Power Reactor Documentation
Complete guide to building a custom power reactor using homemade batteries and solar panels.
Project Overview
This documentation covers the construction of a 5 kWh power reactor using custom-built LiFePO4 batteries and high-efficiency solar panels. The system is designed for off-grid applications, emergency backup, and energy independence.
🔋 Battery System
Custom LiFePO4 battery bank
51.2V, 15 kWh capacity
☀️ Solar Array
2.4 kW solar panel system
6 × 400W panels
⚡ Power Output
5 kW continuous output
48V DC to 120V AC
💰 Estimated Cost
$3,200 - $4,500 total
DIY vs commercial savings: ~60%
Safety Warning
⚠️ HIGH VOLTAGE HAZARD
This project involves dangerous voltages and currents.
Only attempt if you have electrical experience, proper tools,
and personal protective equipment. Lithium batteries can catch
fire if mishandled.
Component List
Battery Components
- LiFePO4 Cells: 192 × 3.2V 100Ah cells (EVE, CATL, or CALB brands)
- BMS: 16S 200A Active Balance Battery Management System
- Bus Bars: ¼" copper bars for cell interconnection
- Battery Enclosure: Fire-resistant metal cabinet with ventilation
- Cell Holders: ABS plastic cell holders for 32 cells each
- Wiring: 2 AWG welding cable, lugs, heat shrink
- Fusing: Class T 250A fuse, disconnect switches
Solar Components
- Solar Panels: 6 × 400W monocrystalline panels
- Charge Controller: MPPT 100A 48V (Victron or comparable)
- Mounting Rails: Aluminum rails, clamps, grounding lugs
- Wiring: 10 AWG PV wire, MC4 connectors
- Combiner Box: 6-string with breakers and surge protection
Power Electronics
- Inverter: 48V to 120V AC, 5000W continuous (low-frequency preferred)
- DC Breakers: 125A DC circuit breakers for battery disconnect
- Shunt: 500A battery monitor shunt with display
- Grounding: Copper grounding rod, wire, and clamps
- Monitoring: Raspberry Pi with Victron Venus OS for remote monitoring
Assembly Steps
Phase 1: Battery Construction
1. Capacity test all LiFePO4 cells (3.0V-3.65V range)
2. Top balance cells to 3.65V using bench power supply
3. Arrange cells in 16 series groups of 12 parallel cells
4. Install cells in holders with compression fixture
5. Connect bus bars with proper torque (typically 5-8 Nm)
6. Install BMS sense wires and balance leads
7. Test each parallel group voltage (should be identical)
8. Install in fire-resistant enclosure with thermal sensors
9. Connect main positive/negative with Class T fuse
10. Initial charge at 0.2C (20A) while monitoring temperatures
Phase 2: Solar Array Installation
1. Install roof mounts or ground mount structure
2. Mount solar panels with aluminum rails and clamps
3. Wire panels in series (3 strings of 2 panels for 48V)
4. Install combiner box with DC breakers
5. Run 10 AWG PV wire to charge controller location
6. Ground all metal components to grounding rod
7. Install surge protection at combiner and charge controller
8. Connect to MPPT charge controller (battery side first!)
9. Verify open circuit voltage is within charge controller limits
10. Test array output at noon on clear day
Phase 3: System Integration
1. Connect battery to DC breaker then to charge controller
2. Connect charge controller to inverter input
3. Install shunt on battery negative for monitoring
4. Connect inverter AC output to transfer switch
5. Install monitoring system (Raspberry Pi + Venus OS)
6. Program charge controller for LiFePO4 settings:
- Absorption: 56.8V (3.55V per cell)
- Float: 54.4V (3.4V per cell)
- Temperature compensation: -3mV/°C/cell
7. Set inverter parameters for 48V input, 120V output
8. Test full system with gradual load increases
9. Calibration of battery monitor for accurate SOC
10. Final safety inspection and labeling
Wiring Diagrams
Battery Bank Wiring (16S12P)
Positive Bus Bar
│
├── Cell Group 1 (12P) → BMS Sense Wire 1
├── Cell Group 2 (12P) → BMS Sense Wire 2
├── ...
├── Cell Group 16 (12P) → BMS Sense Wire 16
│
└── Class T Fuse → Main Disconnect → Inverter/Charge Controller
Monitoring Setup
Use a Raspberry Pi 4 with Victron Venus OS for professional-grade monitoring:
- Hardware: Raspberry Pi 4, 32GB SD card, case, power supply
- Software: RDos OS
- Connectivity: USB to RS485 adapter for BMS communication
- Display: 7" touchscreen or access via web browser
- Remote Access: VPN or secured port forwarding
Maintenance Schedule
| Frequency | Task |
|---|---|
| Weekly | Check battery voltage, SOC, and temperatures |
| Monthly | Clean solar panels, check connections, verify grounding |
| Quarterly | Balance check (cell voltages), torque check on bus bars |
| Annually | Full system test, inverter self-test, BMS firmware update |
Troubleshooting
Problem: Battery not charging from solar
• Check PV voltage at charge controller input
• Verify battery voltage is within charge controller range
• Check all DC breakers and fuses
• Inspect MPPT settings for LiFePO4 profile
• Verify battery voltage is within charge controller range
• Check all DC breakers and fuses
• Inspect MPPT settings for LiFePO4 profile
Problem: Inverter shutting down under load
• Check battery voltage under load (should stay above 46V)
• Verify all connections are tight and not overheating
• Check inverter temperature and ventilation
• Test with reduced load to identify capacity issue
• Verify all connections are tight and not overheating
• Check inverter temperature and ventilation
• Test with reduced load to identify capacity issue
Problem: Cell voltage imbalance
• Check BMS balance current (should be active during charge)
• Top balance all cells individually if imbalance > 0.1V
• Verify BMS sense wire connections
• Consider lower charge voltage to reduce stress on high cells
• Top balance all cells individually if imbalance > 0.1V
• Verify BMS sense wire connections
• Consider lower charge voltage to reduce stress on high cells
Resources & References
- Battery University: LiFePO4 characteristics and charging
- Victron Community: Venus OS setup and configuration
- DIY Solar Forum: Real-world build examples and advice
- NFPA 855: Standard for stationary energy storage systems
- NEC Article 690: Solar photovoltaic systems code
Cost Breakdown
| Component | Cost |
|---|---|
| LiFePO4 Cells (192 × 100Ah) | $1,800 - $2,400 |
| BMS & Electrical | $300 - $500 |
| Solar Panels & Mounting | $600 - $900 |
| Charge Controller & Inverter | $800 - $1,200 |
| Total Estimated Cost | $3,500 - $5,000 |
| Savings vs Commercial Equivalent | $5,000 - $7,000 (≈60%) |
⚠️ Important Notice
This documentation is for educational purposes. Building your own power system carries significant risks including fire, explosion, and electrocution. Always consult local electrical codes, obtain necessary permits, and consider hiring a licensed electrician for final connections. The creator assumes no liability for injuries, damages, or code violations resulting from use of this information.