Does fast charging damage the battery?

Batteries actually age

Uncertainty regarding the service life of e-car batteries is one of the reasons for the current slump in EV sales. The fear of no longer being able to sell the car after a few years due to a weak battery is probably still deterring many potential buyers from purchasing an e-car. The fact is that batteries age and the usable capacity decreases over time. This is known as degradation, which is influenced by calendar age, the number of charging cycles and the extreme temperatures to which batteries are exposed due to weather conditions and charging or driving behaviour. In the meantime, however, various long-term tests with a large number of vehicles have shown that degradation is significantly lower than feared.

What influence does fast charging have on degradation?

Auch als grosse Schnellladefans müssen wir anerkennen, dass schnelles Laden und Entladen allein aus chemischen Gründen einen Einfluss auf die Batteriezellen haben kann. Ein Phänomen, das Forscher spezifisch mit dem Schnellladen in Verbindung bringen, ist die Bildung von sogenannten Dendriten. Die hohen Ströme beim Schnellladen können dazu führen, dass Lithium-Ionen nicht gleichmässig in die Anodenstruktur eingelagert werden und als metallisches Lithium auf der Oberfläche abgelagert werden und sich zu nadelartigen Strukturen, sogenannten Dendriten, verbinden. Das so gebundene Lithium steht dann nicht mehr für die Speicherung von Strom zur Verfügung und verringert die Akkukapazität.

Practice more optimistic than theory

So much for the theory. In practice, the picture is surprisingly different. Current data from 13,000 Tesla models and a study by P3 with over 7,000 different electric car models suggest that there is no significant correlation between charging behaviour and battery degradation. In general, battery ageing is less severe than feared. Even after more than 200,000 kilometres, the battery capacity remains at an average of 87 percent, even with intensive use. The degradation is strongest during the first 30,000 kilometres and then levels off. It can therefore be assumed that most batteries will outlive their cars. As far as charging behaviour is concerned, the field data suggests that even frequent fast charging is not a factor that would influence battery ageing more than others . The manufacturers' battery management systems, which ensure that charging and discharging processes are optimised in such a way that the battery cells are not damaged, are likely to be primarily responsible for this.

What factors influence battery ageing?

As mentioned at the beginning, batteries also succumb to the inevitable fate of aging. Even if an electric car is not moved, high temperatures above 60 degrees and a high state of charge, i.e. high voltage, have a negative effect on battery health. When in use, charging and driving behaviour play a role. Less beneficial are frequent complete discharges and charging of the battery to 100 per cent, but also frequent heavy acceleration or sustained high speeds. So even if a certain degree of degradation cannot be avoided, an electric car battery can be taken care of by taking various factors into account.

Five useful tips for battery care

Avoid putting too much stress on the battery through heavy acceleration and high speeds. Plan fast charging so that the battery is warmed up beforehand by travelling or preconditioning. Maintain a charging mix that also allows for a slower AC charge from time to time. Ideally, always keep the battery charge level between 20 and 80 per cent. Avoid long idle times in a fully charged or fully discharged state. A charge level of between 10 - 50 per cent is considered ideal.