Most of the problem of e-bike fires is about the battery being abused.
The abuse is often about batteries being overheated either by massive currents being drawn by over powered controllers (cobbled together illegally high power bikes) or by over charging through using a charger which supplies too much current, or through use of a higher voltage charger.
As is well known to all here - overheating the battery will result in a very bad day for all concerned.
The reason that top brands are not going up in flames is that the people who buy them use the proper charger and the controller treats the battery gently by not drawing down currents that are much too high. The other end of the market lends itself to idiots doing stupid things, but they also do stupid things with butane lighters and anything else the get their hands on - such as knives. Ebay still sell butane lighters - though not the ones for cigarettes... Cigar lighters are OK though. The specific intent of these items is to set things alight.
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A few batteries may develop short circuits over time with metal dendrites puncturing the separator and creating a short circuit inside a cell which might then go into thermal runaway. The resulting smallish fire would overheat other cells and set them off as well. This might effect very cheap cells more than premium ones, but any cell could do this I would think.
The problem with ebike fires is 99% a people problem. Stupid careless people do stupid careless things. Banning stuff is not the solution.
I'm going to bet that in future we will be riding on ebikes powered by Lithium Iron Phosphate batteries. Bigger and heavier for the same output, but they don't go on fire and if you don't over charge them they last about five times as long as the lithium / manganese / cobalt technology we now use. More and more EV cars now have that technology.