48V Grid-Tied ESS · EG4 314Ah Indoor + FlexBOSS21
16kWh of Certified Energy Storage, Paired With a 16kW Hybrid Inverter
This system pairs one EG4 314Ah Indoor battery (16kWh nominal, 12.86kWh recommended usable) with one EG4 FlexBOSS21 hybrid inverter — up to 16kW of continuous output with PV and grid combined, and up to 21kW of solar input across 3 MPPT trackers and 5 strings. It’s built as a UL 9540-eligible pairing with closed-loop communication, GridBOSS-ready for larger system control, and works grid-tied or fully off-grid.
What’s In This System
Two components, pre-matched and sold together.
Qty 1
EG4 314Ah Indoor Battery
16kWh nominal, IP20 indoor-rated, with a third-generation BMS and Auto-ID setup.
Qty 1
EG4 FlexBOSS21 Inverter
Up to 16kW continuous output with PV and grid combined, and 21kW of max solar input.
What Makes This System Different
16kWh Indoor Battery
12.86kWh of recommended usable capacity, cross-compatible with other EG4 battery models for future scaling.
16kW Combined, 6kW Battery-Only
Up to 16kW continuous with PV and grid working together, or 6kW continuous from the battery alone if grid and solar are both unavailable.
21kW Solar, 3 MPPT / 5 Strings
Three MPPT trackers across five total input strings, for granular tracking on complex or multi-orientation roof layouts.
UL 9540-Eligible Pairing
This battery and inverter combination is built and certified to be paired together for grid-tied energy storage system installs.
GridBOSS Integration
Connects with EG4’s GridBOSS hub for smart load management, AC coupling, and generator support at a system level.
WiFi, Cellular & Ethernet
The inverter ships with a WiFi dongle included by default, plus cellular and Ethernet connectivity options for remote monitoring.
Auto-ID, 3rd-Gen BMS
The battery automatically recognizes and syncs additional units during setup, with improved balancing precision and response time.
Parallels Up to 16 Units
Scales from this single-inverter configuration up to large residential or commercial-style installations on the same platform.
One Number Isn’t the Whole Story
This system’s output rating isn’t a single number — 16kW is what the FlexBOSS21 delivers with solar and grid both contributing, while the battery on its own is rated for 6kW continuous. That distinction matters for sizing: a system that looks oversized on paper at “16kW” is really built around a 6kW battery-only floor, with solar and grid making up the difference the rest of the time. Add in 21kW of possible solar input across three MPPT trackers, and there’s real headroom for larger or more complex roof layouts.
The battery and inverter are sold as a matched pair specifically because BigBattery has built and validated this exact combination for UL 9540-eligible grid-tied installs, with closed-loop communication handling coordination between the two automatically. The inverter connects over WiFi (dongle included), cellular, or Ethernet, and integrates with EG4’s GridBOSS hub for whole-system load management if the install calls for it. The battery stays indoors (IP20), while the inverter’s NEMA 4X enclosure is rated for outdoor installation if that’s where it needs to go.
Full Specifications
Battery — EG4 314Ah Indoor (×1)
Capacity
| Nominal voltage | 51.2 Vdc |
| Nominal energy capacity | 16 kWh |
| Usable energy (80% DoD) | 12.86 kWh |
| Rated capacity | 314 Ah |
Charging & Discharge
| Max continuous charge current | 157 A |
| Max continuous discharge current | 200 A |
| Continuous charge/discharge power | 8 kW / 10.2 kW |
| Peak power | 12.8 kW (3 sec) |
Environmental
| Charging temp range | 32–122°F |
| Discharging temp range | -4–131°F |
| Enclosure rating | IP20 (indoor only) |
Physical & Warranty
| Weight | 293.2 lbs |
| Dimensions (H×W×D) | 34.1 × 18.1 × 9.6 in |
| Cycle life | 10,000 @ 0.5C, 80% DoD |
| Warranty | 10 years or 10,000 cycles |
Inverter — EG4 FlexBOSS21 (×1)
Output
| Continuous output (PV + grid) | 66.7A / 16 kW |
| Continuous output (battery only) | 50A / 6 kW |
| Peak power (0.5s / 1s) | 24,000W / 18,000W |
| Locked rotor amps | 195 A |
| Transfer time | 20ms default / 10ms configurable |
Solar Input
| MPPT channels | 3 (5 strings total) |
| Rated current per MPPT | 26A / 26A / 15A |
| Rec. max solar array (STC) | 21 kW |
| MPPT DC voltage range | 120–440 Vdc |
| Max efficiency (PV to grid) | 97% |
Battery & Grid
| Battery voltage range | 40–60 Vdc |
| Max charge/discharge current | 250 A DC |
| Max grid pass-through | 90 A |
| AC input / output breaker | 90A / 80A |
| Idle consumption | <65 W |
Physical, Connectivity & Warranty
| Dimensions (H×W×D) | 30.43 × 22.28 × 11.22 in |
| Weight | 121 lbs |
| Enclosure rating | NEMA 4X |
| Connectivity | WiFi (included), cellular, Ethernet |
| Max parallel units | 16 |
| Warranty | 10 years |
Inverter certifications: UL 1741, UL 1741 PCS CRD Test, UL 3141. FCC Part 15 Class B. Battery certifications: UL 1973, UN 38.3.
Other Configurations Available
This same battery and inverter platform is sold in several sizes. The row below highlighted in your brand color is the configuration this page describes — everything else is shown for reference if a customer needs a different scale.
| Tier | Inverters | Batteries | Capacity | Max Output |
|---|---|---|---|---|
| Standard | 1× | 1× | 16 kWh | 16 kW |
| Standard | 1× | 2× | 32 kWh | 16 kW |
| Standard | 1× | 3× | 48 kWh | 16 kW |
| Large | 2× | 4× | 64 kWh | 32 kW |
| Large | 2× | 6× | 96 kWh | 32 kW |
| 3-Phase | 3× | 6× | 96 kWh | 48 kW |
Common Questions
What exactly is included in this system?
One EG4 314Ah Indoor battery (16kWh) and one EG4 FlexBOSS21 hybrid inverter, sold as a pre-matched, UL 9540-eligible pair.
Is the output really 16kW, or is that only with solar?
16kW is what the system delivers with solar and grid both contributing. On battery power alone, with no solar or grid available, continuous output is 6kW. Worth sizing around the 6kW floor if backup power without sun or grid matters for your use case.
What does “UL 9540-eligible” mean here?
It means this specific battery-and-inverter pairing has been built and validated together for UL 9540 grid-tied energy storage system installs, rather than being a generic combination assembled after the fact.
Can the whole system be installed outdoors?
Not the battery — it’s IP20 and indoor-rated. The FlexBOSS21 inverter is NEMA 4X and can go outdoors if that placement makes more sense for the install.
How do I monitor the system remotely?
The inverter includes a WiFi dongle by default and also supports cellular and Ethernet connectivity, with app and web-based monitoring.
What’s the warranty?
10 years on both the battery (or 10,000 cycles) and the inverter, covering defects in materials and workmanship.
Do I need a licensed electrician to install it?
Given the voltages, currents, and grid interconnection involved, installation should be handled by a qualified, licensed electrician or solar installer familiar with your local code and utility requirements.
Battery — EG4 314Ah Indoor
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