I don’t think this is true. The cells themselves won’t self combust, but with a direct short everything else will get hot and catch fire.
I believe the types of cells we use (IMR/INR) are “safe chemistry”, similar to lifepo4 with respect to self combustion.
I worry that if one thing catches fire, all my expensive toys will burn. Better than the whole house I suppose…
Exactly this for me. The value of my house and family far outweigh whatever toys I can stuff into even the biggest locker. I will do my best to isolate with drywall panels and such to slow the spread of a fire, but it will be outside in any case.
Looks like a good storage box for unused batteries is almost the price of a quick build > https://zargesusa.com/products/cases/specialty/batterysafe/?attribute_pa_product_sku=40582
Still cheaper than a full house rebuilding 
But seriously that’s the deluxe version. There enough diy box options which will do the job for way less money.
I’ve been planning to store my boards in a keter box (or the shed) in my back garden, but I’ve been dragging my heals for a while now as I was slightly concerned of exposing the packs to extreme hot/cold temperatures. After reading this post, I’ll definitely be kicking them out of the cozy house tomorrow morning.
I realize that that may places on this planet thay can be entirely too hot or too cold at times to safely store these things outside. I’m fortunate to live in an area with a relatively mild climate, as long as I have proper sun protection.
THIS.
I found a spot under my patio awning next to the garden shed, which also shares this shade, exactly 25mm away from the house. Won the wife over by giving her half the locker for her garden stuff 
LiFePO4 won’t go venting like Li-Ion or LiPo spewing flames, and that’s a proven fact.
Shorts will generally only cause equipment failure, at which point the circuit is broken.
I got the drums cleaned up and moved a bunch of crap out of the way so my charging station looks pretty good.
I ordered a second smaller metal cabinet just for storage.
I plan on ordering a bunch of 5/8 drywall to put both inside and outside the storage cabinets. That is going to be a bunch of work…
So received and Installed my Google Nest 2 Fire Alarm now… at least a little bit ease of mind when I am on business trips or not at home.
What an interesting pack layout.
Everything appears isolated and insulated, however it doesn’t seem to be built to be terribly flexible. If I had to make a wild guess at what happened, I might say that over time the flexing and twisting that normally happens (even on stiff ass decks) eventually caused the adhesive to tear at the nickel and a short could have happened from a resulting sharp edge or spike.
Its also possible that insulation may have been tugged at and torn from the cell can by the adhesive as well, causing a short in the process, but the pgroups seem to be isolated with fishpaper so its probably not as likely. If it did happen that way, it may have been from the balance lead tabs which can bend and move slightly if the pack flexes.
In any case, p-groups should be rolled up in fish paper with the ends covered in Kapton. Adhesive inside the series connections was likely working against you here as well since they disn’t allow the pgroups to roll and slide so the pack could twist. (roll and slide is probably the wrong phrasing, but they should be able to slip around slightly)
just my two cents.
How many cycles between the old, bad pgroup and the new one that replaced it?
Thanks for the analysis and valuable info. As I said, I haven’t built this pack. @eBoosted has built it long ago for @Brenternet and I then purchased it from him with a (nearly) full build. I think this dates back to Alan’s early battery building days and he would have very likely done things differently today. Not trying to blame anyone here. I inspected the pack and it looked reasonably well made to me, otherwise I wouldn’t have used it.
The new P-group might have had some 50 cycles less than the old group. If you’re suggesting a problem with charging though, that’s very unlikely. I used smart BMSes since the beginning and kept eye on the voltages at all times. I also didn’t balance the pack. I had the BMS setup to stop charging when the top P-group reaches 4.22V. The new P-group was slightly out of balance with the other groups but not in an unhealthy way. If discharging to ~3.5V, all groups would be in balance at that point and when charged to full, the new group would be ~4.12V when others would be at or close to 4.2V.
Damn man, I’m so sorry to hear this. If you didn’t tag me I wouldn’t have seen this post.
This was was built almost 2 years ago, I effectively used fish paper on all rubbing areas, underneath balance leads and between p-groups which were then connected with flexible 12AWG wires, so even though, the pack was not 100% flexible like the Trampas, it was a bit flexible enough for a 36" Evo.
I don’t think the drift in P-Groups could have caused the venting and I don’t see any points of rubbing worth inspecting either, what p-group is the one you changed?
It was the group 6. The one in upper right corner on the picture. It had several bad welds and one of the cells lost contact with the group, reducing it down to 4P from 5P.
IIRC, I added some more insulation between the two rows of P-groups when I had the pack apart. I also changed the balance leads. They were originally routed to the same side as the discharge wires but I needed them on the other side. At the beginning, I just had extensions but that was clunky so since I was already doing the maintenance, I decided to change the leads as well.
The battery looked in a pretty good shape at that point and I have done hundreds of km on it since then and haven’t touched the battery until the incident. This remains a mystery to me.
Youtube just recommended this video and seemed quite an interesting addition to this discussion. It includes the ingredients to make a DIY protective “barrier” against a direct flame from a propane torch.
It got me wondering if this might be a good homemade solution or if drywall might be enough.
Haha, YouTube recommended this to me as well today 
So i wanted a way to storage my boards and be safe from fires. I already got one of the nobleman firebags, but i kinda wanted something i could stand up. So im trying something out. Feel free to tar and feather me if its a terrible idea. I’ll admit, im not a firefighter or a specialist in this area. I’m going off the concept of removing one of the triads from the fire triangle, which is limiting oxygen.
I got this storage locker off of amazon. Its metal and just big enough for my board. After some assembly, i lined the cracks both inside and outside of the locker with 3M fire barrier sealant. For the vents on the door, i placed electrical tape on the inside and filled in the vent from the outside with the sealant. I know, a fire would eat the tape pretty quick which is why i filled the other side with sealant. Next I’ll be putting some sort of weather stripping around the frame of the locker door. Might not be air tight like a ziploc bag but im hoping it severely reduces the air available for a fire. Like breathing through a straw.
I want to be able to charge my board in it and so i was thinking of making a small hole in the side to thread the charge cable only though and line that side with some fire retardant material. Cuz my concern would be the cable burning mid cable and the expose wire would contact the metal sides. Cuz you know, metal is conductive.
This set up was $150ish. Think i saw some similar lockets for around $80. Mind the messiness. Im not exactly a handy man, this was my first time using a sealant gun.
What do y’all think? Good idea, iffy, wtf?
From what I’ve read you can’t really put out lithium power by blocking oxygen inflow. Commercially available fire containers for lithium batteries are not airtight since there’s a risk that during fire pressure will build up inside the container and it may explode. Instead, the containers are made to contain the fire and to filter the fumes.
I think there’s a chance your container will contain the fire should there be one but I would be careful with the sealant.
Ya the thought of pressure build up did cross my mind too.
I just had a quick look on the topic again and, as I understand, the problem is that even if you make the container airtight it will still contain oxygen initially. If there’s a short circuit that causes fire, it will have some oxygen to feed on and the pressure may go too high before the oxygen runs out.
At any rate, when I researched this topic some time back, none of the commercially available containers I found was airtight, so there’s probably a good reason for that.
