Battery degradation is one of the most concerning problems for electric car owners. Unlike a traditional engine that can last many years, lithium-ion batteries slowly lose capacity with every charge cycle. After several years, drivers often notice a shorter range than when the car was new. Extreme weather, frequent fast charging, and high mileage all accelerate this process. While most manufacturers provide warranties for eight years or more, many owners worry about what happens afterward. The cost of replacing a battery pack can be extremely high, sometimes reaching half the value of the car. This makes resale value a major concern. Some owners have shared that after 100,000 miles, their car lost nearly 20% of its range. Such real experiences help new buyers set realistic expectations and prepare financially for the future of owning an electric car.