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Temperature during Lithium thermal runaway
- Thread starter Dorfie
- Start date
DennisRhodes
Well Known Member
Just watched a NOVA special on renewable and energy storage research. A lot of good tech info on Lithium and lithium ion batteries as well as several battery types I have never heard of. The program was very good and had some footage of Li battery destruction from various methods ie puncture, overcharge and runaway recharge. You don't want to be anywhere around when that happens. I believe I heard somewhere around 1800 Deg F on Li ion battery fault. They had some impressive footage. Might look for a replay of that Nova.
Used to use Li-poly batteries for RC stuff. Used a thing called a battery bunker to store/charge them in. Could handle the 1100 deg fire. Quick search shows the same temp for Li-ion.
Most aluminum melts at around 800.
They also make a ceramic fabric pouch for the same purpose. Check at local hobby stores to find them.
Mike
Most aluminum melts at around 800.
They also make a ceramic fabric pouch for the same purpose. Check at local hobby stores to find them.
Mike
Every time a person asks a question about "Lithium battery", I cringe a little, because I know the next post will be about fires, explosions, and all manner of dangerous things. But there are many different types of Lithium batteries, and they all have different characteristics. Misinformation - especially on the internet - abounds, mostly because, yes, there have been fires associated with many (but not all) Lithium battery types.
If the OP is talking about Lithium polymer batteries, like you find in RC models, then yes - there have been lots of fires. If he's talking about liFePo (Lithium Iron Phosphate) batteries - that's "iron", not "ion" - as are becoming popular in lightweight starter batteries, it's a different story. People carelessly use all these terms interchangeably, thinking it's all the same stuff, just spoken with different accents. But they are different. There are a couple of popular stories floating around about in-air fires in experimental using "Lithium" batteries, but no one has been able to find out exactly which batteries these were, as the people reporting on them are always talking second or third hand.
So be precise in your questions, or the answers you get back will just confuse the issue even more.
So to the OP - which batteries are you talking about?
If the OP is talking about Lithium polymer batteries, like you find in RC models, then yes - there have been lots of fires. If he's talking about liFePo (Lithium Iron Phosphate) batteries - that's "iron", not "ion" - as are becoming popular in lightweight starter batteries, it's a different story. People carelessly use all these terms interchangeably, thinking it's all the same stuff, just spoken with different accents. But they are different. There are a couple of popular stories floating around about in-air fires in experimental using "Lithium" batteries, but no one has been able to find out exactly which batteries these were, as the people reporting on them are always talking second or third hand.
So be precise in your questions, or the answers you get back will just confuse the issue even more.
So to the OP - which batteries are you talking about?
Alan Carroll
Well Known Member
As it happens someone has done a study of this recently. You have to pay if you want the full article but I was able to access it via my university library.
The authors found that thermal runaway occurred when the LiFePO4 battery surface was heated to a temperature of about 126 ?C (=259 ?F). I would venture that your aircraft battery is unlikely to ever see that temperature absent a fuel- or oil-fed fire (in which case you may have bigger problems to worry about).
The measured combustion temperatures were highly variable. Th lowest they reported was 650 ?C, and the highest was 986 ?C (1807 ?F). I think the latter is well above the melting point of any aluminum alloy.
The authors found that thermal runaway occurred when the LiFePO4 battery surface was heated to a temperature of about 126 ?C (=259 ?F). I would venture that your aircraft battery is unlikely to ever see that temperature absent a fuel- or oil-fed fire (in which case you may have bigger problems to worry about).
The measured combustion temperatures were highly variable. Th lowest they reported was 650 ?C, and the highest was 986 ?C (1807 ?F). I think the latter is well above the melting point of any aluminum alloy.
bret
Well Known Member
I have read all the arguments about these batteries for a couple of years now and I have changed my thinking about what to hope for if my Earth X battery self ignites, a lot of folks say steel enclosure for the battery but mine is in this custom homemade aluminum one. So now if this battery self ignites, and burns through the box, I hope I can identify this fire and hope it WILL melt through and then I can pull a momentary 6G pull up to drop the battery out the bottom and switch over to my internal 20 AH backup battery.............wishful thinking but its a thought......any thoughts on this madness.......?
Alan Carroll
Well Known Member
It dawned on me as well that a battery box that melts might be a good thing if it allows the burning mess to simply depart the airplane. Hopefully it doesn't fall on someone (FAR 91.15 comes to mind). I'm not sure though if the cables might tend to hold it in place?
JohnInReno
Well Known Member
Temp strips
https://www.mcmaster.com/#temperature-strips/=166ych3
I have temperature strips directly on the EarthX900 on the firewall. It has not seen 130F since installed Feb 2016 even in an AZ summer.
https://www.mcmaster.com/#temperature-strips/=166ych3
BillL
Well Known Member
If you are talking about something like EarthX LiFePO, then it probably will.
Here is a plot of some batteries forced into thermal runaway and the temperatures. The non Fe batteries (typically) have higher energy per mass and that results in higher temps during runaway. Also, the electrolytes can self ignite on discharge of these higher energy batteries causing fires. Note the excursion line for #1. It appears it began its thermal event around 100C.
Let me know if you want the full report. Lithium Cobalt had peaks around 850-900C - not counting fires. To be sure, Ross has it right: sealed, stainless, vented overboard. Earth X offers aluminum.
Ever been able to correlate with under-cowl air temperature, or post shutdown temperature of engine accessories?
ChiefPilot
Well Known Member
So where exactly would this burning mass of stuff go? Onto the master contactor and associated wiring located directly below your battery box? What happens then?
I've got a spare Shorai LiFePO4 battery that I picked up to install in my -6A which has about 500hrs on the first Shorai battery I installed several years ago. I'm tempted to swap in the new battery and intentionally overcharge the original, capturing it on video. It's just not that exciting of an event - certainly nothing like people are thinking about with Li-Ion, Li-Poly, or other chemistries as Paul alluded to earlier.
failure modes
Does anyone have a list of the lifepo4 battery failure modes? Particularly the EarthX aircraft batteries with the 2 BMS controllers?
Would an alternator overvoltage/runaway cause a battery fire?
Clearly physical impact could cause an "event", anything else?
Does anyone have a list of the lifepo4 battery failure modes? Particularly the EarthX aircraft batteries with the 2 BMS controllers?
Would an alternator overvoltage/runaway cause a battery fire?
Clearly physical impact could cause an "event", anything else?
Alan Carroll
Well Known Member
If you are talking about something like EarthX LiFePO, then it probably will.
Here is a plot of some batteries forced into thermal runaway and the temperatures. The non Fe batteries (typically) have higher energy per mass and that results in higher temps during runaway. Also, the electrolytes can self ignite on discharge of these higher energy batteries causing fires. Note the excursion line for #1. It appears it began its thermal event around 100C.
Let me know if you want the full report. Lithium Cobalt had peaks around 850-900C - not counting fires. To be sure, Ross has it right: sealed, stainless, vented overboard. Earth X offers aluminum.
The full report can be found online here. The red curves ("LFP") are for LiFePO4. The authors found that they began to go generate their own heat ("onset of thermal runaway") when heated to 195±8 °C, which is higher than in the other study I posted. Rapid runaway commenced at some point after that, result in peak temperatures around 400 °C for the LiFePO4 battery. The battery also generates hydrogen and hydrocarbon gases, which as Bill notes can cause a fire (with hotter temperatures).
The excursion for the curve labeled #1 is not actually showing a lower temperature (100 °C) thermal event. Its showing a different experiment that used a faster heating rate.
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moosepileit
Well Known Member
The g-assisted ejection assumes you can overcome friction of any case swelling, melting material binding and post connection strength.
I doubt you could use any treaded post fasteners. You might need mechanical ejection seat tech.
For the LiFePO4, I am about ready to try the ETX900 as my next replacement. I would add some stainless under it as an outer floor skin, in effect completing what I think is worthwhile for any plane- not just a stainless firewall, but a stainless section above the exit cooling area.
My RV-6 battery box is against the firewall but floor-supported.
I doubt you could use any treaded post fasteners. You might need mechanical ejection seat tech.
For the LiFePO4, I am about ready to try the ETX900 as my next replacement. I would add some stainless under it as an outer floor skin, in effect completing what I think is worthwhile for any plane- not just a stainless firewall, but a stainless section above the exit cooling area.
My RV-6 battery box is against the firewall but floor-supported.
I was referring to LiFePO4 batteries. My bad for not stating clearly. I assumed they react in a similar fashion once in thermal runaway.
I was considering making an aluminum case for the battery, which then gets lined on the inside with FibreFax/SS foil, similar to firewall fire protection.
Thanks.
Johan
Carl Froehlich
Well Known Member
Perhaps I just don't get it
For the gain a saving a few pounds, it seems people are bending over backwards to mitigate the risk from these batteries. I'm not going to touch the issue of increased risk as my bi-stable is already thrown that they are not yet ready for prime time.
Every RV I built has two Odyssey PC-625 batteries, with independent master solenoids and each feeding power to half of the panel (e.g. left battery EFIS #1, Comm #1, Nav #1, etc.). No other backup batteries in the plane. Total weight for the two batteries is 30 pounds. No special mounting other that a standard hold down bar (no battery is mounted on the engine side of the firewall).
So my total of 30 pounds provides 34 amp-hours of power and 440 CCA (doing the simple math so don't get picky). The EarthX battery that comes close is the ETX-1200 (at $725). It is light at only 7.7 pounds, but if you are doing the SS battery box and all that other stuff I'd guess you quickly chip away at the weight savings. Add to that back up batteries and you might still come out slightly lighter.
But - every builder has his/her own priorities. I just didn't want any new builders to think that they had to have an EarthX or their plane would be too heavy to get off the ground.
Carl
For the gain a saving a few pounds, it seems people are bending over backwards to mitigate the risk from these batteries. I'm not going to touch the issue of increased risk as my bi-stable is already thrown that they are not yet ready for prime time.
Every RV I built has two Odyssey PC-625 batteries, with independent master solenoids and each feeding power to half of the panel (e.g. left battery EFIS #1, Comm #1, Nav #1, etc.). No other backup batteries in the plane. Total weight for the two batteries is 30 pounds. No special mounting other that a standard hold down bar (no battery is mounted on the engine side of the firewall).
So my total of 30 pounds provides 34 amp-hours of power and 440 CCA (doing the simple math so don't get picky). The EarthX battery that comes close is the ETX-1200 (at $725). It is light at only 7.7 pounds, but if you are doing the SS battery box and all that other stuff I'd guess you quickly chip away at the weight savings. Add to that back up batteries and you might still come out slightly lighter.
But - every builder has his/her own priorities. I just didn't want any new builders to think that they had to have an EarthX or their plane would be too heavy to get off the ground.
Carl
rv7boy
Forum Peruser
NASA Info
NASA has done a lot of study on various types of "Lithium" batteries. Technical Bulletins, which are concise, brief descriptions of the results of these studies, are available to the public.
I'm not sure if these specifically answer the OP's concerns, but they might point the interested reader in the direction of more useful information.
Battery Protection
and
Battery Database/Guideline
NASA has done a lot of study on various types of "Lithium" batteries. Technical Bulletins, which are concise, brief descriptions of the results of these studies, are available to the public.
I'm not sure if these specifically answer the OP's concerns, but they might point the interested reader in the direction of more useful information.
Battery Protection
and
Battery Database/Guideline
