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Thermal Runaway on Purpose
#1
So I've abused a lot of cells and have gotten close, but have never actually induced thermal runaway (thankfully). I accidentally shorted a high discharge cell that reached 235*F/112*C, but CID protected that cell. And on laptop cells that I've shorted on purpose, PTC has protected the cell from thermal runaway. Every thermal runaway video I've seen has either been a lithium polymer battery (no protection, Galaxy Note 7), mutilation (axing an 18650 in half), or externally igniting an 18650 with a propane torch or a heat gun (hi Daromer). I haven't tried overcharging a cell yet (think: hoverboards), and that's next on my list, but I'm just wondering if anyone here has accidentally or on purpose successfully initiated thermal runaway on an 18650 and how you did it? Unlike most of you, I'm dealing with generic cells and trying to do it in a safe way, so I'm doing a lot of independent safety testing, and besides shorting cells, I'm trying to figure out other ways to test my datasheetless cells for worst-case scenarios.
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Formerly known as Dallski
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#2
(10-15-2019, 05:49 AM)Generic Wrote: ...but I'm just wondering if anyone here has accidentally or on purpose successfully initiated thermal runaway on an 18650 and how you did it? Unlike most of you, I'm dealing with generic cells and trying to do it in a safe way, so I'm doing a lot of independent safety testing, and besides shorting cells, I'm trying to figure out other ways to test my datasheetless cells for worst-case scenarios.

I’ve done it by using a motorcycle battery directly connected across the cell under “test” with reversed polarity. This forces reverse charging at incredibly high current levels. The key to making it work was the use of very low resistance wiring/connections to ensure that enough current flowed to initiate thermal runaway before the CID or PTC protection kicked in. I used dual 4AWG wiring for both the pos and neg leads and 3/8” brass bolts for the contacts to the cell under “test”. 

I’m sure a good LiPo pack (or other low IR pack) could do it too. A 24V setup, or higher voltage, can be used to increase the current flow.

External heating is a foolproof way though as it allows bypassing all of the cell’s internal protection devices.
100kwh-hunter likes this post
I only have about 400 cells gathered so far but I do have a bit of gear I use for my day job and cell testing: https://imgur.com/a/x1Jzhx5
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#3
(10-15-2019, 05:49 AM)Generic Wrote: Unlike most of you, I'm dealing with generic cells and trying to do it in a safe way, so I'm doing a lot of independent safety testing, and besides shorting cells, I'm trying to figure out other ways to test my datasheetless cells for worst-case scenarios.

Did you decide on any particular methods yet?
I only have about 400 cells gathered so far but I do have a bit of gear I use for my day job and cell testing: https://imgur.com/a/x1Jzhx5
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#4
Do incendiary 18650-powered grenades count ?
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#5
I have not been able to abuse any 18650 till the point it goes boom except for with external abuse like heat. Over or undercharrg never worked since the cid took ovet before.

Lipo on other hand is easy to overcharge and have a nice fire
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#6
We fuse 18650's in packs in case one shorts out - to save the pack. Can individual LifePo4 prismatic cells 'short out' like 18650 cells? can this cause fire?
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#7
Life can Short too but they dont burn like liion. Risk is alot smaller.
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
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#8
The A123 26650 lifepo4 if you short it against the side of the cell where it punches a hole in it will catch on fire extremely well, I learned the hard way. The fire was comparable if not more violent then some of the 18650 cells I seen on videos. This short was accidental while taking the cells apart, the nickle strip shorted against the side shown in the picture. This is worst case scenario that can occur when disassembling packs of high discharge cells. 

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#9
(10-30-2019, 10:13 AM)BatteryMooch Wrote:
(10-15-2019, 05:49 AM)Generic Wrote: Unlike most of you, I'm dealing with generic cells and trying to do it in a safe way, so I'm doing a lot of independent safety testing, and besides shorting cells, I'm trying to figure out other ways to test my datasheetless cells for worst-case scenarios.

Did you decide on any particular methods yet?

Mooch, I decided that for basic testing, I'm going to use a 12V, 1A power supply directly connected to the battery to test for CID. If the cell has CID, it should pop. If it doesn't have CID, it should blow up. 

Believe it or not, your example, while it seems to be an extreme example, is actually the reason why we fuse our cells despite their CID and PTC protections. Here's a NASA article that basically states that CID and PTC doesn't work in multi-cell and high-voltage packs like it does in single cell packs. So your motorcycle battery is not that different than having 299 cells dump current into a cell that has short circuited for whatever reason.
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Formerly known as Dallski
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#10
(11-15-2019, 04:30 AM)Generic Wrote: Mooch, I decided that for basic testing, I'm going to use a 12V, 1A power supply directly connected to the battery to test for CID. If the cell has CID, it should pop. If it doesn't have CID, it should blow up. 

Believe it or not, your example, while it seems to be an extreme example, is actually the reason why we fuse our cells despite their CID and PTC protections. Here's a NASA article that basically states that CID and PTC doesn't work in multi-cell and high-voltage packs like it does in single cell packs. So your motorcycle battery is not that different than having 299 cells dump current into a cell that has short circuited for whatever reason.

I’ve seen that NASA doc, thanks though!
So easy to overlook something like that when designing a pack.  Smile
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I only have about 400 cells gathered so far but I do have a bit of gear I use for my day job and cell testing: https://imgur.com/a/x1Jzhx5
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