12/24/2023 0 Comments Automatic car battery charger![]() ![]() When the charge in the battery reaches 14.5V, the input to inverting terminal of LM358 is slightly greater than 2.5V at Pin 3 set by LM336. A voltage divider network is used to supply a portion of battery’s voltage to inverting terminal (Pin 2) of LM358. LM336 is used to supply a reference voltage of 2.5V to non-inverting terminal (Pin 3) of LM358. LM358 acts as a comparator and voltage follower. When the 2N4401 is turned ON by the output of 555, the ADJ pin of the LM317 is grounded and its output voltage is 1.3V. The 15V Zener diode is used to set the LM317 to supply 16.2V at output in the absence of load. LM317 acts as voltage regulator and current controlling device. The working of this circuit is explained below. It is a pulsed-charger type circuit which helps in increasing the life of batteries. NOTE: Also get an idea about how to build a battery charging level indicator circuit? 2.Automatic Battery Charger Circuit DiagramĪn Automatic Battery Charger Circuit for sealed lead acid batteries is mentioned in this project. Battery charger should have over voltage protection, short circuit protection and reversed polarity protection. The output voltage of the battery charger should be less than 1.5 times of the battery and the current of the charger should be 10% of the battery current. ![]() As a result Red LED indicates the full of charge. Now the base of the transistor gets the sufficient current to turn on so that the output current from LM317 voltage regulator is grounded through the transistor Q1. When the battery voltage rises to 13.5V, the current flow to the battery stops and zener diode gets the sufficient breakdown voltage and it allows the current through it. At this time zener diode D6 will not conduct because battery takes all the current for charging. If the battery voltage is below 12V, then the current from LM317 IC flows through the resistor R5 and diode D5 to the battery. Resistor R3 is used to protect the green LED from high voltages. In this circuit green LED is used for indicating the charge of the battery. Now base of BD139 NPN transistor gets the current through the zener so that the total current is grounded. When battery charges fully, the zener diode D6 which connected in reverse bias conducts. Here diode D5 is used to avoid the discharge of battery when main supply fails. Lm317 voltage regulator output is applied to the battery through the diode D5 and resistor R5. ![]() The output voltage of this voltage regulator is varied by varying the pot 10k which is connected to the adjust pin of LM317. 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. This unregulated DC voltage is now applied to the LM317 variable voltage regulator to provide regulated DC voltage. Thus the output of the capacitor unregulated Dc voltage. The pulsating DC voltage is applied to the 470uF capacitor to remove the AC ripples. This process is also called as rectification. Here diodes D1, D2 are used to convert low AC voltage to pulsating DC voltage. The output of the transformer is connected to the Diodes D1, D2. 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. ![]() This automatic battery charger circuit is mainly involves two sections – power supply section and load comparison section. Automatic 12v Battery Charger Circuit DiagramĪutomatic 12v Battery Charger Circuit Diagram Circuit Diagram of Automatic Battery Charger. ![]()
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