Fortress Power eFlex MAX 5.4
A tough 5 kWh module for off-grid cabins, boats and small systems that need an outdoor-rated case. Larger inverters need three or more to run at full power.
Current Connected $1,449$1,449
4.0/5
An outdoor-rated 5 kWh battery for owners of a Growatt US hybrid inverter. Owners of other inverter brands get more for less from a rack module.
- 5.1 kWhCapacity
- 60 AOutput
- YesUL 9540A
- 10 yearsWarranty
Check price at Amazon$1,547.55
Price checked October 24, 2026. As an Amazon Associate we earn from qualifying purchases.
Pros
- IP66 enclosure can be mounted outdoors
- UL 1973 and UL 9540A listings help a permitted install
- Pairs closed-loop with Growatt’s US hybrid inverters
Cons
- 60 A per module limits each battery to about 3 kW
- Only 4.6 kWh usable of 5.12 kWh
- Costs far more per kWh than rack modules, and is approved only for Growatt inverters
How it scores
The rating comes from 6 measured or published factors, each scored 0-100 against fixed reference points for its case. How we rank explains each one.
Specifications
| Model number | ALP 5.0L-E2 US |
|---|---|
| Capacity | |
| Case | Wall or floor mount |
| Nominal voltage | 51.2 V |
| Capacity | 100 Ah |
| Energy | 5.1 kWh |
| Usable energy | 4.6 kWh |
| Chemistry | LiFePO4 |
| Power | |
| Continuous discharge | 60 A |
| Max charge current | 60 A |
| Modules in parallel | Up to 8 |
| Safety and communication | |
| UL 1973 | Yes |
| UL 9540A | Yes |
| UL 9540 | No |
| Communication | CAN |
| Works with inverters | Growatt |
| Build | |
| Enclosure | IP66 |
| Dimensions | 28.0 x 7.3 x 11.6 in |
| Weight | 101.4 lb |
| Warranty | 10 years |
| Released | 2024-06 |
Alternatives in this case
ECO-WORTHY Wallbank S100
An inexpensive wall-hung 5 kWh battery for indoor off-grid or backup systems. Pick the UL-listed Cubix100 if you need a permit.
ECO-WORTHY $869.99$869.99
BigBattery Nexus 2 16kWh
For off-grid cabins and homesteads that need a lot of heated storage for the least money and don’t need UL paperwork. Grid-tied homes facing inspection should pick a UL 9540 battery instead.
BigBattery $2,990$2,990
Compare
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