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
The BigBattery Nexus 2 16kWh and the Fortress Power eVault MAX 18.5 are evenly matched, rated 3.9 and 3.9. The BigBattery Nexus 2 16kWh leads on value and features. The Fortress Power eVault MAX 18.5 wins on safety listing. The BigBattery Nexus 2 16kWh costs $3,489 less ($2,990 vs $6,479).
Fortress Power eVault MAX 18.5
One of the largest single 48 V batteries sold, for whole-home or light-commercial systems installed by a dealer. Expect to pay dealer prices and plan for a heavy floor-standing cabinet.
Solamp $6,479$6,479
Prices were last checked October 24, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the BigBattery Nexus 2 16kWh for value ($186 per rated kWh vs $352 per rated kWh) and features (inverter communication, self-heating; no app vs inverter communication; no self-heating).
- Choose the Fortress Power eVault MAX 18.5 for safety listing (UL 1973, UL 9540 listed vs no UL listing).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every wall and floor mount 48V solar battery; a clear win is highlighted. How we rank explains each one.
| Factor weight | BigBattery Nexus 2 16kWh | Fortress Power eVault MAX 18.5 |
|---|---|---|
| Overall rating | 3.9/5 | 3.9/5 |
| Value 35% | 92 $186 per rated kWh | 55 $352 per rated kWh |
| Output 15% | 25 150 A continuous (about 7.7 kW) | 29 180 A continuous (about 9.2 kW) |
| Warranty 15% | 100 12-year warranty | 100 10-year warranty |
| Safety listing 15% | 0 no UL listing | 100 UL 1973, UL 9540 listed |
| Cycle life 10% | 100 8,000 cycles, maker rating | 100 8,000 cycles at 80% depth, maker rating |
| Features 10% | 70 inverter communication, self-heating; no app | 40 inverter communication; no self-heating |
Specifications
| BigBattery Nexus 2 16kWh | Fortress Power eVault MAX 18.5 | |
|---|---|---|
| Capacity | ||
| Case | Wall or floor mount | Wall or floor mount |
| Nominal voltage | 51.2 V | 51.2 V |
| Capacity | 314 Ah | 360 Ah |
| Energy | 16.1 kWh | 18.4 kWh |
| Chemistry | LiFePO4 | LiFePO4 |
| Cycle life | 8,000 | 8,000 at 80% depth |
| Power | ||
| Continuous discharge | 150 A | 180 A |
| Peak discharge | 270 A | 250 A |
| Max charge current | 150 A | 180 A |
| Modules in parallel | Up to 15 | Up to 20 |
| Safety and communication | ||
| UL 1973 | No | Yes |
| UL 9540A | No | Yes |
| UL 9540 | No | Yes |
| Communication | CAN, RS485 (RJ45) | CAN, RS485 |
| Works with inverters | EG4, Victron, Deye, Solis, GoodWe, BigBattery APEX, Pylon protocol | Fortress Envy, Fortress Solo |
| Self-heating | Yes | No |
| App | No | No |
| Build | ||
| Display | - | Yes |
| Built-in breaker | - | Yes |
| Enclosure | IP54 | IP55 |
| Dimensions | 500 x 782 x 400 mm (19.7 x 30.8 x 15.7 in, W x H x D) | 20.3 x 20.3 x 42.2 in (515 x 515 x 1073 mm) |
| Weight | 315 lb | 520 lb |
| Warranty | 12 years | 10 years |
| Released | 2026-10 | 2021-06 |