- Batteries in electric vehicles that regularly use 100-plus-kilowatts fast chargers degrade faster than those that rely primarily on slow charging, a new study suggests.
- Using fast chargers more frequently can cause some packs to lose nearly a quarter of their capacity in eight years, it claims.
- We’ve seen other studies suggest that fast charging has little impact on long-term battery health, so it’s not a settled debate.
America is deploying public fast-charging stations at record speed, as companies build ahead of demand and set 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 may come with unintended consequences for long-term battery health and degradation.
Canada-based research firm Geotab analyzed over 22,700 EVs across 21 models and found that high-powered public fast-charging stations are the single largest contributor to accelerated battery aging. No, that doesn’t automatically mean fast-charging is outright detrimental for batteries. Rather, the study outlined specific charging patterns where the cells experience significantly more stress than they would with slower charging.
BMW iX At Ionna Rechargery
Photo by: Suvrat Kothari
The study outlines that frequently using Level 3 charging stations that deliver over 100 kilowatts of power can lead to double the degradation rates compared to regularly plugging in at slower Level 2 charging stations or fast chargers that deliver under 100 kW of power. EVs that used fast-chargers less than 12% of their total charging sessions experienced 1.5% of average degradation annually. Those that fast charge more than 12% of their total sessions saw 2.5% of annual degradation.
The results got worse when owners used 100+ kW stations for more than 40% of their total charging sessions. They experienced 3% annual degradation. (Note, though, that batteries degrade fastest during their first couple of years, with the degradation rate gradually decreasing over time.) Those who charged at speeds of less than 100 kW for under 40% of their total charging sessions saw the battery capacity drop at a modest 2.2% annually. In other words, it’s the combination of high power and high frequency that appears most detrimental to battery health.
| DC FC Frequency | Group | Average Annual Degradation |
| Low | Under 12% of total sessions | 1.5% |
| High | Over 12% of total sessions | 2.5% |
| High-Frequency Low Power (<100 kW) | Under 40% of total sessions | 2.2% |
| High-Frequency High Power (>100 kW) | Over 40% of total sessions | 3.0% |
While this data is crucial in our understanding of long-term battery health, I’d still approach it with caution. For starters, charging behavior is just one variable of a very complex equation. Battery health is influenced by everything from cell chemistry and the manufacturer’s design choices to driving habits and climate. Extreme heat and cold can stress batteries, though nearly all modern EVs now come equipped with heat pumps, preconditioning and advanced thermal management systems that are designed to keep packs operating within a safe temperature zone.
The study also contradicts another report from battery health and data company Recurrent. After analyzing 13,000 Teslas in the U.S., 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 EVs that were frequently fast-charged was just 344, whereas the size of models that infrequently fast-charged was over 13,000, making it difficult to draw a firm conclusion.
Photo by: Porsche
On average, battery degradation in 2025 was 2.3%, Geotab said in its study, meaning the average pack would have about 81.6% of its original capacity after eight years. That’s up from 1.8% in 2023, but identical to the year 2020, when average degradation was also at 2.3% per year.
The company attributed the increase in degradation from 2023 to 2025 to a growing network of higher-powered charging stations, which are now popping up across North America. Growth is especially robust in the U.S. with networks like Tesla Superchargers, Electrify America, ChargePoint and Ionna, which are all doubling down on their charger deployment despite a projected cooling period for EV sales after the end of the $7,500 federal tax credit. As high-powered stations are more easily available for EV drivers, there’s potentially an impact on long-term battery health, too, Geotab said.
The good news is automakers and battery companies have long been aware of this. Modern EVs are loaded with safeguards within the pack designed to slow degradation regardless of how you charge.
Electrify America’s flagship indoor charging station in San Francisco, California.
To limit stress on the cells, the battery management systems (BMS) automatically taper charging speeds when the battery is nearly full and throttle speeds if the temperature gets too hot. Most automakers also recommend keeping the state of charge between 10-80% for regular driving, since consistently storing a battery at near full or near empty state of charge also accelerates 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 both ends of the usable range. When your display reads 100%, there’s usually unused capacity above that ceiling. The same goes for 0%, where a lower 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 a critical role in protecting the battery.
To me, the takeaway is fairly straightforward. If you care about preserving maximum range over eight to ten years, don’t over-rely on high-powered fast chargers when you don’t need to. At the same time, rest assured that frequent fast-charging isn’t a death sentence for your high-voltage pack. A Tesla Model Y Premium with 357 miles of EPA range when new would still deliver around 285 miles at 80% capacity after eight years. So it would still be extremely usable and road-trip worthy years down the line.
Unless you’re fast-charging constantly, day in and day out, using high-powered 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 away from fast-charging, and using fast chargers will not void your battery warranty. Since battery warranties in the U.S. are eight years and 100,000 miles at a minimum, there’s not much to worry about. Use cheaper slow chargers when you can and don’t lose sleep over the occasional fast-charge stop. Today’s EVs are engineered with enough guardrails to keep their batteries healthy for years.
Have a tip? Contact the author: suvrat.kothari@insideevs.com
