What Is Battery State of Health (SOH) and Why Is It Critical for Your Electric Vehicle?

The heart of every electric vehicle (EV) is its lithium-ion battery. The performance and lifespan of this battery directly influence key factors such as driving range and resale value. This is where Battery State of Health (SOH) becomes essential.

What Is SOH?

Battery State of Health represents the current capacity and performance of a battery compared to when it was new, expressed as a percentage.

  • 100% SOH: The battery retains its factory-fresh capacity.

  • 80% SOH: The battery’s usable capacity has dropped to 80% of its original level.

SOH is calculated by analyzing data such as charge-holding ability, internal resistance, temperature history, and charge/discharge cycles.

Why It Matters

  1. Range and Performance: A lower SOH reduces the distance you can travel on a single charge.

  2. Resale Value: Buyers offer less for a vehicle with a weak battery.

  3. Warranty Coverage: Many manufacturers set warranty thresholds, such as 70% SOH.

  4. Safety and Efficiency: Degraded batteries run hotter and lose energy efficiency.

Factors That Affect SOH

  • Frequent Fast Charging: Regular DC fast charging generates heat and accelerates wear.

  • Over-Discharge or Full Storage: Keeping the battery at 0% or 100% for long periods shortens its life.

  • Temperature Extremes: Very hot or cold environments harm battery chemistry.

Tips to Preserve Battery Health

  • Keep the charge level between roughly 20% and 80% whenever possible.

  • Park in shaded or indoor areas to avoid excessive heat.

  • Follow the manufacturer’s maintenance and software-update recommendations.

Accurate Diagnosis with an Electric Vehicle Inspection Device

Whether you’re buying a used EV or want a clear picture of your current battery’s condition, a professional electric vehicle inspection device is invaluable. These tools communicate directly with the battery pack to provide:

  • The true SOH percentage

  • Cell voltage balance

  • Charge and discharge history

Automotive-grade EV inspection devices go beyond simple range estimates, delivering detailed technical analysis and reliable data. Both buyers and sellers gain transparent insights into the battery’s health, helping prevent unexpected costs.

In short, the Battery State of Health (SOH) is one of the most important indicators of your electric vehicle’s performance, value, and safety. With proper habits and regular professional checks, you can extend battery life and confidently understand your EV’s true condition.