Measurement
State of Charge (SoC) is a measure of the current energy level of a battery expressed as a percentage of its total capacity. An SoC of 100% means the battery is fully charged, while 0% indicates it’s fully discharged. SoC is like a “fuel gauge” for batteries, critical for battery management systems to optimize charging and discharging. In solar-plus-storage systems, maintaining appropriate SoC ranges ensures longevity (for example, avoiding 0% or 100% extremes frequently can extend battery life). Operators monitor SoC to know how much stored energy is available to supply to the grid or a home, especially during times when solar generation is low (night or cloudy periods). Effective SoC management is also important for providing services like frequency regulation or demand response from battery storage.