Maximize your solar efficiency with this Maximum Power Point Tracking (MPPT) charge controller. Unlike standard PWM controllers, this system uses a Synchronous Buck Converter topology to convert excess voltage into additional charging current, increasing efficiency by up to 30%.
An MPPT (Maximum Power Point Tracking) controller is a high-frequency DC-to-DC converter. It takes the DC input from the solar panels, changes it to high-frequency AC, and converts it back to a different DC voltage and current to exactly match the panels to the batteries.
The code implements the "Perturb and Observe" algorithm. It slightly changes the PWM duty cycle and observes the power output. If the power increases, it continues in that direction; if it decreases, it reverses.
The system uses a synchronous buck converter configuration. Precise wiring is critical for efficiency and safety.
| Peripheral | Device Pin | Arduino Pin | Notes |
|---|---|---|---|
| Solar Voltage | Out | Analog A0 | Scaled via 1/10 divider |
| Battery Voltage | Out | Analog A1 | Scaled via 1/5 divider |
| Charge Current | Out | Analog A2 | ACS712 (20A) |
| MOSFET PWM | IN/SD | Digital 9 | High-frequency PWM |
| LCD Display | SDA/SCL | A4 / A5 | I2C Display |
The MOSFETs and Inductor will get hot during high current charging. Use substantial heatsinks and consider adding a small 5V cooling fan triggered by a thermistor.
#define SOL_VOLT_PIN A0
#define BAT_VOLT_PIN A1
#define CUR_PIN A2
#define PWM_PIN 9
float sol_volt = 0, bat_volt = 0, current = 0, power = 0, old_power = 0;
int pwm_value = 0;
void setup() {
pinMode(PWM_PIN, OUTPUT);
TCCR1A = _BV(COM1A1) | _BV(WGM11);
TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS10);
ICR1 = 640; // 25kHz PWM
}
void loop() {
sol_volt = analogRead(SOL_VOLT_PIN) * (25.0 / 1023.0);
bat_volt = analogRead(BAT_VOLT_PIN) * (15.0 / 1023.0);
current = (analogRead(CUR_PIN) - 512) * (20.0 / 512.0);
power = sol_volt * current;
// MPPT Logic: Perturb & Observe
if (power > old_power) {
pwm_value++;
} else {
pwm_value--;
}
pwm_value = constrain(pwm_value, 0, 600);
OCR1A = pwm_value;
old_power = power;
delay(100);
}