Product Description

This is the multi-battery configuration of the NEXUS + APEX 6.5K system: two or three BigBattery NEXUS 48V LiFePO4 batteries — 280Ah and 14.3 kWh usable each, per BigBattery — with the APEX 6.5K all-in-one inverter: 6,500W of continuous split-phase 120/240V output, two MPPT solar inputs rated 5,000W + 5,000W, and built-in charging from grid or generator, per BigBattery. BigBattery sells this as an off-grid and backup power system; it is not sold as a grid-interactive (sell-back) system.

Who This Is For

Cabins, homesteads, and off-grid households whose loads are moderate but constant — refrigeration, lighting, pumps, electronics, and everyday 240V appliances — and who draw on the bank every day or face long overcast stretches. The 6,500W inverter covers the loads; 30–45 kWh class storage covers the nights and the weather. If peak power is your constraint instead, see the APEX 10K version of this kit.

Key Features

  • Choose 2 × NEXUS (30 kWh class) or 3 × NEXUS (45 kWh class) — 28.6 or 42.9 kWh usable, adding BigBattery's 14.3 kWh per-unit figure
  • 6,500W continuous split-phase 120/240V output, 13,000VA maximum output, per BigBattery
  • Two MPPT solar inputs, 5,000W + 5,000W (125–450Vdc MPPT range), per BigBattery
  • Two AC inputs (grid and generator) — up to 80A grid/generator charging and up to 140A solar charging, per BigBattery
  • NEXUS batteries: 6,000+ cycle life, self-heating function, aerosol fire suppression, RS485 / RJ45 / CAN communications, per BigBattery
  • Room to grow: NEXUS parallels up to 15 units and the APEX 6.5K parallels up to 6 units, per BigBattery
  • Inverter certifications: UL1741 / RoHS / EN61000-6-1 / EC61000-6-3 / FCC Part 15 Class B, per BigBattery

Why BigBattery

BigBattery is a US company building LiFePO4 energy storage for off-grid and home backup use; the APEX line is BigBattery's own inverter family, so battery and inverter come from one manufacturer. Kits ship from Texas and are backed by lifetime USA-based technical support, per BigBattery. See our full BigBattery collection.

What's In the Kit

Solar panels, racking, and array wiring are not included. BigBattery's kit listing does not itemize cables or accessories, so call us at (302) 496-3554 before ordering and we'll confirm exactly what ships with your configuration.

Specifications

Batteries 2 or 3 × BigBattery NEXUS, 48V class (51.2V nominal), LiFePO4, 280Ah each
Usable energy 14.3 kWh per battery, per BigBattery — 28.6 kWh (2 units) or 42.9 kWh (3 units) total
Battery max continuous discharge 140A (7.6 kW) per battery, per BigBattery
Battery cycle life 6,000+ cycles, per BigBattery
Battery communications RS485 / RJ45 / CAN
Battery dimensions / weight 19.7 × 27.5 × 15.7 in; approx. 315 lb — each
Inverter APEX 6.5K — 6,500W rated output, 13,000VA maximum, split-phase 120/240Vac
Solar input Two MPPTs, 5,000W + 5,000W; 125–450Vdc MPPT range; 18A + 18A
Charging Up to 140A from solar; up to 80A from grid/generator; two AC inputs (grid & generator)
Inverter parallel capability Up to 6 units, per BigBattery
Inverter certifications UL1741 / RoHS / EN61000-6-1 / EC61000-6-3 / FCC Part 15 Class B, per BigBattery
Inverter dimensions / weight 25.51 × 16.14 × 5.51 in; 48 lb
Battery warranty 12-Year Limited Warranty, per BigBattery
Inverter warranty 5-Year Limited Warranty, per BigBattery
Kit SKU K0192 (2 batteries) / K0193 (3 batteries)

Sizing Your Off-Grid Home

Example assumptions for a lived-in homestead — label and adjust for your own site: refrigerator 1.5 kWh/day, chest freezer 1.0, LED lighting 1.0, well pump 1.5, electronics and internet 1.5, laundry and kitchen 2.0. That is about 8.5 kWh/day before climate loads; a mini-split commonly adds 5–15 kWh/day in season depending on size and climate, bringing many households to 14–20 kWh/day.

Against that: two NEXUS (28.6 kWh usable, per BigBattery's per-unit figure) is a full day and a half to two days of autonomy; three (42.9 kWh) stretches toward three days — the difference you feel in a cloudy week. On power, two batteries support about 280A / 15.2 kW continuous by simple addition of BigBattery's per-unit figures, so the bank carries the 6,500W inverter with headroom to spare.

Installation

Each battery cabinet weighs approximately 315 lb, so plan floor space and the move for two or three of them, plus wall space for the 48 lb inverter. The AC side — panel interconnection, overcurrent protection, grounding, bonding — belongs to a licensed electrician working to the National Electrical Code (NEC) and local codes; most jurisdictions require a permit and inspection for energy storage. Keep the batteries in a dry space above freezing; BigBattery's published charge range starts at 32°F.

Warranty & Support

Batteries: covered by BigBattery's 12-Year Limited Warranty — in BigBattery's words, “BigBattery, Inc. guarantees that its products will be free from defects in material and workmanship for a period of twelve (12) years.” Included accessories are covered for 1 year, and no registration is needed, per BigBattery. Inverter: the APEX 6.5K is covered by a 5-Year Limited Warranty, per BigBattery.

BigBattery publishes a 30-Day Money Back Guarantee; per BigBattery, non-defective returns are refunded at purchase price minus a 20% restocking fee, excluding shipping. All returns require a Return Merchandise Authorization (RMA) before anything ships back — call OffGrid Horizon at (302) 496-3554 and we'll open the RMA or warranty claim with BigBattery. We're a family-owned authorized BigBattery partner, and BigBattery backs the system with lifetime USA-based technical support.

Shipping

This kit ships as palletized freight within the United States — two or three battery cabinets plus the inverter. Inspect every pallet before signing: note any damage on the delivery receipt and contact us promptly — that notation keeps a freight claim simple.

Frequently Asked Questions

What exactly does the listed price include?

The Battery Configuration you select — two or three NEXUS batteries — plus one APEX 6.5K inverter. The price updates with your selection. Panels and racking are separate.

Two batteries or three?

Match storage to your daily consumption and the cloudy stretch you want to ride out. Households near 14–18 kWh/day usually do well at 28.6 kWh usable; heavier consumption or multi-day weather points to three units. And the bank grows later — up to 15 in parallel, per BigBattery.

Is this a grid-tie system?

No. BigBattery sells it for off-grid and backup power applications; the two AC inputs accept grid or generator power for charging, per BigBattery.

Is 6,500W enough with this much storage?

Storage and power are separate questions. If your simultaneous loads stay under roughly 6,500W — typical for cabins and efficient homesteads — this inverter is the right size, and the deep bank is what carries the nights. For bigger simultaneous loads, the APEX 10K version pairs the same batteries with more output.

Do I need an electrician?

Yes — AC interconnection, grounding, and code compliance are work for a licensed electrician, and most jurisdictions require a permit and inspection.

How do the batteries handle cold weather?

Per BigBattery, the NEXUS discharges from −4°F to 113°F and charges from 32°F to 113°F, with a self-heating function. Keep the cabinets in a space that stays above freezing.

Two batteries or three — want a second opinion on your load list? Call OffGrid Horizon at (302) 496-3554. Family-owned, authorized BigBattery partner.

Customers also bought