LM317 three terminal regulator manufactured by National Semiconductors is one of the most used three terminal regulators from the market . Because of the high efficiency provided by the LM317 and number of low parts required this integrated regulator can be used in many power supply circuit projects .
This electronic project , presented in this diagram is a very simple car battery charger electronic circuit that can be used for charging car lead acid batteries . This car battery charger will provide a 12 volt at maximum current .
RS sets output impedance of the car battery charger Zout-Rs=(1+R2/R1) .
Use of RS allows low charging rates with fully charged battery. The 1000 μF is recommended to filter out input transients .