State of Charge / SoC

What is State of Charge (SoC)?

State of Charge (SoC) is the percentage of usable energy remaining in an electric vehicle's battery compared to its total available capacity. It indicates how much charge the battery has left and is displayed as a percentage ranging from 0% (empty) to 100% (fully charged).

In simple terms, SoC meaning is the battery's fuel gauge. An EV SoC of 80% means approximately 80% of the battery's usable charge remains available for driving.

Importance of State of Charge

The battery State of Charge is one of the most important indicators of an EV's readiness. It helps drivers estimate their remaining driving range, decide when to recharge, and plan journeys with greater confidence. The State of Charge is continuously estimated by the vehicle's Battery Management System (BMS), giving drivers a real-time view of the battery's available energy while helping optimise charging and battery performance.

Uses of State of Charge

Common uses of SoC include:

• Monitoring the remaining battery charge before and during a journey
• Estimating the vehicle's available driving range
• Determining when to recharge the battery
• Calculating the estimated charging time to a desired battery level
• Managing charging schedules for commercial and fleet EVs
• Supporting battery management and energy optimisation

Examples of State of Charge

Some practical examples of EV SoC include:

• An EV dashboard displaying 75% SoC, indicating that approximately three-quarters of the battery's usable energy remains.
• A driver charging their vehicle from 20% to 80% SoC before a long trip to reduce charging time while maintaining battery efficiency.
• An EV navigation system recommending a charging stop because the vehicle is expected to arrive with 10% SoC.
• A fleet operator monitoring the battery State of Charge of multiple vehicles to schedule charging and minimise downtime.
• A charging app displaying the current SoC alongside the estimated time required to reach the selected charge level.