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Fortress Power eFlex MAX 5.4 kW - FP-eflex MAX-STD
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Fortress Power

Fortress Power eFlex MAX 5.4 kW

SKU: FP-eflex MAX-STD

$2079.31

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Fortress Power eFlex MAX 5.4 kW

FP-eflex MAX-STD

$2079.31

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High Voltage Batteries

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Product Overview

The Fortress Power eFlex MAX 5.4kWh is a 48V lithium iron phosphate (LFP) battery engineered for residential, off-grid, and DIY solar systems. Its saltwater-resistant aluminum enclosure with IP65 rating handles indoor and outdoor installations without additional protective housing.

Key Features

  • 8,000+ Life Cycles: At 80% depth of discharge with Tier 1 Automotive Prismatic cells and a patented 3/4" aluminum shell
  • Over 98% Efficiency: Ultra-high round-trip efficiency with just 2W standby power loss
  • Scalable to 86.4 kWh: Integrated 300A busbars allow effortless parallel connection of multiple units
  • IP65 Rated: Saltwater-resistant aluminum enclosure for indoor or outdoor installation
  • 125A Lockable Breaker: Built-in for safety and convenience
  • Pre-Threaded Conduit Fittings: Simplifies wiring and reduces installation time and cost
  • 10-Year Warranty: Included with every unit

Safety & Compliance

Equipped with a multi-level Battery Management System (BMS) providing overcharge, deep discharge, cell voltage, and temperature protection. Certified to UL9540, UL9540A (fire safety), and UL1973 for code-compliant installations.

Note: The eFlex MAX 5.4kWh and the eFlex 5.4kWh LFP Battery are NOT compatible with each other.

Product Documents

Spec Sheets

eFlex MAX Datasheet 250515v2.pdf
Download

Manuals & Guides

FP_manual_install_eflexmax_2025.pdf
Download

Warranty

10-Year-eFlex-Warranty-Letter-12.2020-1-1.pdf
Download

Frequently Asked Questions

How long will the eFlex MAX last before needing replacement?+
With 8,000+ rated cycles at 80% depth of discharge, the eFlex MAX is designed for 20+ years of daily use. LFP (lithium iron phosphate) chemistry is the most durable and safest lithium battery technology available for home storage.
Can I install the eFlex MAX outside?+
Yes. The eFlex MAX is rated for both indoor and outdoor installation with a wide operating temperature range. It's built to withstand varying climate conditions, though a sheltered location will maximize longevity.
How many eFlex MAX units do I need for whole-home backup?+
That depends on your daily energy usage. A typical US home uses 30 kWh/day, so 5-6 eFlex MAX units would cover a full day. For essentials-only backup (fridge, lights, Wi-Fi), 1-2 units is often sufficient.
Is the eFlex MAX compatible with non-Fortress inverters?+
The eFlex MAX works with a range of compatible hybrid inverters. While it pairs seamlessly with Fortress Power inverters, check the compatibility list for third-party inverter support.

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