How EV Battery Warranties Actually Work

Federal rules require automakers to warranty EV batteries for at least 8 years or 100,000 miles against complete failure, but “covered” and “still performs well” are not the same thing. Most warranties only kick in once capacity drops below a specific threshold, commonly around 70%.

What’s covered

The federal minimum applies to complete battery failure and, in California and the states that follow its rules, to capacity dropping below the manufacturer’s stated threshold before the warranty period ends. Above that threshold, gradual capacity loss from normal aging is expected and isn’t a warranty claim. Every lithium-ion battery loses some capacity over time, and a car with 90% of its original range at 60,000 miles is behaving normally, not failing.

Some manufacturers offer longer terms than the federal floor, and terms vary by model year and region, so check the specific warranty document for your car rather than assuming a round number applies exactly as advertised.

What voids it

The most common ways owners accidentally void battery coverage: aftermarket modifications to the battery or charging system, using non-approved charging equipment that damages the pack, or skipping manufacturer-specified maintenance tied to the battery management software. Physical damage from an accident is typically handled through insurance rather than warranty, unless the damage reveals a manufacturing defect.

Regular use of DC fast charging isn’t itself a warranty violation on most current vehicles, though very frequent fast charging can contribute to faster degradation over time. That’s a wear-and-tear factor worth knowing about, not a coverage issue.

How a claim gets evaluated

Most manufacturers use the car’s own battery management system to log state-of-health data over the vehicle’s life, and a dealer or service center pulls that data to check the pack’s measured capacity against the warranted threshold. This is why keeping software updated matters beyond new features: an outdated battery management system can make it harder to get a clean read on the pack’s actual condition when you eventually need one.

Buying used: what to check

• Get the remaining battery warranty in writing, including whether it transfers to a second owner, since some do and some don’t
• Ask for a battery health or state-of-health report if the dealer or seller can provide one
• Check the charging history if it’s available; a car charged almost exclusively on DC fast chargers has a different wear profile than one charged mostly at home
• Confirm the capacity threshold that triggers a warranty claim on that specific model, since it varies by manufacturer

The Department of Energy’s overview of EV batteries explains the federal warranty minimums and how degradation is typically measured.

For more on what degradation looks like in practice, see what battery degradation actually measures, and how that connects to long-term ownership costs in what degrades an EV battery over 100,000 miles.

Read the warranty document itself before you buy, not the marketing page. The capacity threshold and transferability terms are usually buried a few pages in, well past the headline number everyone quotes to sell the car.