Understanding Battery Warranty and Battery Degradation in Electric Cars
Electric cars (EVs) have rapidly gained popularity due to their environmental benefits and lower operational costs however, a common concern for EV owners and potential buyers is the longevity of the vehicle's battery—its warranty coverage and how degradation impacts performance over time.
Battery Warranty in Electric Cars
Most electric car manufacturers offer comprehensive warranties on their batteries to address concerns about durability and performance. These warranties generally cover defects, battery failure, or significant degradation over a specific period or mileage, typically ranging from 8 years or 100,000 miles. This warranty provides peace of mind to EV owners.
Battery Degradation
Battery degradation refers to the gradual loss of a battery's capacity to hold a charge over time. A term usually used is state of health (SOH) and is measured in percent. Degradation is a natural process for all rechargeable batteries, including the lithium-ion batteries used in electric vehicles. However, the rate of degradation can vary based on factors such as temperature, charging habits, and overall usage.
EV batteries degrade as they go through charge and discharge cycles. Each cycle contributes to wear, reducing the battery's energy capacity and thus its range. On average, EV batteries lose about 1-2% of their capacity per year. By the end of the warranty period, an EV battery should retain over 80% of its initial capacity. This means that the car has 80% of its initial range.
Fortunately, most modern EVs are designed with sophisticated battery management systems (BMS) that help slow down this degradation by maintaining optimal conditions, such as avoiding extreme temperatures and regulating charge levels. In addition, many manufacturers are using ‘buffers’ in the battery so that it protects the battery even more. The buffer is extra capacity that is reserved to help manage the battery. This often means that a degradation in usable range isn’t seen for a long time as the buffer is used up first.
Factors Affecting Degradation
High Temperatures: Heat accelerates the degradation of lithium-ion batteries. Vehicles driven or parked in consistently hot climates may see faster battery deterioration. An unlikely situation in the UK.
Frequent Fast Charging: While convenient, fast charging generates more heat than slower Type 2 charging and can increase the rate of degradation if used excessively. However, better cooling systems have reduced this risk.
Depth of Discharge: Regularly depleting the battery to near zero and then charging to 100% can cause more stress on the battery than keeping the charge level between 20% and 80%.
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