Description
Big Battery EG4 FlexBOSS21 12kW (21kPV) Hybrid Inverter – INV027
The latest development from the EG4 team, the FlexBOSS21 is a cutting-edge, split-phase hybrid inverter designed to be the keystone of any residential or commercial power system. With an incredible 21kW PV input capacity and an array of advanced features, the FlexBOSS21 provides reliable performance day in and day out, in both on-grid and off-grid settings.
The FlexBOSS21 is one of the highest capacity inverters on the market today, featuring 3 MPPTs supporting up to 5 strings, providing superior flexibility for multi-orientation solar arrays, and the ability to handle 90A of grid feed-through at 120/240VAC, ensuring robust grid-tied capabilities. Plus, the FlexBOSS21 seamlessly integrates with EG4’s GridBOSS MID power gateway for a cost-effective, streamlined setup, helping to reduce installation time and system startup costs, and when you pair these two units together in your system, you’re able to utilize the smart load management, AC coupling, and generator support features if needed.
But that’s not all. EG4 understands the value of enhanced safety and visibility when it comes to your power, and the FlexBOSS21 spares no expense, coming equipped with responsive rapid shutdown, ground fault monitoring, and arc fault protection, all backed by industry-leading safety certifications, and with EG4’s updated monitoring software, you get access to remote management, mobile notifications, and convenient Wi-Fi connectivity for your system.
Combining efficiency, scalability, and cutting-edge technology, the FlexBOSS21 is a top-tier solution, with a safety-first design, for those seeking a reliable, powerful inverter to anchor their energy system. Whether for residential or commercial applications, its advanced features and versatile design provide unmatched value and peace of mind. Elevate your energy independence and power your future with the EG4 FlexBOSS21 Hybrid Inverter today!
Features
- 3 MPPT Inputs
- Remote Monitoring
- Smart Load Control
- AC Coupling Function
- Integrated UPS Module
- Built-In Circuit Breakers
- Seamless Switching In Under 20ms
- High-Frequency Split-Phase Output
- Advanced Parallelability up to 192kW
- Seamless Integration With GridBOSS MID
- 48V Battery Systems
- Residential Solar Systems
- AC Coupled UPS Systems
- Off-Grid Backup Systems
- Emergency Power Systems
- Commercial ESS
Specifications
| AC Voltage | 120V AC / 240V AC |
|---|---|
| AC Frequency | 60 Hz / 50 Hz |
| Max Continuous AC Current | 50A @ 240V AC |
| Max AC Input Power | 12,000 W |
| Max AC Bypass | 90A |
| Operating Voltage Range | 180 – 270V AC |
| Output Voltage | 120V AC / 240V AC |
| Max Continuous Output Current | 66.7A |
| Output Frequency | 60 Hz / 50 Hz |
| Output Power (without PV) | 12,000 W @ 240V |
| Output Power (with PV) | 16,000 W @ 240V |
| Power Factor | 0.99 (Full Load) |
| Reactive Power Adjustment Range | -0.8 ~ 0.8 Leading Adjustable |
| Total Harmonic Distortion (THD) | <5% (Full Load) |
| Transfer Time | 10 – 20 ms (Single) / 20 ms (Parallel) |
| Max Continuous Output Current (Secondary) | 50A |
| Rated Output Voltage | 120V AC / 240V AC |
| Rated Output Power | 12,000 W @ 240V AC |
| Max Output Power (Peak) | 24,000 W (0.5 sec) / 18,000 W (1 sec) / 15,000 W (6 min) / 13,200 W (12 min) |
| Operating Frequency | 60 Hz / 50 Hz |
| Total Harmonic Distortion Voltage | <5% |
| Number of MPPTs | 3 |
| Inputs per MPPT | 2 (MPPT 1 & 2) / 1 (MPPT 3) |
| Max Input Current | 26A (MPPT 1 & 2) / 15A (MPPT 3) |
| Max Short Circuit Input Current | 31A (MPPT 1 & 2) / 19A (MPPT 3) |
| DC Input Voltage Range | 100 – 600 V DC |
| Start Up Voltage | 100 V DC |
| MPPT Operating Voltage Range | 120 – 440 V DC |
| MPPT Voltage | 360 V DC |
| Max Utilized PV Array Power | 21,000 W |
| Max PV Input | 25,000 W |
| Max Efficiency | 94 – 97% |
| Idle Consumption | <80W (Normal) / <60W (Standby Mode) |
| Nominal Battery Voltage | 48 V DC |
| Battery Voltage Range | 40 – 60 V DC |
| Max Charge / Discharge Power | 12,000 W |
| Recommended Battery Capacity per Inverter | >300 Ah |
| Operating / Storage Temperature Range | -13ºF – 140ºF (-25ºC – 60ºC) |
| Altitude | <6,561 ft (2000 m) |
| Relative Humidity | 0 – 100% |
| Typical Noise Emission | <50 dB @ 3 ft |
| Protection Rating | IP65 / NEMA 4X |
| Communications | RS485 / CANBus / WiFi |
| Max Parallel Connections | 16 |
Dimensions
| Weight | 88 lbs (40 kg) |
|---|---|
| Depth | 11.3 in (287 mm) |
| Width | 22.3 in (567 mm) |
| Height | 30.5 in (775 mm) |
What our Experts Think
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Strong 12 kW AC Output: Delivers reliable power for larger homes or light-commercial installations.
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Supports Up to 21 kW PV Input: Enables maximum solar harvesting — excellent for high-generation photovoltaic (PV) arrays.
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Hybrid Operation & Flexibility: Seamlessly manages battery storage, solar generation, and grid power as needed.
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LiFePO4‑Ready & Efficient: Designed for long-life LiFePO4 battery banks, with efficient charging and discharge cycles.
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Smart Energy Management Features: Includes MPPT tracking, load balancing, and real-time monitoring for optimal performance.
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Robust Construction & Low Maintenance: Built for durability and continuous operation with minimal upkeep.
Q&A
Q: What is the Big Battery EG4 FlexBOSS21 Hybrid Inverter used for?
A: Designed for high-capacity off-grid and hybrid solar systems, converting DC from batteries and PV panels into reliable AC power for homes or commercial setups.
Q: What is the power capacity?
A: Provides 12kW continuous output with support for up to 21kW PV input to maximize solar energy harvesting.
Q: Is it compatible with Big Battery systems?
A: Yes, fully compatible with EG4 and other Big Battery LiFePO4 packs for flexible hybrid applications.
Q: Does it support solar input?
A: Yes, it allows direct PV charging up to 21kW, optimizing renewable energy usage.
Q: What protections are included?
A: Features overload, short-circuit, over/under-voltage, and thermal protections for safe operation.
Q: Is installation difficult?
A: Suitable for professional or experienced DIY installation, with clear DC and AC wiring connections.
Q: Why choose the FlexBOSS21 Hybrid Inverter?
A: Users prefer it for high-capacity performance, flexible hybrid operation, and seamless integration with Big Battery systems, ensuring energy reliability and independence.
Maintenance Tips
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Inspect connections: Check AC/DC terminals and wiring monthly for tightness, corrosion, or wear.
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Keep cooling vents clean: Remove dust and debris to prevent overheating.
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Monitor system performance: Use the display or monitoring software to watch for error codes, voltage irregularities, or abnormal temperatures.
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Firmware updates: Apply manufacturer-recommended updates to maintain efficiency and safety.
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Check grounding: Ensure proper grounding to avoid electrical hazards and stabilize performance.
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Avoid overloads: Do not exceed the 12kW continuous output rating to prevent damage and extend lifespan.
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Environmental care: Install in a dry, ventilated area away from direct sunlight, moisture, or corrosive substances.
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