The BMS 3S 20A Li-ion Protection Board is the central "brain" for any 3-cell lithium battery pack. At Electrapac, we recommend this module for anyone building 12V portable power solutions, as it ensures your expensive 18650 cells operate safely and last for hundreds of charge cycles.

Product Overview

This Battery Management System (BMS) is designed for a 3S (3-Series) configuration, providing a nominal voltage of 11.1V and a full-charge voltage of 12.6V. It acts as a sophisticated gatekeeper, monitoring each of the three cells individually to prevent the most common causes of battery failure: overcharging, over-discharging, and short circuits.

Key Features for Electrapac Customers

• Triple Cell Monitoring: The BMS checks the voltage of all three cells independently. If even one cell drops too low or climbs too high, the board cuts power to protect the entire pack.

• High Current Capability: With a 20A limit, this board can handle the high startup "surge" currents required by DC motors and power tools.

• Compact Footprint: Its slim design allows it to be tucked inside battery cases or 3D-printed enclosures alongside the 18650 cells.

• Automatic Recovery: Once a short circuit or over-current event is cleared, the BMS automatically restores power to the output terminals.

• MOSFET Efficiency: Uses low-resistance power MOSFETs to ensure minimal heat generation and maximum energy delivery to your project.

Wiring Guide (Step-by-Step)

To ensure your Electrapac battery pack is safe, follow this specific wiring sequence (0V to 12.6V):

1. B- (0V): Connect to the Negative terminal of the first battery.

2. B1 (4.2V): Connect to the junction between the 1st and 2nd battery.

3. B2 (8.4V): Connect to the junction between the 2nd and 3rd battery.

4. B+ (12.6V): Connect to the Positive terminal of the 3rd battery.

5. P+ / P-: These are your Input/Output terminals. Connect your charger and your load (motor/LED/circuit) here.

Note: Do not mix old and new batteries. For best results, use three cells of the same brand and capacity.

Primary Applications

• 12V Cordless Drill Repairs: Reviving old power tools by replacing Ni-Cd cells with high-performance 18650s.

• Portable Speakers: Powering 12V Bluetooth amplifier boards for DIY boomboxes.

• LED Strip Power: Providing a mobile 12V source for camping lights or photography rings.

• Robot Power Packs: Driving 12V geared motors in autonomous vehicles.

• Uninterruptible Power Supplies (UPS): Building small backup power systems for 12V routers or CCTV cameras.

Why Shop at Electrapac?

We source our 3S 20A BMS Boards with high-quality sensing ICs that provide precise voltage cut-offs to prevent battery swelling. At www.electrapac.com, we provide the safety tech that makes high-energy lithium projects accessible to everyone.