Charger meter and accumulator in the car. Simply connect it to the car's cigarette lighter (voltmeter) to check the accumulator's charge or the voltage of the charger - with the engine running. The voltmeter has a very clear, digital LED display (red numbers), making reading even on a sunny day not a problem. Do not leave it constantly connected to the cigarette lighter - after checking, it should be removed. In the case of 24V, do not use for more than two minutes (12V - for 24V the value can be doubled).