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7.4V 2S 18650 lithium battery protection board

SKU: FA2193-05
Compatible Battery

2S 7.4V lithium-ion (18650 cells)
Full Charge Voltage

8.4V
Overcharge Protection Voltage

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

~2.5V – 3.0V per cell
Continuous Discharge Current

Variant dependent (typically 2A–8A)
Cell Balancing

Yes
Connection Type

Solder pads (spot welding supported)
Module Dimensions

Compact PCB for 18650 packs

The 7.4V 2S 18650 Lithium Battery Protection Board is a compact, essential safety module designed to protect 2-cell (2S) lithium-ion battery packs — specifically those using 18650 cells — from overcharge, over-discharge, and overcurrent conditions. It is specifically engineered for battery packs with a nominal voltage of 7.4V and a full charge voltage of 8.4V, making it an indispensable component for DIY battery packs, power banks, portable electronics, and RC vehicles.

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.

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 safe limits, 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 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.

The 18650 compatibility makes this board ideal for building custom battery packs using the most popular lithium-ion cell format. 18650 cells are widely available, reliable, and offer excellent energy density, making them the preferred choice for DIY power banks, portable speakers, and RC vehicles.

Important Note: This protection board is designed for 2S (2-cell) 7.4V lithium battery packs using 18650 cells. For other configurations, a different protection board or BMS should be used. Always verify the voltage and current ratings match your application before installation.

Whether you are building a custom 2S 18650 battery pack, assembling a portable power bank, or adding safety protection to an RC vehicle, the 7.4V 2S 18650 Lithium Battery Protection Board provides a reliable, cost-effective 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 18650 cells in series with cell balancing

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

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

  • 18650 compatibility — Designed for the most popular lithium-ion cell format

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

  • Compact PCB design — Sized for space-constrained battery packs

  • Simple connection — B+/B-/BM for battery, P+/P- for protected output

  • Wide application range — Power banks, RC vehicles, portable devices, DIY projects

Technical Specifications 

# Parameter Specification
1 Compatible Battery 2S 7.4V lithium-ion (18650 cells)
2 Full Charge Voltage 8.4V
3 Overcharge Protection Voltage ~4.25V – 4.3V per cell
4 Over-discharge Protection Voltage ~2.5V – 3.0V per cell
5 Continuous Discharge Current Variant dependent (typically 2A–8A)
6 Cell Balancing Yes
7 Connection Type Solder pads (spot welding supported)
8 Module Dimensions Compact PCB for 18650 packs

Usage

Getting Started

  1. Identify the battery pack terminals — Locate the positive (+), negative (-), and mid-point (BM) terminals of your 2S 18650 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.

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 Variant dependent 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

  • DIY power banks — Protect 2S 18650 packs in custom portable chargers

  • RC vehicles — Protect 2S batteries in remote-controlled models

  • Portable speakers — Protect batteries in audio devices

  • Solar garden lights — Protect 2S batteries in outdoor lighting

  • Portable electronics — Add safety protection to 2S battery devices

  • Educational projects — Teaching battery safety and protection principles

Notes for Business Buyers

  • 18650 optimized — Designed specifically for the most widely used lithium cell format.

  • Essential safety component — Protects 2S battery packs and devices from damage.

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

  • Suitable for bulk purchasing — Ideal for battery pack assemblers, RC hobby shops, and educational institutions.

Q: What is the 7.4V 2S 18650 Protection Board used for?

It is a safety module that protects 2-cell 18650 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 battery packs using 18650 cells, with a full charge voltage of 8.4V.

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.

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 18650 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: What is the maximum continuous discharge current?

The continuous discharge current depends on the specific variant, typically ranging from 2A to 8A. Check the product specification for your version.

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 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, RC hobby shops, and educational institutions.

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