Nasty LiPo fire

[El_Steak]

From what i read, the fire extinguisher would serve to keep the fire contained and putting out stray flames but the pack will need to burn itself out and run it's course....

yikes, that's a lot of burning for my 24s3p pack...

 

[John in CR]

To me, at the price we're getting these RC packs it's not unreasonable to expect some duds. For anyone interested in compiling everyone's data, I have six 6s 25C Zippy packs (all good with only a couple of cells in 1 pack that lagged in initial balancing...no idea if that's meaningful), and fifteen of the 4s 20C Turnigy hard packs that were on sale for $.26/wh+shipping (1 catastrophic cell failure that took out a never-used pack). For big discount products a 1 in 96 cells failure rate is perfectly acceptable to me, and based on the good results of many my 1% rate is may be higher than average.

However, we've gotta avoid someone getting hurt/killed by a catastrophic cell failure. Storing our lipo stash in a safe spot is just a start. Storing the packs at half charge is a good practice too (anyone have a failure at around 50% SOC?), but that still doesn't help identify problem cells, and that's where I think we need to take this conversation.

John

 

[Ypedal]

strangely enough, i've been doing stupid stuff to some of these cells and nadda..

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=27241

 

[number1cruncher]

So far the only similarity between John and Kepler's fires seem to be new packs, which should be at 50% SOC when shipped. No where near any thresholds. I wonder if cycling would have helped.

Although, maybe Kepler or his friend did cycle the packs, I don't know.

Man this is making my stomach hurt. I've got a 4 month old at home. I could care less if my house burned down, in comparison to my family getting hurt. If it wasn't so hot out, I'd keep them in my shed. Maybe a quick review of free crap on CL will turn up a oven to store them in?

 

[wasp]

strangely enough, i've been doing stupid stuff to some of these cells and nadda..

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=27241

+1 and sorry for the loss
that said the only way ive seen lipo burst into flames is a full short
even the videos on this site show it to be very hard to get them to flame...especially like the photo

 

[StudEbiker]

Crap, I was just over on HK doing some LiPo Nano shopping when I popped over to ES to research chargers and saw this! Maybe I'll wait awhile before going LiPo. :| Too bad about the packs, but glad it wasn't any worse.

 

[wasp]

Crap, I was just over on HK doing some LiPo Nano shopping when I popped over to ES to research chargers and saw this! Maybe I'll wait awhile before going LiPo. :| Too bad about the packs, but glad it wasn't any worse.

don't be afraid of lipo just always be cautious

 

[neptronix]

I've had one pack just decide to puff on it's own after ~3 months of storage at storage voltage.
That one would have burst into flames. in this situation if i would have just charged it up and stuck it on the bike without cycling it a few times.

Yes, HK does sell some duds from time to time.
But it seems like packs that are just straight up defective express their faults in the first two cycles. This is a common thread in John in CR's packs and this instance.

Lyen had a lipo fire too, but he was abusing his cells pretty bad.

 

[snowranger]

I think it is good to balance charge on occasion to see how each cell is behaving. Would a puffed cell show a diminished capacity profile before it is too late?

 

[El_Steak]

Would a puffed cell show a diminished capacity profile before it is too late?

In my experience, all puffed cells had diminished capacity. Its harder to detect however when the bad cell is in parallel with a couple of healthy cells.

That's why I remove all the opaque blue shrink wrap on my packs and replace it with a few layers of transparent wrap. This allows me to see any puffing and sometimes leaking cells.

 

[el_walto]

A Little Off Topic:
How does one know when it's time to retire their LiPo packs without a BMS installed? On a ping battery with BMS the pack will just stop working when some cells get worn out. I'd think that without a BMS eventually certain cells will wear out before other ones and can cause fires etc.

Has anyone tried cycling a single LiPo cell 2000 times to see how it fails? This might be a candidate http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11873. I'd personally test it to find out what happens, but I think my RC charger can only charge/discharge 5 times in a row without restarting it.

 

[John in CR]

Would a puffed cell show a diminished capacity profile before it is too late?

In my experience, all puffed cells had diminished capacity. Its harder to detect however when the bad cell is in parallel with a couple of healthy cells.

That's why I remove all the opaque blue shrink wrap on my packs and replace it with a few layers of transparent wrap. This allows me to see any puffing and sometimes leaking cells.

I like that approach El_Steak. Visual inspection is simple and probably quite effective. What did you use as the clear wrap?

 

[oatnet]

Kepler, I am so glad you are OK, not to mention your building!

I have always pictured an anomoly like this happening in my house-attached garage, and it gives me chills. It only takes one manufacturing defect in the cell to eventually present itself... That is why I have stuck with a123 (the prisimatics weigh pretty much the same as lipo), despite lots of folks saying the new Lipo is "safe" and "superior". I hope all those folks are now safely storing their lipo accordingly, this is a great hobby but not worth dying for.

John, I didn't see your lipo fire thread, gonna go look for it now!

-JD

 

[RVD]

John's situation was the scariest since it seems like the lipo fire just happened when the pack was sitting there undisturbed for a month...

It seems like most accidents happen when charging or immediately after charging. The other time is if you do something stupid (like short lipo...)

I store my lipo in the garage in a fireproof safe. However, I'm thinking that maybe I should just store them outside in my bbq. My garage is still indoors and there's a lot of stuff in there.

The clear wrap does look nice.

 

[flathill]

BTW, would a regular kitchen-type fire extinguisher be of any use on a Lipo fire? I always leave one by the charger alongside a smoke detector.

You need expensive copper powder to stop a large lithium fire. It sinks heat and forms a shell.

I think a good idea is to build "ejector" packs that can save the rest of your bike. Also charge and store your packs in an old oven. One nice thing about boston power cells is the vent location is marked. You don't want to block the vent.

 

[Doctorbass]

I really think and i've read on sandia report that what make cell to catch in fire is often the deformation that make the electrode to short together between the layers near the edge and corners...

When cell heat, they puff, they have deformation of the envelope and internal layers

The way i follow is to avoid this deformation .. Keeping cell compressed certainly help. if pressure build up inside.. it will be released on the top of the cell but the way it could ignite is reduced alot.

Keeping cells compressed also help reducing the heat produced by them because it lower their internal resistance.

I mean.. compresed parallel of the layers.. not the other side as well.

Even if it happen, i have installed FR4 pcb layers between each of my 6s 15Ah groups and also all around the inside of the 1/8 thick aluminum case.

Doc

 

[Kepler]

Just to be clear, this happened at a friends hobby shop, not my place. The bottles on the left were bottles of RC fuel but we never in danger with plenty of distance between the fire and fuel. Still could have been very bad. We did have a fire extinguisher handy but knew it would do little to put the fire out and the location was clear enough not to spread further.

I didn't put the series harness together so I dont know if there was an issue with it. That being said, the owner is a very experienced aero modeler and has used LIPos for many years. However, connecting multiple packs up like we do is not within his normal experience range. The packs wer Zippy 20C packs, brand new, and balance charged on a high end Hyperion charger. This was however their first discharge cycle.

We were having some issues with getting the Hall wires correct. We had the motor turning but it would seem to intermittently turn. We had just tried another hall combo which was wrong as the motor was jerking back and forward. While doing this, suddenly the pack began to smoke. Within about 15 seconds, the pack erupted into flames.

I am going back there again today to carry out a more detailed inspection taking special note to see if the series harness had a problem. When I opened up the controller, there were no visible signs of damage. It did smell burnt but I not sure if this was just burnt wire outside the controller that had got inside the controller. We are sending the controller back to to Edward for a full check and burnt wire replacement.

I am out buying 3 amo boxes today to store my lipos in and also dispose of any dodgy sell I have been keeping. At least my stealth bomber encases most of my lipos in a 2mm thick cro-mo box which does give me a little piece of mind.

 

[dogman dan]

Keeping all my lipo in the fireplace, since Johns episode. New packs on the first cycle. Not much chance you did anything wrong then.

Cheaper lower discharge rate lipo, could mean something, could be random.

 

[donorcycle]

I do not know too much about the evolution of Lipos, but are the "third generation" Lipos that appear to be based on nano-technology safer than the first and second generation technologies? Are the ones that have been igniting first, second, or third generation technologies? Any difference as far as fire hazard? It is my understanding the newer iterations of both batteries and chargers keep getting safer.

FWIW, I have some Hyperion packs that are third generation nano-technology. I was going to use them to build a commuter bike that would be parked inside, unattended at work. They are supposed to be premium packs, with quality control several orders of magnitude better than some of the other brands (hard to quantify), but I wonder if they will be safe enough?

 

[RVD]

from watching ypedal's latest videos, it does appear that the newest lipos are much safer.

but with that said, the variance is pretty high so i wouldn't risk it. lipos are still very dangerous.

i think in general, lipos are dangerous but in the RC world, they are generally used in small quantities such as 2s or 3s 2800 mah, etc. so while things are still dangerous and there is danger to a house burning down, etc. it's a different ballgame when we're all in here creating 88v packs putting 4 6s 5000 mah in series and then putting 4 of these series pack in series so we have essentially a huge 24s4p pack consisting of 16 lipos. one incorrect short by mistake or one short being inadvertently created because your connectors happen to wiggle around can be disastrous. in addition, if you have lipos in parallel, one lipo can get disconnected and you will then discharge that pack more, etc. in short, it's still somewhat error prone with us reconfiguring packs to charge, etc.

we all know it's "proceed with caution" yet "safe enough" for our tolerance level.

i store all of my lipos in hard plastic containers and inside a fireproof safe or bbq just for peace of mind. with that said, i have a box of 3 lipos sitting in my guest room at my house still in the hobbyking box that it came in. i simply figured that it can't be *that* dangerous or else we'd hear of a post office blowing up or heaven forbid, an airplane blowing up while the lipo is in transit, etc. this is why John in CR's incident is so much scarier...his lipo was just sitting on his shelf for weeks...

anyway, even if 95% of lipos fires are caused by user error, even 5% is a huge number.

 

[Kepler]

Just got a little more information on the packs used. Apparently out of the 8 packs ordered, 4 were faulty showing low or dead cells. These were sent back and replaced by Hobby King. Doesn't say much for the cell quality that's for sure.

Personally, I have never had any issues with my Turnigy's and Rhino's. The Hyperion G3 cells are no doubt a better choice again and perhaps worth the extra dollars.

Do we need to perhaps setup a LiPo ranking register? Not necessarily for cells that have caught fire but perhaps to document what cells seem to arrive with faulty cells or packs that have cells fail early in their life cycle. Also perhaps highlight cells that are performing well over extended periods. Not sure how we would do this but possibly worth putting out there.

 

[liveforphysics]

I sacrificed a pack with a sketchy cell in it today.

It took 11minutes at 30amp charging and it was starting out at 4.2v/cell.
The cells all went to 5.4v before blowing.

This failure and John's failure have got to be an impurities thing in the cells. They are just so rugged otherwise.

 

[mud2005]

OMG... I have 4 6s nano-tech packs (almost new) and the is one bad cell which will drop much further than the others on deep discharge. I thought paying more for the nano-techs would guarantee a usable pack, but I guess not.

I'm genuinely worried now about the future of my pack. this really makes me think. how long till that bad cell goes? should I get rid of that pack now? hmmmmmm

by the time they perfect lipo another chemistry will have taken it's place (I hope)

 

[dumbluck]

sorry to hear about the loss

storage suggestion

Dutch oven

you can find these at second hand store many times. They also stack nice so if you have more lipo then will fit in one.

 

[eva-michael]

I really think and i've read on sandia report that what make cell to catch in fire is often the deformation that make the electrode to short together between the layers near the edge and corners...

When cell heat, they puff, they have deformation of the envelope and internal layers

The way i follow is to avoid this deformation .. Keeping cell compressed certainly help. if pressure build up inside.. it will be released on the top of the cell but the way it could ignite is reduced alot.

Keeping cells compressed also help reducing the heat produced by them because it lower their internal resistance.

I mean.. compresed parallel of the layers.. not the other side as well.

Even if it happen, i have installed FR4 pcb layers between each of my 6s 15Ah groups and also all around the inside of the 1/8 thick aluminum case.
Doc

We should thank Doctorbass who provide a very clear explanation. Many Lithium polymer cell is pouch cell. If there is not efficient package to provent shock from outside, deformation will probably happen as ebike is use on the road and not just stop in a garage. The terminal of cell is a tag which is soft. The terminal of li-ion cells are connected by soldering. insufficient solder will cause large heat or even get burn in this soldering joint. Isolation between each cell connections are very very imporant also. Short circuit will cause by terminal deformation and a touch to the tag connection next to it.