I have seen many discussions about the battery heater and most people seem to want it to heat the battery more and faster. Many want this to be a separate setting in the app so they can heat the battery manually (for various reasons). So why doesn't it warm the battery more aggressively? Why is there still a regen limit after preconditioning? Because it is a waste of energy and doesn't help the battery. The battery works just fine at cold temperatures. Only at temps below freezing will it start to show limit at driving and charging. So as long as the battery is just above those temps, there is very little benefit in keeping it warmer but a big hit in energy used. You don't get much extra range out of the battery by heating it up from 10 Celsius (50 F) to 25 Celsius (77 F). But it would require about 8.5 kWh to heat the battery from 10 to 25 degree Celsius. That's almost one full hour of full power charging with a single charger. Since pre-heating only goes on for 20-30 min and a good amount of energy is needed to heat the cabin, you get an idea how much is left to heat the battery. The battery heater itself has a max power of 6 kW. So even if it would run at full power for one hour, it would not be able to heat the battery to a level where it has zero regen limit. So Tesla dropped the ball on their battery heating? No! It's not a design flaw, it's just a matter of the battery not needing to be cozy warm to work. You can drive just fine and the regen limit is only there for the beginning of the drive. Additional heating is free from the losses of the motor and inverter and inside the battery itself. Here is an example: Let's say the battery is at freezing (0 C / 32 F) in the morning. You want to heat it up to be perfectly warm to have no regen limitation (25 C / 77 F). It would require 14 kWh. That's the equivalent of 47 miles of energy. That's more than most people's daily commute! It would be wasted every morning, every day! So Tesla decided to only heat the battery to a point where it's fine to drive with a reasonable limit on regen and save a lot of energy. Using the unavoidable losses in the drive train to further heat the battery as you drive is a much smarter and more efficient way to use energy. Using these losses is free energy to heat the battery. Also keep in mind, the cooler the battery, the better for the longevity. As Elon once said, he expects the battery to last 'forever' in Alaska.