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2S 7.4V 8.4V 20A lithium battery protection board BMS

SKU: FA2193-04-0
Compatible Battery

2S 7.4V lithium-ion / lithium-polymer
Full Charge Voltage

8.4V
Continuous Discharge Current

20A
Peak Discharge Current

Variant dependent (typically 30A–40A)
Overcharge Protection Voltage

~4.25V – 4.3V per cell
Over-discharge Protection Voltage

~2.5V – 3.0V per cell
Cell Balancing

Yes
Connection Type

Solder pads (spot welding supported)

The 2S 7.4V / 8.4V 20A Lithium Battery Protection Board BMS is a high-current safety module designed to protect 2-cell (2S) lithium-ion and lithium-polymer battery packs from overcharge, over-discharge, and overcurrent conditions. With a 20A continuous current rating, this board is engineered for high-drain applications where standard protection boards cannot handle the current requirements — from power tools and e-bikes to RC vehicles and energy storage systems.

At the heart of the board is a BMS (Battery Management System) protection circuit that continuously monitors the voltage of each cell and the total pack current, disconnecting the load or charger if any parameter exceeds safe limits. This protects both the battery pack and your connected devices from damage, extending battery lifespan and ensuring safe operation in demanding applications.

The board provides three critical protection functions:

  • Overcharge protection — Disconnects the charger when any cell voltage reaches approximately 4.25V to 4.3V, preventing damage from excessive charging.

  • Over-discharge protection — Disconnects the load when any cell voltage drops to approximately 2.5V to 3.0V, preventing deep discharge that can permanently damage the battery.

  • Overcurrent protection — Disconnects the output when current exceeds 20A, protecting against short circuits and excessive loads.

The 2S configuration means the board manages two cells in series, balancing the voltage across both cells to ensure they charge and discharge evenly. This cell balancing function is critical for maintaining pack health and maximizing lifespan. Without proper balancing, one cell can become overcharged or over-discharged, leading to premature failure or safety hazards.

The 20A continuous rating makes this board suitable for high-power applications such as power tools, e-bikes, electric scooters, RC vehicles, and energy storage systems. This is a significant step up from standard 2S boards that typically max out at 2A–5A, filling an important gap for high-current 2S applications.

The board features a solder pad design that supports both direct soldering and spot welding. The exposed pads allow you to solder wires directly to the board, while also being compatible with spot-welded nickel strips for professional battery pack assembly. The board includes B+, B-, BM (mid-point), P+, and P- pads for battery and output connections.

Important Note: This protection board is designed for 2S (2-cell) 7.4V/8.4V lithium battery packs. For other configurations, a different protection board or BMS should be used. Always verify the voltage and current ratings match your application before installation. Ensure all wiring and connections are rated for the maximum current your application will draw.

Whether you are building a high-current 2S battery pack, assembling an e-bike battery, or adding safety protection to a power tool, the 2S 7.4V / 8.4V 20A Lithium Battery Protection Board BMS provides a reliable, high-current solution. It is suitable for individual makers, students, and businesses purchasing in bulk for product development or educational programs.

Features

  • 2S dual-cell protection — Manages two cells in series with cell balancing

  • 20A continuous current — High-current capability for demanding applications

  • Comprehensive protection — Overcharge, over-discharge, and overcurrent protection

  • Cell balancing function — Ensures even charge and discharge across both cells

  • High-current MOS — Low resistance for efficient power delivery

  • Solder pad design — Supports both direct soldering and spot welding

  • Wide compatibility — Works with 18650, polymer, and prismatic lithium cells

  • Wide application range — Power tools, e-bikes, RC vehicles, energy storage

Technical Specifications

# Parameter Specification
1 Compatible Battery 2S 7.4V lithium-ion / lithium-polymer
2 Full Charge Voltage 8.4V
3 Continuous Discharge Current 20A
4 Peak Discharge Current Variant dependent (typically 30A–40A)
5 Overcharge Protection Voltage ~4.25V – 4.3V per cell
6 Over-discharge Protection Voltage ~2.5V – 3.0V per cell
7 Cell Balancing Yes
8 Connection Type Solder pads (spot welding supported)

Usage

Getting Started

  1. Identify the battery pack terminals — Locate the positive (+), negative (-), and mid-point (BM) terminals of your 2S battery pack.

  2. Connect the battery — Solder or spot weld the B+ pad to the pack positive terminal, B- pad to the pack negative terminal, and BM pad to the mid-point between the two cells.

  3. Connect the output — Solder your load or output wires to the P+ and P- pads on the protection board.

  4. Test the protection — Verify that the output voltage is present when the pack is within safe limits, and that the output disconnects when any cell voltage drops too low or rises too high.

  5. For high-current applications — Ensure all wiring and connections are rated for the maximum current your application will draw. Use appropriately sized wires and connectors.

Protection Thresholds (Typical)

Parameter Threshold Action
Overcharge ~4.25V – 4.3V per cell Disconnect charger
Over-discharge ~2.5V – 3.0V per cell Disconnect load
Overcurrent 20A Disconnect output

Connection Points

Pad Function
B+ Battery pack positive terminal
B- Battery pack negative terminal
BM Mid-point between cells
P+ Protected output positive
P- Protected output negative

Typical Applications

  • Power tools — High-current protection for drills, saws, and other tools

  • E-bikes — Protect 2S battery packs in electric bicycles

  • Electric scooters — Safe power for personal mobility devices

  • RC vehicles — High-current protection for remote-controlled models

  • Energy storage systems — Protect 2S battery packs in solar storage

  • Portable power stations — High-current protection for portable power

  • Educational projects — Teaching battery safety and protection principles

Notes for Business Buyers

  • High-current capability — 20A rating fills the gap between standard 2S boards and larger BMS systems.

  • Essential safety component — Protects batteries and devices from damage in high-drain applications.

  • Cell balancing included — Ensures even charge and discharge for longer pack life.

  • Suitable for bulk purchasing — Ideal for battery pack assemblers, e-bike manufacturers, and educational institutions.

Q: What is the 2S 20A Protection Board used for?

It is a high-current safety module that protects 2-cell lithium battery packs from overcharge, over-discharge, and overcurrent conditions, with cell balancing for even charge and discharge.

Q: What batteries are compatible with this board?

It is designed for 2S (2-cell) 7.4V lithium-ion and lithium-polymer battery packs with a full charge voltage of 8.4V.

Q: What is the continuous discharge current?

The board is rated for 20A continuous discharge (variant dependent). Ensure all wiring and connections are rated for your application’s current draw.

Q: What are the protection thresholds?

Overcharge protection activates at approximately 4.25V–4.3V per cell. Over-discharge protection activates at approximately 2.5V–3.0V per cell. Overcurrent protection activates at 20A.

Q: What is the difference between B+/-, BM, and P+/-?

B+ and B- connect to the pack positive and negative terminals. BM connects to the mid-point between the two cells. P+ and P- provide the protected output to your load or charger.

Q: Does this board balance the cells?

Yes. The board includes cell balancing to ensure both cells charge and discharge evenly, maximizing pack lifespan.

Q: Can I spot weld this board to the battery?

Yes. The board supports both direct soldering and spot welding. The exposed pads are compatible with spot-welded nickel strips.

Q: Can I use this board with a 1S or 3S battery pack?

No. This board is specifically designed for 2S (2-cell) 7.4V/8.4V battery packs. For other configurations, a different protection board or BMS is required.

Q: Does the board protect against short circuits?

Yes. The board includes overcurrent protection that disconnects the output if a short circuit or excessive current is detected.

Q: Can I purchase in bulk for a product development project?

Yes. This protection board is suitable for both individual users and business purchasing, including battery pack assemblers, e-bike manufacturers, and educational institutions.

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