Skip to content
Enjoy Free USA Shipping On All Orders
Enjoy Free USA Shipping On All Orders

BigBatttery ETHOS + EG4 FLEXBOSS21 ESS

BRAND:

| SKU:

K0241

$6,460.00
Free shipping with delivery between Jun 01 - Jun 08
Quantity

#1 Authorized BigBattery Distributor

All products come with manufactured warranties

Free Shipping + No Sales Tax
 

More money in your pockets for your renewable

Hassle-Free Returns & Exchanges

Safe shopping for your hard-earned money

Talk To A Real Person
 

Get help from our specialists — 

live chat or call anytime

BigBattery ETHOS™ + FlexBOSS21 ESS System | Expandable 48V LiFePO₄ Battery | 21kW PV Input | 12kW Hybrid Inverter

Scalable Energy Storage System with ETHOS™ Lithium Batteries, FlexBOSS21 Hybrid Inverter & Advanced Whole-Home Energy Management

The BigBattery ETHOS™ + FlexBOSS21 ESS System is a complete next-generation energy storage solution designed for homeowners, businesses, and off-grid users seeking maximum flexibility and long-term energy independence. Combining the expandable ETHOS™ 48V lithium battery platform with the advanced FlexBOSS21 hybrid inverter, this integrated system delivers reliable backup power, intelligent energy management, and industry-leading scalability. Featuring up to 21,000W of solar input capacity, 12kW continuous output, three MPPT inputs, and support for over 80kWh of expandable battery storage, this system is engineered to grow alongside your energy needs while maximizing solar production and system efficiency.

Key Features:

  • Complete ESS Solution: Fully integrated battery and inverter package engineered for seamless performance and simplified installation.
  • Expandable ETHOS™ Battery Platform: Easily scale storage capacity beyond 80kWh to meet future energy requirements.
  • 21,000W Solar Input Capacity: Supports large solar arrays with three MPPT trackers for maximum energy harvest.
  • 12kW Continuous Output Power: Delivers dependable energy for whole-home backup and light commercial applications.
  • 120/240V Split-Phase Output: Provides utility-grade power for residential and commercial loads.
  • LiFePO₄ Battery Technology: Safe, stable lithium iron phosphate chemistry designed for long service life and dependable performance.
  • 6,000+ Cycle Life: Engineered for years of daily cycling and long-term energy savings.
  • Closed-Loop Communication: Optimizes charging, discharging, and overall system performance between battery and inverter.
  • GridBOSS Integration: Supports advanced load management, AC coupling, generator integration, and enhanced energy control.
  • Advanced Safety Protections: Includes rapid shutdown, ground fault protection, arc fault protection, and intelligent system safeguards.
  • Remote Monitoring & Alerts: Wi-Fi-enabled monitoring provides real-time system visibility and performance tracking.
  • Maintenance-Free Operation: Designed for reliable long-term performance without routine servicing requirements.

Ideal Applications:

  • Whole-home backup power systems
  • Large residential solar energy storage
  • Commercial and light commercial energy systems
  • Off-grid homes and remote properties
  • Hybrid solar and battery installations
  • Generator-assisted backup systems
  • Scalable energy independence projects

What’s Included:

  • 1 × BigBattery ETHOS™ 48V Battery System
  • 1 × EG4 FlexBOSS21 Hybrid Inverter
  • GridBOSS MID Integration Support
  • Battery-to-Inverter Communication Components
  • Monitoring & Connectivity Interfaces
  • User Manuals & Installation Documentation

Specifications

Parameter Details
Battery Specifications
GTIN-12 (U.P.C.)850061252005
System Voltage48V
Nominal Voltage51.2V
ChemistryLiFePO4
kWh Capacity10.24kWh
Ah Capacity200Ah
Charging Voltage Range55.6 – 57V
Max Charge Voltage57V
Operating Voltage Range48 – 57V
Suggested Low Voltage Cutoff48 – 50.8V
BMS Cutoff Range42 – 47V
Cell Configuration16S 2P
Max Continuous Discharge Current200A
Max Continuous Power10,240W
Max Discharge Peak Current300A (Max 5 seconds)
Max Charge Current200A
Battery Temperature & Operating Conditions
Charge Temperature Range32°F – 113°F (0°C – 45°C)
Discharge Temperature Range-4°F – 140°F (-20°C – 60°C)
Optimal Discharge Temperature Range59°F – 95°F (15°C – 35°C)
Storage Temperature Range (SoC >50%)-4°F – 113°F (-20°C – 45°C) (Max 6 months)
Battery Physical & Installation Specifications
Weight273 lb (123.8 kg)
Depth6.7 in (170 mm)
Width26.5 in (674 mm)
Height43.3 in (1100 mm)
Max ConnectionsUp to 16 parallel connections per control box
Protection RatingIP65 / NEMA 4X
Battery Communications & Certifications
CommunicationsCANBus / RS485
CertificationsUL9540, UL9540A, UL1973, UN38.3
Inverter Specifications
Nominal AC Voltage120/240VAC | 120/208VAC (L1/L2/N required)
Frequency60 Hz (Default) | 50 Hz
Max. AC Current50A @ 240V | 57.7A @ 208V
Max. AC Input Power12000W
Max. AC Bypass90A
Operating Voltage Range180 – 270VAC
Output Voltage120/240VAC | 120/208VAC (L1/L2/N required)
Max. Output Current66.7A
Nominal Output Power (without PV)12000W @ 240V | 12000W @ 208V
Nominal Output Power (with PV)16000W @ 240V | 13800kW @ 208V
Power Factor0.99 (Full Load)
Reactive Power Adjustment Range-0.8 – 0.8 Leading Adjustable
Total Harmonic Distortion<5% (Full Load)
Transfer Time20ms (Default) | 10ms (Configurable) | 20ms (Parallel)
Rated Output Current50A @ 240V | 57.7A @ 208V
Rated Output Power12000W @ 240VAC | 12000W @ 208VAC
Peak Power24000W (0.5 sec) | 18000W (1 sec)
15000W (6 min) | 13200W (12 min)
Operating Frequency60 Hz (Default) | 50 Hz
Total Harmonic Distortion Voltage<5%
Solar MPPT Specifications
No. of MPPTs3
Inputs per MPPT2 (MPPT 1) | 2 (MPPT 2) | 1 (MPPT 3)
Max. Usable Input Current26A (MPPT 1) | 26A (MPPT 2) | 15A (MPPT 3)
Max. Short Circuit Input Current31A (MPPT 1) | 31A (MPPT 2) | 19A (MPPT 3)
DC Input Voltage Range100 – 600VDC
Unit Start-Up Voltage100VDC
MPPT Operating Voltage Range120 – 440VDC
Nominal MPPT Voltage360VDC
Max. Utilized PV Array Power21,000W
Max. Recommended PV Input25,000W
Performance & Efficiency
Max. Efficiency97% (PV to Grid) | 94.5% (PV to Battery) | 94% (Battery to Grid)
Idle Consumption<65W
Recommended Battery Capacity per Inverter>300Ah
Environmental Specifications
Operating / Storage Temperature Range-13ºF – 140ºF (-25ºC – 60ºC)
Operating Altitude<6,561 ft (2000 m)
Relative Humidity0 – 100%
Typical Noise Emission<50dB @ 3 ft
Design TopologyHigh-Frequency / Transformerless
Protection RatingIP65 / NEMA 4X
Communications & Expansion
CommunicationsRS485 / CANBus / WiFi
Max. Parallel Connections16
Physical Specifications
Weight88 lbs (40 kg)
Depth11.3 in (287 mm)
Width22.3 in (567 mm)
Height30.5 in (775 mm)

Understanding Your Power Needs

Power Calculation Guide

Sizing Metric Formula & Example
Energy Consumption (Wh) Formula: Watts × Hours
Example: 60W × 4 hrs = 240 Wh
Battery Capacity (Ah) Formula: Watt-hours ÷ System Voltage (V)
Example: 240 Wh ÷ 12V = 20 Ah
Inverter Size (W) Formula: Total Watts × 1.25 (safety margin)
Example: 300W × 1.25 = 375W → Use 400W inverter
Total Load Power (W) Formula: Sum of all appliance watts used simultaneously
Example: Light (10W) + Fan (75W) = 85W
Runtime (hrs) of Battery Formula: (Battery Ah × Voltage) ÷ Total Load (W)
Example: (100Ah × 12V) ÷ 240W = 5 hrs

Find Your Power Match

Need / Application System Recommendation
Basic lighting + phone charging Recommended Battery: 50Ah – 100Ah (12V)
Inverter Size: 100W – 200W
Notes: For small backup setups
Home office (laptop, fan, TV) Recommended Battery: 150Ah – 200Ah (12V or 24V)
Inverter Size: 500W – 1000W
Notes: For moderate usage with 4–6 hours of backup
Home backup (fridge, lights) Recommended Battery: 200Ah+ (24V or 48V recommended)
Inverter Size: 1000W – 1500W
Notes: Ideal for longer backups or heavier loads
Business / shop power backup Recommended Battery: 300Ah+ (48V system)
Inverter Size: 2000W – 3000W
Notes: Suitable for commercial setups or extended power outages

Why Shop With Us

  • Authorized & Trusted Dealer: We’re fully authorized for every brand we carry, so you get genuine products backed by full manufacturer warranties.
  • Fast, Reliable Shipping: Shipped from U.S. warehouses with quick, dependable freight options — keeping your project on track.
  • 30-Day Hassle-Free Returns: Changed your mind? Enjoy a simple 30-day return process for peace of mind.
  • Real Human Support, 7 Days a Week: Reach us by phone, email, or live chat — no bots, no overseas call centers, just experts who know off-grid power systems.
  • Expert Energy Guidance: Our solar and backup energy specialists are here to help with system design, product questions, and installation tips.
  • USA-Based Service: Local, knowledgeable, and friendly support right here in the U.S.
  • Secure Payments: Shop confidently with encrypted, secure checkout protecting your personal and payment information.
  • Built for Energy Independence: Whether powering a cabin, prepping for emergencies, or going off-grid, our products are chosen for performance, reliability, and sustainability.

BigBatttery ETHOS + EG4 FLEXBOSS21 ESS

$6,460.00