Automatic Battery Charger
Automatic Battery Charger
Have you ever tried to design a battery charger which charges the battery automatically when battery voltage is below the specified voltage? This article explains you how to design an automatic battery charger.
Below charger automatically shut off the charging process when battery attains full charge. This prevents the deep charge of the battery. If the battery voltage is below the 12V, then circuit automatically charges the battery.
Automatic 12v Battery Charger Circuit Diagram
This automatic battery charger circuit is mainly involves two sections – power supply section and load comparison se
ction.
The main supply voltage 230V, 50Hz is connected to the primary winding of the center tapped transformer to step down the voltage to 15-0-15V.
The output of the transformer is connected to the Diodes D1, D2. Here diodes D1, D2 are used to convert low AC voltage to pulsating DC voltage. This process is also called as rectification. The pulsating DC voltage is applied to the 470uF capacitor to remove the AC ripples.
Thus the output of the capacitor unregulated Dc voltage. This unregulated DC voltage is now applied to the LM317 variable voltage regulator to provide regulated DC voltage.
The output voltage of this voltage regulator is variable from 1.2V to 37V and the maximum output current from this IC is 1.5A. The output voltage of this voltage regulator is varied by varying the pot 10k which is connected to the adjust pin of LM317.
Battery charger Using SCR
An automatic battery charger circuit using SCR is implemented in this project. It can be used to charge 12V batteries. Batteries with different potentials like 6V and 9V can also be charged by choosing appropriate components. The working of the circuit is as follows.
The AC supply is converted to 15V DC with the help of transformer and bridge rectifier and the Green LED is turned on. The DC output is a pulsating DC as there is no filter after the rectifier.
This is important as SCR stops conducting only when the supply voltage is 0 or disconnected from supply and it is possible only with pulsating DC.
Initially, SCR1 starts conducting as it receives a Gate voltage via R2 and D5. When SCR1 is conducting, 15V DC will flow through the battery and the battery starts to charge. When the charge on the battery is almost full, it opposes the flow of current and the current starts to flow via R5.
This is filtered with C1 and when the potential reaches 6.8V, Zener ZD1 starts conducting and supplies enough Gate voltage to SCR2 to turn it on.
As a result, the current flows through SCR2 via R2 and SCR1 is turned off as both gate voltage and supply voltage are cut off. The Red LED is turned on indicating a full charge on the battery.
