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BigBattery

BigBattery NEXUS + APEX 6.5K Off-Grid Kit | 15 kWh | 48V LiFePO4

SKU K0191

Regular price: $4,535.00

Regular price: $4,535.00

✅ Order by 12:00 PM EST and processing starts the same day (ships within 1–2 business days). Free, insured US shipping — delivery in 4–7 business days. Oversized items ship via LTL freight and we coordinate delivery with you by phone.

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OffGrid Horizon Family Owned and Operated

🏔️ OffGrid Horizon is family-owned & off-grid obsessed. Read our story →

Shipping: how fast & how it works

Free standard shipping on every US order — no shipping charges at checkout, no hidden fees, and every shipment is insured against loss or damage.

Processing: 1–2 business days. Order before 12:00 PM EST and processing begins the same day.
Delivery: 4–7 business days via USPS, UPS or FedEx. Tracking is emailed the moment your order ships.
Large items (solar kits, batteries, shelters): delivered by LTL freight carriers such as FedEx Freight, Old Dominion or XPO. The carrier calls ahead to schedule a delivery window — please inspect the pallet and note any damage on the delivery receipt before signing, and we’ll take care of the rest.

Questions about delivery to your location? Call (302) 496-3554 (Mon–Fri, 9am–4pm EST) — we’re happy to check before you order.

What is your Return Policy?

At OffGrid Horizon, we want every customer to shop with confidence. If something doesn’t go as planned, we’ve made returns and refunds simple and fair. Here’s how it works:

1. Return Window

You can request a return within 30 days of receiving your order. Unfortunately, we’re unable to accept returns after that time frame.

2. Who Pays for Return Shipping?

If your item arrives damaged, defective, or incorrect, we’ll cover the return shipping cost — and you’ll receive a full 100% refund or replacement, including any original shipping costs.
If you’re returning an item because you changed your mind, you’ll be responsible for return shipping, and a 25% restocking fee applies.

3. Damaged or Defective Items

Received something broken or not working properly? Contact us within 30 days. We’ll provide a prepaid return label and once the item is returned and inspected, we’ll issue either a full refund or a replacement.

4. Changed Your Mind?

If you no longer want the item, you can return it within 30 days — as long as it’s unused, unopened, in its original packaging, and in resellable condition.

5. Refund Processing

Once we receive and approve your return, we’ll send a confirmation email and issue a refund to your original payment method within 7 business days. Please allow additional time for banks or credit card companies to process and reflect the refund.

How to start a return: email sales@offgridhorizon.com or call (302) 496-3554 (Mon–Fri, 9am–4pm EST) with your order number — we’ll send return instructions and your RMA right away.

Product Description

The entry point to the NEXUS off-grid line: one BigBattery NEXUS 48V LiFePO4 battery — 15 kWh of storage in a single cabinet — paired with the APEX 6.5K all-in-one off-grid inverter. This is a complete power core for a cabin, small homestead, workshop or backup circuit panel: the APEX 6.5K combines a 6,500W split-phase inverter, an MPPT solar charge controller and a battery charger in one wall-mounted unit, so the battery, solar input and AC output are all managed by a single piece of equipment.

What's in this kit

1 × BigBattery NEXUS 48V LiFePO4 battery (15 kWh) — high-capacity lithium iron phosphate storage with a built-in battery management system (BMS) that monitors and protects the cells. A single NEXUS holds substantial reserve on its own, and additional NEXUS units can be combined later to scale total capacity.
1 × APEX 6.5K off-grid inverter — an all-in-one unit built for 48V battery systems: 6,500W of split-phase 120/240V output, integrated MPPT solar charge controller, and battery charger in a single chassis.

Is this the right size for you?

This configuration fits a cabin, guest house, seasonal property, well-equipped workshop or a defined set of backup circuits — refrigeration, lighting, pumps, electronics and similar loads. The 6,500W inverter carries both 120V and 240V appliances, and 15 kWh of storage covers overnight use and a cloudy stretch for loads of that scale.

Size up if you are powering a full-time family home, running mini-splits for long hours, or your site sees extended overcast periods — storage is what carries you through those. The same system is available with two or three NEXUS batteries (30 kWh and 45 kWh configurations), and because NEXUS units combine, starting here does not lock you in: additional batteries can be added as your needs grow.

Consider the APEX 10K version if your peak loads are the concern rather than storage — for example, starting large motors or running several 240V appliances at once.

Specifications

Item	Specification
Battery	1 × BigBattery NEXUS, 48V LiFePO4, 15 kWh
Battery chemistry	LiFePO4 (lithium iron phosphate)
Battery management	Built-in BMS with cell monitoring and protection
Inverter	APEX 6.5K all-in-one: 6,500W split-phase 120/240V output
Solar charging	Integrated MPPT solar charge controller (solar array sold separately)
Battery charging	Integrated charger in the APEX 6.5K
System voltage	48V
Expansion path	Additional NEXUS batteries can be combined; 30 kWh and 45 kWh kit configurations are also available

Warranty & support

Battery: the NEXUS is covered by BigBattery's 12-year manufacturer warranty, backed by lifetime USA-based technical support. Inverter: the APEX 6.5K carries a 5-year limited manufacturer warranty.

Common questions

Can I install this myself?

Placing the battery and mounting the inverter are within reach of a competent owner, but the AC side — tying the inverter into a distribution panel, grounding, bonding and code compliance — is work for a licensed electrician, and in most jurisdictions it must be permitted and inspected. Have your electrician review the system before ordering.

Does this kit include solar panels?

No. The APEX 6.5K's MPPT input is ready for a solar array, but panels, mounting hardware and array wiring are sized to your site and sold separately. The system can also run as battery-plus-charger without solar.

How does the battery handle cold weather?

LiFePO4 chemistry loses usable capacity in the cold, and charging cells below freezing damages them. The NEXUS should live in a space kept above freezing — a conditioned utility room, insulated enclosure or similar.

Can I add more storage later?

Yes. NEXUS batteries are designed to combine, so you can start with this single-battery kit and add units later rather than buying maximum capacity up front. If you already know you need more, the 2 × NEXUS (30 kWh) and 3 × NEXUS (45 kWh) versions of this kit are listed separately.