How to Make a DIY Lithium Battery Charger Using a USB Cable

In this project, to build a simple DIY lithium battery charger using a USB cable charger is designed to safely charge a 3.7V lithium battery using a charging module. The project is beginner-friendly and requires only a few basic components.

Step 1: Understanding the Charging Module

The charging module is the core component of this project. It regulates voltage and current to safely charge the 3.7V lithium battery. The module typically features:

Micro USB Input: Connects to a USB power source.

Battery Terminals: For connecting the lithium battery.

LED Indicators: Indicate charging status (usually red for charging and green for fully charged).

Step 2: Preparing the USB Cable

Cut one end of a USB cable to expose the internal wires.

Identify the red (positive +) and black (negative -) wires, which provide power.

Strip the insulation off these wires to make proper connections.

Step 3: Connecting the Charging Module

Solder the red (+) wire from the USB cable to the IN+ terminal of the charging module.

Solder the black (-) wire from the USB cable to the IN- terminal of the charging module.

Step 4: Connecting the Lithium Battery

Insert the 3.7V lithium battery into the battery holder.

Connect the holder’s positive (+) terminal to the BAT+ pin on the charging module.

Connect the holder’s negative (-) terminal to the BAT- pin on the charging module.

Step 5: Securing the Setup

Mount all components onto a transparent acrylic sheet using double-sided tape or screws.

Arrange the wiring neatly to avoid short circuits and ensure safe operation.

Step 6: Testing the Charger

Plug the USB cable into a power source (such as a laptop or wall adapter).

Observe the LED indicators:

Red LED: Charging in progress.

Green LED: Battery is fully charged.

Check the voltage of the battery using a multimeter to verify proper charging.