1. Daily kWh, then autonomy
A cabin with a fridge, lights and Starlink often uses 1.5–2.5 kWh/day. Two to three days of autonomy is common for off-grid; three days is safer if winter sun is weak.
Off-grid sizing is a loop: daily load decides the bank, the bank decides the array, and the array has to refill the bank on the worst realistic day.
LiFePO4 is a good fit for daily cycling because 80% depth of discharge is usable and cycle life is long. The two failure modes to design out are charging below freezing and undersizing the array for cloudy days.
Sizing rule: daily Wh first, then autonomy, then the model.
The arithmetic is simple; the mistakes come from using running watts instead of surge, or Ah without the voltage.
A cabin with a fridge, lights and Starlink often uses 1.5–2.5 kWh/day. Two to three days of autonomy is common for off-grid; three days is safer if winter sun is weak.
Required Wh = daily Wh × autonomy ÷ (0.8 × inverter efficiency). Then divide by system voltage for Ah. Round up to the next model or parallel count.
Plan for 3–4 kWh of PV per kWh of daily load in good sun, more in winter or high latitudes. Use an MPPT controller with a LiFePO4 profile and leave headroom for cold-weather Voc rise.
Example: 2,000 Wh/day, 2 days, 24V. Required ≈ 2,000 × 2 ÷ (0.8 × 0.85) = 5,882 Wh, or about 230Ah at 25.6V. One 24V 200Ah (5,120Wh) is close; two in parallel (10,240Wh) gives real autonomy. A 12V 314Ah pair in series is another route.
Assumes 80% depth of discharge and 85% inverter efficiency. Cold weather, ageing and higher inverter losses need extra margin.
Start with the smallest pack that covers the load, then check the bay and the inverter surge.
Three times the capacity of the 100 Ah pack in one box — fewer parallel connections and a 200 A BMS.
Best for: Full-time vans, larger 12V banks, long runtime without recharging.
Bank limit: 4S4P
The largest pack we list today: 5.1 kWh in one 24V case, parallel up to 1S4P.
Best for: Home backup, larger 24V house banks, multi-day off-grid loads.
Bank limit: 1S4P
The everyday 12V pack. Light enough to swap by hand, with 100 A continuous output and 4S4P expansion.
Best for: Weekend RVs, camper vans, 12V fridges, small boat electronics.
Bank limit: 4S4P
Not sure? Use the sizing calculator, or send us the load list and we will check it.
Include the application, daily runtime, inverter size and destination market. We will reply with a model recommendation and the matching datasheet.