🏕️ Michigan Off-Grid Cabin – DIY Solar + Battery Build

Here’s a full breakdown of an off-grid energy system we helped design and troubleshoot for a cabin in Michigan. What started as a solar generator with lead-acid batteries eventually turned into a full-blown LFP system with a Magnum inverter and MidNite Classic controller. This blog dives into the build.

🔋 Battery System

• Chemistry: Lithium Iron Phosphate (LFP)
• Configuration: 16S28P (16 series × 28 parallel)
• Nominal Voltage: 51.2V
• Capacity: 700Ah (28 × 25Ah cells)
• Total Energy: ~35.8 kWh (around 30 kWh usable)
• Cell Type: 25Ah LFP Prismatic – Buy here
• BMS: JK BMS with active balancing and Bluetooth monitoring - Buy here

⚡ Inverter / Charger

• Model: Magnum Energy MS4448PAE
• Voltage: 48VDC input → 120/240VAC output (split-phase)
• Continuous Output: 4,400W
• Features: Integrated charger, programmable charge profiles, generator support, compatible with ME-RC50 & ME-AGS

🔌 Charge Controller

• Model: MidNite Solar Classic 150 MPPT
• Max PV Input Voltage: 150VDC

🪵 Backup Generator

• Model: Kohler 12RESV
• Fuel: Propane (LPG)
• Output: 12 kW

☀️ Solar Array

• Modules: 12 × SolarWorld SW 280 Mono
• Total Size: 3.36 kW (12 × 280W)
• Likely Wiring: 3 strings of 4 in series (Vmp ≈ 126V, ideal for Classic 150)

🛠️ Real-World Challenges

This wasn’t just a textbook install. The system had legacy components (like a Magnum inverter and aging lead-acid setup) that made troubleshooting tricky. Some highlights:

• Initial system had no pre-charge circuit, potentially causing blown fuses and board damage
• The BMS wasn’t connecting properly
• Eventually got the JK BMS configured and balancing properly

Sometimes the hard part isn’t the build, it’s understanding what went wrong before you got there.

🔧 System Overview & Lessons Learned

This video dives into the quirks of this site and how I solved problems in the field. This is an ongoing project and likely needs an inverter replacement next!

Ready to build your own off-grid system? All the core components used in this project—from prismatic cells and BMS to compression kits and accessories—are available now at OGSolarStore.com.