How to Use Lithium Ion Polymer Battery 3.7v 2000mAh: Examples, Pinouts, and Specs

The Lithium Ion Polymer Battery 3.7V 2000mAh (Manufacturer Part ID: 2011) by Adafruit is a rechargeable battery designed for use in portable electronic devices. It provides a nominal voltage of 3.7V and a capacity of 2000mAh, making it ideal for applications requiring lightweight, high-energy-density power sources. This battery is commonly used in projects involving wearables, IoT devices, robotics, and other portable electronics.

• Wearable devices (e.g., fitness trackers, smartwatches)
• Internet of Things (IoT) devices
• Portable audio systems
• Robotics and small drones
• DIY electronics projects

The battery is equipped with a JST-PH 2-pin connector. Below is the pin configuration:

1. Connecting the Battery:

   • Use the JST-PH 2-pin connector to connect the battery to your circuit or charging module.
   • Ensure the polarity matches the circuit's requirements (red wire for positive, black wire for ground).

2. Charging the Battery:

   • Use a dedicated Lithium-Ion Polymer battery charger (e.g., Adafruit Micro Lipo Charger).
   • Set the charging voltage to 4.2V and the charging current to 0.5C (1A) for optimal performance.
   • Avoid overcharging or discharging below 3.0V to prevent damage.

3. Powering a Circuit:

   • Ensure the circuit's current draw does not exceed the battery's maximum discharge rate (4A).
   • Use a voltage regulator if your circuit requires a voltage lower than 3.7V.

• Safety: Lithium-Ion Polymer batteries are sensitive to overcharging, over-discharging, and short circuits. Always use a protection circuit or battery management system (BMS).
• Storage: Store the battery in a cool, dry place at ~50% charge to prolong its lifespan.
• Handling: Avoid puncturing or exposing the battery to high temperatures.

To power an Arduino UNO with this battery, you can connect it to a voltage regulator module (e.g., a 5V boost converter) to step up the voltage to 5V. Below is an example of Arduino code to monitor the battery voltage using an analog pin:

// Example code to monitor battery voltage using Arduino UNO
const int batteryPin = A0; // Analog pin connected to battery voltage divider
const float voltageDividerRatio = 2.0; // Adjust based on your resistor values
const float referenceVoltage = 5.0; // Arduino UNO's reference voltage

void setup() {
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  int rawValue = analogRead(batteryPin); // Read analog value
  float batteryVoltage = (rawValue / 1023.0) * referenceVoltage * voltageDividerRatio;

  // Print the battery voltage to the Serial Monitor
  Serial.print("Battery Voltage: ");
  Serial.print(batteryVoltage);
  Serial.println(" V");

  delay(1000); // Wait for 1 second before the next reading
}

Note: Use a voltage divider circuit to scale down the battery voltage to a safe range for the Arduino's analog input (0-5V).

1. Battery Not Charging:

   • Cause: Charger not set to the correct voltage or current.
   • Solution: Verify the charger is configured for 4.2V and 0.5C (1A).

2. Battery Drains Quickly:

   • Cause: Excessive current draw or aging battery.
   • Solution: Ensure the circuit's current draw is within the battery's discharge limits. Replace the battery if it has degraded.

3. Battery Overheats:

   • Cause: Overcharging, short circuit, or excessive discharge rate.
   • Solution: Use a protection circuit and ensure proper handling.

4. Arduino Reads Incorrect Voltage:

   • Cause: Incorrect voltage divider ratio or reference voltage.
   • Solution: Double-check the resistor values in the voltage divider and the Arduino's reference voltage.

• Q: Can I use this battery without a protection circuit?
  A: It is not recommended. Always use a protection circuit to prevent overcharging, over-discharging, and short circuits.

• Q: How long will the battery last on a single charge?
  A: Battery life depends on the load current. For example, at a 500mA load, the battery will last approximately 4 hours (2000mAh ÷ 500mA).

• Q: Can I connect multiple batteries in series or parallel?
  A: Yes, but ensure proper balancing and use a battery management system (BMS) to avoid damage.

• Q: What is the shelf life of this battery?
  A: When stored properly (cool, dry place, ~50% charge), the battery can last several years.