How to Charge 3.7V LiPo Cells with USB Board
By Kunkune | Published: 2026-10-19
Category: How-to Guides
Learn how to safely charge a 3.7V lithium polymer cell using a Type-C USB charging protection board with 5V 2A boost converter. Step-by-step guide for hobbyists.
Quick Answer
To charge a 3.7V LiPo cell with a USB board, connect the battery's positive and negative wires to the B+ and B- pads on a Type-C Lithium Battery Charging Protection Board, then plug a 5V USB source into the board's Type-C port.
Why Use a Dedicated Charging Board?
A 3.7V lithium polymer cell lacks built-in overcharge, over-discharge, and short-circuit protection. A dedicated USB charging board integrates constant-current/constant-voltage (CC/CV) charging and protection circuits, preventing battery damage or fire risk. The Type-C Lithium Battery Charging Protection Board also includes a 5V boost converter, letting you power 5V devices from the same battery.
Choosing the Right Battery
Not all 3.7V LiPo cells are the same. The 250mAh 3.7V Lithium Polymer Li-Po Cell 602025 is a compact, low-capacity option for wearables or small IoT projects. For higher capacity needs, select a cell with a compatible current rating—the charging board's 2A boost output suits cells rated for at least 1C charge rate (e.g., 250mAh = 0.25A charge current).
Step-by-Step Charging Setup
- Identify the board terminals: Locate the B+ (battery positive) and B- (battery negative) pads on the Type-C charging board. Also identify the OUT+ and OUT- pads if you plan to use the boost converter output. Double-check polarity markings; reversing B+ and B- can damage the board or battery.
- Connect the LiPo cell: Solder the red wire of your 3.7V LiPo cell to B+ and the black wire to B-. Use a short, insulated wire and avoid solder bridges. For the 602025 cell, the wires are typically pre-tinned. Do not apply heat for more than 3 seconds per pad to avoid damaging the board's components.
- Connect a USB power source: Plug a standard USB-A or Type-C cable (5V, at least 1A) into the board's Type-C port. The board's red LED should light up to indicate power. If the LED does not light, check the cable and source; some cheap cables may not support data/power lines properly.
- Monitor the charging status: The board's blue LED will turn on during charging and turn off (or change color) when the cell reaches 4.2V. Charging a 250mAh cell from empty takes roughly 1.5 hours at 0.25A. Never leave a charging LiPo unattended; if the cell gets hot (over 60°C), disconnect immediately.
- Test the boost converter output: Once charged, you can power a 5V device by connecting its positive wire to OUT+ and negative to OUT- on the board. The boost converter provides up to 2A. Do not exceed 2A continuous load; the board may overheat or shut down.
Products Used in This Guide
- Type-C Lithium Battery Charging Protection Board USB 5V 2A Boost Converter + USB A: Type-C Lithium Battery Charging Protection Board USB 5V 2A Boost Converter This board handles charging and protection in one compact module, so you don't need separate charger and protection circuits.
Type-C Lithium Battery Charging Protection Board USB 5V 2A Boost Converter + USB A - 250mAh 3.7V Lithium Polymer Li-Po Cell 602025 Rechargeable: 250mAh 3.7V Lithium Polymer Li-Po Cell 602025 Rechargeable Its 250mAh capacity is ideal for low-power projects, and the 602025 form factor fits tight enclosures.
250mAh 3.7V Lithium Polymer Li-Po Cell 602025 Rechargeable
