What is the key difference between State of Charge (SOC) and State of Health (SOH) in a battery?

The key difference between State of Charge (SOC) and State of Health (SOH) in a battery is that SOC indicates the current level of charge in the battery relative to its present maximum capacity, while SOH indicates the overall condition and performance capability of the battery relative to its original specifications. State of Charge (SOC) is expressed as a percentage, ranging from 0% (empty) to 100% (fully charged), and represents the amount of energy currently stored in the battery. SOC is a dynamic parameter that changes frequently based on the battery's charging and discharging activities. Estimating SOC accurately is critical for controlling the power flow in and out of the battery, managing energy consumption, and preventing over-discharge, which can damage the battery. State of Health (SOH), on the other hand, represents the long-term condition of the battery and its ability to perform as originally designed. SOH also is often expressed as a percentage, where 100% represents a new battery and lower percentages indicate degradation. SOH takes into account factors such as capacity fade, which is the reduction in the battery's maximum energy storage capability, and internal resistance increase, which affects the battery's ability to deliver power. Unlike SOC, which fluctuates rapidly, SOH changes gradually over time due to chemical and physical degradation processes within the battery. While SOC is a short-term indicator of the battery's current energy level, SOH is a long-term indicator of the battery's overall condition and remaining useful life. Monitoring both SOC and SOH is crucial for effective battery management and predicting when a battery needs maintenance or replacement.