Fortress Power eFlex Max 5.4kWh LFP Battery

The Fortress Power eFlex MAX 5.4 kWh is a rugged, ultra-efficient Lithium Iron Phosphate (LFP) battery designed for extreme versatility. Built with a patented aluminum enclosure that offers superior thermal performance, this IP65-rated battery is equally at home in a server rack, mounted on a wall, or sitting on a floor—indoors or outdoors. It features advanced closed-loop communication and a robust lifespan of 8,000+ cycles.

Product Specifications

• Voltage Range: 48V – 55V

• Max Continuous Current: 100 A (Charge) / 100 A (Discharge)

• Recommended Current: < 55 A (Charge) / 60 A (Discharge)

• Surge Power: 130 A (5 seconds)

• Round Trip Efficiency: > 98%

• Cycle Life: 8,000 Cycles (@ 80% DoD

Why Choose eFlex MAX 5.4kWh

The eFlex MAX is the “Swiss Army Knife” of lithium batteries. Its defining feature is flexibility: it fits standard 19″ server racks for high-density storage, yet has a rugged, waterproof IP65 shell that allows for outdoor wall-mounting in harsh climates. If you have limited indoor space or need a system that can withstand humidity and dust (like in a garage, shed, or marine environment), the eFlex MAX is the superior choice over standard indoor-only rack batteries.

Benefits of eFlex MAX 5.4

• Triple Mounting Options: Unlike most batteries that are “rack-only” or “wall-only,” the eFlex MAX supports Server Rack, Wall Mount, and Floor Standing installations, adapting to any site constraint.

• Outdoor Resilience: The anodized aluminum enclosure is IP65 rated (dust-tight and water-jet resistant) and saltwater-resistant, making it durable enough for outdoor or marine applications.

• Superior Thermals: The patented aluminum case design acts as a heat sink, providing 4x better thermal performance than competitors, which helps maintain efficiency and longevity in hot environments.

• Smart & Connected: Features built-in Wi-Fi for remote monitoring and “closed-loop” communication with major inverters like Sol-Ark, Schneider, and Victron, ensuring precise charging and improved safety.

General Data

• Dimensions (L x W x H): 17.5 x 7.2 x 24.2 inches (446 x 184 x 616 mm)

• Weight: 112 lbs (51 kg)

• Mounting: Wall, Floor, or 19″ Server Rack

• Operating Temperature: -4°F to 131°F (-20°C to 55°C) [Discharge]

• Certifications: UL 1973, UL 9540, UL 9540A, UN 38.3, CEC

Frequently Asked Questions

Q1: What is the difference between “eFlex” and “eFlex MAX”?

They are distinct generations. The eFlex MAX is the newer version with an updated BMS and different firmware. Important: The eFlex MAX is not compatible with the older eFlex 5.4 model; you cannot mix them in the same battery bank.

Q2: Can I install this battery outside?

Yes. The eFlex MAX is IP65 rated against water and dust and features a corrosion-resistant aluminum enclosure, making it suitable for protected outdoor areas or high-humidity environments.

Q3: Does it fit in a standard server rack?

Yes. The unit is designed with standard 19-inch width dimensions to fit perfectly into industrial server racks, allowing for high-density, clean installations.

Q4: Do I need a specific inverter?

The eFlex MAX is compatible with most 48V inverters but works best with brands that support closed-loop communication, such as Sol-Ark, Schneider, Victron, Outback, and SMA.

Q5: How many can I stack?

You can parallel up to 30 units for a total capacity of roughly 162 kWh, making it suitable for large residential or light commercial projects.