Look, I‘m no scientist. I just see the effects in real life. Obviously the amount of material affects the energy effectively released. One job of our fire department is to spread awareness and in those messages, you are better on the safe side and be extra cautious. If you are a scientist or know exactly what you are doing, feel free to handle it the way you want to. Based on the message of OP I knew they were inexperienced. That‘s why I would never recommend solutions which are not super clear and super safe. Water and battery can work - but it can also clearly fail if done wrong.

Oh, it will help, but only for a very short amount of time. Those metals will get pretty hot, the expanding steam will make the water splash out of the bucket and the rest of it will evaporate quickly. The fire will only stop, if the battery reaches a temperature of about 70°C (158°F). For that you need a lot of cooling material.

Yesterday in the news was a fire of a Tesla car battery, needing 36.000 gallons of water to extinguish it. They had to use two hose (the big ones) for over one hour to have it under control.

So if you put a small battery in a pool, then you are safe, I absolutely agree. I only criticize the wrong assumption that a bucket of salt water is the „only safe way“ to handle a battery.

I actually had to check some resources myself, as I was unsure if it was really useful in that case. Those blankets usually help stopping a fire by limiting the amount of oxygen that gets to it - without oxygen, no fire. Unfortunately, many batteries have oxygen in them, not much, but enough to keep it going. So the fire won’t stop in that case. But what the fire blanket does, is give a layer of insulation, thus reducing sparks flying around and reducing the temperature directly above it.

Fire blankets are always a very useful tool, as they are easy to use and at least protect the person holding it (in small fires, obviously). If it doesn’t help, it does not make it any worse.

What you are describing is just dangerous, for the simple fact that people then think they are safe, as soon as they put the battery into salt water. You even say yourself that it takes days until fully drained. During those days, the battery could still ignite. When that happens, the salt water will not help at all. What then will happen is, that the water will immediately turn into steam. You know what happens if you put water into hot oil - similar effect, just less dangerous. The water will be gone in no time and everything around it starts to burn.

That‘s why we always recommend what I was suggesting in my initial comment. And please don‘t say things like „it is the only fully safe way“. This is just straight up wrong.

The battery will most likely not explode, but just ignite. The melting of the chemicals and metals just gets really really hot, so anything else around it will start to burn eventually. So don’t treat it like a bomb, more like a very hot iron. If you can, find a temporary spot for the battery. Maybe in a garage or basement. If also possible, use a metal container. Dirt/sand is also a good option.

Every bloated battery can start igniting any second. So please remove it and store it somewhere outside, ideally on concrete. Li-Ion fires cannot be stopped, not even with water.

Source: I‘m a firefighter.