How to Use Adafruit BQ24074 Solar-DC-USB Lipo Charger: Examples, Pinouts, and Specs

The Adafruit BQ24074 Solar-DC-USB Lipo Charger is a versatile charging module designed for lithium polymer (LiPo) batteries. It supports charging via solar panels, DC power sources, or USB connections, making it ideal for portable and renewable energy projects. This module features built-in battery management, overcharge protection, and status indicators, ensuring safe and efficient power management.

• Solar-powered IoT devices
• Portable battery-powered projects
• Wearable electronics
• Backup power systems
• Renewable energy experiments

Below are the key technical details of the Adafruit BQ24074 Solar-DC-USB Lipo Charger:

The Adafruit BQ24074 module has the following pinout:

1. Connect the Power Source:

   • Attach a 6V solar panel, USB power source, or DC power supply to the VIN pin.
   • Ensure the input voltage is within the range of 4.4V to 6.2V.

2. Connect the Battery:

   • Attach a single-cell LiPo battery to the BAT pin.
   • Ensure the battery is compatible with a 4.2V charging voltage.

3. Connect the Load:

   • Connect your circuit or device to the LOAD pin.
   • The module will regulate the output voltage to power your device.

4. Monitor Status Indicators:

   • Use the CHG and DONE pins or onboard LEDs to monitor the charging status.
   • The PG pin can be used to check if the input power is good.

5. Optional Configuration:

   • Adjust the input current limit by changing the resistor on the module (refer to the datasheet for details).
   • Use the EN pin to enable or disable the LOAD output as needed.

• Solar Panel Selection: Use a 6V solar panel with a power rating between 1W and 2W for optimal performance.
• Heat Dissipation: Ensure proper ventilation or heat sinking if the module operates at high currents.
• Battery Safety: Only use single-cell LiPo batteries with built-in protection circuits to prevent over-discharge.
• Input Voltage: Avoid exceeding the maximum input voltage of 6.2V to prevent damage to the module.
• Load Current: Ensure the load current does not exceed the module's maximum output capability.

The Adafruit BQ24074 can be used to power an Arduino UNO via the LOAD pin. Below is an example of how to monitor the charging status using the Arduino:

// Pin definitions for the BQ24074 status outputs
const int CHG_PIN = 2;  // CHG pin connected to Arduino digital pin 2
const int DONE_PIN = 3; // DONE pin connected to Arduino digital pin 3

void setup() {
  pinMode(CHG_PIN, INPUT);  // Set CHG pin as input
  pinMode(DONE_PIN, INPUT); // Set DONE pin as input
  Serial.begin(9600);       // Initialize serial communication
}

void loop() {
  int chargingStatus = digitalRead(CHG_PIN); // Read CHG pin status
  int doneStatus = digitalRead(DONE_PIN);   // Read DONE pin status

  if (chargingStatus == LOW) {
    Serial.println("Battery is charging...");
  } else if (doneStatus == LOW) {
    Serial.println("Battery charging is complete.");
  } else {
    Serial.println("No charging activity detected.");
  }

  delay(1000); // Wait for 1 second before checking again
}

1. Module Overheating:

   • Cause: High input current or insufficient ventilation.
   • Solution: Reduce the input current limit or improve airflow around the module.

2. Battery Not Charging:

   • Cause: Incorrect battery connection or incompatible battery.
   • Solution: Verify the battery polarity and ensure it is a single-cell LiPo battery.

3. No Output on LOAD Pin:

   • Cause: EN pin is pulled low or no input power.
   • Solution: Check the EN pin state and ensure a valid power source is connected.

4. Status LEDs Not Working:

   • Cause: Faulty connections or damaged module.
   • Solution: Inspect solder joints and verify connections. Replace the module if necessary.

• Can I use a higher voltage solar panel?
  No, the input voltage must not exceed 6.2V to avoid damaging the module.

• What happens if the battery is fully charged?
  The module will stop charging and the DONE LED will light up, indicating the battery is full.

• Can I power my circuit without a battery connected?
  Yes, the module can power your circuit directly from the input source via the LOAD pin.

• How do I adjust the charging current?
  The charging current can be adjusted by changing the onboard resistor. Refer to the datasheet for resistor values and corresponding current limits.