check your numbers again. this time in 20 below temps with batteries that are half way through their life cycle.
>> “with batteries that are half way through their life cycle.” <<
.
If you use desulfators, the life cycle issue essentially disappears, as long as you check electrolyte levels at no more than 90 day intervals. My oldest bank of batteries is now 14 years old and still performing as new.
The OP said he's in southern California, I saw no need to bring charging / discharging temperature compensation into the discussion at this point or are you really trying to say that in 20 below temps with batteries that are 50% through their life they will charge at .001 efficiency?