The 100Ah prismatic LiFePO4 cell has become the default building block for solar storage in markets where the grid is unreliable. It is the size most pack builders standardise on, it is available in volume, and it scales cleanly from a single battery box up to a rack of modules.
The question buyers ask us most often is not which cell to buy, but which nominal voltage to build around — 12V, 24V or 48V. The answer comes from the load, the cable run and the inverter, not from the battery. This guide walks through that decision in the order it actually matters.
One cell, three pack voltages
A 100Ah prismatic LiFePO4 cell sits at 3.2V nominal and stores roughly 320Wh. Series-connect them and the capacity stays at 100Ah while the voltage and stored energy scale with the string count:
| Configuration | Nominal voltage | Capacity | Energy | Typical use |
|---|---|---|---|---|
| 4S | 12.8V | 100Ah | ≈1.28 kWh | Lighting, small inverters, RV and marine retrofit |
| 8S | 25.6V | 100Ah | ≈2.56 kWh | Small off-grid homes, telecom repeaters, 1–3 kW inverters |
| 16S | 51.2V | 100Ah | ≈5.12 kWh | Residential hybrid inverters, rack-mounted ESS, 3–10 kW systems |
That is why a single cell SKU can carry an entire product family. The cell, the BMS architecture and the enclosure logic are the same at all three voltages; only the string count and the BMS channel count change. If you are building a range rather than a one-off, standardising on one 100Ah cell keeps your spares, your test rigs and your documentation consistent.
What each voltage is actually good for
12V (4S) — small loads, short runs
12V is the right choice for lighting circuits, small inverters up to roughly 1 kW, gate and access control, and retrofits where the existing wiring is already 12V. The constraint is current. A 1 kW load at 12.8V draws about 78A at 90% inverter efficiency, which needs a genuinely heavy cable and a fuse to match. Keep runs short and loads modest and 12V is simple and cheap.
24V (8S) — the middle ground
24V halves the current for the same power, which is why it dominates small off-grid homes, telecom repeater sites and light commercial backup. It is the voltage to pick when a 12V system would need cable you cannot reasonably buy or bend, but a 48V inverter is more than the site needs.
48V (16S) — the modern default
51.2V nominal is now the standard for residential hybrid inverters and rack-mounted storage, and it is what most solar installers in Asia and Africa reach for first. A 5 kW load draws roughly 108A at 51.2V, which is comfortably handled by 25–35 mm² cable over normal indoor runs. If the system may grow later, start at 48V: adding parallel packs at 48V is straightforward, whereas upgrading a 12V site to 48V means replacing the inverter, the cable and the battery bank.
The cable and fuse maths people skip
Voltage selection is usually decided by current, not by load. Current is power divided by voltage, adjusted for inverter losses:
| Inverter size | at 12.8V | at 25.6V | at 51.2V |
|---|---|---|---|
| 1 kW | ≈87A | ≈43A | ≈22A |
| 3 kW | ≈260A | ≈130A | ≈65A |
| 5 kW | ≈434A | ≈217A | ≈108A |
Those figures assume 90% inverter efficiency. They are the reason a 12V system above about 1 kW stops being a battery question and becomes a copper question. Once you add cable length, voltage drop and the cost of the fuse and breaker you need at 260A, 48V frequently wins on total installed cost even though the pack itself costs more.
Strings, BMS and the mistake to avoid
- Do not series four 12V batteries to make 48V. Four separate BMS boards cannot see each other, so they drift apart in state of charge and one pack ends up working harder than the rest. Build a 16S pack with a single 16-channel BMS instead.
- Charging below 0°C damages LiFePO4. Charge between roughly 0°C and 45°C; discharge down to around −20°C is normally acceptable with reduced capacity. If the site freezes, specify a BMS with a low-temperature charge cut-off, or a pack with a heating pad.
- Standard charge rate is 0.2C to 0.5C. For a 100Ah cell that is 20A to 50A. Higher rates are possible with the right cell grade, but they shorten life and require thermal headroom.
- Keep the strings matched. Cells in one pack should be capacity- and internal-resistance-sorted by the supplier. Ask for the sorting criteria in writing.
A sizing example
Take an off-grid house with a daily consumption of 8 kWh and two days of autonomy. Usable energy needed is 16 kWh. At a depth of discharge of 80% — a conservative figure for daily cycling — the nominal bank is 20 kWh. That is four 51.2V 100Ah packs at 5.12 kWh each, giving 20.5 kWh nominal, or about 16.4 kWh usable.
The same house on 12V would need sixteen 100Ah packs and cable sized for hundreds of amps. The energy is identical; the installation is not.
What to check before you compare price
- Cell grade and sorting. Grade A cells, capacity- and IR-matched within the pack. Ask what the supplier rejects.
- Cycle life at a stated depth of discharge. A cycle figure without a DoD and a temperature is marketing, not data.
- BMS capability. Cell-level voltage and temperature monitoring, over- and under-voltage protection, over-current protection, low-temperature charge cut-off, and the communication you actually need — CAN, RS485 or Modbus.
- Documentation. A UN38.3 test summary and an MSDS travel with the shipment and are required for air and sea freight. IEC 62619 is the standard industrial battery buyers ask for as a target.
- Enclosure and ingress protection. IP54 for indoor racks, IP65 or better for anything outdoors or in a dusty workshop.
How EcoDyny supplies it
We manufacture the 100Ah prismatic LiFePO4 cell and build packs around it at 12V, 24V and 48V nominal, with the BMS and enclosure configured for your application. Cells and custom packs are in our LiFePO4 cells and custom packs line, and complete residential storage systems are in residential energy storage.
If you tell us the load, the autonomy you need and the market you are selling into, we will come back with a pack configuration, the documentation you need for import, and a quotation. Request a quote.