SLA (Sealed Lead Acid) Batteries are used in different types of applications like vehicles, inverter, ups and toys etc.., it can be called as Valve Regulated Lead Acid (VRLA) Battery. Here 12V SLA battery charger circuit designed with few easily available components. This independent charger circuit gives regulated 12 Volt DC supply to SLA Battery with constant current. This circuit has 1N4007 diode at output to provide reverse current protection.
This 12 volt SLA battery charger circuit converts 230V AC supply into Regulated 12 Volt DC supply through Bridge Rectifier and Regulator stage. This circuit can charge SLA batteries range upto 4.5Ah.
- Step down transformer 15V AC
- Bridge Rectifier Module or 1N4007 = 4
- Capacitor 1000µF/25V = 2
- Capacitor 0.1µF
- Positive Regulator 7812
- Capacitor 22µF/16V
- Diode 1N4007 / 1Amps
Construction & Working
12V SLA Battery charger circuit made like a common bridge Rectifier circuit and Starts with Step down transformer, 15 Vac is obtained from Transformer secondary and Rectified into 15V DC through Bridge Rectifier module After Rectification DC supply is applied through C1, C2 and C3 filter capacitors to remove ac ripples and distortions.
IC 7812 is a Positive Voltage Regulator element with three pin and GND pad it comes in different package and we can choose it depends on our application and product space, here we have taken IC 7812 with TO-220 package for prototype. First terminal of this IC is Input and second one is Ground and third terminal is output terminal. It will provide current up to 1A and has internal thermal overload protection and short circuit protection.
After filter stage the DC voltage regulated by the positive regulator IC7812 and C4 provides additional filter to the Output DC from Regulator at the End Charging DC supply taken out through reverse current protection diode 1N4007. Then this supply can be applied to the SLA battery.