Solid state battery indicator

The most simple solid state battery indicator electronic project can be designed using few common electronic parts . As you can see in this circuit diagram this solid state battery indicator is based on some zener diodes .

This solid state battery indicator is designed for a 12 volts car battery , but you can modify this design for some other batteries .
L1, L2 and L3 are simple light emitting diodes (LEDs) and Z1, Z2 and Z3 are zener diodes .
Z1 is a 9.8 volt zener diode , Z2 is a 11.1 volt zener diode and Z3 is a 11.5 volt zener diode .

R1,R2 and R3 are 47ohms resistors and R4 is a 39 ohms resistor .
V- and V+ terminals must be connected directly to the battery terminals ( V- at the negative terminal and V+ to the positive terminal ) .

When L1 and L2 will light indicates that the voltage on battery is ok . When just L1 LED is lighting indicates that the voltage of the battery is low .
When all three LEDs are on indicates that the output of the battery is in overvoltage state .