Join Date: Aug 2010
Location: Fort Frances, ON, CA
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A battery in reasonable condition shouldn't freeze above -40 C (the battery in my truck is not in reasonable condition and didn't freeze at -42 C). If you are regularly discharging this battery below 11.6 volts, you are severely limiting it's lifespan. Most 12v batteries are considered discharged at around 11.85v, and should be recharged.
As I mentioned before, increasing the capacity of your bank will increase it's longevity, but you still can't neglect them and hope they'll last. You may want to consider some form of auxiliary charging system (solar/wind) to help prolong the life of the battery bank.