LiFePO4 Battery Protection Board (BMS/PCM) - 5S/12S High Voltage Li-Fe Protection
Professional Battery Management System (BMS) / Protection Circuit Module (PCM) specifically designed for high-voltage LiFePO4 (Lithium Iron Phosphate) battery packs. Available in two configurations: 5S (16V, 20A) and 12S (38.4V, 24A). Features comprehensive protection including overcharge, over-discharge, overcurrent, and short circuit protection. Perfect for DIY LiFePO4 battery packs, solar systems, electric vehicles, and high-power applications requiring reliable battery protection.
Key Features
- High Voltage Support: 5S (16V) and 12S (38.4V) configurations
- High Current Rating: 20A and 24A continuous current
- LiFePO4 Specific: Calibrated for Li-Fe voltage characteristics
- Comprehensive Protection: Overcharge, over-discharge, overcurrent, short circuit
- Cell Balancing: Built-in balancing function for multi-cell packs
- Quality Components: Reliable MOSFETs and protection ICs
- Low Self-Consumption: Minimal power drain
- Temperature Protection: Built-in thermal protection
Package Contents
- 1× LiFePO4 Protection Board (BMS/PCM) - configuration as selected
Available Configurations
| Configuration | Voltage | Current | Size (mm) | Best For |
|---|---|---|---|---|
| 5S 20A | 16V (5 cells) | 20A | 42 × 126 | E-bikes, power tools, 16V systems |
| 12S 24A | 38.4V (12 cells) | 24A | 63 × 126 | Solar systems, electric vehicles, 36V systems |
Technical Specifications
| Parameter | 5S 20A | 12S 24A |
|---|---|---|
| Nominal Voltage | 16V (5S) | 38.4V (12S) |
| Continuous Current | 20A | 24A |
| Overcharge Protection | 3.65V per cell | 3.65V per cell |
| Over-discharge Protection | 2.5V per cell | 2.5V per cell |
| Board Size | 42mm × 126mm | 63mm × 126mm |
| Balance Function | Yes | Yes |
| Weight | ~100g | ~100g |
Protection Features
| Protection Type | Function |
|---|---|
| Overcharge Protection | Disconnects when any cell exceeds 3.65V |
| Over-discharge Protection | Disconnects when any cell drops below 2.5V |
| Overcurrent Protection | Disconnects when current exceeds rated limit |
| Short Circuit Protection | Instantly disconnects on short circuit |
| Cell Balancing | Balances cells during charging |
| Temperature Protection | Protects against overheating |
Step-by-Step Installation Instructions
✅ Follow These Steps Carefully for Safe Installation
Step 1: Preparation & Safety
- CRITICAL: Ensure all power sources are disconnected
- Verify you have the correct BMS (5S for 16V or 12S for 38.4V)
- Count your battery cells to confirm configuration
- Prepare tools: soldering iron, solder, wire cutters, multimeter, heat shrink tubing
- Use appropriate wire gauge: 12-14 AWG for 20-24A applications
- Work in a well-ventilated area with proper lighting
- Wear safety glasses and work gloves
Step 2: Identify Connection Points
- Locate the following connection points on the BMS:
- B- (Battery Negative): Connect to negative terminal of battery pack
- B+ (Battery Positive): Connect to positive terminal of battery pack
- P- (Load/Charger Negative): Output negative terminal
- P+ (Load/Charger Positive): Output positive terminal
- Balance Wires:
- 5S: B-, B1, B2, B3, B4, B+
- 12S: B-, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, B11, B+
- Refer to the wiring diagram on the board or documentation
Step 3: Connect Balance Wires
- For 5S (16V):
- B- to negative terminal of cell 1
- B1 to connection between cell 1 and cell 2
- B2 to connection between cell 2 and cell 3
- B3 to connection between cell 3 and cell 4
- B4 to connection between cell 4 and cell 5
- B+ to positive terminal of cell 5
- For 12S (38.4V):
- B- to negative terminal of cell 1
- B1 through B11 to each connection point between cells
- B+ to positive terminal of cell 12
- Use 22-24 AWG wire for balance connections
- Label each wire before connecting
- Double-check sequence before soldering
Step 4: Connect Main Power Wires
- Battery Side:
- Connect B- to battery pack negative terminal using 12-14 AWG wire
- Connect B+ to battery pack positive terminal using 12-14 AWG wire
- Load/Charger Side:
- Connect P- to load/charger negative using 12-14 AWG wire
- Connect P+ to load/charger positive using 12-14 AWG wire
- Ensure all connections are solid and well-insulated
- Use crimped ring terminals for secure connections if possible
Step 5: Verify All Connections
- BEFORE applying power, verify:
- All balance wires are connected in correct sequence
- No reversed polarity on any connection
- All solder joints are solid and insulated
- No short circuits between adjacent wires
- Use multimeter to check voltage at each balance point
- Verify total pack voltage matches expected value
Step 6: Initial Testing
- Connect battery pack to BMS
- Measure voltage at P+ and P- terminals
- Should read full pack voltage (16V or 38.4V nominal)
- If no output voltage, BMS may be in protection mode
- Connect charger briefly to wake up BMS
- Test with low-current load first (1-2A)
- Monitor BMS temperature during initial use
- Verify protection functions work correctly
Step 7: Final Assembly & Insulation
- Apply heat shrink tubing to all exposed connections
- Secure BMS board inside battery pack enclosure
- Use foam padding to prevent BMS from touching cells
- Ensure adequate ventilation around BMS
- Route wires neatly to avoid pinching
- Label positive and negative output terminals clearly
- Perform final voltage and continuity checks
Important Installation Precautions
⚠️ CRITICAL SAFETY WARNINGS
Before Installation:
- ❌ NEVER use 5S BMS on 12S battery or vice versa
- ❌ Do NOT exceed rated current (20A or 24A)
- ❌ Do NOT reverse polarity - will destroy BMS instantly
- ❌ Do NOT skip balance wire connections
- ✅ Verify cell count matches BMS configuration
- ✅ Ensure all cells are balanced before installation
- ✅ Use proper wire gauge (12-14 AWG for main power)
Balance Wire Connection Tips:
- Work methodically from B- to B+
- Label each wire with cell number before connecting
- Use different colored wires if possible
- Keep balance wires away from high-current wires
- Double-check sequence - incorrect order will damage BMS
- Test each connection with multimeter before final assembly
Common Mistakes to Avoid:
- ❌ Connecting balance wires in wrong order
- ❌ Using wire gauge too small for current
- ❌ Forgetting to insulate solder joints
- ❌ Mounting BMS directly against battery cells
- ❌ Not testing before final assembly
- ❌ Exceeding current rating
Troubleshooting:
- No output voltage: BMS in protection mode, connect charger to reset
- BMS shuts off under load: Check current draw, verify wire gauge adequate
- Won't charge: Verify balance wires correct, check charger voltage
- BMS overheating: Current exceeds rating or poor ventilation
- Cells not balancing: Check balance wire connections
Common Applications
5S 16V 20A Applications:
- Electric bicycles (16V systems)
- Power tool battery packs
- Portable power stations
- DIY battery projects
- Small electric vehicles
12S 38.4V 24A Applications:
- Solar energy storage systems (36V nominal)
- Electric bicycles and scooters (36V systems)
- Golf carts and small EVs
- Marine and RV house batteries
- UPS and backup power systems
- High-power portable generators
Why Choose LiFePO4 BMS?
Essential Protection:
- Prevents overcharging - extends battery life significantly
- Prevents over-discharge - protects cells from permanent damage
- Balances cells during charging - ensures even wear
- Protects against short circuits and overcurrent
- Required for safe multi-cell LiFePO4 operation
Long-Term Benefits:
- Maximizes battery pack lifespan (2000+ cycles)
- Maintains cell balance for optimal performance
- Prevents costly battery replacement
- Provides peace of mind for high-value applications
Warranty & Support
We stand behind the quality of our BMS boards. If you experience any issues, please contact us for support. Always follow installation instructions carefully and verify all connections before applying power. Improper installation may void warranty.