Why is SoC estimation required?

Unlike voltage, current, and temperature, State of Charge (SoC) is an internal state of the battery and cannot be measured directly during operation. It must therefore be estimated from measurable battery signals and knowledge of battery behaviour.

Accurate SoC estimation is essential for the safe and efficient operation of rechargeable batteries. Without reliable information about the remaining charge, a battery management system cannot determine how much energy is available or when charging and discharging limits have been reached.

Reliable SoC estimation provides several important benefits:

• Prevents overcharging and overdischarging.
• Estimates the remaining operating time or driving range.
• Improves energy management and power allocation.
• Supports battery protection and cell balancing.
• Extends battery lifetime by operating within safe limits.

Because SoC cannot be measured directly, several estimation techniques have been developed. The simplest and most widely used method is Coulomb Counting, which estimates the remaining charge by tracking the current flowing into and out of the battery.