Fire!! Never cover LiFePO4 with wood!!!

diyernh

Solar Enthusiast
Joined
Feb 5, 2021
Messages
103
I'm still thinking the temperature sensor for the fans. It was discounted quickly. The sensor had a battery lug for mounting. I would think that would be positive It could have been pinched between the wood and the the post. I would guess that post is about 9 to 12V negative potential from the more positive fan lug. Just a small pinch would be enough. You don't need the spark to carry enough heat to melt the battery. It just needs some glowing embers on the wood.

The fans were running. This could have been the perfect fire starter with a 9V battery. Only the owner could know where the wire was, how the fans could have drawn the fire/flame. Maybe there's pictures during the disassembly. We are asking a lot for him to remember where the wires were, how the smoke was billowing up past the wood, His house was on fire. I can't even remember where I put my multimeter 15 minutes ago.


 

Zoomyn

Solar Enthusiast
Joined
Feb 14, 2021
Messages
25
Makes compelling evidence to try and use dinky-doo 18, 20, 22awg as fusible links... err... BMS / Balancer sense / pickup wire...

I have looked down while driving at 70mph and seen the floor lit orange from the glow of radio/amp wiring up under the dashboard - and blistered my arm & hand up tearing it out while still in motion & lockstep in traffic trying to pull over.

It’s not the peak amperage involved it’s the duration, if the wire doesn’t part immediately the glowy wire resistance keeps increasing but its heat-lamp action keeps going until the last of the conducting metal has oxidized...
 

toms

Solar Addict
Joined
Jul 24, 2020
Messages
746
Makes compelling evidence to try and use dinky-doo 18, 20, 22awg as fusible links... err... BMS / Balancer sense / pickup wire...

I use 22awg silicon insulated tin cable. It self fuses at 10amps and the insulation doesn’t melt. Perfect for BMS sensing wires.
 

Zoomyn

Solar Enthusiast
Joined
Feb 14, 2021
Messages
25
whic
I think you guys are missing the burnt ring around one terminal. How could a shorted balance lead cause that ring?

Which came first? A hot primary crimp or loose bolt encourages smaller cables to join in the disaster, in all the places they shoun't.
 

diyernh

Solar Enthusiast
Joined
Feb 5, 2021
Messages
103
I think you guys are missing the burnt ring around one terminal. How could a shorted balance lead cause that ring?
Maybe a piece of chip board, lighting on fire from a small ember, fanned by the fans? Just like starting a fire with a 9V battery and a foil gum wrapper. Starts small and gets larger. Eventually the board will charcoal itself, falling down on the battery.
 

fafrd

Photon Sorcerer
Joined
Aug 11, 2020
Messages
2,264
What is the simplest explanation?

That internal damage resulted in one or two cells with increased internal resistance which resulted of very hot terminals from continued modest discharge levels overnight. I-squared-R, baby, I-squared-R.

I’m speculating about the internal damage but having seen those tear-down videos, those wires are incredibly small/fragile...
 

diyernh

Solar Enthusiast
Joined
Feb 5, 2021
Messages
103
What is the simplest explanation?
I don't know.

Each of us will do what we think is right. If there are more occurrences, we will learn more. If we don't, we could be considered "unsafe" and need a government license to avoid damage to others and property by not knowing better.
 

diyernh

Solar Enthusiast
Joined
Feb 5, 2021
Messages
103
Does anyone know where this fan sensor burn area was? Was it on that burned post? That's a nice, localized burn area on that cable.


1615865469690.png
 

ArthurEld

Photon Sorcerer
Joined
Aug 3, 2020
Messages
2,069
Location
Palm Harbor, Florida
Damn, I thought we were going to get the obvious simple answer so we could lay this to rest.
I'd like to have that cell to see if I could find something wrong with the internal resistance.
For some reason I don't think IR is the answer.

Something caused that one terminal to heat up more than everything else. It could have been a short, a loose connection or internal resistance.
Unless fhorst comes up with some convincing new information we will never know

edit: one thing I have concluded is that these incidents don't seem to cause a roaring fire unless combustible material is present. It seems to me that the fire could be easily contained. Especially if there is a smoke detector over the battery.

So, my latest plan is to make sure there is nothing near the battery that can catch fire. There's a simple idea

Some type of non flammable barrier over (around?) each battery like drywall, ceiling tiles or cement backing plate makes sense to me.

I'll put a smoke detector over my batteries too.
 
Last edited:

ArthurEld

Photon Sorcerer
Joined
Aug 3, 2020
Messages
2,069
Location
Palm Harbor, Florida
I bet everyone that come up with an explanation thinks theirs is the simplest. hehe

I still think arcs may have been involved. I'm not sure if it's still called an arc if a wet piece of wood is aiding the connection.
And I suspect fhorst's paralleled cells may have made things worse.
 

Just John

Photon Sorcerer
Joined
Aug 15, 2020
Messages
2,381
Battery terminal capable of withstanding 8NM (foot-pounds) was subjected to full weight of 150# man, causing internal damage and release of stored energy into terminal.



(y) 😁
That does seem likely to me as well.
 

HRTKD

Boondocker
Joined
Apr 24, 2020
Messages
6,055
Location
Somewhere South of Denver
While I stopped reading all the kookie theories at about page three, I don't recall reading that fhorst actually stood on the wood when it was on top of the batteries. I stand to be corrected (pun, brutally intended).
 

Just John

Photon Sorcerer
Joined
Aug 15, 2020
Messages
2,381
While I stopped reading all the kookie theories at about page three, I don't recall reading that fhorst actually stood on the wood when it was on top of the batteries. I stand to be corrected (pun, brutally intended).
He did say he knelt on it while hooking something up on the wall behind it. I think he also indicated that particular stud was slightly higher than the rest and would have thus born the brunt of the weight. Without going back and reading everything again, that's my recollection and seems the simplest explanation.
 
Top