Battery Charger
Build a simple 12V battery charger using a TIP120 transistor. Safely charges lead-acid batteries with automatic current regulation for protection.
TIP120 battery charger circuit
Battery Charger with TIP120 is a safe and simple to assemble circuit that has been developed to charge 12V lead-acid or lithium batteries. The TIP120 Darlington transistor is used as a series pass element to regulate the current flowing to the battery. The charging current can be regulated by moving the potentiometer in the circuit, so that charging will be safe and the battery will not be charged excessively. This charger is based on a basic voltage reference, a diode rectifier, and a filtering capacitor to convert AC into DC. The TIP120 has control of the output current and voltage, enabling it to be charged effectively. The circuit can be used in small batteries in cars, UPS systems, or for storing solar energy. The low number of components it uses makes it a good project for DIY electronics lovers and offers safety against cases of overcurrent.
automatic battery charging circuit
A TIP120-based battery charger is an automatic, regulated charger that charges batteries with 12V of safe and efficient battery charging.
Work / Installation (Inputs → Outputs)
- AC Adapter Input → Rectifier and filter convert AC to DC.
- TIP120 Transistor Stage → Controls current flow to the battery.
- Voltage & Current Adjustment → Potentiometer sets safe charging level.
- Battery Output → Receives regulated DC until fully charged.
Testing & Final Adjustments
Connect a 12V power supply and battery after assembling. Watch the output voltage and use the potentiometer to set it to the right charging current. Check the voltage on the battery with a multimeter. Check the TIP120 to see that it does not overheat, and add a heat sink when necessary. Test the charger by emptying and refilling the battery to make sure that it works each time. Make sure all the AC/DC connections are insulated. Lastly, ensure that the charger turns off/reduces the current when the battery is full. Adequate changes will save the battery and increase its lifespan.
Frequently Asked Questions - Battery Charger:
What is TIP120 used for in this circuit?
It acts as a series pass transistor to regulate charging current.
What battery voltage can it charge?
It is suitable for 12V lead-acid or lithium batteries.
Is current adjustment possible?
Yes, using a potentiometer in the circuit.
Does it prevent overcharging?
Yes, current regulation prevents overloading the battery.
What is the input voltage required?
Typically 15–18V DC from a rectified AC adapter.
Is a heat sink required?
Yes, for high current charging to prevent TIP120 overheating.
Can it charge automotive batteries?
Yes, it can charge car or motorcycle 12V batteries.
How many components are needed?
Only a few resistors, diodes, capacitors, and TIP120 transistor.
Is this circuit suitable for beginners?
Yes, it is simple and easy to build.
Can it work with solar panels?
Yes, as long as the input voltage is compatible.
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