Fire departments have had to buy special equipment to put them out. One of them is pretty much an underbody nozzle similar to those pressure washer attachments

Fire departments have had to buy special equipment to put them out. One of them is pretty much an underbody nozzle similar to those pressure washer attachments used to clean under your car. Since car batteries contain both the oxidizer and reducer, they are self sustaining. This makes smothering the fire impossible. The only way to slow or stop them is to prevent thermal runaway in uncompromised cells with a ton of water.