Small in size and price, but compared to ordinary 5-10x expensive products to good quality and this indicates what we want to know, namely respectively the battery voltage. Charge voltage with the engine running. I will not get into (0.1 V more or less do not matter here) on the accuracy of the display. Note only that the location of the cigarette lighter can affect the readability of the display, because the device does not swivel. Even with continuous operation always reliable, so 5 star and a buy recommendation (for the needs it).