High-power fast charging is the main cause of EV battery degradation: Report

High-powered EV charging stations are becoming commonplace in North America. This is how it affects batteries.

• Batteries in electric vehicles that regularly use fast chargers of more than 100 kilowatts degrade faster than those that rely primarily on slow charging, a new study suggests.

• More frequent use of fast chargers can cause some packs to lose nearly a quarter of their capacity in eight years, it claims.

• I’ve seen other studies that suggest fast charging has little impact on long-term battery health, so it’s not a settled debate.

America is installing public fast-charging stations at a record pace as companies build ahead of demand and lay the groundwork for an increasingly electric future. Stopping at these high-powered charging stations is undeniably convenient, helping drivers get back on the road quickly. But according to a new study, using them in certain ways can have unintended consequences for long-term battery health and degradation.

Canadian research firm Geotab analyzed more than 22,700 electric vehicles from 21 models and found that high-power public fast-charging stations are the biggest contributor to accelerated battery aging. No, this does not automatically mean that fast charging is bad for batteries. Rather, the study highlighted specific loading patterns in which cells experience much more stress than they would under slower loading.

The study points out that frequent use of Level 3 charging stations that provide more than 100 kilowatts of power can double degradation rates compared to regularly connecting to slower Level 2 charging stations or fast chargers that provide less than 100 kW of power. Electric vehicles that used fast chargers for less than 12% of their total charging sessions saw an average annual degradation of 1.5%. Those who fast-load more than 12% of their total sessions saw an annual degradation of 2.5%.

The results worsened when owners used stations above 100 kW for more than 40% of their total charging sessions. They suffered an annual degradation of 3%. (Note, however, that batteries degrade fastest in the first two years, with the rate of degradation gradually decreasing over time.) Those who charged at rates below 100 kW for less than 40 percent of their total charging sessions saw their battery capacity decline at a modest 2.2 percent annually. In other words, it is the combination of high power and high frequency that seems most detrimental to battery health.

While this data is critical in our understanding of the battery’s long-term health, I would still approach it with caution. To begin with, loading behavior is only one variable of a very complex equation. Battery health is influenced by everything from cell chemistry and manufacturer design choices to driving habits and climate. Extreme heat and cold can stress batteries, although almost all modern electric vehicles are now equipped with heat pumps, preconditioning and advanced thermal management systems that are designed to keep the packs operating in a safe temperature zone.

The study also contradicts another report by battery health and data company Recurrent. After analyzing 13,000 Teslas in the US, it found that there was no statistically significant difference in the range of EVs that were frequently fast-charged versus those that relied more on slow charging. However, that study had a massive caveat. The sample size of electric vehicles that were frequently fast-charged was only 344, while the size of models that rarely fast-charged was over 13,000, making it difficult to draw a firm conclusion.

On average, battery degradation in 2025 was 2.3 percent, Geotab said in its study, meaning the average pack would have about 81.6 percent of its original capacity after eight years. It is up from 1.8% in 2023, but identical to 2020, when the average decay was also 2.3% per year.

The company attributed the increase in degradation from 2023 to 2025 to a growing network of higher-power charging stations now appearing in North America. Growth is particularly strong in the U.S., with networks like Tesla Superchargers, Electrify America, ChargePoint and Ionna all doubling their charger installations, despite a projected cooling period for electric vehicle sales after the $7,500 federal tax credit ends. Because high-power stations are more readily available to EV drivers, there is potentially an impact on long-term battery health, Geotab said.

The good news is that car manufacturers and battery companies have been aware of this for a long time. Modern electric vehicles are loaded with safety measures in the package designed to slow down degradation no matter how you charge.

To limit stress on the cells, battery management systems (BMS) automatically reduce charging speeds when the battery is nearly full and throttle speeds if the temperature gets too hot. Most car manufacturers also recommend keeping the state of charge between 10-80% for normal driving, as constantly storing the battery at a near-full or near-empty state of charge also accelerates aging.

For drivers who regularly need to charge up to 100% and discharge the battery for whatever operational reasons—think ride-sharing or delivery drivers—manufacturers typically build in buffers at both ends of the usage range. When the display shows 100%, there is usually unused capacity above that ceiling. The same is true for 0%, where a smaller buffer prevents the pack from entering a deep discharge state, which can harm the battery. You and I will never see these margins in the real world, but they play an essential role in protecting the battery.

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For me, the takeaway is pretty simple. If you care about keeping your maximum battery life beyond eight to ten years, don’t rely too heavily on high-powered fast chargers when you don’t need them. At the same time, rest assured that frequent fast charging is not a death sentence for your high voltage pack. A Tesla Model Y Premium with 357 miles of EPA range when new would still deliver about 285 miles at 80% capacity after eight years. So it would still be extremely usable and travel-worthy years down the line.

Unless you’re fast-charging consistently, day in and day out, using high-power stations, severe degradation remains unlikely, as several other studies have also concluded. It’s also important to follow your manufacturer’s recommendations. Most don’t warn users against fast charging, and using fast chargers won’t void your battery warranty. Since battery warranties in the US are eight years and 100,000 miles at least, there’s not much to worry about. Use cheaper slow chargers when you can and don’t lose sleep over the occasional fast charge stoppage. Today’s EVs are designed with enough handrails to keep their batteries healthy for years.

Do you have a tip? Contact the author: suvrat.kothari@insideevs.com