Well, our winters are fairly mild compared to other parts in the world, but I've come to the conclusion it are the regular lead/acid batteries that usually croak during the winter.
I bought into the AGM hype and both discharged rapidly below zero degrees, to the point that they would barely crank the engine over. I switched both vehicles back to regular lead acid batteries and the below zero barley cranking problem went away. Dollar for dollar I am better off replacing my lead acid batteries a year early instead of spending the additional amount on an AGM battery hoping it lasts longer. It has also been my experience that batteries croak in the winter. Nomally when the parts store is closed. Your climate may vary.
