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.
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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
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.
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Bloated??
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 ?