Electrolyte Freezing
WARNING: This page is about a different car, the 2006 Suzuki XL-7. 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 a battery, it should be protected against freezing by keeping it in a fully charged condition. If a battery is frozen accidentally, it should not be charged until it is warmed.