S2 Lithium Battery Protection Board 18650 - Balance - 20A | ATMOSFÆR ENGINEERING

Battery Management System (BMS) protection board for 2-cell lithium-ion battery packs (7.4V nominal, 8.4V max). Provides overcharge, over-discharge, overcurrent, and short circuit protection for safe charging and discharging. Suitable for 18650, 26650, and polymer lithium cells. Ideal for DIY power banks, electric tools, e-bike batteries, and portable power systems.

Technical Specifications:

• Configuration: 2S (2 cells in series)
• Battery Type: Li-ion/Li-Po (3.7V nominal, 4.2V full charge per cell)
• Charging Voltage: 8.4V - 9.0V DC (2S: 7.4V nominal, 8.4V fully charged)
• Continuous Discharge Current: 20A (reduce if cooling is inadequate)
• Peak Discharge Current: 25A (brief periods)
• Continuous Charge Current: 10A max
• Overcharge Protection: 4.25V ± 0.025V per cell
• Over-discharge Protection: 2.5V ± 0.1V per cell (typical)
• Overcurrent Protection: ~25A
• Short Circuit Protection: Yes
• Battery Cell Compatibility: 18650, 26650, polymer Li-ion/Li-Po (any size)
• Dimensions: 45mm x 15mm x 3.4mm (standard version)
• Operating Temperature: -20°C to +60°C (typical)
• PCB Material: FR4

Power Ratings:

• Suitable for resistive loads up to 168W (8.4V x 20A)
• Compatible with power tools up to 50W drawing ≤25A
• Ideal for cordless drills, electric screwdrivers, LED lighting

Pin Configuration:

• B+: Positive terminal of battery pack
• B-: Negative terminal of battery pack
• P+: Positive output/charge terminal
• P-: Negative output/charge terminal
• Balance Wires: Connection between cells for voltage monitoring

Protection Features:

• Overcharge protection (prevents cell voltage >4.2V)
• Over-discharge protection (prevents cell voltage <2.5V)
• Overcurrent protection (limits discharge current)
• Short circuit protection
• Cell balancing (balancing version only)

Applications:

• DIY 2S lithium battery packs (7.4V systems)
• Power banks and portable chargers
• Electric bicycles and scooters (7.4V systems)
• Cordless power tools (drills, drivers)
• RC vehicles and drones
• Portable lighting systems
• Emergency backup power supplies

Important Notes:

• Use appropriate 8.4V Li-ion charger (CC-CV, 8.4V cutoff)
• Ensure adequate cooling for high-current applications (>15A continuous)
• Match BMS current rating to application requirements
• Connect battery cells in series correctly (check polarity)
• Balancing version recommended for long-term battery health

Compatible with standard 18650, 26650, and polymer lithium cells. Requires 8.4V lithium battery charger (not included).