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EV Battery Degradation: What Is It?
With increasing popularity for electric vehicles (EVs), ever more are finding there is distinct technology at work with these vehicles: lithium-ion batteries. Among owners and prospects for EVs is one primary concern: battery degradation—how and why and at what pace an EV battery degrades to lose capacity to hold a charge over a period of weeks and months. Information about degradation is vital to informed decisions about EV ownership and maintenance and meeting long-term costs.
What Is EV Battery Degradation?
Deterioration of a battery is a gradual loss of the capacity to hold and deliver energy. That is to say, with time and many charging and discharging cycles, it can hold less and less energy compared to when it was brand new when bought by its owner. For an electric car, it is comparable to decreasing driving ranges with age.
Example:
If a new EV would go 300 miles per charge, after a number of years and many thousands of miles it might only go 250 miles per charge.
Why Does Battery Degradation Happen?
The majority of newer EVs have lithium-ion batteries, like those found inside your phone or laptop but significantly larger. All lithium-ion batteries fade with age at a steady rate, primarily because of:
- Charge and Discharge Cycles: Every time you deplete and reuse the battery, you go through a cycle. Each cycle induces very small chemistry shifts for the battery that accumulate with time.
- Heat: High temperatures cause batteries to degrade fast. That is why some EVs are provisioned with cooling to avoid overheating of batteries.
- High Voltage (State of Charge): Always charging and leaving the battery at full charge or draining it completely can equally tax the battery.
- Fast Charging: Charging at fast chargers like those at highways produces more heat and stresses the battery more compared to slower charging at home.
At What Rate Does Degradation Happen?
Battery degradation is not instantaneous. Most EV batteries lose 2% to 3% per annum of initial capacity, but this is a figure based upon factors like weather, driving habits, charging regimes, and battery type utilized.
Real-World Data:
Tesla has published findings showing most vehicles still retain in excess of 90% initial battery capacity after driving over 100,000 miles.
Nissan Leaf owners, particularly those with hot climates, have at times experienced quicker degradation, though advances in battery chemistry and cooling have mitigated this.
Can Battery Deterioration Be Minimized?
Yes. There are certain things EV owners can do to maintain healthy batteries:
- Avoid extreme temperatures whenever you can (such as parking in the shade or using pre-conditioning capabilities).
- Don’t always charge to 100% unless you are going to need the range for a trip.
- Charge with slower chargers during day-to-day charging; save fast charging for road trips.
- Use battery maintenance and software updates recommended by the manufacturers.
The majority of carmakers offer battery warranties (typically 8 years or 100,000 miles) to cover excessive degradation.
Should EV Battery Degradation Worry You?
For most people, degradation of batteries will not be a huge consideration for their typical lifespan with car ownership. Studies show vehicle batteries will have plenty of range left after 10 years and beyond. Even when its capacity is below being effective for transportation, it can be recycled and/or used for stationary storage batteries.
Conclusion
EV battery degradation is a reality and a natural process, but state-of-the-art technology and prudent driving behavior make it a manageable factor. Most EVs are designed to last beyond the life of a normal car by some margin, and battery replacements are less and less common with continuously improving technology.
Reference: Du, J., Zheng, T., Yan, Y., Zhao, H., Zeng, Y., & Li, H. (2019). Insulation Monitoring Method for DC Systems with Ground Capacitance in Electric Vehicles. Applied Sciences, 9(13), n/a.
