Temperature-Dependent Discharge Capability of High-Power LFP Battery Cells for Starter Battery Applications

This study investigates the temperature-dependence performance of high-power lithium iron phosphate (LFP) cells for automotive starter batteries. Temperature effects on high-power LFP cells are contextualised based on pertinent literature in order to compare the typical capacity behaviour of lead–acid batteries with LFP. Experiments were conducted on five cylindrical LFP cell types in a thermal chamber across ambient temperatures from +45 °C to −30 °C using a 9 C discharge regime aligned with automotive standards. Electrical and thermal behaviours were analysed, including energy yield, power output, and surface temperature monitored by sensors and thermal imaging for room temperature. Energy output decreased exponentially with temperature but remained above 70% for most LFP cells at −18 °C, while only one cell type was functional at −30 °C. Thermal analysis at ambient temperature confirmed homogeneous temperature distribution without hotspots and low overall heating (from 2 °C to 14 °C), indicating no need for additional cooling for starter battery applications. A conservative power analysis indicated that 4 kW at −30 °C would require a 28P4S 26650 configuration, representing a lower-bound estimate. We argue that even this conservative figure suggests a potential for weight reduction compared with lead–acid systems. Energy-based Pb-equivalence factors of approximately 1.2 at −18 °C and 3 at −30 °C were derived. A preliminary guideline for cell dimensioning based on measurements at 25 °C is proposed to address discrepancies between data sheet specifications and actual performance for pack configuration based on required power.