Battery and Cables

WARNING: This page is about a different car, the 2018 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.

The battery is a 12V DC source connected in a negative ground system and is a voltage stabilizer for the 12V electrical system.

NOTE: The primary purpose of the battery eye is to be a quick indicator of the battery's state-of-charge for assembly plants and dealership pre-delivery processes.

The battery eye indicates the battery state-of-charge by responding to the specific gravity of a single battery cell electrolyte. The battery eye has a viewing plate, 2 colored balls of different specific gravity and a small passage. As the battery's state-of-charge and specific gravity changes, the balls change their position in the passageway and display a different color in the viewing eye.

Do not install a new battery based only on the battery eye color. The battery eye color simply indicates the battery state-of-charge, not its condition. For example, a red or yellow/black battery eye usually indicates the battery is discharged, not defective. If the battery eye indicates the battery may be discharged, recharge the battery before testing its condition.

Red - low state-of-charge
Yellow/Black - between high and low state-of-charge
Green - high state-of-charge
No color can occur after the battery has been in service for several years and some of the plate material has coated the balls
A clear battery eye can occur if the battery case becomes damaged and the electrolyte has fallen below the plates