Fast charging not that bad for batteries

Electric cars haven’t been around for very long. That means that there aren’t many that have been driven – and recharged – over long periods of time. And because of that, there are a lot of ‘received wisdoms’ about fast charging and its effects on battery health.

However, a recent study by Recurrent Auto, a company specializing in EV battery data, sheds new light on these beliefs, challenging widespread notions and offering crucial insights.

Their research, involving data from over 12,500 subscribers, specifically compared Tesla vehicles that predominantly use fast charging (over 90% of the time) with those that seldom do (less than 10%). The findings were revealing: there was no significant difference in range degradation between the two groups​​. This counters the prevalent belief that frequent fast charging is more detrimental to battery health.

Recurrent’s analysis extends beyond Teslas, suggesting that the study’s conclusions are applicable to other EV brands. However, they are conducting further detailed research on various popular EV models to confirm this​​. The robustness of modern EVs’ thermal, voltage, and battery management systems plays a crucial role in shielding batteries from potential damage due to routine fast charging.

Recurrent’s results show no statistically significant difference in range degradation between Teslas that fast charge more than 90% of the time and those that fast charge less than 10% of the time.

Despite dispelling the primary myth, Recurrent acknowledges certain conditions where fast charging might impact battery health. They advise against fast charging in extreme temperatures without preconditioning the battery. Preconditioning involves pre-cooling or warming the battery through the car’s thermal management system, allowing it to accept higher charge rates without overheating or underperforming. Additionally, it’s recommended to avoid charging in very high or low states of charge due to increased battery resistance​​.

Understanding charging speeds also remains a grey area for many EV owners. While a DC fast charger might be rated at, say, 250 kW, the actual charging speed an EV can handle is regulated by its software, battery limitations, and factors like temperature and battery age​​.

Most EV manufacturers suggest to charge the battery only to 80% full and, where possible, to use slow chargers. In fact, almost all electric vehicles have software that will reduce charge speeds when that 80% figure is reached. At that stage it is recommended to switch to a slower charger for the last 20%, as it may be as quick — or quicker (and possibly cheaper). Although, practically, it won’t often be possible to make the switch in the same charging session. 

Recurrent is a startup that’s been set up to provide more confidence to buyers and sellers of electric cars by collating information on battery health and history.  You can sign up and connect your car, as long as it’s one of 66 different models, to get remote monitoring of your battery health and performance. When you want to sell the car, the data can be made available to potential buyers to give them confidence in the car.

This study appears to provide good news to drivers, manufacturers and charging companies alike. Speed of charging is a key factor in convincing petrol car drivers to make the switch to electric.

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