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5S 18.5V/21V 15A 18650 Lithium-Ion Battery Charger with Protection Board – 5 Cells in Series

SKU: FA2193-13-2
Compatible Battery

5S 18.5V lithium-ion (18650 cells)
Full Charge Voltage

21V
Continuous Discharge Current

15A
Overcharge Protection Voltage

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

~2.5V – 3.0V per cell
Balance Function

Yes
Charging Support

Yes
Connection Type

Solder pads (spot welding supported)

The 5S 18.5V / 21V 15A 18650 Lithium-Ion Battery Charger with Protection Board is a high-performance BMS (Battery Management System) and charging module designed to protect and charge 5-cell (5S) lithium-ion battery packs — specifically those using 18650 cells. With a 15A continuous discharge rating and balance function, this board is engineered for moderate to high-drain applications including power tools, solar energy storage, LED lighting, and portable power systems where reliable battery safety and charging are essential.

At the heart of the board is a BMS 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 15A, protecting against short circuits and excessive loads.

The 5S configuration means the board manages five cells in series, balancing the voltage across all five 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 5S configuration provides a nominal voltage of 18.5V and a full charge voltage of 21V, making it suitable for a wide range of applications that require higher voltage than 4S packs. This voltage range is ideal for power tools, solar storage systems, and high-power LED lighting.

The 15A continuous rating makes this board suitable for moderate to high-drain applications such as power tools, solar storage, LED lighting, and portable power stations. This provides reliable performance for a wide range of 5S applications, filling the gap between standard 10A boards and higher-current 20A+ boards.

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-, BM1, BM2, BM3, BM4 (mid-points), 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 power tools, solar storage, and DIY projects.

Important Note: This BMS is designed for 5S (5-cell) 18.5V/21V lithium battery packs using 18650 cells, with a maximum continuous current of 15A. For higher-current applications, a BMS with a higher current rating 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 custom 5S 18650 battery pack for a power tool, assembling a solar storage system, or adding safety protection to an LED lighting project, the 5S 18.5V / 21V 15A 18650 Lithium-Ion Battery Charger with Protection Board provides a reliable solution. It is suitable for individual makers, students, and businesses purchasing in bulk for product development or educational programs.

Features

  • 5S five-cell protection — Manages five 18650 cells in series with cell balancing

  • 15A continuous discharge — Moderate to high-current capability for demanding applications

  • Balance function — Ensures even charge and discharge across all five cells

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

  • Charging support — Integrated charging circuit for 5S packs

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

  • Wide voltage range — 18.5V nominal / 21V full charge

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

Technical Specifications 

# Parameter Specification
1 Compatible Battery 5S 18.5V lithium-ion (18650 cells)
2 Full Charge Voltage 21V
3 Continuous Discharge Current 15A
4 Overcharge Protection Voltage ~4.25V – 4.3V per cell
5 Over-discharge Protection Voltage ~2.5V – 3.0V per cell
6 Balance Function Yes
7 Charging Support 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 (BM1, BM2, BM3, BM4) terminals of your 5S 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, BM1 to the first mid-point, BM2 to the second mid-point, BM3 to the third mid-point, and BM4 to the fourth mid-point.

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

  4. Connect the charger — Connect your 5S lithium battery charger to the appropriate charging input pads (if separate from the output).

  5. 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.

  6. 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 15A Disconnect output

Connection Points

Pad Function
B+ Battery pack positive terminal
B- Battery pack negative terminal
BM1 First mid-point between cells
BM2 Second mid-point between cells
BM3 Third mid-point between cells
BM4 Fourth mid-point between cells
P+ Protected output positive
P- Protected output negative

Typical Applications

  • Power tools — Moderate to high-current protection for drills, saws, and other tools

  • Solar energy storage — Protect 5S battery packs in solar storage systems

  • LED lighting — Reliable power for high-power LED lighting systems

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

  • E-bikes — High-power protection for electric bicycles

  • Educational projects — Teaching battery safety and protection principles

Notes for Business Buyers

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

  • Wide voltage range — 18.5V nominal / 21V full charge for higher-power applications.

  • Balance function included — Ensures even charge and discharge for longer pack life.

  • Charging support — Integrated charging circuit simplifies system design.

  • Suitable for bulk purchasing — Ideal for battery pack assemblers, power tool manufacturers, and solar integrators.

Q: What is the 5S 18.5V/21V 15A BMS used for?

It is a safety module that protects and charges 5-cell 18650 lithium battery packs from overcharge, over-discharge, and overcurrent conditions, with a balance function for even charging.

Q: What batteries are compatible with this BMS?

It is designed for 5S (5-cell) 18.5V lithium-ion battery packs using 18650 cells, with a full charge voltage of 21V.

Q: What is the continuous discharge current?

The BMS is rated for 15A continuous discharge. 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 15A.

Q: What is the balance function?

The balance function monitors each cell during charging and bleeds off excess charge from cells that reach full voltage before others, ensuring all cells reach the same voltage.

Q: What is the difference between B+/-, BM1/BM2/BM3/BM4, and P+/-?

B+ and B- connect to the pack positive and negative terminals. BM1 through BM4 connect to the mid-points between the five cells. P+ and P- provide the protected output to your load or charger.

Q: Can I spot weld this BMS 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 BMS with a 4S or 6S battery pack?

No. This BMS is specifically designed for 5S (5-cell) 18.5V/21V battery packs. For other configurations, a different protection board or BMS is required.

Q: Does the BMS protect against short circuits?

Yes. The BMS 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 BMS is suitable for both individual users and business purchasing, including battery pack assemblers, power tool manufacturers, and solar integrators.

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