Car battery monitor circuit diagram

How it works : When the battery voltage is 11.5V or less transistor Q1 is turned on and the LED D1 will be bright. When the battery voltage is between 11.5 and 13.5 V, the transistor Q2 is turned on and the LED D2 will light up. When the battery voltage is 13.5V transistor Q3 will be on the D3 and the LED will light.

pinit fg en rect gray 20 Car battery monitor circuit diagram

The schematic diagram come from circuit: Car Battery Monitor with 3 LED power supply. Go to that page to read the explanation about above power supply related circuit diagram.