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Car fires-EVs vs. ICE cars

Tech Talk

First off, let's talk about all those initials in the headline. EV stands for an electric vehicle. And ICE stands for internal combustion engine, at least in this case.

An EV has no gasoline engine and gets its power from a large battery needing external power. Technically, that leaves out all the hybrid vehicles with a battery and a gas engine, but I'll lump hybrids and EVs together for this column.

We see news stories of EVs that catch fire, usually with the word "mysteriously" tossed in there somewhere. But only a few stories about ICE cars catching fire. So, do EVs catch fire more than ICE cars?

Let's talk a bit about how cars catch fire.

Gasoline is a flammable liquid. The liquid part of gasoline rarely catches fire. It's the dense vapors that gasoline gives off that ignite. Gasoline vapors are heavier than air and flow downward and like to pool in low spots. Gasoline vapors can ignite at temperatures as low as -45 degrees Fahrenheit. Also, it doesn't take much vapor to ignite. Even less than a 2% gasoline vapor-to-air ratio can ignite. An open flame isn't necessary to ignite gasoline vapors; a spark will do it. That spark can come from static electricity, faulty wiring in the car, and excessive heat in the engine compartment.

EVs need a battery, a big battery. And that big battery is typically a Lithium-Ion (Li-Ion) battery. These batteries need to contain a lot of energy in as small a space as possible, making them a potential safety hazard. They include a flammable electrolyte and can become pressurized if damaged. Poor cooling, overcharging, damage from a crash, manufacturing flaws, or aging can cause Li-ion battery fires. When overheated or overcharged, Li-ion batteries may suffer thermal runaway. The smoke from thermal runaway in a Li-ion battery is flammable and toxic.

Since most vehicles on the road today are ICE cars, the insurance industry uses a percentage of 100,000 vehicles sold to get meaningful comparisons.

Data from the National Transportation Safety Board, Bureau of Transportation Statistics and recalls.gov shows that overall, lumping EVs and hybrids together compared to ICE cars, more ICE cars caught fire than EVs; 0.3% for EVs and 1.05% for ICE cars.

Strictly among EVs, hybrid cars had more fires than battery-only cars, probably because of the gasoline-powered engine of the hybrid.

Various components can cause a fire in an ICE car, but the Li-ion battery almost always causes an EV fire.

If a car catches fire, first responders are better trained to deal with a gasoline fire than a Li-ion fire. In a Li-ion fire, the battery pack underneath the car must cool off to stop the thermal reaction. And excess energy in a battery pack can reignite even days after extinguishing the initial fire.

All car fires are dangerous, but the chances of your car catching fire are low.

The genie of the lamp

Bob goes to an antique shop and spots a brass lamp for $20. He buys it and takes it home and starts polishing it. There's a flash, and a genie appears.

"I am the genie of the lamp. I shall grant you three wishes."

Surprised and stumped, he blurts out the first thing he thinks of. "I hate flying, but my grandma lives in London. I wish for a highway across the Atlantic to drive my electric car and visit her whenever I like."

The genie is not happy. "Do you know what you are asking for? I'll have to put in massive columns all along the route. Your highway will have to be taller than the largest wave. The materials, planning, logistics, and magical expenditure could kill me!"

"Too hard, eh? Okay, I wish to understand the female mind. All of a woman's moods, impulses, and logic."

The genie says, "So, on this road, will four lanes be enough, and how about a charging station every 100 miles?"

Do you have a computer or technology question? Greg Cunningham has been providing Tehachapi with on-site PC and network services since 2007. Email Greg at [email protected].