SOC errors in LFP batteries: the $1 million per GWh challenge for BESS
Written by Darya Rüwald, Director of Battery Intelligence
Full article covered in Modern Power Systems
Grid-scale battery energy storage system (BESS) projects are now dominated by lithium iron phosphate (LFP) batteries, where they have overtaken nickel manganese cobalt (NMC) technology. This is due to their cost-effectiveness, durability, reduced safety concerns, and supply chain advantages. But LFP technology comes with a persistent challenge: accurately estimating the battery’s state-of-charge.
Traditional battery management systems (BMS) use two methods to estimate SOC: Coulomb counting; and the voltage method. Coulomb counting tracks current flow, in and out, but is prone to error accumulation. Voltage-based calibration can correct this persistent drift, yet LFP cells have a flat open-circuit voltage (OCV) curve that makes voltage a poor indicator of charge. The result is widespread inaccuracy.
For operators, unreliable SOC estimation is more than a nuisance. Their dispatch and trading decisions depend on these values. Overestimation risks overselling power and triggering penalties, causing operators to implement wide safety margins in their trading decisions, directly cutting into usable capacity and potential revenue. Underestimation, on the other hand, leaves capacity idle and unsold.
Read full the article in Modern Power Systems.
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