Testing LFP Battery Failure Modes With Overcharging | Hackaday
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As great as batteries are, it’s essential to understand their risks and how to keep them from going spicy. Recently there has been a bit of a fuss about the dangers of LiFePO4 (LFP) batteries after someone’s dedicated LFP battery shed got shredded into matchsticks by a hydrogen explosion, following said LFP batteries having a thermal event. The thing about the LFP chemistry is that if it suffers such a thermal event, it generates hydrogen gas, which is one of the most explosion-happy gases known to man. This is demonstrated in a recent video by [Will Prowse].
To kick things off, a single prismatic LFP cell is overcharged for half an hour after it was already at 100% state of charge. This ultimately pops the vent as the cell begins to release hydrogen gas into the aquarium that the cell was placed in. Using a spark generator it’s then attempted to ignite the gas, which initially takes a bit as enough hydrogen has to collect first.
Once there’s ignition, however, it happily keeps burning as more and more hydrogen pours out of the by now bulging cell’s vent. If any other LFP cells had been nearby these too would be at risk of suffering thermal runaway, showing how just one bad LFP cell is enough to potentially set an LFP battery bank ablaze.
In a commercial setting you will have precautions such as hydrogen sensors, ventilation and spark generators to deal with any generated hydrogen gas, as well as blow-out panels in case things end up going squirrely in a hurry.
While a benefit of LFP chemistry is that it does not generate its own oxygen as with other lithium-ion chemistries, hydrogen gas is a major problem due to how incredibly volatile it is. It’s not just a headache with battery storage, but also in the nuclear power sector, where zirconium fuel rod cladding can very efficiently turn steam into hydrogen and oxygen. This was the reason why some of Fukushima Daiichi’s buildings suffered detonations, with the nuclear plant operator opting to not install recommended hydrogen gas mitigation systems.
21 thoughts on “Testing LFP Battery Failure Modes With Overcharging”
Sorry, but this does NOT look like a hydrogen explosion. Hydrogen would not burn yellow, and much more violent.
Instead i think, this is electrolyte vapor combusting.
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Oxygen plus two parts hydrogen well mixed is truly scary in the speed and power of the explosion (can easily kill if ignited inside a sealed container). But 78% Nitrogen, ~1% Argon, ~21% Oxygen and a tiny trickle of hydrogen not well mixed burns. As a very small kid I use to play with hydrogen a lot, and you learn a thing or two (as long as you do not screw up).
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Why is the flame yellow and not blue?
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Insufficient oxygen for complete combustion so a sooty yellow flame
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So it reacts with what? Nitrogen? CO2?
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Hydrocarbons have incomplete combustion. Hydrogen either oxidizes to make H₂O or doesn’t.
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Hydrogen does not work that way. No carbon no soot.
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…and where do the Hydrogen come from in the first place?
As far as I know there is no Hydrogen involved in the LiFePO4 reaction from either of the two electrodes, or the electrolyte…
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The hydrogen is produced as the solvent in the battery is breaking down due to the heat. The solvents used to suspend the lithium are all hydrocarbons containing anywhere between 4 and 10 hydrogen atoms in each molecule.
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Electrolysis of the water in the aqueous electrolyte
Same reason lead acid batteries start producing hydrogen on overcharge
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There’s no water in LFP.
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https://pmc.ncbi.nlm.nih.gov/articles/PMC7078597/
Ideally yes. They all leak, eventually, and the cathode is hygroscopic up to a couple hundred ppm and that much water will break down the cathode and eventually you end up with a fire.
Probably a good battery tech for arid dry areas, probably not the best tech in a rain forest.
Kind of like how ideally steel does not have water but in real life all steel eventually corrodes when it sucks water right out of the air.
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Lead acid are far worse they produce hydrogen and oxygen.
I know someone who was knocked out when part of the plastic case shot at their head. The well mixed oxygen hydrogen when ignited instantly forms steam, so imagine what kind of pressure on any container is generated with a stoichiometric detonation velocity 2,800 to 3,000 meters per second.
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Because it isn’t just hydrogen in the tank. By the appearance, it is mostly other stuff. That is to say, the hydrocarbons from the solvents in the battery. There might be some hydrogen, but from the look of it there’s a lot more of the other stuff.
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So, abused with max...