Using a cigarette lighter Voltmeter to check alternator charge.

This Voltmeter plugs into the cigarette lighter and checks the car battery voltage (with engine off), and also the Alternator charging voltage when the engine is running. The voltage indicated when the engine is running should be around 14.2 - 14.5 Volts (for this particular vehicle), if the alternator is charging correctly.
A higher charging voltage will charge the battery faster, but may result in decreased battery life over an extended period of time.

Note - An almost 'fully charged' battery should give a reading on the voltmeter of somewhere between 13.5 to 13.8 Volts (without the engine running), but in most cases the voltage indicated will more likely read around 12.5 - 13 Volts, as most car batteries do not get 'fully charged' with around-town running.