Electrolyte Freezing
WARNING: This page is about a different car, the 2010 Suzuki Kizashi. However, it is still accessible from the selected car via links, so may be relevant.
The freezing point of electrolyte depends on its specific gravity. Since freezing may ruin the battery, protect against freezing by keeping the battery in a fully charged condition. If a battery is frozen accidentally, it should not be charged until it is warmed.