As more players enter the electric vehicle market, automakers need something to help them stand out from the competition. For many, the answer is vehicles with longer driving ranges, greater power output and faster recharge times.
Pushing batteries further and further has consequences, however. One of them is excess heat generation.
Thermal management has become a hot topic for automakers and suppliers. That's because optimal battery performance depends on keeping the battery pack from getting too warm — or too cold.
"We're trying to keep the battery temperature ... at about human [comfort] level," said Dana Nicgorski, Bosch system engineering lead for thermal management of electric vehicles. "Batteries are happy at basically human temperatures."
Batteries heat up during driving, when the electricity is flowing out, and during charging, especially fast-charging, when power is flowing in. Ambient conditions around the pack can also heat the battery.
"Over time, at high temperatures, you lose capacity, you lose reliability, and if you have a thermal runaway, you can actually have fire," said Sanjay Misra, senior scientific principal at Henkel, a provider of thermal interface materials.
"Your gas tank doesn't get hot when you're filling it. Your gas tank doesn't get hot when you're draining it, when you're running the car. So EV batteries, lithium ion batteries, are kind of special 'gas tanks' because if you fill them, if you charge them, they get hot, and the faster you charge them, the hotter they get," Misra said at an October Shift conference in Detroit.
"We're talking about an explosive system with very tight temperature limits, all packed tightly in a vehicle, and you're sitting in it, so it's a challenge."