Originally Posted by scottalexander

I just bought one of the cigarette lighter voltage meters and used it today for the first time.

I plugged it into the cigarette lighter and here's what I learned.

I pressed the start button

Within 1 second the voltage reading was down to 10.7 volts (this must have been battery voltage?)

Within 2 seconds the reading was 12.1 volts

Within 4 seconds the reading was at 14.4 volts (this must have been alternator voltage)

For the next 15 minutes of regular driving the reading fluctuated up and down between 14.1 volts and 14.3 volts

When the car is idling the reading was steady at 14.2 volts

It was apparent the DME was intelligently trying to monitor and manage the voltage.