Fortress Power eForce 48V Stackable LiFePO4 Battery, 9.6kWh Per Module, IP65 Heated Enclosure, Quick-Plug Installation, Up to 153kWh Scalable

About the Fortress Power eForce Stackable LiFePO4 Battery

The Fortress Power eForce is a modular lithium iron phosphate battery system that stacks vertically and integrates directly with the Fortress Power Envy inverter line. Each 9.6kWh module uses 15 Tier-1 prismatic LFP cells rated for 8,000 cycles with a 20-year design life. Modules click together using quick-connect terminals with no cables between batteries, and the Envy inverter mounts directly on top of the included eWay wire management system. The result is a single integrated tower from batteries to inverter, with all wiring routed through a built-in busbar and conduit system.

Clean Installation, Minimal Components

The eForce eliminates the pieces that make other battery installations complicated. There are no external racks, no separate busbars, and no long cable runs between the batteries and inverter. The eWay that ships with each bundle provides built-in busbars, conduit entrance ports, an emergency shutoff switch, and LED status indicators. Every connection is contained in one vertical footprint, which speeds up installation and reduces wiring errors.

Built for Any Climate

The eForce is IP65 rated for indoor or outdoor installation without a separate enclosure. Built-in heating elements activate automatically below 32°F, enabling operation in ambient temperatures as low as -4°F. The discharge range extends from -4°F to 140°F, making the eForce suitable for desert heat, northern winters, and coastal humidity. The BMS monitors individual cell voltage and temperature with overcharge, overdischarge, overcurrent, and short circuit protection.

Scalability

Start with a single 9.6kWh module for essential loads and add modules later as your needs grow. Each stack holds up to three modules (28.8kWh), and stacks can be paralleled for larger systems up to 268kWh. The eForce supports up to 250A continuous charge and discharge in closed-loop communication with an Envy inverter, with surge discharge up to 14,400W for 10 seconds to handle motor starts on compressors, well pumps, and HVAC equipment.

Monitoring and Communication

RS485, CAN bus, and Wi-Fi communication enable remote monitoring through the Fortress Power Guardian app. The app displays real-time battery SOC, cell voltages, temperatures, and fault history. Closed-loop communication with the Envy inverter provides optimized charging and discharging behavior without manual configuration.

15S Cell Configuration and Permitting Advantages

The eForce uses a 15-cell series (15S) design with a 48.0V nominal voltage, compared to the 51.2V nominal used by most other "48V" batteries. Fortress Power chose this configuration to keep each module at 9.6kWh, which means a two-module stack (19.2kWh) stays below the 20kWh residential ESS limit defined by UL 9540 and NFPA 855. In states like California that enforce this limit strictly, the eForce's smaller module size allows installers to maximize total permitted storage capacity across multiple ESS units without triggering additional fire testing or permitting requirements.

The 15S voltage profile requires matched inverter settings (55.2V absorption in closed-loop), and 15S batteries should not be combined with 16S batteries in the same system. The eForce is designed for new installations paired with a Fortress Power Envy inverter.

Certifications and Warranty

Certified to UL 1973, UL 9540 (system-level with Envy inverter), and UN38.3. When installed as a complete system with the eForce, Envy inverter, and Guardian Gateway, the battery qualifies for Fortress Power's 15-year warranty (or 8,000 cycles at 80% DOD). Standard warranty without the full system is 10 years. VPP approved for participating utility demand response programs.