Fortress Power eFlex MAX
Fortress states 5.376 kWh nominal energy (Fortress Power eFlex MAX 5.4, United States).
Fortress states 3 kW continuous power (Fortress Power eFlex MAX 5.4, United States, DC).
Warranty terms: 10 years (Fortress Power eFlex MAX 5.4, United States).
Brand: Fortress
Published figures
No figures have been collected for usable energy, motor-start current, end-of-warranty capacity, and warranty throughput.
| Figure | Value | Publisher | Source |
|---|---|---|---|
| Nominal energy, Fortress Power eFlex MAX 5.4 | 5.376 kWh | Manufacturer Not yet checked | Spec sheet, at p.2 / Battery specifications (5.4P1), retrieved Sep 25, 2026 |
| Continuous power, Fortress Power eFlex MAX 5.4 (DC) | 3 kW | Manufacturer Not yet checked | Spec sheet, at p.1 / Discharge specifications, retrieved Sep 25, 2026 |
| Peak power, Fortress Power eFlex MAX 5.4 (power side and duration not stated) | 5 kW | Manufacturer Not yet checked | Spec sheet, at p.1 / Discharge specifications, retrieved Sep 25, 2026 |
| Surge power, Fortress Power eFlex MAX 5.4 | 6.6 kW | Manufacturer Not yet checked | Spec sheet, at p.1 / Discharge specifications, retrieved Sep 25, 2026 |
| Units per system, Fortress Power eFlex MAX 5.4 | 16 units | Manufacturer Not yet checked | Spec sheet, at p.1 / Electrical specifications, retrieved Sep 25, 2026 |
| Largest stack, Fortress Power eFlex MAX 5.4 | 86.4 kWh | Manufacturer Not yet checked | Spec sheet, at p.1 / Electrical specifications, retrieved Sep 25, 2026 |
| Lowest operating temperature, Fortress Power eFlex MAX 5.4 (discharging) | −20°C | Manufacturer Not yet checked | Spec sheet, at p.1 / Temperature specifications, retrieved Sep 25, 2026 |
| Lowest operating temperature, Fortress Power eFlex MAX 5.4 (charging) | 0°C | Manufacturer Not yet checked | Spec sheet, at p.1 / Temperature specifications, retrieved Sep 25, 2026 |
| Highest operating temperature, Fortress Power eFlex MAX 5.4 (charging) | 45°C | Manufacturer Not yet checked | Spec sheet, at p.1 / Temperature specifications, retrieved Sep 25, 2026 |
| Highest operating temperature, Fortress Power eFlex MAX 5.4 (discharging) | 55°C | Manufacturer Not yet checked | Spec sheet, at p.1 / Temperature specifications, retrieved Sep 25, 2026 |
| Weight, Fortress Power eFlex MAX 5.4 | 51 kg | Manufacturer Not yet checked | Spec sheet, at p.1 / Mechanical specifications, retrieved Sep 25, 2026 |
See it on the home battery chart
Stated stack range
One unit: 5.376 kWh nominal. Largest stated stack: 86.4 kWh (energy basis not stated) (16 units).
Stated temperature limits
Stated charging range: 32°F (0°C) to 113°F (45°C), Fortress Power eFlex MAX 5.4.
Stated discharging range: −4°F (−20°C) to 131°F (55°C), Fortress Power eFlex MAX 5.4.
Warranty terms
| Term | Figure | Document |
|---|---|---|
| Warranty, United States | Fortress Power eFlex MAX 5.4: 10 years | Warranty, at p.1 / Limited Warranty, retrieved Sep 25, 2026, dated May 10, 2024 |
Features the manufacturer states
Configuration: Fortress Power eFlex MAX 5.4.
| Feature | Stated | Source |
|---|---|---|
| Chemistry | LFP Not yet checked | Spec sheet, at p.2 / Battery specifications, retrieved Sep 25, 2026 |
| Compatible inverters | Schneider, Sol-Ark, Midnite Solar, OutBack Power, Morningstar, Phocos, Victron Energy, Growatt Not yet checked | Spec sheet, at p.1, retrieved Sep 25, 2026 |
| Enclosure rating | IP65 Not yet checked | Spec sheet, at p.1 / Mechanical specifications, retrieved Sep 25, 2026 |
| Nominal battery voltage | 51.2 V Not yet checked | Spec sheet, at p.1 / Electrical specifications, retrieved Sep 25, 2026 |
| Dimensions | 446 x 184 x 616 (L x W x H) mm Not yet checked | Spec sheet, at p.1 / Mechanical specifications, retrieved Sep 25, 2026 |
Government and program lists
This product is on none of the lists this site reads.
Installs
No install count this site publishes covers this product.
Recalls and safety notices
No notice in the recall sources this site reads is matched to this product. That is not a safety finding. See every recall notice.
- UL 9540 listed: Yes (Fortress Power eFlex MAX 5.4) standalone DC ESS, 1-4 batteries
- UL 9540A tested: Yes (Fortress Power eFlex MAX 5.4)
The maker states the listing or test. The listing body's records have not been checked.
Backup hours from your load
This battery has no maker-stated usable energy on this site.