are absolutely wrong.
Not ZERO reason for the wires to be placed like that.

Each wire set is +, - lug, and temperature sensor, that is clamped with shrink wrap on the positive terminal, temperature sensor is non conductive, no electrical contact at all with the terminal.

Yes, my DIYBMS has 1 module per cell and needs 2 wires.
And optionally external temperature sensor.

With my setup, I almost can't replace a BMS cell module if it would fail.
It would require to remove the top layer, untighten all the screws, and if you followed my luck on those fantastic threads and strength of the terminals, that's "not an option".

Alternative: longer wires
What is normal, each other BMS has longer wires.

Each wire is crimped on a lug, no bare wire strands, and all the ends are safe, with a standard connector.

Wire connection between the plastic connector is soldered with shrink wrap.

IMG_20210711_211808_712_copy_480x270.jpg
If this isn't safe, no BMS wire is!!

IMG_20210706_113959_319_copy_480x270.jpg

No BMS was installed during this time.
Just Jikong BT active balancer 1A on the 280Ah layer,
And 5* S4 1.2A small active balancers.
That's 4+1, overlap.
Why not one large 16?
Read above, "impossible to replace".
This way, if one would fail, others would do most of the work.

Besides that, it's "extra".
The DIYBMS can burn off (passive balancing) 1.5A per cell.

While your input is often appricated,
@Supervstech , this time you are totally misinformed, or thinking " what a mess...
This must be the source.

IMG_20210725_101520.jpg

This is how it looked like when the mess was untangled.

No stress on any wire, no where clamped or compressed.
Not yet in this picture, Onided tape to keep them fit in the 2 round edges of between the cells.
Protected from the threaded rods.
Who don't move/shift but possibly could give a little pressure on the wires.
Still movable up and down, just not a "free" move.

Absolutely ZERO knowledge of the installation and SHOUTING that spaghetti wires are bad ??

Aka all BMS.
Except perhaps Batrium for $1000 (for 16 cellay, for 80 cells... I don't wa t to know)

So please....
Before you make a statement like that....
And make you look stupid...
If you don't understand, ask!!
Instead of jumping to conclusions!

2021-7-26 7-37-41.jpg
One of the wires, this one special for you with just one shrink wrap.

The end of the wire:
2021-7-26 7-37-45.jpg

So please.
Enlighten me!
What isn't safe about this??

And...
How is it any less safe then this?

IMG_20210726_074110_copy_1000x750.jpg
Probably the sight of more then 17 wires?

Yes, 80 cells isn't for everyone to do.
It's complicated.
160 wires, 40 pair from the terminals, 40 pair from the thermal sensor on each layer.
Looks easy messy when not yet connected.

Not unsafe.

Edit:
FYI, to make it even more clear:

The second layer was placed.
IMG_20210715_111429.jpg

The spaghetti wires "mess" was untangled and as nice as this:
IMG_20210725_101520.jpg

On all the cells.

The wires for the second layer DYIBMS where not yet there, nor where the Bus-bars.

As I started in my topic start...

Some people like an easy score.
Those people frustrate me, and are the reason many people opt out sharing their mistakes, what is the most educational!

I didn't think/expect @Supervstech is one of them!!


If you don't understand what you see, ASK!
 

Attachments

  • IMG_20210716_112203_212_copy_270x480.jpg
    IMG_20210716_112203_212_copy_270x480.jpg
    44.5 KB · Views: 16
Last edited:
Top