How many LiFePO4 cells do I need for a 10 kWh battery?

A 10 kWh bank at 48V requires 10,000/48 = 208 Ah. With 280Ah cells in a 16S configuration (16 cells in series for 51.2V), one parallel group gives 280Ah = 14.3 kWh — enough for 10 kWh at 70% DoD. So 16 cells total for a 16S1P pack.

What BMS do I need for a 16S LiFePO4 pack?

For a 16S (48V) pack, choose a BMS rated for 48-60V and at least 1C continuous current. For a 280Ah bank: 280A continuous minimum. Popular options: Daly, JK, Seplos. The BMS must match your system voltage exactly.

What is the difference between 280Ah and 304Ah LiFePO4 cells?

Both are Grade A prismatic cells in the same housing. 304Ah and 320Ah cells offer 9-14% more capacity per cell. The 280Ah remains widely stocked and best-value in 2026. Upgrading only makes sense if you're borderline on parallel groups.

LiFePO4 Battery Calculator

How many LiFePO4 cells do you need? Enter your energy use and system voltage — get cell count, configuration, and BMS spec.

Energy requirements

Daily energy consumption?

Wh/day

Days of autonomy?

Battery specifications

System voltage?

Depth of discharge (DoD)?

Cell capacity?

Battery bank required

6.3 kWh (15S1P)

Bank capacity (Ah)131 Ah @ 48V

Cell configuration15S1P (15 series × 1 parallel)

Total cells needed15 cells (280Ah each)

Estimated weight83 kg (182 lbs)

BMS spec needed48V / 131A continuous

Estimated cell cost~$438 (cells only)

BMS must match your system voltage and have a continuous current rating above your peak inverter draw. Estimated cell cost at ~$0.07/Wh (2026 pricing, excludes BMS, busbars, and enclosure).

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How to Use This Calculator

Enter your daily energy consumption

Add up all your appliances: watts × hours per day = watt-hours. A typical off-grid refrigerator uses ~1,200 Wh/day, LED lighting ~200 Wh/day, and a laptop ~60 Wh/day. The days of autonomy setting controls how many days the battery can supply all loads with zero solar input — important for cloudy weather resilience.

Set system voltage

LiFePO4 cells are 3.2V nominal each. They're wired in series to reach system voltage: 4 cells in series (4S) = 12.8V, 8S = 25.6V, 16S = 51.2V. 48V is strongly recommended for any system above 1 kWh — it reduces current by 4× compared to 12V, dramatically reducing wire size, heat, and losses.

Set depth of discharge

LiFePO4 batteries are rated for 3,000-6,000 cycles at 80% DoD. Increasing DoD to 90% gains 12% more usable capacity but accelerates degradation. The 80% default is the industry standard for long-term reliability in off-grid systems.

Enter cell capacity

The 280Ah prismatic cell is the dominant DIY choice in 2026 — widely available, well-tested, and approximately $70-90 per cell. The calculator determines how many cells in parallel (P groups) are needed to reach the required capacity, then multiplies by the series count for total cells.

The Formula

Total energy needed = Daily Wh × Days of autonomy Battery capacity (Wh) = Total energy needed ÷ (DoD / 100) Battery capacity (Ah) = Battery Wh ÷ System voltage LiFePO4 cell series count = System voltage ÷ 3.2V (nominal per cell) Parallel groups needed = Battery Ah ÷ Cell Ah (round up) Total cells = Series count × Parallel groups BMS continuous current = Battery Ah × 1C (conservative sizing)

The configuration notation (e.g., 16S2P) means 16 cells in series × 2 parallel groups. The 16 series cells create the target voltage (16 × 3.2V = 51.2V), and the 2 parallel groups double the total amp-hour capacity. For the 280Ah cell example: one 16S1P pack = 280Ah at 51.2V = 14.3 kWh usable at 80% DoD.

Example

Off-grid home — 5,000 Wh/day, 2-day autonomy

A homeowner wants a LiFePO4 battery bank to power 5,000 Wh/day with 2 days of autonomy. They plan to use 280Ah cells at 48V with 80% DoD.

Daily consumption5,000 Wh/day

Days of autonomy2 days

Total energy needed10,000 Wh

DoD80%

Required bank capacity10,000 / 0.80 = 12,500 Wh

Capacity in Ah (48V)12,500 / 48 = 260 Ah

Cell Configuration

Series cells (48V)48 / 3.2 = 15, round to 16 cells (16S)

Parallel groups (280Ah cell)260 / 280 = 0.93, round up to 1P

Configuration16S1P

Total cells16 cells

Actual capacity280Ah × 51.2V = 14.3 kWh (11.5 kWh usable)

Estimated cost~$1,000 (cells only at $0.07/Wh)

The 16 × 280Ah cells form a single 16S1P pack. A 48V/100A BMS handles 4,800W continuous — sufficient for most off-grid inverters up to 3,000W. Total assembly weight approximately 88 kg (194 lbs). Additional hardware needed: BMS (~$80-150), busbars, battery enclosure or rack, and a 48V charger or MPPT charge controller.

FAQ

How many cycles do LiFePO4 batteries last? ▼

Quality LiFePO4 prismatic cells are rated for 3,000-6,000 cycles to 80% capacity at 1C, 80% DoD. At one cycle per day, that's 8-16 years of service. At 80% DoD instead of 100%, cycle life is significantly extended. In practice, temperature and charge quality matter more than DoD — cells kept at room temperature (25°C) and charged with a properly calibrated BMS often outlast their rated cycle count. LiFePO4 has by far the best cycle life of any common lithium chemistry.

What is a BMS and do I really need one? ▼

A Battery Management System (BMS) is mandatory for any LiFePO4 pack. It monitors cell voltages, temperature, and current to prevent overcharge, deep discharge, overcurrent, and thermal runaway. Without a BMS, a single cell charged above 3.65V can cause permanent damage and fire risk. The BMS also performs cell balancing — equalizing charge across all cells so no single cell reaches dangerous limits first. For DIY packs, an active balancer (separate from the BMS) significantly extends pack life by continuously equalizing cells during charge.

Should I buy a pre-built battery or build my own? ▼

Pre-built batteries (like the Renogy, Epoch, or EG4 branded packs) include BMS, balancing, and warranty support — typically $0.20-0.40/Wh. DIY using raw 280Ah cells runs $0.07-0.12/Wh including BMS — 2-4× cheaper for the same capacity. DIY requires buying cells, a BMS, busbars, a charger, and assembling the pack. The risk is cell quality — buy from reputable vendors who provide capacity test results. Many off-grid enthusiasts build DIY and report excellent results; a 16S 280Ah pack is a straightforward first build with widely available guides.

Can LiFePO4 batteries be charged in cold weather? ▼

LiFePO4 can be discharged down to -20°C (-4°F) with reduced capacity. However, charging below 0°C (32°F) causes lithium plating — permanent damage to the anode. Many modern BMS units include a low-temperature charge cutoff to prevent this. In cold climates, insulate your battery enclosure and consider a self-heating BMS or a small heating pad for winter. This is a critical consideration for van builds, off-grid cabins, and any installation that experiences freezing temperatures.

What is the difference between 280Ah and 304Ah or 320Ah cells? ▼

All are Grade A LiFePO4 prismatic cells in the same physical housing. The 280Ah was the dominant cell in 2022-2024; 304Ah and 320Ah cells from the same manufacturers (EVE, CATL, CALB) became available in 2024-2026. Higher capacity cells cost more per unit but reduce parallel groups needed and simplify assembly. The 280Ah cell remains excellent value and widely stocked. For a 16S bank, upgrading from 280Ah to 320Ah cells gains 14% more capacity with the same 16 cells — worth considering if you're on the borderline between 1P and 2P.