4S 20A 14.4V / 14.8V BMS Protection Board for 18650 Lithium Battery

Is a 4S BMS protection board designed for packs of 4 lithium batteries connected in series, such as compatible 18650 Li-ion cells or LiPo packs.

For 18650 Li-ion batteries, a 4S pack has an approximate nominal voltage of 14.8V and a full charge voltage of 16.8V. For LiPo packs, the listed nominal voltage is 14.4V. This board helps protect the battery pack against unsafe operating conditions, improving safety and battery life.

The module provides protection against overcharge, overdischarge, overcurrent and short circuit, making it suitable for electronics projects, backup power supplies, LED lighting, small compatible inverters, power modules and other low-consumption compatible devices.

The listed maximum working current is 10A, with a maximum peak current of 20A. For discharges above 3A, the batteries used must have a suitable discharge rating. The supplier indicates cells with at least 3C discharge capability. For example, a 2000mAh battery rated at 3C can supply up to approximately 6A.

Wiring must strictly follow the battery pack points: B- / 0V, B1 / 3.7V, B2 / 7.4V, B3 / 11.1V and B+ / 14.8V. After the initial wiring, an initial charge may be required to activate the board voltage output.

Main features

BMS protection board
Battery configuration: 4S
Battery type: lithium / 18650 Li-ion / compatible LiPo
Number of cells in series: 4 cells
Nominal voltage for 18650 Li-ion: 14.8V
Nominal voltage for LiPo: 14.4V
Full charge voltage: 16.8V
Maximum working current: 10A
Maximum peak current: 20A
Overcharge protection: yes
Overdischarge protection: yes
Overcurrent protection: yes
Short-circuit protection: yes
Overcharge voltage: 4.25V to 4.35V ±0.05V per cell
Overdischarge voltage: 2.3V to 3.0V ±0.05V per cell
Quiescent current: 6µA
Listed internal resistance: 45mΩ
Working temperature: -40°C to +50°C
Storage temperature: -40°C to +80°C
Approximate dimensions: 35 x 35 x 3.0mm
Connection points: B-, B1, B2, B3 and B+
Main application: 4S lithium battery pack protection
Suitable for electronics projects and low/medium-current battery packs

Recommended applications

4S 18650 Li-ion battery packs
Compatible 4S LiPo packs
Backup power supplies
Battery-powered LED lighting
Small compatible inverters
Portable power modules
Lithium battery electronics projects
Low-power backup systems
Low-consumption electronic equipment
Repair and assembly of compatible battery packs
DIY projects using 4S batteries

Important note

Before use, always confirm the battery chemistry, nominal voltage, maximum charge voltage, discharge current, cell C-rate, wiring diagram, polarity and compatibility with the equipment. This board is intended for 4S lithium battery packs, but it is not compatible with LiFePO4 batteries.

Do not use with electric drills, high-current motors above 4A, xenon lamps or electric vehicle battery packs, according to the supplier’s indication. The board’s maximum working current is 10A, although the listed peak current is 20A, so it should not be used with heavy startup loads or high continuous-current applications without technical validation.

Incorrect wiring of B-, B1, B2, B3 and B+ may damage the board, batteries or connected equipment. When working with lithium battery packs, always proceed carefully, avoid short circuits, use matched cells in good condition and ensure proper insulation.