I do a lot of parking in ski area parking lots and Lithium batteries do not do well in freezing temps so I have AGM.
I need to keep my heater on low when I am out skiing so my dog stays warm and the propane furnace fan can drain batteries in a day or 2. For me, relying on solar in winter is too risky so I carry a Honda 2200watt generator and 1000watt electric heater (great for drying out wet gear) as well as battery charger and computer and phone chargers.