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Can LiFePO4 Batteries Combust in Thermal Runaway Event?

RV10flyer said:
Oh yes, the case is connected somehow, with a very high resistance to the positive terminal. More or less so on each individual cell. If you put a wire from the alim case to the cell negative terminal, it will conduct the above numbers I mentioned. It doesn't produce any measurable heat, but it would drain your cells if you put the cells in a metal compartment that connected to the neg terminal of battery or car or ebike or tractor or airplane....and you wore a hole through the thin blue plastic. A good reason to insulate between cells and around all of the cells once your battery is complete, especially in her mobile application.
Click to expand...
I was just trying to clear up the statement @timselectric made where he claimed that there was a DIRECT connection from one of the cell terminals to the case .... Oh, and I believe you liked that post .... there is a low leakage current pathway, but no where near a direct connection.
In any case, there's a potential for problems if the aluminum case is shorted to some other metal.
 
Bob B said:
I was just trying to clear up the statement @timselectric made where he claimed that there was a DIRECT connection from one of the cell terminals to the case .... Oh, and I believe you liked that post .... there is a low leakage current pathway, but no where near a direct connection.
In any case, there's a potential for problems if the aluminum case is shorted to some other metal.
Click to expand...
I stand corrected.
I seen it stated many times. So when I received my first EVE cells, I put a voltage meter on it to confirm.
I never went further into it. I was just verifying the cautions that were being made. So, it appears that it's not a direct connection. But, the caution is still valid.
Just moved from Defcon 1 to defcon 3. lol
 
High resistance leakage between cell terminals and metal container case of cell is caused by excess electrolyte between cell wrap and metal case.

Electrolyte filling is a pretty messy process done under vacuum that gets some spillage around the outside of cell wrap.

This is pretty common.
 
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Will Prowse said:
Check out this picture. Lifepo4 is flat line on bottom because it is not self propagating. It's quite literally impossible due to its materials:
View attachment 112124
They need to stop calling it runaway when it's not self propagating. They should say it's combustible, like wood. Or many other things once it reaches a certain temperature in this oxygen rich planet.
Click to expand...

While still crap tompared to LFP, happy to see NMC below NCA.
 
Gazoo said:
I don't think it is. We have been through this many times before and I believe it's leakage current at least with the EVE cells. But I also think there are certain scenarios that could cause problems and it's good to put insulation between the cells especially in a mobile environment.

In the spec sheets one of the manufacturers state the "cans" are not to touch each other. I don't recall off hand which manufacturer that was. Best practice is to keep cells insulated from each other and any metal fixture and keep the cells mounted upright if possible.
Click to expand...
One side is copper, the other side is aluminum in the jelly roll. All you see is incidental leakage current caused by the chemistry (and the fact the case is aluminum).
 
Bob B said:
I was just trying to clear up the statement @timselectric made where he claimed that there was a DIRECT connection from one of the cell terminals to the case .... Oh, and I believe you liked that post .... there is a low leakage current pathway, but no where near a direct connection.
In any case, there's a potential for problems if the aluminum case is shorted to some other metal.
Click to expand...
Yes, there is a reason they wrap the cells. The leakage is incidental, and the cell casing should be insulated. If there is a direct connection, it is a manufacturing defect.
 
Bob B said:
I was just trying to clear up the statement @timselectric made where he claimed that there was a DIRECT connection from one of the cell terminals to the case .... Oh, and I believe you liked that post .... there is a low leakage current pathway, but no where near a direct connection.
In any case, there's a potential for problems if the aluminum case is shorted to some other metal.
Click to expand...
Yes, there is a reason they wrap the cells. The leakage is incidental, and the cell casing should be insulated. If there is a direct connection, it is a manufacturing defect.
 
Cell wraps on these metal cased cells is open at the top to allow foil terminals to escape wrap. The bottom of wrap is folded over plastic with some heat sealing but it is not fully guaranteed to be sealed.

What primarily determines the combustibility between various Li-Ion chemistries is the amount positive cathode oxygen created during thermal runaway. LFP produces the least amount of oxygen from cathode during thermal runaway. All Li-Ion chemistries use pretty much the same electrolyte chemicals which is somewhat flammable but needs oxygen and ignition heat source to burn

cell open can via top.jpg
Top of double pouch 2.jpg
Bottom double pouch seal 2.jpg
 
Bob B said:
I was just trying to clear up the statement @timselectric made where he claimed that there was a DIRECT connection from one of the cell terminals to the case .... Oh, and I believe you liked that post .... there is a low leakage current pathway, but no where near a direct connection.
In any case, there's a potential for problems if the aluminum case is shorted to some other metal.
Click to expand...
I troubleshoot motors all the time on 240V A/C compressors and fan motors. If I'm seeing less than 240,000 ohms to ground, it's not good. It may still run for a while longer, but it's just a matter of time. I measured 4,500 ohms on one of my cells. Of course it's only 3.2 V, but it could definitely drain the battery. It can be considered a "direct connection" whether it is a wire or electrolyte to the average solar diy'er. I would prefer it be insulated completely from either the negative or positive terminal. That means my fortune 100aH cells that cost a lot more didn't have as much leakage during manufacturing.

We all come from different backgrounds, different experiences, different educations and different areas of the country or world. The main thing is that we are enjoying each other's company, sharing knowledge and it makes us dig deeper into the various subjects while collecting as much free power from the sun as we can.
 
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Yes it can! it is really horrible and frightening !!! can't you imagine when internal thermal runway happened suddenly what is going on ! fire and explosion! it started with an shortcircuit inside a 280Ah lifepo4 cell in a 4S battery pack during rebalancing a 200 handred cycled 4S battery! I can't still think about what happened in just a 30 second in front of my eyes! just tell all of guys here and everywhere "If a battery cell starts to swell quickly and suddenly" don't waste time, runaway! even if there were thousand of reseans that thermal runway will not happen in a lifepo4 cell in theory in practice it will!

Lifepo4 battery can catch fire easly because of internal short circuit and if their safety valve Don't work at the moment cause explosion! fortunately in our case it worked although after firing the cells!
this is what happened exactly:
After a cells dropped below soc with respect to the other cells in a 4S pack I opened the packs and wired the cells in parallel configuration and top balanced all the cells around 3.75V and let the current dropped to zero ! after a day I opened the parallel cells and let cells rest separately for one more day I checked the cells voltage and found the lowest soc cell before top balance again fall below 3.39V while all of the others are above 3.6 again I put that cell on a power supply but this time raise the voltage up to 4V ! (maybe this is my first fault!) and again let the current dropped below 0.5A finally I repacked cells in 4S but when I tried to fasten the cells busbars properly I did the "second mistake" I tightened this weakest overcharged cells busbars with a torque of above 8 N.M maybe 10! but quickly understand and again opened it and again fasten with 6 N.M like the other cells everything start here after ! just in a couple of seconds this cells start inflaming and suddenly catch fire and other tribble happening that I can't still imagine it !
So guys as my experience don't do these 4 never with lithium cells at least lifepo4 cells:
1- Never overcharg them near the margin line every one tell you that this cells can still 4.2V but their safe voltage is below 3.65!
2- Never tighten their poles with torque above 4~6 please refer to datasheet and still consider some margin
3-Never use the lithium battery without a bms 4- never just relay on theory and consider safty as much as possible!
 
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LightSpeed said:
Yes it can! it is really horrible and frightening !!! can't you imagine when internal thermal runway happened suddenly what is going on ! fire and explosion! it started with an shortcircuit inside a 280Ah lifepo4 cell in a 4S battery pack during rebalancing a 200 handred cycled 4S battery! I can't still think about what happened in just a 30 second in front of my eyes! just tell all of guys here and everywhere "If a battery cell starts to swell quickly and suddenly" don't waste time, runaway! even if there were thousand of reseans that thermal runway will not happen in a lifepo4 cell in theory in practice it will!

Lifepo4 battery can catch fire easly because of internal short circuit and if their safety valve Don't work at the moment cause explosion! fortunately in our case it worked although after firing the cells!
this is what happened exactly:
After a cells dropped below soc with respect to the other cells in a 4S pack I opened the packs and wired the cells in parallel configuration and top balanced all the cells around 3.75V and let the current dropped to zero ! after a day I opened the parallel cells and let cells rest separately for one more day I checked the cells voltage and found the lowest soc cell before top balance again fall below 3.39V while all of the others are above 3.6 again I put that cell on a power supply but this time raise the voltage up to 4V ! (maybe this is my first fault!) and again let the current dropped below 0.5A finally I repacked cells in 4S but when I tried to fasten the cells busbars properly I did the "second mistake" I tightened this weakest overcharged cells busbars with a torque of above 8 N.M maybe 10! but quickly understand and again opened it and again fasten with 6 N.M like the other cells everything start here after ! just in a couple of seconds this cells start inflaming and suddenly catch fire and other tribble happening that I can't still imagine it !
Click to expand...
Yes, that was your fault.
You purposely overcharged the cell without any type of protection in place.
 
LightSpeed said:
Yes it can! it is really horrible and frightening !!! can't you imagine when internal thermal runway happened suddenly what is going on ! fire and explosion! it started with an shortcircuit inside a 280Ah lifepo4 cell in a 4S battery pack during rebalancing a 200 handred cycled 4S battery! I can't still think about what happened in just a 30 second in front of my eyes! just tell all of guys here and everywhere "If a battery cell starts to swell quickly and suddenly" don't waste time, runaway! even if there were thousand of reseans that thermal runway will not happen in a lifepo4 cell in theory in practice it will!

Lifepo4 battery can catch fire easly because of internal short circuit and if their safety valve Don't work at the moment cause explosion! fortunately in our case it worked although after firing the cells!
this is what happened exactly:
After a cells dropped below soc with respect to the other cells in a 4S pack I opened the packs and wired the cells in parallel configuration and top balanced all the cells around 3.75V and let the current dropped to zero ! after a day I opened the parallel cells and let cells rest separately for one more day I checked the cells voltage and found the lowest soc cell before top balance again fall below 3.39V while all of the others are above 3.6 again I put that cell on a power supply but this time raise the voltage up to 4V ! (maybe this is my first fault!) and again let the current dropped below 0.5A finally I repacked cells in 4S but when I tried to fasten the cells busbars properly I did the "second mistake" I tightened this weakest overcharged cells busbars with a torque of above 8 N.M maybe 10! but quickly understand and again opened it and again fasten with 6 N.M like the other cells everything start here after ! just in a couple of seconds this cells start inflaming and suddenly catch fire and other tribble happening that I can't still imagine it !
Click to expand...
You should never exceed 3.65V...

4V? And you are surprised?
 
LightSpeed said:
Yes it can! it is really horrible and frightening !!! can't you imagine when internal thermal runway happened suddenly what is going on ! fire and explosion! it started with an shortcircuit inside a 280Ah lifepo4 cell in a 4S battery pack during rebalancing a 200 handred cycled 4S battery! I can't still think about what happened in just a 30 second in front of my eyes! just tell all of guys here and everywhere "If a battery cell starts to swell quickly and suddenly" don't waste time, runaway! even if there were thousand of reseans that thermal runway will not happen in a lifepo4 cell in theory in practice it will!

Lifepo4 battery can catch fire easly because of internal short circuit and if their safety valve Don't work at the moment cause explosion! fortunately in our case it worked although after firing the cells!
this is what happened exactly:
After a cells dropped below soc with respect to the other cells in a 4S pack I opened the packs and wired the cells in parallel configuration and top balanced all the cells around 3.75V and let the current dropped to zero ! after a day I opened the parallel cells and let cells rest separately for one more day I checked the cells voltage and found the lowest soc cell before top balance again fall below 3.39V while all of the others are above 3.6 again I put that cell on a power supply but this time raise the voltage up to 4V ! (maybe this is my first fault!) and again let the current dropped below 0.5A finally I repacked cells in 4S but when I tried to fasten the cells busbars properly I did the "second mistake" I tightened this weakest overcharged cells busbars with a torque of above 8 N.M maybe 10! but quickly understand and again opened it and again fasten with 6 N.M like the other cells everything start here after ! just in a couple of seconds this cells start inflaming and suddenly catch fire and other tribble happening that I can't still imagine it !
So guys as my experience don't do these 4 never with lithium cells at least lifepo4 cells:
1- Never overcharg them near the margin line every one tell you that this cells can still 4.2V but their safe voltage is below 3.65!
2- Never tighten their poles with torque above 4~6 please refer to datasheet and still consider some margin
3-Never use the lithium battery without a bms 4- never just relay on theory and consider safty as much as possible!
Click to expand...
NOBODY tells anyone that LIFEPO4 cells can be charged over 3.65V. EVER!

4.2V is for LiNMC cells. Or pouch packs.

4V was not your first mistake, 3.75V was. That is .10V over the MAXIMUM the cell should EVER reach.
 
Supervstech said:
NOBODY tells anyone that LIFEPO4 cells can be charged over 3.65V. EVER!

4.2V is for LiNMC cells. Or pouch packs.

4V was not your first mistake, 3.75V was. That is .10V over the MAXIMUM the cell should EVER reach.
Click to expand...

Not trying to be a dick, but a LOT of "dumb" BMS have their cut-off set to 3.75V. Do we all remember when the EG4 were 3.9V????

EDIT: :P (smiley added)
 
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Three years ago, in each box with the older threaded terminal CATL cells, there was a little pamphlet. Needless to say, I didn’t come close to using those extremes.
IMG_1255.jpeg
 
sunshine_eggo said:
Not trying to be a dick, but a LOT of "dumb" BMS have their cut-off set to 3.75V. Do we all remember when the EG4 were 3.9V????

EDIT: :p (smiley added)
Click to expand...
True, but some of the earlier cells were tested to those levels. Sinopoly, CALB, Winston come to mind... then they got wise and lowered the numbers. less issues for their cells. now we have bargain basement makers pumping out cells and they cannot even be safely charged to 3.65 more than once or twice a year for balancing purposes.... that and red handed thieves who sell rebadged used units from chineese bus's as new grade "A" EV levels cells...
 
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