Does fast charging damage EV batteries?

As the technology is continuously advancing and the demand of electric vehicles (EVs) continue to gain popularity as a sustainable and environmentally friendly mode of transportation, various myths and misconceptions surrounding their technology have emerged.

One common myth that often circulates among EV owners is the belief that DC fast charging can damage their vehicle’s battery. In this article, Gadinsider aims to provide some important details, which might debunk this myth and provide clarity on the impact of DC fast charging on EV batteries.

What is fast charging?

For EV owners, fast charging refers to chargepoints rated between 7kW and 22kW that is typically found in homes, providing the electricity via alternating current (AC). However, EV batteries only store direct current (DC) energy, so fast (i.e. AC) charging has to be converted via a converter in the car. It’s this extra step that makes AC fast charging slower than DC (i.e. rapid) charging.

Rapid chargers are growing in popularity, with more appearing in the public charging network every year, because they charge much faster. 

Fast charging of EVs for up to 22kW has no detrimental effect on EV batteries. It's always advised by EV manufacturers that if any EV owner wants to maintain a healthy battery, they should keep their electric car between 20 and 80% and out of extremely cold or hot temperatures.

However, frequent use of faster rapid charging has been shown to slightly increase the rate of battery degradation. A study testing two Nissan Leafs showed that exclusive DC rapid charging increased the rate of degradation by 16% when compared to AC fast charging.

How to preserve battery life while using rapid charging

For EV owners, looking for ways to maximise the lifespan of their EV batteries while using rapid charging , here are some important guidelines to follow:

1. Monitor battery temperature regularly: A high battery temperature strains the lithium-ion cells. The high voltage and current during rapid charging generate heat, which is normally controlled by the car’s battery management system. 
2. Priorities fast charging: EV owners need to use fast charging as much as possible, like when parked at home overnight or at work. Reducing the frequency of rapid charging will help you maintain good battery health.
3. Avoid overcharging: Owners need to charge their EV up to 80% and then unplug their EV. Once your battery hits this number, charging slows down significantly, which removes the key benefit of rapid charging – its speed.