How to Use Adafruit USB DC Solar LiPo Charger: Examples, Pinouts, and Specs

The Adafruit USB DC Solar LiPo Charger is a compact and versatile charging module designed to charge lithium polymer (LiPo) batteries efficiently. It features dual input options: a USB port and a solar panel input, making it ideal for portable, renewable energy projects. The built-in charging circuitry ensures safe and efficient energy management, making it a popular choice for powering low-power electronics in off-grid or mobile applications.

• Solar-powered IoT devices
• Portable battery-powered projects
• Environmental monitoring systems
• Wearable electronics
• Educational and DIY renewable energy projects

The Adafruit USB DC Solar LiPo Charger is designed to provide reliable and efficient charging for LiPo batteries. Below are its key technical details:

1. Connect the Battery: Attach a single-cell LiPo battery to the BAT and GND pins. Ensure correct polarity to avoid damage.
2. Choose an Input Source:
   • For USB charging, connect a 5V USB power source to the USB port.
   • For solar charging, connect a solar panel (4.4V to 6V) to the DC IN pin.
3. Power External Devices: Connect your load (e.g., microcontroller, sensors) to the LOAD and GND pins. The charger will regulate power delivery to the load while charging the battery.
4. Monitor Charging Status: Use the STAT pin to monitor the charging state. You can connect an LED or microcontroller to this pin for visual or digital feedback.

• Solar Panel Selection: Use a solar panel with an open-circuit voltage (Voc) between 4.4V and 6V for optimal performance.
• Charging Current Adjustment: To change the charging current, solder a resistor to the PROG pad. Refer to the datasheet for resistor values corresponding to different currents.
• Heat Management: Avoid placing the charger in enclosed spaces without ventilation, as it may generate heat during operation.
• Battery Safety: Only use single-cell LiPo batteries with built-in protection circuits to prevent overcharging or over-discharging.

The Adafruit USB DC Solar LiPo Charger can power an Arduino UNO via its LOAD output. Below is an example of how to monitor the charging status using the STAT pin:

// Example code to monitor charging status using the STAT pin
const int statPin = 2; // Connect STAT pin to digital pin 2 on Arduino

void setup() {
  pinMode(statPin, INPUT); // Set STAT pin as input
  Serial.begin(9600);      // Initialize serial communication
}

void loop() {
  int chargingStatus = digitalRead(statPin); // Read the STAT pin state

  if (chargingStatus == LOW) {
    Serial.println("Battery is charging...");
  } else {
    Serial.println("Battery is fully charged or no charging source connected.");
  }

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

1. Battery Not Charging:

   • Ensure the battery is properly connected to the BAT and GND pins.
   • Verify that the input source (USB or solar) is providing sufficient voltage and current.
   • Check the PROG resistor value if the charging current needs adjustment.

2. Overheating:

   • Ensure adequate ventilation around the charger.
   • Reduce the charging current by adjusting the PROG resistor if necessary.

3. Load Not Powering:

   • Confirm that the load is connected to the LOAD and GND pins.
   • Check the battery voltage to ensure it is not depleted.

4. Solar Panel Not Working:

   • Verify that the solar panel's open-circuit voltage is within the 4.4V to 6V range.
   • Ensure the solar panel is receiving sufficient sunlight.

Q: Can I use this charger with a multi-cell LiPo battery?
A: No, this charger is designed for single-cell (3.7V nominal) LiPo batteries only.

Q: How do I increase the charging current?
A: Solder a resistor to the PROG pad. Refer to the datasheet for the appropriate resistor value for your desired current.

Q: Can I charge the battery and power a load simultaneously?
A: Yes, the charger supports simultaneous charging and load powering. However, ensure the input source can handle the combined current demand.

Q: What happens if the input voltage exceeds 6V?
A: Exceeding 6V may damage the charger. Always use input sources within the specified voltage range.