— James Locke (@arctechinc) April 11, 2018
While the addition of the icon is new for some owners, the behaviour of the vehicle in warming up the battery is not. Tesla has always recommended warming up the battery in cold weather to get the best efficiency. One of the ways they recommend doing this in their Winter Driving Tips is to open the Tesla app and turn on the climate controls.
Now the app will show you when your battery is cold and is still being warmed up, so you’ll know before getting in the car if you will have limited regenerative braking.
The behaviour is also independent of whether the vehicle is plugged in to charge, the new icon will appear if the battery is cold enough to warrant warming up.