High-power fast charging is a major cause of EV battery degradation: report

Fancy, high-powered EV charging stations are becoming more common in North America. Thus they affect the battery.

• Batteries in electric vehicles that regularly use 100-plus-kilowatt fast chargers degrade faster than those that rely primarily on slow charging, a new study shows.

• Using fast chargers too often can cause some packs to lose around a quarter of their capacity in eight years, it claims.

• We’ve seen other studies show that fast charging has little effect on long-term battery health, so this isn’t a settled debate.

America is deploying 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 undoubtedly convenient, helping drivers get back on the road faster. But according to a new study, using them in certain ways can have unintended consequences for long-term battery health and degradation.

Canada-based research firm Geotab analyzed more than 22,700 EVs across 21 models and found that high-power public fast-charging stations are the biggest contributors to rapid battery aging. No, this does not automatically mean that fast-charging is harmful to batteries. Instead, the study outlined specific charging patterns where cells experience significantly more stress than they do during slower charging.

The study noted that frequent use of Level 3 charging stations that deliver more than 100 kW of power can have twice the rate of degradation than regularly plugging into slow Level 2 charging stations or fast chargers that deliver less than 100 kW of power. EVs using fast chargers less than 12% of their total charging sessions experienced a 1.5% annual average decline. Those who fast-charged more than 12% of their total session saw a 2.5% annual decline.

Results worsened when owners used 100+ kW stations for more than 40% of their total charging sessions. They experienced a 3% annual decline. (Note, however, that batteries degrade most rapidly during their first two years, declining gradually over time.) Those charging at speeds below 100 kW for less than 40% of their total charging sessions saw a modest decline in battery capacity of 2.2% annually. In other words, it is the combination of high power and high frequency that seems to be most detrimental to battery health.

Although this data is important to our understanding of long-term battery health, I would still approach it with caution. For starters, charging behavior is only one variable in a very complex equation. Battery health is influenced by everything from cell chemistry to driving habits and the manufacturer’s design choices for weather. Extreme heat and cold can stress batteries, although almost all modern EVs are equipped with heat pumps, preconditioning and advanced thermal management systems designed to keep the packs operating in safe temperature zones.

The study also contradicts another report from battery health and data company Recurrent. After analyzing 13,000 Teslas in the United States, it found that there was no statistically significant difference in the range of EVs that mostly relied on fast charging, versus those that relied on slow charging. However, that study had a big caveat. The sample size of frequently fast-charging EVs was only 344, while the size of occasional fast-charging models was more than 13,000, making it difficult to draw firm conclusions.

On average, battery degradation in 2025 was 2.3%, Geotab said in its study, meaning the average pack will have about 81.6% of its original capacity after eight years. That’s up from 1.8% in 2023, but similar to 2020, when the average decline was also 2.3% per year.

The company attributes the decline from 2023 to 2025 to a growing network of high-powered charging stations, which are now popping up across North America. Growth has been particularly strong in the U.S. with networks like Tesla Superchargers, Electrify America, ChargePoint and Ionna doubling their charger deployments despite an anticipated cooling period for EV sales following the end of the $7,500 federal tax credit. As high-powered stations become more readily available for EV drivers, there’s also likely to be an impact on long-term battery health, Geotab said.

The good news is automakers and battery companies have long been aware of this. Modern EVs are packed with safety measures inside the pack designed to minimize falls regardless of how you charge them.

To limit the stress on the cells, the Battery Management System (BMS) automatically slows down the charging speed when the battery is full and increases the throttle speed if the temperature is too hot. Most automakers recommend keeping the state of charge between 10-80% for regular driving, as storing the battery at a full or near-empty charge will cause aging.

For drivers who must regularly charge to 100% and run the battery down for whatever operational reasons—think rideshare or delivery drivers—manufacturers typically build in buffers at either end of the usable range. When your display reads 100%, there is usually unused capacity above that ceiling. The same goes for 0%, where the lower buffer prevents the pack from entering a deep discharge state, which could damage the battery. You and I will never see these margins in the real world, but they play an important role in protecting the battery.

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For me, the takeaway is pretty straightforward. If you care about preserving maximum range over eight to ten years, don’t rely too much on high-powered fast chargers unless necessary. At the same time, rest assured that repeated quick charges are not a death sentence for your high-voltage pack. With an EPA range of 357 miles, the Tesla Model Y Premium when new will still deliver about 285 miles at 80% capacity after eight years. So it will still be extremely usable and road-tripable years down the line.

Unless you’re constantly charging fast, day in and day out, using high-powered stations, serious degradation is unlikely, as many other studies have also concluded. It’s also important to follow your manufacturer’s recommendations. Most users won’t shy away from fast-charging, and using fast chargers won’t void your battery warranty. Since battery warranties in the US are a minimum of eight years and 100,000 miles, there’s not much to worry about. Use cheap slow chargers when you can and don’t lose sleep over the occasional fast-charge stop. Today’s EVs are engineered with enough rails to keep their batteries healthy for years.

Have a tip? Contact the author: suvrat.kothari@insideevs.com