Climate & Environment
State of Charge (SOC)
Definition
State of charge is the amount of energy currently stored in a battery expressed as a percentage of its nominal capacity — 100% full, 0% empty. It is the central parameter of battery management: SOC estimation (by coulomb counting, voltage correlation or model-based methods) governs charging limits, range prediction in electric vehicles and dispatch decisions in grid storage, and operating within defined SOC windows extends battery life.
References
Source imported for editorial provenance.
This reference provides supporting context for how “State of Charge (SOC)” is defined and used.
Overview
How it is used
The parameter structures battery management systems, EV range and charging display, grid storage trading strategies and battery passport data fields.
Why it matters
The energy transition runs on stored electrons; state of charge is how we keep count of them.