Thanks for that Larry. J
One factor not mentioned earlier deserves mentioning as regards to lithium-ion (or LiFePo and any battery chemistry cells for that matter) cells---and that is, 'form factor'. Two primary forms of battery cells are typically considered: Cylindrical and Prismatic.
Most (all?) of the hydrogen/flame test results that are pointed at as regards dramatic lithium-ion battery failure modes are with cylindrical battery cells. Tesla's battery cells are an example of this and are exactly the type that flew thru the windows of 2 homes this month in Oregon and started fires. The structure of these cells goes back to some of the earliest batteries made---a central electrode spiral wrapped with layered elements until the outer electrode is reached. Cylindrical capacitors are similarly structured. This structure is completely different than a prismatic cell where the electrodes are on opposite sides of a stack of materials with surface area left in a plane instead of wrapped. The entire heat, power and other transfer equations are completely different. And so, let's say you puncture a cylindrical cell with a nail. What you are actually doing is shorting thru multiple parallel layers of material in the cell. Heat tries to escape and has to travel thru all those layers to do so. You can imagine how the heat buildup at the core goes thru the roof! Do the same now to a prismatic cell and what happens? You have created a single, localized short, yes, but you have not created multiple ones, nor have you created a hot spot that has a difficult time getting heat out. CALB batteries and similar LiFePo batteries are prismatic and benefit from this. Same is true of Enerdel and the many other "pouch" style planar prismatic Li-ion cells out there. Further, in the case of many (most?) of these prismatic Li-ion cells, the electrodes are at opposite ends of the cell entirely, minimizing risk of shorting.
Another factor that is brushed over is anode type. Many (most?) lithium-ion batteries used graphite as the anode for optimum power reasons as I understand. Enerdel chose to use solid carbon for their anodes, ostensibly for safety reasons.
Bottom line: We don't do ourselves a good service by using broad generalizations about an entire battery family when material choices, structure, form factor and other factors add up to defeat those generalizations. In the early days of LiFePo batteries, there was but one manufacturer that EV enthusiasts got them from --- Thundersky. Likely very few of those batteries are in use today and many of them died very early. And if I recall correctly, the earliest of these batteries also did not do well with the nail puncture test. We have come a long way since then and quality, reputable prismatic LiFePo cells are quite safe. It is my argument that quality, prismatic and reputable Li-ion battery cells are also, while not likely "equally" safe, they are reasonably so.
Don't get me wrong: I am not speaking out for others to ditch LiFePo in favor of Li-Ion. I don't have any horse in the race and don't care if anyone else uses them on boats. I only know that a specific cell stack has worked well for me and a local friend of mine for propelling our boats. I have no regrets with my decisions that have led me to this point. And if these surplus batteries were 20x cheaper, I'd take one of them and slowly submerge it in a barrel of water just to see what happens. Frankly, I'd like to know whether anything at all would happen---I'm doubting that anything would happen with fresh water. Sure, I can see that with the conductivity of salt water, cells would discharge. But would they discharge at greater than a 10C rate to cause overpressure and gas to escape? I'd probably bet against that.
-MT
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