This is a battery charger circuit with adjustable current for Ni- MH or Ni -Cd . It can be used for a constant current power , which can be set to any value from a few milliamps to about 500 mA . The maximum current is 500 mA , because that is the limit of transistor BC140 . The input voltage must be above 5.25V output voltage , this is due to losses as 1.25V current limit and approximately 4V regulator . Battery Charger Ni-Cd and Ni-MH Adjustable constant current Circuit Diagram The LM317 regulator is used , it should have a sink . C omponents R1 100Ω resistor VR1 trimpot or potentiometer 500Ω Capacitor C1 0.1μF C2 Capacitor 0.01μF Diode D1 1N4001 Q1 Transistor BC140 IC1 Voltage Regulator LM317