Battery indicator

Many newer cars no longer offer voltmeters or ammeters; instead, these vehicles typically have a light with the outline of an automotive battery on it.

In the adjacent picture, the ammeter is marked "Alternator" and the symbols are "C" (charge) and "D" (discharge).

Both ammeters and voltmeters individually or together can be used to assess the operating state of an automobile battery and charging system.

Computers may give a signal to users that an internal standby battery needs replacement.

As a battery discharges, the EMF may drop or the internal resistance increase; in many cases the EMF remains more or less constant during most of the discharge, with the voltage drop across the internal resistance determining the voltage supplied.