Battery Health Index in an Electric Vehicle (SOH)

Over time, every battery in an electric vehicle loses the amount of energy it can store and the amount of energy it can supply due to usage. The question is how much and how long?

When purchasing a new electric vehicle, the battery starts its life with a rating of 100%. Over time, due to wear and tear from age, the nature and frequency of vehicle use, there is a decline in the battery's performance in the electric vehicle. Parameters such as weather and even road quality can "contribute" to the decline in performance. The rating allows for informed decisions when using the electric vehicle, and also in the future when we want to sell the vehicle.

What is the Battery Health Index?

The Battery Health Index in an electric vehicle (State of Health, or SOH) describes the current state of the battery compared to its condition at the time of manufacture. The SOH unit will be 100% at the time of manufacture, and over time the percentage will decrease due to wear and tear from parameters such as age, nature and frequency of vehicle use, weather, and even road quality.

When will we know that the battery health requires attention? The Institute of Electrical and Electronics Engineers (IEEE) has determined that the electric vehicle battery requires maintenance or replacement when the SOH is below 80%. When the battery reaches an SOH of 70% or less, it requires a more comprehensive examination to assess the battery's efficiency. Such a situation usually occurs after about ten years of driving the electric vehicle on the road.

A battery analysis company from Seattle, Recurrent Motors, conducted a study on the durability of the electric vehicle battery over time. The study collected data including charging patterns, battery levels, and estimated driving ranges. The conclusion was that the electric vehicle battery is very reliable to the extent that it may last longer than the electric vehicle itself. Moreover, even after driving about 160,000 km, the battery's SOH was at least 90%. Additionally, the company claimed that only 1.5% of electric vehicle owners needed a battery replacement.

Why is it Important to Know the Battery Health?

The decline in the battery's performance in the electric vehicle is caused by a collection of parameters. Naturally, as time passes, there is natural wear and tear that causes a decrease in battery efficiency. The nature and frequency of use of the electric vehicle also have an impact, as well as environmental factors such as weather and road quality.

When we want to sell the electric vehicle, the battery's SOH will be a part of the purchase considerations. A low or borderline SOH can affect the vehicle's price and sometimes cast doubt on the feasibility of purchasing the vehicle.