Circuit diagram

Rapid battery charger schematic

The First ac voltage from tranformator will be rectified and filtered to the LM723 voltage regulator and the NPN pass transistors setup for constant current supply. The 470 Ohm resistor is limit trickle current the momentary pushbutton (S2) is depressed, the SCR turn  on , and the current flows through previously determined resistor  network.SCR will be turn off if thermal cutout inside the battery pack opens up.