The BMS 4S 20A is a lithium-ion battery protection board designed for 4S battery packs, with a 14.8V nominal voltage and 16.8V full-charge voltage. It is suitable for cordless drills and power tools, providing protection against overcharge, over-discharge, overcurrent and short circuit.

Full Description

The BMS 4S 16.8V 20A Lithium Battery Protection Board is designed to protect and manage 4-series Li-Ion battery packs used in cordless drills and other portable power tools.

A typical 4S Li-Ion battery pack has a 14.8V nominal voltage and reaches 16.8V when fully charged. The BMS monitors the individual cell groups and provides essential protection against overcharging, over-discharging, excessive current and short circuits.

This type of BMS is commonly used in 14.4V–16.8V drill battery packs, particularly packs built using 18650 lithium-ion cells.

There are several versions of 4S 20A BMS boards on the market. Some specify 20A continuous current, while others specify a lower continuous current with 20A as an instantaneous limit. The exact rating should therefore be matched to the actual board version.

Technical Specifications

Note: Physical dimensions and charging-current specifications vary between different 4S 20A BMS versions, so they should not be listed as fixed specifications without matching the exact board version.

Product Applications

• Cordless drill battery packs
• Power tools
• 4S 18650 battery packs
• Portable power equipment
• Repair and battery rebuilding projects
• DIY electronics
• 14.8V Li-Ion battery systems