State of Charge (SoC) refers to the current level of energy stored in a battery compared to its total capacity. It is usually expressed as a percentage, where 0% means the battery is empty and 100% indicates it is fully charged. SoC is crucial for managing battery performance and longevity, especially in electric vehicles and renewable energy systems. Monitoring the SoC helps users understand how much energy is available for use and when to recharge the battery. Accurate SoC readings can prevent overcharging or deep discharging, which can damage batteries like those found in electric vehicles or solar energy storage systems.