One of the fall rituals observed in a boatyard I worked in many years ago involved the removal of batteries from most of the boats that were wintering over. The batteries were placed in a heated shed and charged periodically, the logic being that because batteries always seem to have less power when cold, keeping them warm during the winter must be better for them. In hindsight, this was a less-than-ideal approach. The potential for damage to the battery as well as the boat, not to mention the backs of the poor souls doing the lifting, was significant, and as it happens, flooded and SVRLA batteries endure extreme cold just fine. In fact, the reason a battery has less oomph when it's cold is because the falling thermometer is slowing down the battery's internal chemistry, sending it into a sort of hibernation, which is actually desirable when it's not being used, with one provision: The battery must remain charged. A fully charged battery won't freeze, while a dead or weak one will. If a battery is allowed to freeze, it will almost certainly suffer internal, and possibly external, damage that may result in a fire or even an explosion should a charge be applied-either while still frozen or after the battery thaws out. The axiom here is: Leave the battery aboard, make certain all its loads are disconnected, and charge it periodically-once a month is probably enough for flooded batteries, and every three months for SVRLAs.
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