A heat wave will cook an electric car battery, if you let it

financialpost.com:

Consider it ironic, or at least a little poetic: Electric vehicles, great for combating climate change, don’t do well in extreme heat. It’s a paradox being thrown into relief as multiple United States states bake under heat waves that are becoming more frequent and more intense.

High temperatures aren’t kryptonite for battery-powered vehicles. An EV in a hot climate has to work harder to keep its battery and its passengers cool, but the car will function just fine. On a chemical level, though, extreme heat is akin to heart disease for EV batteries, or a mellow and slow-moving form of cancer.

That’s because when temperatures climb, the ions in a car battery speed up. Once that happens, they often have trouble attaching to the anode or cathode. The pressure and speed can also create small cracks, which slow chemical reactions and make for less usable battery life.

To some degree, this happens with any fast-charging cycle. Using a Tesla Inc. Supercharger will move ions more quickly than plugging into a wall outlet, and the heat generated by rapid charging is one reason smartphone batteries aren’t speedier. But on extremely hot days, the ions in an EV battery whizz around even when the car isn’t driving or plugged in, and that can curtail range irreversibly.

“The worst case really is a car that sits in an unconditioned garage in Phoenix all summer without being plugged in,” says Scott Case, co-founder and chief executive officer of Recurrent, a startup that generates battery health reports for EV customers and dealers. “That will cook the battery really quickly.” If the car is plugged in, it can use charging power to keep its battery cool.

Cold weather also impacts EV batteries. The colder it is, the slower the chemical