Start at the top of a mountain road with a cold-soaked battery. Turn-on range mode (which turns-off the battery heater) and coast down the mountain. The regen will never start because you didn't have any in the first place and you're not using power from the motors/battery to enable any warming. You'll get to the bottom of the mountain still with no regen and will have wasted a lot of energy in the form of heat via the brakes. A lot of heat. I can't imagine the amount of energy required to warm the battery is more than the amount lost to the brakes.