What Is a LiFePO4 Battery?
LiFePO4 — lithium iron phosphate — is a lithium-ion chemistry whose cathode is made from iron phosphate rather than cobalt or nickel. That single material choice is why it dominates stationary storage, telecom backup and safe UPS batteries.
How the cell works
During discharge, lithium ions move from the graphite anode to the iron-phosphate cathode through the electrolyte; charge reverses the flow. The cell nominal voltage is 3.2 V — lower than the 3.6–3.7 V of NMC, but very flat across the discharge curve, which makes voltage-based SoC estimation stable.
Building a pack
- 12 V pack: 4 cells in series (4S) = ~12.8 V nominal.
- 48 V pack: 16 cells in series (16S) = ~51.2 V nominal, the standard telecom backup voltage.
Why specifiers choose it
- Safety. The phosphate cathode is thermally stable; it does not go into thermal runaway the way cobalt chemistries can.
- Cycle life. 2,000–6,000 cycles at 80% depth of discharge — far beyond lead-acid.
- Efficiency. ~95% round-trip, vs ~80% for lead-acid.
The trade-off
Lower specific energy than NMC, so LiFePO4 packs are bigger and heavier for the same kWh. For stationary and backup use that rarely matters. See LiFePO4 vs Lead-Acid for the head-to-head.