we’ve just driven from Seattle to Ohio along I-90, and we’ve experienced cabin heating problems when the battery is 50% or less. We get no heat from the vents even with the temps set at HI. External temps have been in the 20’s to low 30’s. Range mode is OFF. Firmware is 2018.12. We don’t have the cold weather package. However, if the vehicle is charged to 90% or more, we get plenty of heat from the vents with temps set at 70 - 75 deg. I called the Tesla tech assistance folks, and they didn’t have any idea why this is happening. Is anyone else experiencing this lack of heat problem?