For a few weeks now I have been using TM-Spy, a little app that shows data from the Model S that is not available in the normal UI. Out of interest I was keeping an eye mostly on battery temperature. I was surprised to see how the car seems to warm up the battery quite a bit all the way to 105-110 F. Definitely well above ambient temperature. In those last weeks the temperatures here in Los Angeles were between 60 and 80. The app shows the temperature of the coolant going into the battery module and coming out. There are two separate sensors. It makes it possible to see if the car is trying to warm or cool the battery depending on what temperature is higher or lower. What I saw is when I started driving (after a few miles) the input temperature was always higher than the output, thus the car was actively heating the battery. The difference in temperature was small. Only 2-3 degree difference, but it stayed that way until the battery reached well over 100 degree F. It takes a while, so only on longer drives did the battery reach this temperature. I was surprised why Tesla decided to bring the battery up to such a high temperature all the time. After several days of seeing this I realized that I had turned on 'Range Mode' a while ago an forgot to turn it off. So I turned it off. Now I saw that the car doesn't seem to heat up the battery as much any more. The battery temperature still goes up when you start driving, but I can see that the input temperature is lower than the output so the battery just gets warm on it's own from use, but isn't actively been heated on top of it. Driving with range mode off I have never seen the battery as high as 105, which was the norm when Range Mode was on. To be sure I just did another test drive. After driving for 35 miles with Range Mode OFF the battery was at about 89 F. The input temperature was just 1 or 2 degree lower than output. I switched to range mode, and within 2 minutes I saw the input temperature climb up 3-4 degree over the output and over the next 20 minutes the battery started to warm up to 98. I highly doubt the car turns the battery heater on. I think what happens is that when in range mode, the car directs the coolant through the motor and inverter and then directly into the battery. The inherent losses of the motor/inverter are used to warm the battery to about 105. A warmer battery has a slightly higher capacity than a cooler one thus giving the car a touch more range. It makes sense to have a warmer battery when trying to get the maximum range. I don't have a lot of time to do all sorts of tests, so I'm hoping others with access to the CAN bus can do their own tests and hopefully verify what I found. I do believe when the battery is below a certain temperature, it will always start warming it up, regardless of what Range Mode is set to. The only difference might be that when Range Mode is turned on, the car will bring the battery temperature higher than without it. Maybe it is different with newer cars with dual motors. Mine is a 2014 RWD 85. I did read that Range Mode will prevent the battery heater (a separate energy sucking electrical heater) from coming on, which ends up being counter productive when the car is charging and plenty of power would be available.