Compatible with older iPhone models like the 3GS, perfect for on-the-go charging

Ideal for DIY electronics enthusiasts looking to modify and customize their devices

Two 18650 batteries are wired in parallel, with each battery’s positive and negative terminals connected to two separate wires: Positive Terminal 1 connects to the positive terminal of the USB boost converter board, while Positive Terminal 2 connects to the positive terminal of the battery protection board.

Negative Terminal 1 connects to the negative terminal of the USB boost converter board, and Negative Terminal 2 connects to the negative terminal of the battery protection board.

Link to purchase the 5V boost board: https://e.tb.cn/h.SrQskD8GdxYRfyu?tk=NSHifiH25eh

Link to purchase the battery protection board: https://m.tb.cn/h.SJEyVLt?tk=9L7ofiH43Y9

You can source the 18650 batteries yourself—just choose your preferred type.

If you’re using a different model of battery protection board, feel free to send me a private message; I’ll provide you with an editable STEP file so you can modify it according to your needs.