I worked with a technology company in southeast Michigan about 10 years ago, constructing lithium-ion test cells for the major automotive companies.  The company provided and sold battery technology to numerous automotive companies.  One thing I learned is the you can not extinguish a lithium-ion battery fire. But technology might have changed over the last ten years or so. I had the local fire chief into the plant to educate them on this fact.  You can only let it burn itself out.  With the battery test cells, we controlled the fire and exited the heat, smoke and flame through the roof with fire/heat proof fans and fire rated construction.  I was quoted, at this point in time, that one cell out of about 16,000 would or could be prone to failure and fire.  Depending on the number used in vehicles, models varied, but could fail. Most engineers

I got to know were much more positive about fuel cell technology and considered batteries just temporary until fuel cells were better developed.  I could not find another place to post this information but just wanted to provide accurate information.