12V 400Ah lithium iron phosphate deep cycle battery. 5120Wh high-capacity energy storage for demanding RV, marine and off-grid applications.
Product Overview
The 12V 400Ah LiFePO4 battery delivers 5120Wh of deep-cycle energy in a single unit built for extended off-grid autonomy. Designed for large RVs, liveaboard boats, and off-grid cabins that need multiple days of power without recharging, it replaces four 12V 100Ah lead-acid batteries with a fraction of the weight and far more usable capacity.
- 5120Wh usable energy — multi-day autonomy for large RVs and boats
- 250A continuous BMS — handles high-draw inverters up to 3kW
- Deep-cycle LiFePO4 — thousands of cycles, 10x lead-acid lifespan
- Expandable — parallel expansion for larger banks (e.g. 4 units = 20.48kWh); maximum parallel count confirmed per project
For distributors and installers serving the premium RV and marine market, this battery covers the top end of the 12V range. See also our 12V 300Ah model and 12V 200Ah model for smaller options in the same family.
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Technical Specifications
| Group | Parameter | Value | Status |
|---|---|---|---|
| Electrical | Nominal voltage | 12.8V | Typical |
| Electrical | Rated capacity | 400Ah | Typical |
| Electrical | Energy | 5120Wh | Typical |
| Electrical | Cell chemistry | LiFePO4 | Typical |
| BMS | Continuous discharge | 250A | Typical |
| BMS | Protections | Overcharge, over-discharge, over-current, short-circuit, temperature | Typical |
| Physical | Dimensions | To be confirmed | To Be Confirmed |
| Physical | Weight | Approx. 38-42 kg | To Be Confirmed |
| Environmental | Operating temperature | Charge 0-55C / Discharge -20-60C | Typical |
Reference values. Final specifications confirmed in formal quotation.
Autonomy Sizing: How Long 5,120Wh Actually Lasts
Autonomy is the reason to buy this battery, so size it honestly. Using about 90% of the rated energy as the practical planning figure (≈4,600Wh usable), one unit covers roughly:
| Daily consumption | Typical user | Autonomy on one 400Ah unit |
|---|---|---|
| 1.0kWh/day | Frugal camper / small boat systems | About 4.5 days |
| 1.5kWh/day | Typical efficient RV | About 3 days |
| 2.0kWh/day | Full-time RV with fridge, lights, devices | About 2.3 days |
| 3.0kWh/day | Liveaboard boat / off-grid cabin | About 1.5 days |
| 4.0kWh/day | Cabin with larger appliances | About 1.1 days |
If your autonomy target is longer than the table shows, the answer is parallel units (e.g. 4 units = 20.48kWh, with the count confirmed per project) or a smaller daily load — not a deeper discharge habit. Tell us your measured or estimated daily consumption and your target days, and we will size the bank before quoting.
One 400Ah Unit vs. Four 100Ah Units
The same 400Ah can be built as four separate 100Ah batteries. For large house banks, the single-unit format has practical advantages:
- One BMS, one protection point: the whole bank’s 250A discharge runs through a single coordinated BMS instead of four units whose protection can trip unevenly.
- Simpler wiring: one pair of main cables instead of a parallel harness with matched cable lengths — fewer connection points to loosen, corrode, or heat up.
- Simpler sourcing and spares: one SKU to stock, ship, and warranty for distributors; one unit for the installer to mount and commission.
The four-unit layout still wins where the battery space is split into small compartments or where a single unit’s size (dimensions and final weight confirmed in the quotation) cannot be handled in the installation space. Choose by the boat or vehicle, not by habit.
Applications
- Large RV and motorhome house systems
- Liveaboard sailboats and trawlers
- Off-grid cabins and tiny homes
- Mobile workshops and food trucks
Wholesale, OEM & ODM
We are not limited to listed SKUs. Capacity, BMS, housing, and features customizable per project. Request a Quote
For the trade, this model anchors the premium end of a 12V deep-cycle family — the same range continues down through the 12V 300Ah and 12V 200Ah models, so distributors can cover mid-size and large house banks from one supplier relationship, one specification standard, and one reorder channel. OEM options per project include housing and label branding, BMS feature configuration, and packaging for retail channels.
Frequently Asked Questions
How many days of power does 5120Wh provide?
Depends on daily consumption. At 1.5kWh/day (typical efficient RV), about 3 days. At 3kWh/day, about 1.5 days.
Can I parallel multiple units?
Yes. Parallel expansion is supported (e.g. 4 units = 1,600Ah / 20.48kWh); the maximum parallel count is confirmed per project. Use identical units at equal voltage.
What size inverter can it run?
The 250A continuous BMS supports high-draw inverters up to about 3kW at 12V. Check your inverter’s surge rating against the BMS with us if you run induction loads such as air conditioning or power tools.
Can it be charged in cold weather?
Per the specification, the operating range is charge 0–55°C and discharge −20–60°C — charging below freezing is outside the rated range. Installations in cold climates should plan battery placement or heating accordingly; ask us about configuration options for cold-region use.
What charger does it need?
A charger with a LiFePO4 (lithium) charge profile matched to a 12.8V nominal pack. Reusing a lead-acid charger is only acceptable if it has a true lithium setting — confirm the charger model with us before relying on it.
Where This Battery Is Used
This high-capacity deep-cycle pack is specified for large house banks and storage systems across our RV Battery Solutions, Marine Battery Solutions and Off-Grid Energy Storage pages. Send us your daily consumption and autonomy target for a bank sizing check.