135. Which of the following procedures represents the best method to prevent the freezing of lead-acid batteries continuously exposed to low temperatures?

Maintaining a full charge lowers the electrolyte's freezing point, preventing freezing in lead-acid batteries exposed to low temperatures. Electrolyte freezing point is dependent on state of charge; a discharged battery contains more water, raising the freezing point and increasing the risk of damage. Disconnecting the charger, removing caps, or sealing vents are ineffective and potentially dangerous.