Battery with charge indicator

Fig 1: Locating Magic Eye

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Distinguishing features

These batteries have a charge indicator.
This charge indicator -arrow- provides information on the electrolyte level and charge of the battery to be tested.
Three different color indications are possible:

Green → Battery is adequately charged.
Black → Battery is not charged, or inadequately charged.
Colorless or yellow → critical electrolyte level has been reached, topping off with distilled water essential.

NOTE: Please observe that if the battery is older than 5 years and the color of the charge indicator is colorless, the battery is to be replaced with a new one.

Test sequence

NOTE:

Air bubbles may form under the charge indicator, particularly if a battery has been recharged, i.e. even if the battery has been charged while driving. These air bubbles falsify the color indicator of the charge indicator.
If batteries are installed with caps for production reasons, these are covered with plastic sheeting.
Before performing a visual check, lightly and carefully tap onto the charge indicator using a screwdriver handle.
This will cause the air bubbles to disappear
Read color indication of "charge indicator".