Mitigation of risk 1. Ensure every carpark in the country has a sprinkler system
Mitigation of risk 2 Mandate manufacturers to install failsafe devices in batteries/cars
I would surmise that 2 works in most cases as it should. The Leaf for example is a very conservatively engineered product and has an excellent record so far at Chez Falcon. Battery pack temp never gone above 4 bars mostly at 2 or 3. Whether it is a matter of fact or just interpreting incidents to suit the story you want to tell, it appears that up to now, the record of fires in EV's is considerably better than in other vehicles. Some may take the opposite view, bring in the relative severity of fires and and shout it very loudly on youtube.
Failsafe devices and systems probably need "beefing up" to the point where even if there is a manufacturing defect which in a very small set of circumstances can result in overheating and subsequent fires, there is "ABS-like" immediate response to both shut down the battery and activate an emergency fire prevention system...I'm not an engineer but a "flood it with some kind of "goo"" sort of approach.
As of now clearly there have been some manufacturing defects in some batteries which have resulted in fires. I have no greater insight than my own personal experience, but the Leaf has a what is now regarded as small capacity battery pack (24kWh), has a top and bottom buffer on the usable capacity so difficult to overcharge it, and originally came with a long-life mode to charge it up to a recommended max of 80% state of charge. It has a low power gentle at-home charging routine, and little on-road rapid charging which is at 50kW DC.
Some of the largely unnecessary quest in my view for more powerful on road chargers. and larger and larger capacity batteries can only add to the risk factors. Watch out for the news over coming years of the row of chargers behind the petrol-half of the station taking out half of Gateshead.
Not an in-parking bay sprinkler in sight...not that they would do any good!
Neil