battery heater

I have seen several threads on the effects of cold weather on battery dynamics and had an idea: If I were faced with severe cold weather and wanted to maximize both the longevity of the battery and availability of regenerative braking the goal would be to maintain the optimum battery temperature...

I bet you didn't. I'll bet you're thinking right now, "no, that's nonsense, that can't be right, let me get in this thread and tell this idiot off". Or maybe "what makes you think that, where'd you get that data?". Perhaps "no, that's just because DC charging causes the battery to heat up"...

I can't seem to get the battery heater to come on in the morning. Temperature is around freezing, car is charged for at least an hour immediately before I depart and cabin heated for 15 - 30 minutes, but still I have almost zero Regen on setting off and don't get full regen for 30 minutes...