Technical Library

Lithium iron phosphate (LiFePO₄) is a lithium-ion battery chemistry that uses iron phosphate as the cathode material. LFP batteries have a nominal cell voltage of approximately 3.2V and are characterized by high thermal stability, long cycle life (typically 3,000–10,000 cycles depending on operating conditions), and relatively lower energy density compared to NMC or NCA chemistries.

The iron-phosphate bond structure requires temperatures above 270°C to undergo exothermic decomposition, compared to 150–180°C for NMC cathodes. This makes LFP the preferred chemistry for applications in occupied buildings, enclosed installations, and environments where thermal runaway risk is a regulatory concern. Relevant certification standard: IEC 62619:2022.

Note: LFP does carry a thermal runaway risk under specific abuse conditions. All LFP installations require a BMS with hardware-enforced protection thresholds.

Valve-regulated lead-acid (VRLA) batteries are sealed lead-acid batteries that recombine hydrogen and oxygen internally rather than venting during normal operation. The two primary VRLA technologies are AGM (absorbed glass mat) and gel-cell. VRLA batteries do not require watering or electrolyte maintenance but are not fully maintenance-free — float voltage calibration and impedance testing are recommended quarterly for critical applications.

VRLA batteries have a nominal cell voltage of 2.0V and energy density of 30–50 Wh/kg. Float life at 25°C is typically 10–12 years; elevated ambient temperature significantly reduces calendar life.

Depth of discharge is the percentage of rated capacity removed from a battery during a discharge cycle. Cycle life ratings are always stated with a corresponding DoD — a 10,000-cycle rating at 80% DoD does not imply 10,000 cycles at 100% DoD.

For VRLA batteries, operating at high DoD (above 50%) significantly reduces cycle life. LFP handles high DoD cycling better than VRLA — 80–100% DoD cycling is operationally feasible for LFP in applications with appropriate BMS protection.