BigBattery APEX-6.5K Off-Grid Inverter

The BigBattery APEX-6.5K Off-Grid Inverter Delivers 6.5kW of Split-Phase 120/240V Power With Solar and Generator Inputs

The BigBattery APEX-6.5K is a 6.5kW off-grid hybrid inverter that delivers split-phase 120/240V pure sine wave power at 50 or 60Hz. It is built for cabins, tiny homes, homesteads and off-grid properties with moderate loads.

It runs on a 48V battery bank and communicates in closed loop with BigBattery NEXUS, ETHOS and HUSKY 2 INV batteries, and EG4 280Ah and 314Ah All Weather and Indoor wall-mount batteries in off-grid installations. An 80A pass-through keeps large appliances and critical circuits running, and two MPPT solar inputs accept up to 10,000W (5,000W + 5,000W) of PV. BigBattery backs the APEX with a 5-year warranty and lifetime USA-based technical support, and it ships from Texas.

BigBattery APEX-6.5K Off-Grid Inverter Features

6.5kW Split-Phase Output

The APEX-6.5K supplies 6.5kW of continuous 120/240V split-phase power, with a maximum of 13,000VA for motor starts and surges. It can start motors up to 4 HP.

Dual MPPT Solar Input

Two MPPT trackers accept 10,000W (5,000W + 5,000W) of solar in total, with a 125V to 450V operating range, 550V maximum open-circuit voltage and up to 18A per input.

Fast Battery Charging

Solar charging reaches 140A, and grid or generator charging reaches 80A.

Generator and Grid Inputs

The APEX-6.5K has two AC inputs, one for the grid and one for a generator, so both can be connected at the same time. It also has a CT input.

80A Pass-Through

Large loads and critical circuits can pass straight through to the output while the inverter charges the batteries.

Closed-Loop Battery Communication

The APEX reads true state of charge from compatible lithium batteries for accurate charging. BigBattery lists BigBattery NEXUS, ETHOS and HUSKY 2 INV batteries, and EG4 280Ah and 314Ah All Weather and Indoor wall-mount batteries. It also supports lead-acid and user-defined battery settings.

Expand With Parallel Units

Connect up to 6 APEX inverters in parallel. Three or more units can form a three-phase output.

Installer-Friendly Design

Bottom-entry wiring keeps conduit runs neat, an intelligent fan keeps noise under 60dB, and an optional Wi-Fi or GPRS module adds remote monitoring.

Real-World Applications

Off-grid cabins and tiny homes. Run lights, a refrigerator, a well pump and 240V tools from solar and batteries.

Homesteads. Combine solar with a backup generator on its own dedicated input.

Home backup. Keep essential 120V and 240V circuits running during outages.

Paired systems. Combine with a BigBattery NEXUS 2 or ETHOS battery for a complete off-grid energy system.

How It Compares to Common Alternatives

Versus 120V-only inverters. Many off-grid inverters supply only 120V. The APEX provides 120/240V split-phase power for well pumps, ranges, dryers and other 240V loads.

Versus grid-tied hybrid inverters. Grid-tied hybrids with UL 9540 battery certification suit permitted grid-interactive systems. The APEX is designed for off-grid and backup systems, and its battery communication is listed for off-grid installations that do not require UL 9540.

Is This APEX Inverter the Right Fit

• Battery. 48V battery bank, 40V to 60V DC.
• Solar array. Strings within 125V to 450V MPPT range and 550V maximum open-circuit voltage, up to 10,000W (5,000W + 5,000W) in total.
• Location. Indoor installation only (IP20), such as a garage or utility room. Operating range 14°F to 131°F, derating above 113°F.
• Space and weight. 25.51 x 16.14 x 5.51 in, 48 lbs.

This may be a good fit if

• You are building an off-grid home, cabin or homestead
• You need 120/240V split-phase power
• You want solar and generator charging in one unit
• You use BigBattery or EG4 48V batteries

Common Questions

Is the APEX UL 9540 Certified?

No. BigBattery lists APEX closed-loop battery communication for off-grid installations that do not require UL 9540. For UL 9540 grid-tied systems, BigBattery points to the EG4 FlexBOSS18, FlexBOSS21 or 18kPV instead.

Which Batteries Work With It?

Closed-loop communication is supported with BigBattery NEXUS, ETHOS and HUSKY 2 INV batteries, and EG4 280Ah and 314Ah All Weather and Indoor wall-mount batteries. Any 48V battery bank can be used with the appropriate settings.

APEX 6.5K or 10K, Which Do I Need?

Choose the 6.5K for cabins, tiny homes and properties with moderate loads. BigBattery suggests the 10K if you run a well pump, air conditioning and heavy circuits together.

Can I Connect Grid and Generator Together?

Yes. The 6.5K has separate grid and generator inputs, unlike the APEX-10K, which has a single AC input.

Can It Run a Well Pump?

In most homes, yes. It provides 240V split-phase power and can start motors up to 4 HP. Check your pump's starting current against the inverter's surge rating before you buy.

What Is the Warranty?

5 years, with lifetime USA-based technical support from BigBattery.

What's Included

• 1 x BigBattery APEX-6.5K Off-Grid Inverter
• 2 x M6x60mm Expansion Screws
• 2 x M5x30mm Plastic Expansion Screws
• 2 x Phillips M6x10mm Screws
• 2 x Backup M6x10mm Screws
• 2 x SC35-6 Copper Lugs
• 4 x Black M3x6mm Screws
• 1 x Parallel Communication Cable
• 1 x Wi-Fi Logger (optional)
• 2 x CT (optional)
• 1 x User Manual
• 1 x Warranty Card
• 1 x Quality Certificate
• 1 x Outgoing Inspection Report

Off-Grid Power for the Whole Property

The BigBattery APEX-6.5K gives off-grid homes clean split-phase power, solar and generator charging, and closed-loop battery communication in one inverter. At Outbound Power, we help customers choose the right parts for their solar and battery systems. If you have questions, our team is happy to help.

BigBattery APEX-6.5K Off-Grid Inverter Manual