NFPA Journal - January/February 2020 - 34

If EV incidents become more common, "it will put more resources out of
service and impact our ability to respond to other emergencies," he said.
For departments outside Silicon Valley, a similar battery breach
incident poses myriad additional questions beyond just a drain on
resources. Chief among them: Faced with similarly extreme conditions,
what should a fire department do if it can't call in a bevy of nearby EV
engineers to assist?
"Certainly, I would say from this experience that the fire service is
not prepared to fully mitigate these fires," Diaz told a group of NFPA
employees during a conference call a month after the crash. "If Tesla
had not come out we might have left it burning there on the freeway.
We had no other choice."

THE BIG FUTURE OF
ELECTRIC VEHICLES

3.1 million

ESTIMATED NUMBER OF ELECTRIC VEHICLES
WORLDWIDE IN 2017*

130 million
30%

PROJECTED NUMBER OF EVs BY 2030*

PERCENTAGE OF VEHICLES SOLD GLOBALLY BY
2025 THAT ARE HYBRID OR FULLY ELECTRIC**

800%

PROJECTED PERCENTAGE INCREASE IN GLOBAL
PRODUCTION OF LITHIUM-ION BATTERIES
BETWEEN 2017 AND 2022

55%

PROJECTED PERCENTAGE INCREASE OF
LITHIUM-ION BATTERY DEPLOYMENTS
BETWEEN 2017 AND 2022

1 in 10 million
HIGH-END ESTIMATE OF BATTERY CELL
FAILURE RATE

250,000

NUMBER OF US FIREFIGHTERS WHO HAVE
COMPLETED NFPA ONLINE EV TRAINING

1.1 million

NUMBER OF FIREFIGHTERS IN THE US
*Source: International Energy Agency **Source: JP Morgan
*** Source: LG Economic Research Institute

34 | NFPA JOURNAL * J A N U A R Y / F E B R U A R Y 2 0 2 0

GETT Y IMAGES

NO GOOD OPTIONS
The primary challenge faced by Mountain View firefighters that day
was stranded energy, a widely overlooked issue with little scientific
literature, according to researchers interviewed for this story. Stranded
energy is any scenario where electrical energy remains in a battery
without an effective means to remove it. This typically happens when
the battery is damaged-by force, a coolant leakage, heat, or water
intrusion-and normal function ceases. This can also lead to thermal
runaway. How much energy remains in the battery when it's damaged
can greatly affect the severity and duration of the reaction.
The Mountain View crash "happened early in the morning, so we
think the battery was close to 100 percent charged. It would make sense
then that it would still have enough energy to reignite a week later,"
Diaz said. "You really don't know that you've completed 100 percent
extinguishment on an electrical vehicle until you know for sure that
that battery has been drained of all of its energy." High levels of energy
trapped in the battery could also explain the intensity of the popping
and hissing noises that came from the battery after the accident-a telltall sign of thermal runaway.
There are currently no ways for responders to determine how much
energy remains in a damaged battery, and no way to drain that energy
to reduce the threat. The battery industry is working to improve safeguards so that thermal runaway and stranded energy are no longer
issues, said Don Karner, the founder of Electric Applications Incorporated, a company that helps battery manufacturers test products and
tailor them to new applications. Even with the best technology, however, Karner said, some risk will always exist, especially with batteries
being used in more applications and under more extreme conditions.
"Nothing is ever perfect," he said, especially regarding batteries in EV
applications. "We are essentially taking a battery pack and throwing
it down the road at 75 miles an hour and crashing it into another one
coming the other way at 75 mph-the margin for error is extremely
small," said Karner, who is also chair of the committee on stranded
energy for the Society for Automotive Engineering. "You never quite
know if everything is going to go perfectly, so you always have a contingency if the battery catches fire."
In addition to the Mountain View incident, dozens of similar incidents have occurred recently around the world, from New Hampshire
to Moscow, where built-in battery safeguards did not work as expected.
Each resulted in difficult, time-consuming cleanups for responders
who, without a means to remove stranded energy from a damaged battery, had limited options at their disposal.
Using water to cool a damaged battery in thermal runaway is currently the dominant strategy for responders and is the tactic taught
NFPA Journal - January/February 2020

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