Fire!! Never cover LiFePO4 with wood!!!

technerd1988

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Mar 25, 2021
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Actually use of Loctite or any thread locker is a good idea. I don't know what cells you are using but the threads in these cells are very weak. The EVE cells have 5 or 6 threads to work with and the cell terminal threads are soft aluminum. Generally tapped by the suppliers.

4nm or 35 in lbs is what we have found to be a safe torque. EVE's specs state to limit torque to 8nm to prevent damage to the cells terminal. I think Lishen is in the same ball park. However recently cells are being sold with laser welded studs. This might present it's own problems because we are not sure how many amps the connection can support.

The bulk if not all of the current is carried by the busbars, not the machine screws or studs. If a busbar is loose then of course it could heat up and cause problems. I am not so sure that's what happened here. There has been a lot of speculation and it's all interesting. No one knows for sure what caused the fire and we will most likely never know.

Who is the manufacturer of the cells you have had in service for many years? Are they aluminum cased cells? And what type of metal are your cells terminals constructed of?
I'm not exactly sure. I know my oldest are calb ones and I have a lot of aluminum cells too from various manufacturers. I use them in my box truck conversion RV. I just compress them and nothings ever come lose. I use overkill wire sizes too 0 awg, even though I only draw 50-75 amps per pack. I have never had one come lose. I just make sure the batteries can't move. you don't want to increase the resistance in any way shape or form which is what thread locker will do. This is in a mobile installation.
 

cinergi

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I'm not exactly sure. I know my oldest are calb ones and I have a lot of aluminum cells too from various manufacturers. I use them in my box truck conversion RV. I just compress them and nothings ever come lose. I use overkill wire sizes too 0 awg, even though I only draw 50-75 amps per pack. I have never had one come lose. I just make sure the batteries can't move. you don't want to increase the resistance in any way shape or form which is what thread locker will do. This is in a mobile installation.

The current carried by the bolt/stud/nut is insignificant and can be 0 without compromising the battery. The current is carried between the surface of the terminal and the bus bar / lug on top of it. Nothing more is needed. Any additional high-resistance connections (including stainless steel bolts which will not conduct as well, regardless of loctite) is not a big deal and will not heat up. It not only electrically makes sense, but it's been proven in practice (including by yours truly).
 

Supervstech

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The current carried by the bolt/stud/nut is insignificant and can be 0 without compromising the battery. The current is carried between the surface of the terminal and the bus bar / lug on top of it. Nothing more is needed. Any additional high-resistance connections (including stainless steel bolts which will not conduct as well, regardless of loctite) is not a big deal and will not heat up. It not only electrically makes sense, but it's been proven in practice (including by yours truly).
HOWEVER... if you have a bad connection to the terminal, like sloppy loctite between it and the bussbar/lug... yeah, that bolt will get VERY HOT...
 

Just John

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Something tells me loctite is a no no on battery threads. You don't need it. I've had many of these cells in service in my rv for years now. It looks like nothing shorted rather, but you made a horrible connection. NEVER cover batteries with wood, especially the vent side. clamp your cells together and torque to 5ft lbs and your good to go, even in a mobile situation like me. On these batteries the machine screw stud is part of the amp carrying capacity. Don't EVER use loctite again
The battery terminal to busbar surface area carries the current, not the studs or screws. If you've dealt with these specific cells, you would understand the physical clamping (screws, studs, nuts and bolts) are different and a weak part of the cells. Loctite is used to hold the studs and should not be used on the terminal surface that carries the current. It's purpose in this application is to hold the non current carrying stud and prevent it moving and possibly being driven through the terminal into the cell while allowing adequate physical force to be applied to ensure good connections between the current carrying surfaces (terminal to busbar surface).
 

Gazoo

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HOWEVER... if you have a bad connection to the terminal, like sloppy loctite between it and the bussbar/lug... yeah, that bolt will get VERY HOT...
Of course it will. I think that's a given and 0 awg or larger cable will not help with that. Common sense should prevail as far as clean terminals, busbars, and torque. However in some cases it does not and even if common sense is used mistakes are made. I have learned a lot due to my own mistakes and from the mistakes of others. Busbars properly mounted to the cells terminal carries the current between the cells. Not the studs and nuts or screws used to mount them. It's a good point to revisit in case a newcomer stumbles across this....:) And could have something to do with the OP's fire. We don't know for sure.
 

LeRoy Christensen

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MDF is non-conductive, or at least rated as such. MDF also will typically not burst into flame but if kept above combustion temps will smolder which seems to be what you had happen. Is it possible something else shorted under the MDF and generated high enough temperatures?
 

ArthurEld

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However in some cases it does not and even if common sense is used mistakes are made. I have learned a lot due to my own mistakes and from the mistakes of others.
When I make a mistake it causes me to concentrate on that subject for a long time. I would never learn the subject so thoroughly if it wasn't for the mistake.
 

Terrapin

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Metal, concrete (perhaps tile backer board), sheetrock.
Sheetrock/plaster has the particular characteristic of absorbing heat as it breaks down and releases water. It is used in fire resistant safes.
+1 on tile backer board. Tile was my business and we would use the hardibacker brand because it had no small styrofoam looking beads as in other types though. This board is the standard for tile walls behind wood or pellet stoves. To creat a super insulating 'Box you could cut srtips of it and use them as studs to layer the sheets... as many a you fell needed or do some homework by learning the temp. of litium burns and consulting with architectural or your local fire fighting or building code service/resources.

Glad your story ended as well as it did! But sorry for the hard lesson though. TY for sharing it.
 

fhorst

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What BMS were you using?
At that time just my 2A active Balancer.

Any BMS wouldn't have stopped the fire.

I have the DIYBMS, and like it a lot.
There is now version 4.40 with a new controller. Most parts are in, PCB's (partly populated) can come in any day now.

Good thing about DIYBMS is that it has a per cell (or parallel cell set) module that have the possibility for external temperature sensor (one)
That way you can monitor almost all busbars for temperature.

Why the busbars? They are close to the cell temperature, and mostly,if there is a failure contact, that's one of the parts that heat up the most.

Diybms can do different things based on different readings, and has 4 contactors who can turn something on or off.

If any cell (connection) would get to hot, it can disconnect all power.

That should have stopped the problem, probably.

If it was the temperature sensor wire that got crushed between stud and sheet, and with it making Falce contact with other terminal (short)...
The fire still would have happened.

Funny thing:

I've cycles the heaviest "damaged" cells several times, discharge with capacity tester, and (top) charge.
Both with 10A.

Surprised to see that they aren't behaving any different from the other cells.
Even have similar capacity left.

What I do notice, capacity testing 48 cells (probably 60 as a few have more cycles) is that the voltage fluctuate!!
Not during the test, but between the different tests.

I have 3 of them, and at the same SOC discharge, and same 10A, cells give different voltages, sometimes surprising much. (Like 3.1 and 3.3v)
At the end they all have the same capacity, give it take a few AH.
The difference is not related to the discharger, I've tested same cells on different testers.

For me once again an indication that voltage is a really bad indicator for SOC.
Only "empty", "not empty", "probably full" and "fully charged" can be measured.

Percentages are impossible as they aren't the same for each cell with that SOC and similar charge or discharge rate.

Funny to see this.
I hope none of you ever needs to do capacity test for so many cells, living off grid.
(Is charging only during sun hours, not with MPPT, buy individual cells or sets of 4)
It's a monster job that takes already +3 weeks.
 

Sanwizard

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I use Tap Magic also. Someone else pointed out that it's "just" kerosene, but I don't care. It's in a convenient bottle and may have some secret sauce. Besides, it did really well in the Project Farm test.

Love project farm!
 

MrX

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Jan 3, 2020
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I've not read through more than seven pages, so someone else might have suggested this. Anyway, to me it looks like the whole pack was shorted. Looking at your first picture, heat seems to have been dissipated at the most negative terminal. If two cells where shorted in the middle of the pack, that would not happen. The rest of the damage to the pack is arbitrary and by my theory related to how much resistance there was between the different connections (resistance) between the busbars and terminals. Is it possible that the board somehow shorted the thick wires connected to most positive and most negative?
 

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