So we know a few facts: 1. Batteries have internal resistance, and both the battery and the motor generate heat while driving. 2. Model S has an active pack heater that consumes a large amount of energy to heat the pack while driving in colder weather. So i've often wondered why there isn't a "passive heating" mode while driving. Suppose you have a long trip and need as much range as you can get. Wouldn't you prefer to have power and regen limits vs. burning 4-600 Wh/mi for quite a while on the trip? In those cases, I'd rather the pack just heat up naturally...much more slowly, while maintaining power and regen limits as necessary. This would result in significantly smaller range loss on cold days. So why hasn't Tesla done this (at least as an option)? If it's ok to drive the car when the pack's cold, why not just let it warm up passively, as long as power/regen limits are respected?