Hi
555 is used to charge 12 volt battery
Capacitor 15 mf used as battery
When capacitor charges and volts reach 13.5 the green full light comes on
When capacitor volts drops upto 10.4 volts the red charging light comes ON
Zener diodes value changing will adjust the battery upper and lower voltages limit
10K resistor is a dummy load to discharge capacitor (battery)
In real life realay must more then 5Amps
Regards
Ashfaq Ahmed
ashfaqsamikhan22@gmail.com
