Another LIPO FIRE ! Be careful !

[neptronix]

Yup. not just money. Small, light, cheap, powerful, easy availability, easy assembly ( versus something like buying pouch cells )..

Don't act like you've never seen a battery spec sheet before

[jonescg]

Y'know, if A123 decided to make their amazing 20 Ah pouch cells in say, a 5 Ah format, roughly 50 mm by 140 mm and 9 mm thick, I would leap at them in a heartbeat. Wonder what it would take to get them to re-tool?

[Jason27]

Ya but look what it did to that bike.. yikes!

[boppinbob]

If A123 had at least 5c discharge rate it would be viable for a lot more lipo users. It's kinda of like the firecracker world. Black cats seem lame after setting off M80's.

[amigafan2003]

Ya but look what it did to that bike.. yikes!

Best not drive a petrol powered car either

Remember, risk management isn't about avoiding or eliminating risk but rather about ensuring the level of risk is understood and is proportional to the expected benefits.


For me personally all my EV bike stuff is stored in the garage that's detached from the house. It, along with the Westfield sportscar, high end mountain bike and ALOT of tools that also live in the garage are all adequately insured. A serious lipo fire would merely be an inconvenience so I wont lie awake at night worrying if it's going to go pop.

[boppinbob]

I will be staying with lipo, I've got enough safety checks in place to make it a manageable risk for a short range ebike, however if I go ahead with my plans for an electric motorcycle I will have to go with some type of large format cell. That's just to much juice in too small of a place. Too bad. Lipo has so many pros but that one con is too big for me to ignore at least when I need at least 30Ah and a minimum 100v system. That means I would need about 20 zippy battery packs.

[liveforphysics]

It, along with the Westfield sportscar,

Pics!!! 7's are my favorite car on earth.

[miro13car]

Those threads about LiPolymer fires start to pop too often for my taste.
Definitely it is not for absent minded person.
Seems it is only question of time.

[auraslip]

I've left my ping pack connected to my old bikes dc-dc and controller for 3 months.

But I also left the whole bike connected to meanwells tuned to 3.45v per cell. Mostly because they're the fanless units and I forgot they're were powered on. When I realized it a few weeks in I figured it be better to just leave the system as is so the bike will always be ready to ride.

This reminds me of the recent tesla bricking debacle. You simply can't leave EVs sitting for months with out physically disconnecting the pack.

[John in CR]

If A123 had at least 5c discharge rate it would be viable for a lot more lipo users. It's kinda of like the firecracker world. Black cats seem lame after setting off M80's.

Bob, A123's have a 30C continuous rating, and since a couple of pounds of weight makes a difference only to those who don't know any better or those who go airborne, size is where RC lipo enjoys it's only real advantage.

[auraslip]

that and it's easier to build a pack from RC lipo and there is no "hobby king of a123"

lets be honest - if we could get a123 4s5ah packs for $25, most of us would be using them.

[neptronix]

^--- no kidding

I'd pay more for something safer.

Dow Kokams are over twice the cost per kWhr.
lifepo4 is just to big.
Konions are hard to come by and, don't have the convenience factor.

I want a pack with over a hundred mile range. I don't need powerful, but i do need cheap, light, and small.
Also not interested in soldering tabs or doing cell welds.

Better options will come in time, but for now...

[karma]

i am so glad i sold the cells i had. lipo always made me Nervous,

[dnmun]

again a lot of misinformation about how lipo fires start. it is not because they were overdischarged as in this case or because they are punctured.

thermal runaway in lithium polymer is initiated when the cell is pushed beyond the 4.2V level where it is already 100% charged. at some point while exposed to this high voltage, the crust that forms on the anode as the lithium is deposited, breaks off in sections which then exposes the underlying anode to the charge and this causes an exothermic reaction to begin which then causes more of the crust on the anode to break off and lead to more heat released as it is charging, and the continuation is thermal runaway. this leads to the fire as the pouch burns because the organic polymer will burn in the presence of air.

in this pack, which had been allowed to discharge to the point where some of the cells would not take charge (which allowed some to imagine that the fire was caused by overdischarge) so that when the full voltage of the bulk charger was applied across all the cells, some of the cells had low voltages and therefore some were pushed past the 4.2V limit until it ignited.

there is no reason to fear using lipo, but it should be treated with common sense. methods sells a simple and effective solution and the new zephyr BMS that gary and richard have designed also will protect the battery from allowing any one cell to be overcharged past the 4.2V level.

with this level of surveillance there is no reason to fear that lipo will inevitably lead to fires. literally billions of cellphones and other devices have lipo batteries and the incidence of failure is very low, because they all use a BMS built into the charging electronics in the cellphone.

so with a proper BMS, there is no real reason to be unnecessarily afraid of using them. i don't think the packs have to be removed from the bike and stored in the oven like some think since the risk is during charging so just monitoring the charging along with use of a BMS should essentially eliminate the risk of thermal runaway.

that being said, users should be prepared to deal with a fire if they do bulk charging without a BMS, including having a shovel or some way to pick up the pack and move it to a safe location while it is on fire, and never leave the charger unattended, especially inside a building that can itself catch on fire. if you charge the pack on the bike, keep it in a location that allows you to move it outside to a safe location. don't wait for the fire department or someone else, put the fire out yourself.

the risk is not during storage, only during the charging process.

even when john's pack shorted out internally while stored on his shelf and melted the pouch, it did not go into thermal runaway and cause a fire.

[amigafan2003]

It, along with the Westfield sportscar,

Pics!!! 7's are my favorite car on earth.

I can do better than that

http://web.bethere.co.uk/amigafan2003/index.html

Note - it has black Team Dynamics Pro Race 1.2 wheels on it now.

[boppinbob]

Ammo cans came in today. The lipo's will be in there if I'm gone a week or so.

[liveforphysics]

again a lot of misinformation about how lipo fires start. it is not because they were overdischarged as in this case or because they are punctured.

thermal runaway in lithium polymer is initiated when the cell is pushed beyond the 4.2V level where it is already 100% charged. at some point while exposed to this high voltage, the crust that forms on the anode as the lithium is deposited, breaks off in sections which then exposes the underlying anode to the charge and this causes an exothermic reaction to begin which then causes more of the crust on the anode to break off and lead to more heat released as it is charging, and the continuation is thermal runaway. this leads to the fire as the pouch burns because the organic polymer will burn in the presence of air.

It's actually not anything remotely like that. Where do people get this stuff?

You de-Lithiate the cathode during over-charge to the point that it liberates oxygen that reacts with the solvent. If the cell was old and the anode side wasn't built with much capacity overhead, then it sometimes can intercalte all the lithium ions and forms plating, and lithium has strong tendencies to form dendrites, which damage the structure of things, but aren't what drives the fire. The polymer seperator just becomes additional fuel, but isn't driving any reaction, and certainly doesn't burn in the presence of air, lol, I have a dozen various polymer seperators out on my desk right now, which would be a much more exciting desk if they burned in the presence of air. They are exactly as hazardous as a chunk of a plastic bag, meaning, if you light them, they burn, if you blast them with O2 while on-fire, they burn impressively (along with wood or anything else on fire you blast with O2.)

You can learn about what happens here, which is remarkably a decently correct paper.

http://www.intechopen.com/source/pdfs/1 ... teries.pdf

there is no reason to fear using lipo, but it should be treated with common sense. methods sells a simple and effective solution and the new zephyr BMS that gary and richard have designed also will protect the battery from allowing any one cell to be overcharged past the 4.2V level.

with this level of surveillance there is no reason to fear that lipo will inevitably lead to fires. literally billions of cellphones and other devices have lipo batteries and the incidence of failure is very low, because they all use a BMS built into the charging electronics in the cellphone.

so with a proper BMS, there is no real reason to be unnecessarily afraid of using them. i don't think the packs have to be removed from the bike and stored in the oven like some think since the risk is during charging so just monitoring the charging along with use of a BMS should essentially eliminate the risk of thermal runaway.

With healthy cells, I agree with all of this. However, it seems not all cells are healthy, some have some included impurity or tear or flaw that causes them to literally randomly have a thermal event. I've not seen it myself, but I trust JohnInCR absolutely, and he had one burn just chilling on his desk. The same desk I have sat and worked at years ago in fact.

the risk is not during storage, only during the charging process.

even when john's pack shorted out internally while stored on his shelf and melted the pouch, it did not go into thermal runaway and cause a fire.

We don't know his pack shorted internally. We only know that it was sitting and then released a ton of heat. I agree that it's awesome that it was sitting with other packs and didn't catch any of them on fire or spread. The pack itself actually just looked like an extreme thermal venting rather than a flaming event, which is great, but doesn't mean it couldn't have just as easily been a flaming event, which jumps the temps up drastically.







The problem is not that it's LiPo. The safest cells in the world right now happen to be LiPo (not RC LiPo obviously, but grid storage cells). The problem is that we've seen a few events of defects showing up in RC cells (which have terrible QC) that resulted in random catastrophic failure modes. That's the part that sucks.

For making large packs that get stored in homes etc, we really need to be using Tier1 grade automotive LiPo. It's not as high of C-rate, it's saggy, it sucks to build packs with it, it generally always ends up being heavier and bulkier than you wanted, it has limited form-factors for packaging. And yes, all those things suck about it, but your cycle life is in the 3000's to 10,000's of cycles, they are matched so well your meter won't even read precise enough to try to improve the balance on them, they handle being over-charged to 8v and do nothing, the handle being over-discharged and reverse charged and crushed and over-heated and just sit and do nothing. Unfortunately, none of the Tier1s will even talk business if your purchase volumes aren't in the $10,000,000 range, and your design needs to be thoroughly approved by there teams.

[emergence]

@dnmun. What about tef's fireball bike that he posted recently?

http://endless-sphere.com/forums/viewtopic.php?f=14&t=36895&p=535962#p535962

It this the only case of spontaneous ignition? I thought there had been a couple of others.

Seems like it's possible that this is new pack syndrome where a couple of full charge/discharge cycles would have revealed a dodgy cell but still....

[auraslip]

Thanks for posting that link LFP.

I never thought they went through so much trouble to build fire protection into the cells. I assumed they picked a chemistry that was inherently safe and spent lots of money on QC.

Is it that RC lipo prefers performance over safety and simply doesn't opt for these safety features that make other cells fail more gracefully?

[flathill]

with this level of surveillance there is no reason to fear that lipo will inevitably lead to fires. literally billions of cellphones and other devices have lipo batteries and the incidence of failure is very low, because they all use a BMS built into the charging electronics in the cellphone.

How many amps are those cellphones and other small electronic devices drawing? How fast do they charge? How come we aren't scavenging prismatic lico pack from power tools?

[boppinbob]

One positive about lipo. If some one steals your bike and has no idea how to treat lipo and also stores his ill gotten gain in his house, it might burn it down along with his family who probably shares his criminal gene there by improving earths human gene pool.

[liveforphysics]

One positive about lipo. If some one steals your bike and has no idea how to treat lipo and also stores his ill gotten gain in his house, it might burn it down along with his family who probably shares his criminal gene there by improving earths human gene pool.

Yes. I have a similar intrinsic security system on my deathbike. I just lean it up against a wall when I arrive somewhere, no lock, no key, no protection.

I know if someone gets on it to steal it, and the flip the switches to "On" and "Pain" (which means enable), I will find the bike just a short distance from where I left it, with some red-smears and drips leading up to it's stopping point. Not too much different than when I let someone test-ride it, but I don't have to feel bad this way, because they didn't ask first.

[boppinbob]

and the flip the switches to "On" and "Pain" (which means enable),

Actually I've been meaning to put a switch up front that is a toggle switch under a red cover switch that warplane sometimes use as a missile arming switch. The one pictured is blue but you get the idea.

[liveforphysics]

and the flip the switches to "On" and "Pain" (which means enable),

Actually I've been meaning to put a switch up front that is a toggle switch under a red cover switch that warplane sometimes use as a missile arming switch. The one pictured is blue but you get the idea.

I run the same switch with a red cover for my 2nd and 3rd stage nitrous enables on my racecar.

[karma]

which ones the Ejection Seat

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