3S Li-ion Battery Protection Board (Code 21) — Product Introduction

Overview

This protection board uses the PWCHIP PW7126 protection IC together with two PW4406A MOSFETs to deliver complete overcharge, over-discharge, overcurrent, and short-circuit protection for 3S lithium-ion battery packs (11.1 V nominal, 12.6 V fully charged). The continuous discharge current is 3 A, and the overcurrent protection threshold is approximately 4 A. The integrated PW4053A asynchronous boost charger supports 5 V / 3 A USB input and provides up to 1 A charge current to the battery.

Specifications

Parameter	Specification
Battery Type	3S (3-series Li-ion, 11.1 V nominal, 12.6 V fully charged)
Continuous Discharge Current	3 A
Overcurrent Protection Threshold	Approx. 4 A
Protection IC	PW7126
MOSFETs	PW4406A × 2
MOSFET Package	SOP-8
Charging Input	USB 5 V / 3 A
Charging IC	PW4053A
Charging Topology	Asynchronous boost charging
Battery-Side Charging Current	1 A

Key ICs

PW7126 is a dedicated 3-cell lithium-ion protection IC integrating overcharge, over-discharge, overcurrent, and short-circuit protection. It supports high-precision voltage detection.

PW4053A is an asynchronous switching boost charger with conversion efficiency up to 90 %. It is suitable for 5 V USB input boosted to 12.6 V at 0.5 A–1 A. The IC integrates input OVP, disabling charging when the input exceeds 6 V, and withstands input voltages up to 30 V.

Key Features

· Single-board protection and charging solution for 3S battery packs

· PW4053A boost charger: 5 V USB input boosted to 12.6 V

· 1 A charge current, higher than the PW4053A-N variant

· Integrated 6 V OVP shutdown and 30 V input withstand

· PW7126 protection IC plus two PW4406A MOSFETs for 4 A overcurrent protection

· Suitable for 3S USB-charged battery products that require higher charging current

Schematic

Code 21 Schematic

PCB Photo

Code 21 PCB Photo

Typical Applications

Bluetooth speakers, portable LED lights, electric toys, USB-charged 3S battery products, small power tools.

Wiring Notes

Connect the battery as indicated on the schematic. The charge/discharge terminals are P+ and P-.

Documentation & Technical Support

We provide chip samples, technical documentation, and circuit design support. For more information or to request materials, please contact us at support@pwchip.com or reach an authorized distributor at https://www.pwchip.com/page/180.html.