High performance charger circuit for car battery

This electronic charger schematic circuit diagram is a high performance charger that quickly charges gelled lead-acid batteries and turns off the charger process at full charge . When the battery is nod fully charged the charge current is held at 2 A , but as buttery voltage rise , current decreases .

When the current falls to 150 mA , the charger automatically switches to a lower float voltage to prevent the overcharging . When the charging process is finish the transistor Q1 make the LED1 to glow , to indicate the state of charging process . The small value resistors R2, R3 , R6  must be 1 watt resistors and R7 must be 5 watts resistors.

When the push button  switch is pushed ,  the output voltage  of the charger goes to 14.5 V and when the battery approaches to full charge, the charging current decreases and the output voltage is reduced to about 12.5 V .

The input voltage for this battery charger electronic circuit must be around 18 volts DC .