DIY Easily Make a Universal Any Type of Battery Charge Controller At Home

If you’re into DIY electronics or renewable energy projects, you’ve probably faced the challenge of managing battery charging effectively. Building a universal battery charge controller at home is a cost-effective and rewarding solution. In this guide, we’ll show you how to construct your own battery charge controller using the ATmega328P IC and a few basic components. This controller works with multiple battery types, offering you flexibility and control.

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Why Build a Universal Battery Charge Controller?

1. Cost-Efficiency: Commercial charge controllers can be expensive. DIY options save money.
2. Customizable: Tailor the controller to your specific needs.
3. Learning Opportunity: A perfect project to enhance your electronics skills.

Components Required

To build this project, you’ll need the following components:

Component	Quantity	Purpose
ATmega328P Microcontroller	1	Brain of the controller.
16MHz Crystal Oscillator	1	Provides clock frequency for the microcontroller.
22pF Capacitors	2	Stabilizes the crystal oscillator circuit.
Voltage Divider Circuit	1	Measures input voltage through A0 pin.
Relay Module	1	Controls the charging process (connected to D12).
Resistors and Capacitors	Assorted	For voltage divider and additional filtering.
Power Supply	1	To power the circuit and charge the battery.
Breadboard or PCB	1	For circuit assembly.

How It Works

The ATmega328P microcontroller acts as the heart of this charge controller. It monitors the battery’s voltage using a voltage divider circuit connected to the A0 pin and controls charging using a relay connected to the D12 pin. Here's the step-by-step breakdown:

1. Voltage Monitoring:

   • The voltage divider scales down the battery’s voltage to a level readable by the ATmega328P (0-5V range).
   • The microcontroller reads this value through the A0 analog input.

2. Relay Control:

   • When the battery voltage is below a predefined threshold, the relay (connected to D12) activates, starting the charging process.
   • Once the battery reaches the desired voltage, the relay is turned off, stopping the charge to prevent overcharging.

3. Clock Stabilization:

• The 16MHz crystal oscillator ensures accurate timing for the ATmega328P’s operations, stabilized by the 22pF capacitors.

Circuit Explain:

Main Sections of the Circuit

1. Power Supply Regulation:

   • DC Input (DC1): The circuit is powered by an external DC source. The input voltage is regulated to a stable 5V for the ATmega328P and other components using the 7805 voltage regulator (U2).
   • Components for Regulation:
     • R1, R2: These resistors may be part of a voltage divider or used for a pull-down function.
     • C3, C2 (100pF): Capacitors for noise filtering and stability in the power supply.
     • X2 (12MHz Crystal Oscillator): Provides a clock signal for the ATmega328P, stabilized by the capacitors.

2. Microcontroller Unit (ATmega328P):

   • Microcontroller (U1): The ATmega328P is the core of this circuit, controlling the relay and monitoring inputs.
   • The clock signal for the microcontroller is provided by the 12MHz crystal oscillator (X2) with the 100pF capacitors acting as stabilizers.
   • Power supply pins for the microcontroller are connected to the regulated 5V output from the 7805.

3. Relay Control:

   • Relay Module (LOAD1): A single-channel relay is connected to the load. The relay allows the microcontroller to switch high-power devices on and off.
   • Q2 (BC547): A general-purpose NPN transistor is used to drive the relay. The base of the transistor is connected to the microcontroller's output pin via a current-limiting resistor (R10 = 1kΩ). The transistor acts as a switch, controlling the relay coil.
   • D2 (1N4007 Diode): This flyback diode protects the circuit from voltage spikes generated when the relay coil is de-energized.
   • R3 (10kΩ): This pull-down resistor ensures the transistor stays off when no signal is applied.

4. Relay Activation Control:

• The ATmega328P controls the relay via one of its digital output pins (likely D12 or equivalent based on the connected pin in your code).
• When the microcontroller sends a HIGH signal, the transistor (Q2) switches on, energizing the relay coil and allowing current to flow to the connected load.

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Key Functionalities

1. Relay Operation:

   • The microcontroller monitors an input (like voltage or user command) and activates the relay based on programmed conditions.
   • For instance, if the input voltage (measured via a voltage divider circuit on an analog pin) is below or above certain thresholds, the microcontroller will toggle the relay.

2. Voltage Regulation:

   • The 7805 voltage regulator ensures a stable 5V supply for sensitive components like the microcontroller and logic circuits.

3. Relay Protection:

   • The 1N4007 diode prevents back EMF from damaging the transistor or microcontroller.

Step-by-Step Instructions

1. Setting Up the Circuit

• ATmega328P Microcontroller:

  • Connect the 16MHz crystal oscillator to the microcontroller’s clock pins (XTAL1 and XTAL2).
  • Add 22pF capacitors to stabilize the crystal and connect them to ground.

• Voltage Divider:

  • Use resistors in series to step down the battery voltage to a range between 0-5V.
  • Connect the divided voltage output to the A0 pin.

• Relay Control:

  • Connect the relay module’s input pin to D12 of the microcontroller. Ensure proper connection for power and ground.

2. Writing the Code

Here’s a simple Arduino-based code for the charge controller:

const int relayPin = 12;  // Pin controlling the relay
const int voltagePin = A0; // Pin for reading battery voltage

float voltage = 0.0;

void setup() {
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, LOW); // Ensure relay is off initially
  Serial.begin(9600);
}

void loop() {
  int analogValue = analogRead(voltagePin);
  
  // Convert the analog value to voltage
  voltage = (analogValue * 5.0) / 1023; 
  voltage = voltage * (dividerRatio); // Adjust for your divider's ratio
  
  Serial.println(voltage);

  // Define charging thresholds
  if (voltage < 11.5) { 
    digitalWrite(relayPin, HIGH); // Start charging
  } else if (voltage >= 13.8) { 
    digitalWrite(relayPin, LOW); // Stop charging
  }

  delay(1000); // Wait for a second before next reading
}

Replace dividerRatio with the ratio of your voltage divider.

3. Testing the Controller

1. Connect the circuit to a power supply and test with a dummy load.
2. Monitor the voltage readings using a multimeter.
3. Adjust the thresholds in the code as per your battery type.

Tips for Success

• Ensure proper heat dissipation for the relay if handling high currents.
• Use fuses or protection circuits to safeguard against overcurrent or short circuits.
• Test the circuit on a breadboard before soldering onto a PCB.

Applications

• Solar charging systems.
• Portable battery pack projects.
• DIY power banks or UPS systems.

Video Reference

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Every electronic device needs PCBs. Are you looking for the Best PCB order? PCBWay is one the best PCB manufacturing companies. Order 10 pcs PCB for only $5. Visit now https://www.pcbway.com/?from=technology4power

💡 PCBWay 7th Project Design Contest: https://www.pcbway.com/activity/7th-project-design-contest.html

Conclusion

Building a universal battery charge controller using the ATmega328P is not only a great DIY project but also a practical tool for managing batteries effectively. With just a handful of components and some programming, you can create a versatile device suitable for multiple applications. Start today, and take your DIY skills to the next level!

Let us know your thoughts or questions in the comments. Don’t forget to share your results if you try this project!