This is the circuit of a simple 12 volt battery charger for Lead Acid battery. It gives 12 volt and 5 Amps current for quick charging of the battery. If the battery is partially discharged, full charge will be attained in one hour.
The circuit uses a 0-14 volt 5 Ampere Step down transformer and a 10 Amps Bridge rectifier module to convert AC to DC. Since pulsed DC is good for Lead Acid battery, a low value smoothing capacitor is used as C1.To monitor the charging status, Ampere meter is provided in the positive rail. LED act as the Charger on status.
When the output is connected to the battery terminals, the meter shows a higher reading depending on the current flow into the battery. As the battery attains full charge, its terminal voltage rises to 13.8 volts and current through the meter ceases. The meter reading then returns to zero. This indicates the full charge state and the charging can be terminated.