Fortress Power eFlex MAX 5.4kWh Battery
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.
*The eFlex MAX 5.4kWh and the eFlex 5.4kWh LFP Battery are NOT compatible with each other.
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.
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 99% 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.
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.
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.
Specifications:
| General | |
| Name | eFlex MAX 5.4 |
| Total Energy(kWh) | 5.4 |
| Max. Charge Current (Continuous) [A] | 100 |
| Max. Discharge Current (Continuous) [A] | 100 |
| Nominal Capacity [Ah] | 105 |
| Voltage Range [V] | 48-55 |
| Charging Temperature [F] | 32 ~ 114 |
| Discharging Temperature [F] | -4 ~ 131 |
| Storage Temperature [F] | 20 ~ 95 |
| Dimension [L x W x H, inch] | 17.5 x 24.2 x 7.2 |
| Weight [lbs] | 108 |
| Life Cycles | 8000 @ 80% DoD |
| Round Trip Efficiency | >98% |