In this tutorial, we are going to make a “12V Lead Acid SLA Battery Charger Circuit”.
A Sealed Lead Acid battery is a secondary cell battery, meaning it can be re-charged. Charging an SLA battery is accomplished by sending electrons through the battery to reverse the chemical reaction that creates the energy output of the battery. Sending electrons back through the battery, or charging it, causes a reaction that converts the battery components back to their charged state. It can be called a valve-regulated Lead Acid (VRLA) Battery. Here we design a 12V SLA battery charger circuit with a few easily available components.
It gives a regulated 12 Volt DC supply to the SLA battery with a constant current. This circuit has a 1N4007 diode at the output to provide reverse current protection. This 12-volt SLA battery charger circuit converts a 230V AC supply into a regulated 12-volt DC supply through the bridge rectifier and regulator stage. This circuit can charge SLA batteries ranging up to 4.5Ah.
Hardware Components
The following components are required to make Battery Charger Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Step down transformer | 15V AC | 1 |
| 2. | Diode | 1N4007 | 4 |
| 3. | Electrolyte Capacitor | 1000µF, 22µF | 2, 1 |
| 4. | Positive Regulator IC | 7812 | 1 |
| 5. | Ceramic capacitor | 0.1µF | 1 |
7812 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 7812
Battery Charger Circuit
Working Explanation
As shown in the circuit, begin with a step-down transformer. Which step-down the voltage, 15 Vac is obtained from transformer secondary and through bridge rectifier module rectified into 15V DC. This rectified DC supply is applied through C1, C2, and C3 filter capacitors to remove ac ripples and distortions. This 12V SLA battery charger circuit is made like a common bridge rectifier circuit. Hereafter the filter stage, the DC voltage is regulated by the positive regulator IC7812, the first terminal of this IC is the Input and the second one is the ground, and the third terminal is the output terminal. It will provide current up to 1A and has internal thermal overload protection and short circuit protection. Now the output DC from the regulator goes through an additional filter capacitor C4. At the end charging DC supply is taken out through reverse current protection diode 1N4007. Then this supply can be applied to the SLA battery.
Applications
SLA (Sealed Lead Acid) batteries are used in different types of applications like vehicles, inverters, ups, toys, etc.,
