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Description
Fortress Power eFlex MAX 5.4kWh 48V Lithium Iron Phosphate (LFP) BatteryThe eFlex MAX 5. 4 kWh is a high performance 48V lithium iron phosphate (LFP) battery engineered for maximum flexibility, reliability, and long term energy savings. Designed to operate in demanding environments from homes and apartments to off grid cabins, RVs, and boats it delivers uninterrupted backup power with smart inverter integration and advanced system communications. With a guaranteed 8,000+ cycle life, a 10 year warranty, and built in safety
The eFlex MAX 5.4 kWh is a high-performance 48V lithium iron phosphate (LFP) battery engineered for maximum flexibility, reliability, and long-term energy savings. Designed to operate in demanding environments — from homes and apartments to off-grid cabins, RVs, and boats — it delivers uninterrupted backup power with smart inverter integration and advanced system communications. With a guaranteed 8,000+ cycle life, a 10-year warranty, and built-in safety protections, the eFlex MAX meets the highest standards for quality and performance. Whether used for solar self-consumption, backup power, or off-grid storage, it's a versatile solution built to last.
Key Features & Benefits
Durable, Outdoor-Ready Design (IP65): Built with a saltwater-resistant anodized aluminum enclosure, the eFlex MAX is engineered for both indoor and outdoor use — no additional protective housing required.
Industry-Leading Battery Lifespan: Enjoy over 8,000 cycles and a 10+ year lifespan, thanks to the battery's patented ¾" aluminum shell, which delivers superior thermal regulation and durability — even under high-power loads.
Ultra-High Efficiency with Minimal Standby Loss: The eFlex MAX operates at up to 98% round-trip efficiency and consumes just 2W in idle mode, making it ideal for off-grid systems and maximizing energy savings.
Effortless Scalability: Expand your system with ease with the optional busbar package, supporting higher current loads and reducing wiring complexity. Up to 16 modules can be paralleled for a total of 86.4 kWh.
Streamlined Installation, Indoors or Out: With an IP65 waterproof front cover and flexible wall or floor mounting options (wall mount kit optional), the eFlex MAX ensures a clean, fast, and code-compliant installation.
Advanced Battery Management System (BMS): Features individual cell voltage and temperature monitoring and balancing for maximum reliability and longevity. Includes integrated 125A breaker, minimal idle consumption (2W), and advanced closed-loop communication with most 48V inverters via CANbus and Modbus.
Remote Monitoring & Firmware Updates: OTA firmware updates and remote monitoring capabilities allow for easy system management.
Tier 1 Automotive Prismatic LFP Cells: Built with top-level prismatic automotive lithium iron phosphate cells for the longest cycle life and highest safety standards.
Maximum Value, Minimum Cost per kWh: Delivering premium performance at an accessible price, the eFlex MAX offers best-in-class LFP technology, high output, and unbeatable long-term value.
Technical Specifications
| Specification | Detail |
|---|---|
| Nominal Voltage | 51.2V |
| Nominal Capacity | 105 Ah |
| Rated Capacity @ 0.5C (50A) | 5.374 kWh |
| Resistance | <10 mΩ |
| Efficiency (at 0.5C) | >98% |
| Self-Discharge | <1% / Month |
| Maximum Modules in Parallel | 16 (86.4 kWh total) |
| Depth of Discharge | Up to 95% |
| Cycle Life | 8,000 cycles @ 80% DoD |
| Recommended Charge Current | <55A |
| Maximum Charge Current | 100A |
| Recommended Charge Voltage | 55.2V |
| BMS Charge Voltage Disconnect | >56V |
| Recommended Continuous Discharge Rate | 60A (3 kW DC) |
| Peak Continuous Discharge Rate | 100A (5 kW for 60 min) |
| Maximum Surge Power Rate | 130A (6.6 kW for 5s) |
| Recommended Low Voltage Disconnect | 48V |
| Battery Low Voltage Protection | <45V |
| Battery Recovery Voltage | 45V |
| Fault Current | 3000A, 5ms |
| Discharge Temperature | -4°F to 131°F (-20°C to 55°C) |
| Charge Temperature | 32°F to 114°F (0°C to 45°C) |
| Storage Temperature | 20°F to 95°F (-6°C to 35°C) |
| Dimensions (L×W×H) | 17.5" × 7.2" × 24.2" (445 × 183 × 615 mm) |
| Weight | 112 lbs (51 kg) |
| Terminal Type | M8 |
| Ring Terminal Size | 3/8" or larger |
| Terminal Torque | 5.1 – 5.7 ft-lb (7.0 – 7.7 Nm) |
| Case Material | Anodized Aluminum |
| Enclosure Protection | IP65 |
| Cell Type Chemistry | Tier 1 Automotive Prismatic – LiFePO₄ |
| Communication | RS485 / CAN |
| Certifications | UL1973, UL 9540 DC ESS 2023, UL 9540A, CAN |
| Shipping Classification | UN 38.3, CLASS 9 |
| Warranty | 10 Years (limited) |
Product Documents
- Installation Manual: Download Manual
- Datasheet: Download Datasheet
- Warranty: Download Warranty
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy