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Electric vehicle battery life & warranties

Last updated 11/16/2017

The battery in your electric car is designed for extended life, but as with any other rechargeable battery, it will degrade over time. To protect customers, manufacturers of electric vehicles offer warranties on their batteries. It is important to know both what your battery warranty covers and how you can prevent your battery from a loss of capacity.  

What causes reduced electric car battery life?

Your EV's battery life can be impacted negatively in several ways:

  1. High temperatures. Operating an EV in high temperatures can degrade the battery. Additionally, parking an EV in the sun for long periods of time can have similar degradation effects.
  2. Overcharging/high voltages. Charging an EV beyond its voltage limit can cause internal resistance in the battery. Most batteries have built-in battery management systems (BMS), so overcharging is rarely an issue, but it is good practice to not charge your battery right up to 100% when possible.
  3. Deep discharges/low voltages. Draining most of a battery’s capacity frequently, or completely draining an EV battery, reduces battery capacity over time.
  4. High discharges or charge current. Pulling too much current from a battery over a certain amount of time can have detrimental effects on battery life. When possible, avoid aggressive driving patterns that might pull high amounts of current from your battery all at once.

All EV batteries will degrade over time, but avoiding the above situations can help you maximize your EV battery life.

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Electric vehicle battery life warranties

To protect customers, manufacturers of electric vehicles offer battery warranties. These warranties usually cover a certain amount of time and a certain number of miles driven, and end when the threshold of one or the other is met. The warranty typically guarantees that the battery won’t degrade past a certain percent of the original charge capacity during the warranty term.

For example, let’s say a manufacturer offers a five-year/50,000 mile warranty at a percentage guarantee of 80 percent. If your full charge battery capacity ever drops below 80 percent of the original battery capacity before five years of ownership or 50,000 miles is driven (whichever comes first), you can get your EV battery replaced and serviced for free. In this scenario, if your original battery capacity is 100 miles, this warranty guarantees you will get at least 80 miles from a full charge after five years or 50,000 miles of driving.

This formula for battery warranties is not universal, and it is important to examine your warranty closely to make sure you know what protection you have. Here are some battery warranties for several top electric vehicles on the market:

Warranties for popular electric cars

Electric car model Warranty period Percentage guarantee
Nissan Leaf 8 years/100,000 miles ~75%
Chevrolet Bolt 8 years/100,000 miles 60%
Tesla Model S 8 years/unlimited miles None
Tesla Model X 8 years/unlimited miles None

A couple of notes to keep in mind:

  • The Nissan Leaf has a percentage guarantee of approximately 75 percent because they guarantee in “bars”, their own measurement for battery life. A full Leaf battery has 12 bars, and the included battery warranty guarantees for 9 bars of charge
  • Both Tesla models have unlimited mileage in their warranties, but they do not specify a percentage guarantee. The point at which Tesla will replace a degraded battery under warranty is unknown. However, Tesla batteries typically show very little range degradation over their lifetime. As a brand highly concerned with their image and customer satisfaction, customers unsatisfied with their batteries will likely be helped by Tesla.

When do battery warranties matter?

EV battery warranties are most applicable for shorter range vehicles. This is because a regular commute might only drain a small percentage of a long-range battery, but that same commute might constitute a “deep discharge” on a lower-capacity battery, which degrades battery life more significantly over time.

For example, the Nissan Leaf has a range of 107 miles brand new, and the Tesla Model S has a range of 265 miles. Driving 50 miles on one charge would use about 47 percent of the Leaf’s battery capacity, and only about 19 percent of the Tesla’s capacity. Thus, commuting on the Leaf represents a much deeper discharge than a higher capacity car like a Tesla.

Deeper discharges lead to more rapid battery degradation. It’s important to make sure the warranty you receive will cover your driving habits, especially for those who want a lower range vehicle. For more information about EV range, check out EnergySage’s overview of ranges for popular electric cars.

Regardless of which EV you decide to purchase, it is essential to talk with the manufacturer and verify the warranty you will be receiving. Especially with such an expensive part of your new vehicle on the line, it is always a good idea to confirm the specifics in the rare case that your vehicle’s battery does end up degrading rapidly.

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