Car battery charger with MC78T12

Car battery charger with MC78T12 circuit

It is a very simple circuit that can be used to charge car batteries. In this circuit there are facilities to control the charging current and voltage.

The circuit is based on The MC78T12ABT IC. IC is just a 7812 in TO-3 package capable of 3A. The transformer T1 steps down the mains voltage and the diodes D1 and D2 does the work of rectification. The capacitor C1 and C2 is the filter acts as a decoupling capacitor.

The ground terminal of IC1 is raised to 2.1V with the diodes D3, D4 and D5. So the output of IC1 is regulated 14.1V (12 2.1). The battery is recharged through diode D6 D6.The blocks the reverse flow of current from the battery to the load circuit when the voltage is not available. Metro M1 shows the load current and M2 shows the load voltage.

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24V/7AH Lead Acid Battery Charger Circuit

The circuit given here current lead acid battery charger famous variable voltage regulator IC LM 317. The charging current depends on of resistor R2 and here it's set to be 700mA. Resistor R3 and POT R4 determines the charging voltage. Transformer T1 steps down the mains voltage and bridge D1 of rectification. C1 filter capacitor. Diode D1 prevents the reverse flow of current from the battery when charger is or when mains power .

Notes.

• Assemble the circuit on a good quality PCB.
• T1 can be a 230V primary, 35V/3A secondary step down transformer.
• If 3A Bridge is not available, make one using four 1N5003 diodes.
• LM317 must be fitted with a heat sink.
• R2 = 0.85 ohm is not a standard value. You can obtain it by combining a 6.2 ohm and 1 ohm resistors in parallel.
• F1 can be a 2A fuse.
• To setup the charging voltage, power ON the charger and hook up a voltmeter across the output terminals and adjust R4 to make the voltmeter read 28V. Now the charger is ready and you can connect the batteries.
• This charger is specifically designed for two 12V/7AH/6 cell lead acid batteries in series OR a 24V/7AH/12 cell lead acid battery.

READ MORE - 24V/7AH Lead Acid Battery Charger Circuit