This circuit is a high-performance charger for gelled-electrolyte lead-acid batteries. This charger quickly recharges the battery and shuts off at full charge. It uses the well-known LM301A and LM350 ICs.
Initially, charging current is limited to 2A. As the battery voltage rises, current to the battery decreases, and the current had decreased to 150 mA, the charge switches to a lower float voltage which prevents overcharge.
When the start switch is pushed, the output of the charger goes to 14.5V. As the battery approaches full charge, the charging current decreases and the output voltage is reduced to 14.5V to about 12.5V, terminating the charging. Transistor then lights the LED as a visual indicator of full charge.