Electrolyte Freezing
WARNING: This page is about a different car, the 2007 Suzuki SX4. 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.