Just FYI, there now appear to be at least 3 large battery manufacturers producing 100ah Group 31 low temperature batteries (that is, with internal, BMS-driven heating elements):
Battle Born (see above)
Of interest, the Battle Born set-up incorporates a manual on/off switch. Curiously, LifeBlue claims their battery can be discharged and charged down to a battery temperature of -4F (-20C).
Documentation is a bit lacking for all 3, with Battle Born being the most complete.