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Fortress Power eFlex Max 5.4kWh Lithium Battery

Fortress Power eFlex Max 5.4kWh Lithium Battery
$1,449.00 - $1,449.00
$1,449.00
$1,449.00 - $1,449.00
$1,449.00
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eFlex MAX 5.4kWh Lithium Battery Storage

The Fortress Power eFlex MAX 5.4 kWh Battery is a high-performance 48V lithium iron phosphate (LFP) battery designed for reliable energy storage, long-term durability, and flexible installation across residential and mobile applications. Built to deliver consistent backup power, the Fortress Power eFlex MAX 5.4 kWh Battery is ideal for solar energy systems, off-grid setups, RVs, boats, and whole-home backup solutions. Its advanced LFP battery chemistry provides enhanced safety, thermal stability, and long cycle life, making it a dependable choice for users looking to maximize energy efficiency and reduce reliance on the grid. The system integrates seamlessly with compatible hybrid inverters, enabling smart energy management and optimized performance in both grid-tied and off-grid environments.

Engineered for longevity and real-world performance, the Fortress Power eFlex MAX 5.4 kWh Battery offers 8,000+ charge cycles and is backed by a 10-year warranty, ensuring dependable operation and long-term energy savings. Built-in safety protections and advanced communication capabilities allow for secure operation and seamless system monitoring.


Whether used for solar self-consumption, backup power during outages, or as part of a scalable energy storage system, the Fortress Power eFlex MAX 5.4 kWh Battery delivers efficient, flexible, and reliable power storage. Please note that the eFlex MAX 5.4 kWh Battery is not compatible with the standard eFlex 5.4 kWh LFP Battery, so system configurations should be planned accordingly.

Fortress Power eFlex MAX

Fortress Power eFlex MAX 5.4kWh Specs

  • Total Energy: 5.4kWh
  • Max. Charge Current (Continuous): 100A
  • Max. Discharge Current (Continuous): 100A
  • Nominal Capacity: 105 Ah
  • Voltage Range: 48-55V
  • Charging Temperature: 32 ~ 114 F
  • Discharging Temperature: -4 ~ 131 F
  • Storage Temperature: 20 ~ 95 F
  • Dimension: 17.5" L x 24.2" W x 7.2" H
  • Weight: 108 lbs
  • Life Cycles: 8000 @ 80% DoD
  • Round Trip Efficiency: >98%
  • Compatibility: Fortress Power Envy Inverters, Fortress Power Solo 6.5K Inverter, Fortress Power Guardian Products, Fortress Power DuraRack and FlexTower

Fortress Power eFlex MAX 5.4kWh Features

  • Durable, Outdoor-Ready Design: Built with a saltwater-resistant aluminum enclosure, the eFlex MAX is engineered for both indoor and outdoor use — no additional protective housing required.
  • Effortless Scalability: Expand your system with ease with the optional busbar package, supporting higher current loads and reducing wiring complexity.
  • 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.
  • Streamlined Installation, Indoors or Out: With a waterproof front cover and flexible wall or floor mounting, the eFlex MAX ensures a clean, fast, and code-compliant installation — no external conduits needed.
  • Ultra-High Efficiency with Minimal Standby Loss: The eFlex MAX operates at up to 99% round-trip efficiency and consumes just 2W in idle mode, making it ideal for off-grid systems and maximizing energy savings.
  • 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.

Your Satisfaction with Fortress Power is Guaranteed:

  • 10-Year Limited Warranty
  • Lowest Price Guarantee