Electric vehicles have only been on US roads for ten years, but they are quickly becoming as common as rush hour traffic.
There are currently 19 different models of all-electric drive vehicles available to US buyers. Automakers shipped more than 300,000 new units in the first half of 2021, and two-thirds of all domestic EV sales have come in the last three years.
With automakers and the federal government moving towards a zero-emissions ideal, EVs will become even more popular in the coming years.
Their draw is understandable, for more than just the obvious environmental reasons. Electric motors are remarkably simple and have fewer mechanical parts to fail compared to their internal combustion counterparts; they also generate far less heat, which leads to longer component life.
EVs also offer a tremendous weight savings and can run so quietly that in 2019, European and US automotive regulation agencies mandated artificial noise at speeds up to about 20 miles per hour to protect pedestrians.
Almost every EV on the market today is at the forefront of design and engineering technology. The space and weight savings of electric motors have allowed manufacturers to load their EVs with things like electronically controlled transmissions, GPS navigation, and driver assistance steering and braking systems. The main screen in a Tesla S is bigger than an iPad.
And while the energy required to fuel all of those computer-based systems is significant, the main power consumer in any electric vehicle is the motor. To move 3000-5000 pounds at up to 70 MPH for hundreds of miles at a time requires a tremendous amount of battery capacity.
The industry has settled on two highly efficient battery compositions: nickel-metal hydride and lithium ion. Nickel-metal hydride is considered by far the safer of the two, but is much heavier than lithium ion.
Li-ion batteries also charge faster than their older NiMH cousins and maintain their capacity much better over time and repeated charge cycles. All of these factors make them very attractive to EV manufacturers.
But two months ago, Chevy recalled every one of the 142,000 Bolts it had sold in the car’s five-year lifespan due to problems with Li-ion battery fires. This followed Hyundai’s recall of 90,000 Kona models for identical incidents.
In early EV models, fires were primarily the result of crashes. But since manufacturers responded by introducing better shielding technology, most have been in vehicles that are parked and charging, and nearly all were in vehicles with lithium ion batteries.
The batteries are subject to overheating and a phenomenon called “thermal runaway,” where the aluminum used to separate a battery’s cells helps conduct heat energy and can cause fires to reignite several times.
The persistent and white-hot blazes can prove very stubborn to fight. When a Tesla Model S burst into flames after a crash near Houston,
"Eight firefighters ultimately spent seven hours putting out the fire. They also used up 28,000 gallons of water — an amount the department normally uses in a month. That same volume of water serves an average American home for nearly two years.By comparison, a typical fire involving an internal combustion car can often be quickly put out with approximately 300 gallons of water, well within the capacity of a single fire engine."
Ironically, it is the effectiveness of the casing around the batteries – originally introduced to reduce collision-related fires – that is to blame for the runaway heat-based conflagrations.
In doing its job of keeping the batteries protected from impact and the elements, the casing also shields burning batteries from firefighting chemicals.
This leads to persistent re-ignition of the fires as the heat generated spreads from cell to cell. And the volume of batteries in some models means the chemically fueled flames can burn for hours.
A simple solution would be to ban the use of Li-ion batteries and go back to the heavier but safer NiMH standard, but neither manufacturers nor consumers would be happy with the subsequent loss of range and performance.
But with the pressure of recent large recalls, automakers’ labs across the world are no doubt busy with engineers looking for forward-facing solutions.
Automatic fire suppression systems have greatly reduced the severity and frequency of racing fires; perhaps a similar system will soon be found in every EV battery compartment.
Maybe the solution will require a different chemical composition and an entirely new battery technology, or a casing made of an insulating material in place of aluminum.
Toyota, GM, Honda, Ford, and Volkswagen have all had to issue massive recalls in recent history, and last I checked they were all still in business.
But with auto sales already slumping as a result of COVID-19, manufacturers will be pressed to quickly fix any issue that might dent sales, so look for a solution to the battery fire problem soon.
And then look for electric vehicle sales to catch metaphorical fire again.