thermal runaway

This is not a new term but one that has entered mainstream communications because of the large number of battery fires we are getting from e-scooters and e-bikes that have lithium batteries.  The process is that one cell is damaged or overloaded and produces excessive heat, causing the cell to melt and produce explosive gasses.  The temperature rise in that cell causes the next one to overheat, and then the next, and so on along the set of cells in the battery.  The heat rise happens in a fraction of a second and the explosion can be fierce. It is not just lithium batteries that are subject to this.  It can happen in any battery but the lithium ones that we are using can be unregulated and cheap, and suffer easily from damage or from being charged with a charger that doesn’t match the battery. Once the chain reaction has started the only thing to do is to get out fast because it is unstoppable.