Want to have a tool-kit that easily monitor your 12V battery? Below we provide you with DIY electronic equipment 
about making a DC voltage-monitoring that allows you to connect 5-14V and get up to 8 levels voltage-monitoring via LEDs light. You can mount it maybe on your car, tractor, or boat dashboard.
You will need these semiconductors to fulfill this purpose: 2pcs LM324, 20pcs of resistors from various Ohms, 8pcs red, yellow,green small/large LEDs, a trimmer, 2pcs 1N4148 diode, 2pcs Zener Diode for each 1N4733 and 1N4737, a connector 2P terminal block and a PCB. This DC voltage-monitoring device provides an early warning of your battery conditions such flat batteries or other embarassing incidents on your car, tractor or boats.
The device can be designed to monitor different range of DC voltages since the changing voltages are indicated through the LEDs, you will see as L1 to L8 in the schematic section. Detailed informations about DC Voltage-Monitoring Circuit Device for Monitoring Your 12V Battery can be found here. You can find LEDs configurations, complete semiconductors’ value, application note, and the circuit schematic of this device (source: eidusa.com).
