EV Battery Degradation
The battery in an all-electric vehicle is basically made to last the lifetime of the vehicle. However, over time, and depending on how you treat them, EV batteries can slowly begin to lose the amount of energy they can store. This phenomenon is called “battery degradation” and can result in reduced energy capacity – which affects range and therefore the convenience of driving your EV.
Unfortunately, battery degradation is not easy to predict. Not all brands perform the same, and every vehicle is different in how it is driven, charged and maintained. On the bright side, it’s not uncommon for modern EV batteries to last more than 10 years, and some will go well beyond that before needing to be replaced. The average electric car owner will sell their car long before they need to replace the battery pack.
It’s important to note that battery degradation has been known to worsen in a couple of scenarios:
- If an EV battery is repeatedly driven down close to zero range, and then is charged from almost zero to a full charge routinely
- If an EV battery is continually charged at Level 3, also known as DC Fast Charging (DCFC)
Some automakers suggest limiting Level 3 DC Fast Charging (DCFC) and not making it a primary source of charge. For instance, Kia Motors suggests, “Frequent use of DC Fast Charging can negatively impact battery performance and durability, and Kia recommends minimizing use of DC Fast Charging.”
Environmental factors, such as continued exposure to extreme temperatures, will impact battery performance and may lead to degradation, as well. In particular, batteries don’t perform very well when the temperature is below 20 degrees Fahrenheit. When it’s really cold and you’re using the car’s heater, your range can temporarily drop by as much as 40 percent.
To maintain a battery pack at peak performance, it is recommended to keep EVs charged to between 60 percent and 80 percent, minimize fast charging and avoid extreme temperatures over long periods of time.
How Does Battery Degradation Happen?
Battery degradation doesn’t happen all at once. On average, electric car batteries might lose only about one to two percent of their range per year depending on the factors discussed earlier. Fortunately, most batteries are designed for durability and will outlast the usable life of a vehicle.
If we look at Tesla battery degradation and a Tesla S model battery, researchers have found that traveling 500,000 miles on the original battery should not be a problem. Just because the battery degrades does not mean it is not drivable; it simply loses some of its range and charging efficiency.
In blog posts, Tesla model S owners have noted that approximately 95 percent of the battery retains its battery function during the first 50,000 miles. A 5 percent battery degradation could equal 20 miles of range. Oddly enough, the battery only degraded another 5 percent during the next 100,000 miles. So, 150,000 miles of active driving only resulted in a total average of 10 percent total battery degradation. Typically, you wouldn’t need to consider replacing your battery until degradation reaches 50-65 percent.
There is also a time component to battery life — it degrades even if you don’t drive the car long distances. Hybrid batteries are designed to perform for at least 10 years, though many last far longer than that! To cover any unexpected failure, time-based warranties are now standard in the industry. There is a federal mandate for warranties to cover eight years of hybrid car battery life, so most automakers offer warranties of eight years or more.
If you're faced with replacing a battery on an out-of-warranty car, there's no need to panic. The cost of a new battery pack continues to decline. Some technicians can even install an approved used battery pack salvaged from a wrecked vehicle, which would greatly reduce the potential repair cost.
How to Prevent Battery Degradation
It is predicted that EV battery life could be up to 500,000 miles. New electric vehicles cannot overcharge, over-discharge, or overheat thanks to safeguards that are in place. However, there are a number of steps you can take to help extend the life of your EV battery.
- Avoid Discharging Below 20 Percent: Making sure that you do not operate your EV below a 20 percent charge will add life to the battery and also make sure you always have plenty of charge to get you home.
- Only Charge Up to 80 Percent: For most EV owners, the range of their EV is more than enough for daily commutes and errands and charging up to 80 percent is plenty for a day’s travel. A full charge to 100 percent is not good for lithium-ion batteries. You can lower the maximum charging limit with your EV’s onboard charger.
- Keep Your Car at the Right Temperature: Lithium-ion batteries are at their best within the same temperature range that is comfortable for humans. If it is too hot or too cold outside for you, it is likely not good for your EV. Park your car in the shade on hot days and in the garage when it is cold.
- Don’t Be a Lead Foot: Moderate acceleration is key to extending battery life. Smooth, even acceleration will avoid depleting the battery.
- Limit DC Fast Charging: It is much better to charge your EV at home overnight using Level 1 or Level 2 charging rather than utilizing a DC Fast Charger at a charging station in town. It avoids pushing so much electricity into the battery pack all at once. Using one of these DC Fast Chargers while on a trip is fine, just don’t make it a daily habit.
