18650 fire cases & 18650 vs 21700 comparison

[batteryGOLD]

check this pic comparing Japan Sony VTC6 3000mAh 30A vs 21700 cell 4800mAh
is better to build a battery based using 18650 or 21700 cells? vs price Ah per area
offtopic: Elon musk patented cell?
Li-Ion danger (similar to pyrotechnics, but instead gunpowder, it contains xtreme flammable electrolyte )

..anyway here is a pic

 

[batteryGOLD]

some google source:

"Can 18650 catch fire?
Is lithium battery electrolyte flammable?
Unfortunately, they are highly volatile and flammable and show flash points (FPs) around room temperature (between 16 and 33°C). In combination with an oxidant and an ignition source they can cause fires and explosions."

solid state battery soon?

I have nothing more to say..

 

[Hillhater]

I have nothing more to say..

Good !…….you have said nothing new that was not already well known .

 

[vicriz]

I believe 21700 better than 18650 in term of energy density

 

[Hillhater]

I believe 21700 better than 18650 in term of energy density

You may believe that, but you would be incorrect.
Check the data sheets.

 

[leffex]

some google source:

"Can 18650 catch fire?
Is lithium battery electrolyte flammable?
Unfortunately, they are highly volatile and flammable and show flash points (FPs) around room temperature (between 16 and 33°C). In combination with an oxidant and an ignition source they can cause fires and explosions."

solid state battery soon?

I have nothing more to say..

Do you have had an experience with a fire?

Lipo cells being charged is very dangerous but 18650 cells using products that are following regulations and not has history of being tampered with or opened by a customer will have more safety build in to minimize a fire being started. However as the 18650 cells contain different liquids some, most I guess are less volatile and flammable than those who are.

 

[leffex]

I would use 21700 as often as I can as it cuts down the cost of time consumed to make and build a battery. If you have your cost on a sheet you can decide when 18650 wins as per definition over the 21700 cells.

 

[batteryGOLD]

Do you have had an experience with a fire?

Yes Sir, three cases. Soon I post some pics.

case #1 - onewheel XR fall into water , than removed from river. everything ok but with some water inside..
after 15minutes, the owner was ready to put into the trunk of a brad new sport Porsche cayenne.. than suddenly the onewheel went on crazy firee! porsche saved because onewheel not inside car, but at ground on flames.. a lucky case..
Imagine putting onewheel inside porche trunk at minute 10.. the owner closes car trunk and goes to a great sport drive. than a crazy fire starts at back of tha car.. what a movie... do insures cover lithium fires inside cars?
fortunately everyone safe and sport porsche ok 50miles on it, smells like new!
lithium fire is similar to oxygen feeded fire, very high temperatures. cause melted part of onewheel structure.. ++660Celsius??

case#2 one trotinete/patinete tube battery containing 30cells @ 30% charge level inside aluminium tube.
trying to open battery with a hammer and a screwdriver and happened one cell strike.. the tube went on crazy rocket fire mode, a lot of fire output 60cm long and a lot toxic smoke, I had to jump above fire flame to exit lab What a movie!!
after 10min tube seems ok.. ready to go outise for safety. but tube was gettin more and more hot. just one cell fire. 29cells left for the show..
tube drooped outside building, than after some time it started a rocket type flame, a lot of loud sound pfffff melody type, and similar to elon musk rockets.. just a lot of somke & fire 1,5 meter long but no thrust power.. just a flame thrower
it was just a 30% SOC battery.. imagine more scenario when charged at 100%

case#3 a person with x2 citycoco20Ah 67V batteries inside house. but one had a bms faulty no top cutting voltage and battery debalenced.. the person left it chargin with a 2A charger, and after some hours, guess?
one battery starts a crazy fire inside house!!
one battery crazy fire and shouts incandescent stuff and hit the other battery. but second battery only plastic case with melted spots. the fire starter battery all burned!! 2nd battery saved.
everything ok and a house black wall.. but everyone safe and wall painted again!

never trust unknow bms protection! another scary movie!

I have nothing more to say.
Thanks for your time reading this.

PS: Sorry my PT english

 

[eMark]

I believe 21700 better than 18650 in term of energy densty.

You may believe that, but you would be incorrect.
Check the data sheets.

Isn't a 21700 (5000mAh) a bigger fire cracker than a 18650 (3000mAh) ... explosion wise (energy density) ??
Assuming both were mistakenly overcharged causing an explosion ... energy density = mAh, say with similar MCD amp rating

 

[batteryGOLD]

Isn't a 21700 (5000mAh) a bigger fire cracker than a 18650 (3000mAh) ... explosion wise (energy density) ??

more or less

more energy Wh packed means more fuel for tha fireworks.
but the intensity of fire works depends at how much current cell is able to supply.

high current cells means more fireworks show

see LiPo packs example. put a nail on it.. those go insane flame thrower.
high current means more fire intensity but less time show
1000mAh 100C Lipo will produce more fire than a 18650 3000mAh 30A 18650cell (100A vs 30A)

 

[leffex]

Important to keep your home and workplace safe. No charging or storing of unknown customer batteries...

For me I like to have more than one safety parameter. One is the cell you use so a 18650 is OK for that matter in comparison to lithium Manganese Oxide I think is the most dangerous 18650 type. Also Samsung ICR 26F I guess is next on the dangerous level because of personal experience although not more than squirting liquid and heat.

The other safety parameter is controlled charging in a way. Walk in when you know the charge is done. Set it up so that your battery has a BMS that cuts' charging at a certain voltage level.

"Search results

• LiCoO2 (Lithium Cobalt Oxide – LCO)
• LiMn2O4 (Lithium Manganese Oxide – LMO)
• LiNiMnCoO2 (Lithium Nickel Manganese Cobalt Oxide – NMC)
• LiNiCoAlO 2 (Lithium Nickel Cobalt Aluminum Oxide – NCA)
• Li 2TiO 3 (Lithium Titanate – LTO)
• LiFePO4 (Lithium Iron Phosphate – LFP)"

I'd like a third safety measurment and its kinda to see your device when your walking around in the home or at work working. I got two at the moment but of course more is always welcome.

A third can be that the charger, of course does charge to the correct voltage level (as you can use a 36v charger to charge a 24v battery but that ain't the normal thing to do.

So then I kind of have three levels of safety build in to my charging already.

 

[batteryGOLD]

Hi there lithium people.
I have something kind of interesting..
trotinete/patinete battery after fire -- see open aluminium spots, Al_13 melts at 660degrees , soo maybe a 1000degrees celscius fire output from 18650
&
onehell after tha crazy fire.
soon I take picture of onehell damaged structure




Goggle soource "What is lithium in a periodic table?
Lithium is a chemical element with symbol Li and atomic number 3.

 

[batteryGOLD]

question to Google. "What is Li ion battery electrolyte made of?"

The most commonly used electrolyte is comprised of lithium salt, such as LiPF6 in an organic solution.

another question to google "is lithium salt flammable?"
Hazard Class: 4.3 (Water Reactive/ Dangerous when wet) Lithium is a COMBUSTIBLE SOLID which is WATER REACTIVE and the powder or dust may SPONTANEOUSLY IGNITE in AIR.

soo, maybe if you throw water into a 18650 in fire, maybe it goes more fire similar to throw water into hot oil?

Have a nice lithium weekend!

 

[lnanek]

I don't use wet extinguishers with lithium battery fires. That said, I've seen it argued, that the cooling effect of water can be useful despite the harm it otherwise causes. Like if you have a single cell or p-group undergoing thermal runaway, dunking and covering the pack in sand in a metal trash can is what I do. However, dunking in water is still going to keep the temperature down at the boiling point of water, 100 degrees, which is lower than the worst reactions, and will prevent the whole pack from undergoing thermal runaway.

I have tossed individual cells and old packs in water buckets outside to see what happens - I take apart used batteries pretty often, so I often have ones that are accidentally dented from prying the welds off and starting to heat up. The cell had to sit in water a day before it vented and shorted and turned the water black. The pack similarly didn't short immediately and I was able to transfer it to an old ammo can full of dirt. Theoretically that could be better in certain situations than letting it all burn up, one cell reaching thermal runaway, the heat from that triggering another cell, then eventually the whole battery.

Why isn't it just lithium + water = boom? Because we're not dealing with pure elemental lithium here. We're dealing with a lithium salt in a solvent. The lithium salt starts decomposing over 150 degrees:


Then for the solvent in my Samsung cells:


You can see both with and without the presence of water (which admittedly does make it happen earlier), the solvent starts to decompose over 100 degrees as well:


So if water is all you have, there could be some value in using it to help the temperature down, even if the presence of water makes the harmful chemical reactions somewhat worse.

 

[Hillhater]

Its a pretty well accepted …and proven…fact that a lithium pack fire (or thermal runaway) is best contained by dunking in a water bath. The more water, the better. Some fire dept’s have large water skips to dunk burning EVs into when possible.
For domestic use , old cells are best “de-energised” before disposal by dunking in a bucket of salt warer For a day or two.

 

[Hillhater]

Isn't a 21700 (5000mAh) a bigger fire cracker than a 18650 (3000mAh) ... explosion wise (energy density) ??……

mAh’s are not a measure of energy density (Wh/kg or Wh/ltr),..which is similar or even less for 21700 compared to 18650s
…but yes,, a 21700 is simply a bigger fire cracker in the same way a gallon of gas is a bigger fire than a litre of the same gas !

 

[batteryGOLD]

some chemistry study & lessons

Sir, it "doesn't matter" the chemistry study (but very interesting)
The matter is the proven (observed/seen) cases of real fires at lithium cells

once one cell ignite, soon pass heat & fire to surround cells, sure start kind of a hell scenario!!
fire output melts aluminium, soo fire is more that 660 degress celsius

PS: beach sand is lithium fire fighter! it will soak battery fire and maybe after that U get melted sand lava and after that sand turns into glass!

 

[lnanek]

You don't even need a chemistry lesson to know boiling water won't exceed 100 degrees. Just go stick a pot on the oven and stick a thermometer in.

 

[batteryGOLD]

U are correct.
world population on Jan. 1, 2023, is 7,942,645,086
soo, I presume all people in tha world knows water temp limit/boiling point is at 100 degrees celsius (i dont know fahrenheit)

anyway, I've seen fires of trotinetes/patinetes under water, the fire keeps goin under water!
if U throw a fire battery into water, fire will not extinguish, it keeps on fire under water

 

[batteryGOLD]

That value is out of date!
see we now have 8 billions

World Population Clock: 8 Billion People (LIVE, 2023) - Worldometer

 

[Diggs]

Back on the original topic, I think you still pay a premium for 21700 cells vs. the same ah in 18650. It used to be quite a difference but has been coming down. It's still more economical (last time I checked) to build with 18650 cells over 21700 for the same ah.

 

[batteryGOLD]

Back on the original topic, I think you still pay a premium for 21700 cells vs. the same ah in 18650. It used to be quite a difference but has been coming down. It's still more economical (last time I checked) to build with 18650 cells over 21700 for the same ah.

take this example:
21700 Samsung 40T 35A 4000mAh (€3.64 per unit without VAT pack 100)
vs
18650 Samsung 35E 3500mAh 7A (15A peak) (€3.26 unit without VAT pack 100)

#21700 Samsung 40T
3,6Vx4Ah=14,4Wh cost 3.64eur equals 3,96Wh per euro

#18650 Samsung 35E
3,6Vx3,5Ah=12,6Wh cost 3,26eur equals 3,87Wh per euro

soo we see18650 cost less than 21700 for this specific comparative (almost same price per Wh)
but peak current is 15A for 35E vs 35A continuous(70A peak) for the Samsung 40T. Soo maybe 40T is a better option becaus for almost tha same price Wh per eur U get much more current peak output
21700 also needs more area/volume for the same Wh compared to 18650

 

[batteryGOLD]

here we have some scientific study table.
some science in a table, but needs to add column price euro/dollar per Wh, per liter volume & per kilo
90% of cases what matters is tha final consumer price!

and also need table metric convertion to USA gallons, pounds etc..



conclusion: maybe 21700 is a winner or tryin to!
see energy density Wh per liter volume (dont know gallons)
18650 is 670Wh per liter vs 684.2Wh per liter usin 21700 (Volume of 1 liter = 10 cm by 10 cm by 10 cm cube) (aprox. 4inch by 4inch by 4inch)

question to google:
What volume is 1 gallon? 231 cubic inches
(gal, U.S.) There are 231 cubic inches = 128 ounces = 8 pints = 4 quarts in a gallon. 1 gallon = 3.785 liters.07/02/2022
cubic square of 231 equals 6.1357 inches. One gallon is a 15.58cm by 15.58cm by 15,58cm cube

sooo, for tha same volume. 21700 maybe wins at energy density (but we dont know tha price of that specific cells, so cost could be twice of a 18650 build..

PS: remember 99% of bms's have a low cut voltage at 2,7V or 3V. any cell energy bellow that is uselesss. soo capacity of cells could decrease from adverted value, because useless energy from 2,0V-2,7V window
maybe CO2 or liquid nitrogen to combat lithium fireworks?

google source:
"What puts out a lithium fire?"
google Talkin: "For best results dousing a lithium-ion fire, use a foam extinguisher, CO2, ABC dry chemical, powdered graphite, copper powder, or soda (sodium carbonate) as you would extinguish other combustible fires. Reserve the Class D extinguishers for lithium-metal fires only.21/03/2023"

or use the low cost fire stop method, usin beach sand..

table source:
ShieldSquare Captcha

 

[batteryGOLD]

one more picture 21700 vs 18650 theory
for real scenario need to include price comparative

 

[docw009]

I read a study that showed cells at 30% SOC will still go into thermal overload if heated to the right temperature. WHat is not clear is if a cell at 30% SOC has enough energy to do the same if short circuited. Then there are both CID's to break an external short circuit, and thermal vents to counteract pressure build up.

When I was a kid, I read in a comic book how to fold a paper bowl, place it on a gas burner, and boil water in it. The water never let the paper get above 100C, but you had to keep the open flame from hitting the sides of the bowl. I am sure hundreds of these paper pots caught on fire. Mine did,