If the battery warning light (a light in the shape of a battery symbol) appears on the dashboard while you are driving, this means that the charging system does not work, but the fault may be something other than the battery.
A loose or corroded battery cable or other wire connecting
components of the charging system could be the cause of the battery light, or
it might be a problem with the alternator or voltage regulator. The alternator
produces the power stored in the battery. If the alternator fails, or the
accessory belt driving the alternator is broken or lose, you will end up with a
dead battery.
The car battery itself can be the cause if it has inside
corroded cable terminals, bad wiring, damaged cells or plates or if electrolyte
leaks. This article specifically applies to traditional vehicles with
conventional 12-volt batteries; more electrified vehicles and those electrical
systems with higher voltages may differ.
When you start the car, the charging system warning light
should show up for a few seconds, but if the battery light shows up while
driving the vehicle, that light signals an issue. Among other signs that the
alternator or other parts of the charging system don’t work are dim headlights
or time-loss clocks.
If the car’s dashboard battery light comes on, you might be
able to make it home or to a service facility for a repair. The car will
continue running as long as some juice is left in the battery, but if the
charging system isn’t working or you have a bad alternator, your car’s engine
will stop running once the battery is drained. When you shut off the engine,
you will not be able to restart it if there is not enough charge left for the
battery to drive the starter motor on the engine.
If the battery light is on and you are still driving the
car, switching off as many electrical devices as possible, such as a stereo,
air conditioning or fan, and stop using electrical controls such as power
windows.
Reducing the amount of electricity, the car consumes will increase the distance you can drive before it discharges the battery. Get to a mechanic as quickly as possible and check the battery, wires and charging system to find out what causes the problem and what needs to be repaired or replaced.