Shift Magazine - November 25, 2019 - 26

HOT

TOPIC

Thermal management in EVs key to optimal battery performance
BY ALEXA ST. JOHN

s more players enter the electric vehicle market, auto"Your gas tank doesn't get hot when you're filling it. Your
makers need something to help them stand out from
gas tank doesn't get hot when you're draining it, when you're
the competition. For many, the answer is vehicles with
running the car. So EV batteries, lithium ion batteries, are kind
longer driving ranges, greater power output and faster
of special 'gas tanks' because if you fill them, if you charge
recharge times.
them, they get hot, and the faster you charge them, the hotter
Pushing batteries further and further has consethey get," Misra said at an October Shift conference
quences, however. One of them is excess heat
in Detroit.
generation.
"We're talking about an explosive system
Thermal management has become a hot
with very tight temperature limits, all
topic for automakers and suppliers. That's
packed tightly in a vehicle, and you're
because optimal battery performance
sitting in it, so it's a challenge."
depends on keeping the battery pack
Which cooling method is best
from getting too warm - or too cold.
depends on the automaker and
"We're trying to keep the battery
the vehicle architecture. Options
temperature ... at about human
include air cooling, direct or indi[comfort] level," said Dana Nicgorski,
rect liquid cooling, refrigerants or
Bosch system engineering lead for
even "phase change materials,"
thermal management of electric
which absorb and release heat by
vehicles. "Batteries are happy at basimelting and resolidifying.
cally human temperatures."
"In the next several years, we
Batteries heat up during driving,
really think that liquid cooling - basiThe Audi e-tron uses a liquid
cooling system.
when the electricity is flowing out, and
cally your glycol-water-mix cooling plate
during charging, especially fast-charging,
- I think that's going to be the predomiwhen power is flowing in. Ambient conditions
nate way to cool it," Misra said.
around the pack can also heat the battery.
MANAGING HEAT
"Over time, at high temperatures, you lose capacity, you lose
Driving
range is to a great extent based on the energy density
reliability, and if you have a thermal runaway, you can actually
of
the
pack.
But you need to be able to pull the heat out as fast
have fire," said Sanjay Misra, senior scientific principal at Henkel,
as
energy
is
put in. Without adequate thermal management,
a provider of thermal interface materials.
26

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Shift Magazine - November 25, 2019

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