Battery with "Magic Eye"

Fig 1: Locating Magic Eye

Courtesy of VOLKSWAGEN UNITED STATES, INC.

The "magic eye" - arrow - gives information regarding the acid level and the charge level of the battery. Three different color indications are possible:

Color indication	Battery charge condition
Green	Battery is sufficiently charged.
Black	No charge or charge too low.
Colorless or yellow	Critical acid level reached, battery must be recharged or replaced.

NOTE:

If the battery is older than 5 years and the color indication of the magic eye is transparent, the battery should be replaced with a new one.

Work procedure

NOTE:

When recharging the battery (but also while driving), air bubbles can form below the "magic eye". These corrupt the color indication of the "magic eye".
If batteries are equipped with sealing plugs due to manufacturing conditions, they are covered with a plastic foil.
Before performing a visual check, lightly and carefully tap onto "magic eye" using a screwdriver handle; as a result the air bubbles will disappear.
Read color indication of the "magic eye" → Battery with "Magic Eye" .