Best Variable Power Supply and Battery Charger

I have come across various inquires where my beautiful facebook visitors are asking me for a powerful variable power supply / battery charger circuit for professional use. So here is a powerful yet very reliable circuit that can charge your Power Banks, Motorcycle batteries, Car batteries, Mobile batteries, General purpose batteries; and, it can also power up your all types of gadgets and projects. It is very accurate and can be used by professionals.

I am using multi-turn potentiometers in this circuit as they are more accurate, however you can replace them with low cost ordinary potentiometers with same values though. But, I recommend multi-turn potentiometers.

I am using a powerful 12-0-12Volt 10Ampere transformer (from Guru Company) for this variable power supply. I am using both the 12V AC outputs of the transformer to attain 24 Volts AC and once this voltage passed through a 15AMP full wave rectifier and filtered using 4700uf capacitor the peak voltage value reaches around 30Volts DC.

Best Variable Power Supply and Battery Charger

Section 1 (Controlling the Voltage)

This 30Volts DC is fed to (Section 1) and into LM317 regulator IC and a multi-turn variable 5K trimpot that is fixed between Adj pin and the Ground controls the voltage between 1.5V – 30V. LM317 works only when a feedback resistor (in this 220ohm) resistor is connected between the Vout and Vadj pin. At the Vout I have fixed a small 0.1uf 63V capacitor for all the small filtrations (remember it has to be a 63V capacitor).  At this stage you can use this output voltage from section of 1.5V to 30V but at a 1.5Amps (max) only and that too with a heat sink on LM317. However, the scope of this project is much bigger.

Section 2 (Controlling the Current)

The output from the Section 1 is now fed to Section 2. The regulated voltage output from the Vout of LM317 is now fed to the collector of the BD139 transistor. Now to control the current we need to affix a 10K multi-turn potentiometer (trimpot) between the collector and the emitter and the central pivot (pin 2) to the base of the transistor. That is it, this Section 2 will now be able to control the output current of the circuit – the max current still can be drawn upto 1.5 amps only. So we still need something to make it work for 10AMPs.

Section 3 (Completing the Variable Power Supply)

Now we need something that can handle and power a load of upto 10 Amps at 30 volt max. So I have used two power transistors 2N3055 in parallel. The variable current and the variable voltage output from Section 2 is fed to the base of these transistors. The collectors of these transistors will get the 10AMP 30Volt supply directly from the bridge. Each emitter of the 2N3055 is capable of delivering 5Amps. The output from the emitters of 2N3055 is connected to the load through 1ohm 5Watt Wire Wound shunt resistors (on each emitter). Please note, I have used a heat sink to keep these transistors cool. J

If you wish to recharge your batteries or mobile phones then please ensure to add a diode at the output to prevent any reverse current damage to the circuit. This circuit can easily charge Motorcycle batteries, Car batteries, Mobile batteries, Power Banks… and it can also power up your all types of gadgets and projects.

It is very reliable and easy to assemble. I have tried to explain this in simple English so that you can understand the working of this circuit.

Hope you like my work.

Components Required

• Transformer 12-0-12 (10A)
• Resistor 220O
• Resistor (Shunt) 1O 5Watt x 2
• Capacitor 4700uf 50V
• Capacitor 0.1uf 63V
• 15 Ampere Rectifier
• Regulator IC 7805
• Regulator LM 317
• Trimpot 5KO (Multi-Turn)
• Trimpot 10KO (Multi-Turn)
• Transistors 2N3055 x 2
• Transistor BD139 x 1
• Digital Volt / Amp Meter EC-1581
• Fuse

PRICE: Rs. 750/-

Pictures of Some of the Major Components of Power Supply: