What makes a battery so very different from a tank full of gasoline?

 Both store energy right? That is perhaps as far as the casual observer ever gets in thinking about it.

There is of course a tremendous difference.  Once the gasoline is consumed - that's the end of the energy storage system for combustion engine powered automobiles.  What remains is an empty metal or plastic tank (HDPE in the US).  Both materials having been designed over the years to survive all but the most extreme crashes.  Plastic is preferred as it is lighter and more malleable in the event of an accident and therefore is less likely to leak.  What then is so different about an EV battery pack?  Its case is rather inert too isn't it?

The dead, completely out of charge batteries still contain an enormous amount of stored chemical energy.  Chemical energy that can be ignited various ways with extremely dangerous results.  Let's take a closer look.

A typical automotive EV battery pack stores 75 kW of electrical energy when fully charged.  That's around 270 million Joules of electrical energy.  When it is completely exhausted it still has 25 million Joules of chemical energy that thermal runaway can emit.  A completely charged pack can emit both energy types and can liberate 400 million Joules!  

So you see there is a profound difference in how these propulsion system choices work and what they can do.  Read on!

So let's think about what 25 and 400 million joules looks like in a real world example The minimum and maximum effect of a battery pack thermal runaway like some Volvo EX30s are experiencing globally right now. The lower the state of charge the "safer" the situation. 

25 million Joules is akin to a large bon-fire burning for about an hour.  You probably don't want that to happen anywhere near your home or in a parking garage.  This is why repair shops often require EV's that need repair to be stored safely away from anything flammable.  So if your EV has a fender-bender park it away from anything flammable until the manufacturers technicians can tell you that the battery pack hasn't been damaged and you are safe to continue using your car.  By the way many manufacturers play it safe and condem a pack that has been in a car that was in an accident.  So new battery, not under warranty.  So DO NOT GET INTO AN ACCIDENT!  

400 million joules - that's a local TV news worthy event. Radiant heat would be felt tens of meters away, fire fighters need proper gear to get close to it, suppression will take hours and anything near it could be blasted by jets of flame.  A bad day for everybody. 

But that's not all.  The fumes are often MORE dangerous than the flames. Hydrogen fluoride is made during the combustion of the battery pack which can burn your lungs, eyes and exposed skin. Human respiratory failure can happen even hours after exposure.  If you cant get free of the fumes just a few breaths at high concentration will kill you.  There is also carbon monoxide, cyanide compounds and acidic aerosols from pack materials.  Lastly, metallic particulates get airborne from lithium salts, nickel, cobalt and manganese battery components.  The smoke often fills an enclosed space in seconds.  By the way, the toxic cloud may be lethal to breath 50 meters or more down wind from the conflagration.  Some of these toxins are odorless so be careful!

Fire departments consider an EV fire Immediately Dangerous to Life or Health (IDLH) and only approach the scene with HAZMAT gear which is de-contaminated after use.    People who have been exposed to some degree of exposure and survived report, a burning sensation in their throats and chest, temporary blindness, nausea and shortness of breath that gets worse with time.  Some of these toxins could effect your quality of life for the rest of your life. 

So understand the risks you are taking and what you need to do if you decide to go the EV route or if you see an EV on fire.  Stay far away,  Even an e-bike fire in your apartment can be lethal. This is why laws are being put in place to bar the storage of e-bikes in apartments.

There's a different way of reacting to an EV fire than the old fashioned gasoline powered car, e-bike or e-scooter.  A leaking gas tank may catch fire or not.  Can usually be extinguished in minutes, if not stay away from the vehicle because any burning car can liberate foul toxic fumes of various species.  But Ev fires involving the battery packs present an especially serious situation.  Now you know.