I know we have beat the e-bike thing to death here, but this is a great interview with the Toronto fire chief about that ebike fire on NYE last year
For those who don't take the time to view.
The interview first off shows video of the explosion from within the subway car and you get a very clear sense of the suddenness and substantial toxic smoke, which appears with great speed.
Then the discussion veers to Toronto Fire's investigation.
While they were unable to discern a definitive cause of the device failure........they noted.
1) The manufacturer advised that this device was not to be used in winter (it was)
2) The manufacturer advised this device was not to be used for commercial purposes (it was) (food delivery)
3) The Battery was not certified.
4) The Battery contained a courtesy charger (that you could use through USB to charge your phone). This was deemed to be a high risk point of entry to the battery for water and/or road salt, and very high risk.
***
TFS Deputy chief comes away w/the strong view that all batteries should be subject to mandatory certification for sale in North America (or at least Canada) and clearly is not enthused by courtesy USB charging ports as a design feature.
The fact that bike/battery was used contrary to manufacturer instructions, one of which was 'No winter use' is why the TTC ban for now is winter, as this was deemed a higher-risk period.