This simple circuit makes it posible to monitor the charging process to a higher level.
Final adjustsments are simple and the only thing needed is a digital voltmeter for the necessary accuracy.
Connect an input voltage of 12.65 volt between the positive and negative poles and adjust the 10K trimmer potentiometer until Led 10 lights up. Lower the voltage and in sequence all other Led’s will light up. Check that Led 1 lights up at approximately 11.89 volts.
At 12.65 volt and higher the battery is fully charged, and at 11.89 is considered ’empty’.
The green Led’s indicate that the battery capacity is more than 50%, the yellow Led’s indicate a capacity of 30% – 50% and the red Led’s less that 30%. This circuit, with the components shown, uses less than 10mA.