5S 18.5V 21V 15A Li-ion Lithium Battery BMS Protection Board

5S 18.5V 21V 15A Li-ion Lithium Battery BMS Protection Board is a 5-series (5S 18.5V nominal / 21.0V full charge) Battery Management System (BMS) PCB engineered to protect and manage 5-cell 18650, 21700, and lithium-polymer battery packs. Delivering 15A continuous discharge current (up to 25A–30A instantaneous surge) with individual cell voltage monitoring (`B1`–`B4`), it safeguards 18V/20V Max cordless power tools, handheld vacuums, e-scooters, and solar storage packs from overcharging, deep discharging, overcurrent, and short circuits.

Key Features:

• 5-Series (18.5V / 21.0V) Individual Cell Protection: Monitors all five series cell groups (`5 × 3.7V = 18.5V` nominal, `5 × 4.2V = 21.0V` full charge) to block overcharging above 4.25V/cell and deep discharging below 2.70V/cell.
• 15A Continuous / 30A Peak Current Capacity: Low-$R_R_DS(on) MOSFET array handles 15A continuous load current (~300W) and up to 30A short-duration startup surges.
• Fast Short-Circuit & Overcurrent Cutoff: Immediately disconnects output terminals during external load short circuits or overcurrent spikes, recovering automatically once cleared.
• Direct High-Reliability Solder Pads: Features clearly labeled solder pads (`B-`, `B1`, `B2`, `B3`, `B4`, `B+`, `P+`, `P-`) for permanent vibration-proof wiring inside power tool battery housings.
• Ultra-Low Standby Drain (≤30µA): Prevents self-discharge when 18V/21V battery packs sit stored in a toolbox for months.

Technical Specifications:

• Supported Battery Configuration: 5S (5 Series 3.7V Li-ion / 18650 / 21700 / LiPo Cells — 18.5V Nominal)
• Maximum Charging Voltage: 21.0V DC CC/CV (4.20V × 5)
• Continuous Discharge Current: 15A Max
• Instantaneous Peak Current: 25A to 30A
• Overcharge Detection Voltage: 4.25V ± 0.05V per cell (Release: 4.15V ± 0.05V)
• Over-Discharge Detection Voltage: 2.70V ± 0.10V per cell (Release: 3.00V ± 0.10V)
• Quiescent Current: ≤ 30 µA
• Operating Temperature Range: -40°C to +85°C

Mechanical Specifications:

• PCB Material: FR-4 Double-Sided High-Copper Fiberglass PCB
• Terminals: Direct Tinned Solder Pads (`B-`, `B1`, `B2`, `B3`, `B4`, `B+`, `P+`, `P-`)

Dimensions:

• Length: ~55 mm to 60 mm
• Width: ~40 mm to 45 mm
• Thickness: ~3.5 mm
• Weight: ~12 g

Pinout and Wiring:

• B- (0V): Connect to Cell 1 Negative terminal (Pack Negative).
• B1 (3.7V): Connect between Cell 1 Positive and Cell 2 Negative.
• B2 (7.4V): Connect between Cell 2 Positive and Cell 3 Negative.
• B3 (11.1V): Connect between Cell 3 Positive and Cell 4 Negative.
• B4 (14.8V): Connect between Cell 4 Positive and Cell 5 Negative.
• B+ (18.5V/21V): Connect to Cell 5 Positive terminal (Pack Positive).
• P+ & P-: Connect to 18V/21V load and 21.0V CC/CV charger.

Datasheet Reference:

• Protection Architecture: 5S Li-Ion Hardware Protection IC + Parallel Low-$R_R_DS(on) Power MOSFET Stage

Commonly Used in:

• 18V / 20V Max / 21V Cordless Drill, Impact Wrench, and Saw Battery Packs
• 18.5V Cordless Stick Vacuum Cleaners and Garden Trimmers
• 5S 18650 Portable Power Banks & Laptop DC Supplies
• Robotics & Electric Skateboards

Applications:

• Replaces failed BMS boards inside 18V/21V cordless drill and impact driver 5-cell/10-cell (`5S1P` / `5S2P`) 18650 packs.
• Protects custom 18.5V lithium battery packs powering 19V–20V laptops or mini PCs directly without DC-DC conversion loss.
• Pairs with a `5S 18.5V Li-ion Balancer Board` (`PID 3361`) to maintain cell balance across hundreds of charge cycles.

Equivalent Models:

• 5S 18.5V 21V 15A 18650 Lithium Battery BMS Protection Board with Cable: 5S 15A BMS variant supplied with a detachable plug-in balance wire harness (`PID 29823`).
• 6S 12A BMS Board 18650 Lithium Battery Protection: 6-cell (22.2V/25.2V) 12A BMS module.

Package Includes:

• 1 × 5S 18.5V 21V 15A Li-ion Lithium Battery BMS Protection Board