This project is very simple to construct using cheap few components and easy circuit lay-out. Regulation of this project uses the fixed 3 terminal regulator 7815 as we know. You may noticed that 7815 will give an output of 15volts but because of the 3 amperes rectifier diode connected right after the output of the regulator, it drops the voltage down to 14.3volts furthermore the pass transistor used on this circuit are wired in series pass configuration, it adds another voltage drop down to 13.6volts which is pretty close to 13.8volts, anyway to beef-up the required current, two sets of 2N3771 NPN transistors capable of 30amps each connected in parallel and in series pass configuration.
In the construction make sure that the heat sink is large enough to provide sufficient dissipation of the heat generated by the two power transistor. Large diameter wire must be also used such #12 WAG stranded wire for the wiring of the circuit. If desired you can also add a small air blower to control the temperature of the power supply. ...73 de hevir
