Too-frequent DC fast charging can theoretically damage an EV’s battery, causing it to lose capacity, and thus driving range, faster than would otherwise be the case. However, there’s little hard data on the long-term effects of frequent fast charging.
Now battery data specialist Recurrent has made a substantial contribution to the literature on the subject. Recurrent studied fast charging on over 12,500 Tesla vehicles in the US to learn if the software and safety mechanisms in the battery management system (BMS) prevent damage to the battery.
Recurrent compared cars whose owners use fast charging almost exclusively to cars whose owners very rarely fast charge. The results of the study show no statistically significant difference in range degradation between Teslas that were fast charged more than 90% of the time and those that were fast charged less than 10% of the time.
Initial analysis by the Recurrent team suggests that the study findings can be applied across Tesla models and other EV manufacturers, although the company is still conducting detailed research on other popular EV models. EV makers have invested in robust thermal, voltage and battery management systems in order to protect their batteries from damage with routine fast charger use, and Recurrent’s study results indicate that these systems are effective.
The short answer to the question on every EV owner’s mind, according to Recurrent: “Occasional fast charging is fine.”
Fast charging can have an impact on EV battery life, however. Recurrent cautions against fast charging in extreme heat or extreme cold without battery preconditioning. Preconditioning refers to a feature of an EV’s thermal management system that pre-cools the battery so it can accept a higher charge rate without overheating. Typically, if a driver uses the car’s navigation system to locate a fast charging station, the battery will be preconditioned by the time it arrives.
One should also avoid fast charging an EV at very low or very high states of charge, as battery resistance will be higher.
EV drivers who insist on fast charging their cars to 100% are the scourge of busy charging hubs. In fact, as Recurrent explains, most EVs have software that will curtail fast charging speeds above an 80% state of charge in order to avoid stressing the battery, so hanging around to get that last 20% is pointless.
Recurrent also points out that the stated charging speed in kW of a particular fast charger doesn’t tell you exactly how fast the car can charge. Real-world charging speed is dependent on many factors, including software and battery limitations, temperature, state of charge, and battery age. (That’s why Charged seldom repeats automakers’ claims about charging speed.)