One of the biggest concerns with fast charging is that it can, theoretically, damage the battery by pushing too much energy into your car too quickly. This would lead to irreparable, long-term range loss.
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. With Labor Day travel coming up, this is the perfect time to share what is fact and what is fiction when it comes to fast charging.
Will fast charging hurt my EV battery?
The short answer is that occasional fast charging is fine.
We compared cars that fast charge at least 90% of the time to cars that fast charge less than 10% of the time. In other words, people who almost exclusively fast charge their car and people who very rarely fast charge. The 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.
In the charts above, the y-axis shows the percentage of original range as shown on the cars’ dashboards. Note that the dashboard range in Teslas is different from its Real Range, which is a value that factors in the range effects of temperature, drive style, and terrain.
Initial analysis by the team at Recurrent suggests that the study findings can be applied across Tesla models and other EV manufacturers, although detailed research is being conducted on other popular vehicles that Recurrent supports. In short, the robust thermal, voltage, and battery management systems that EV makers have invested in do protect their batteries from damage with routine fast charger use.
When is fast charging more likely to cause damage?
There are several times when fast charging may have a bigger impact on your EV battery.
- Avoid fast charging in extreme heat without preconditioning your battery. Preconditioning is when the car’s thermal management system pre-cools the battery so it can accept a higher charge rate without overheating. Typically, if you set your car’s navigation to a fast charge station, the battery will be preconditioned.
- Similarly, precondition the battery before fast charging in extreme cold. Often, driving a bit before fast charging is enough to warm up the battery, or get to the fast charger using your car’s navigation.
- Avoid fast charging your EV at very low states or very high states of charge, since battery resistance will be higher.
DC fast charging: fact or fiction?
Quick refresher on DC fast charging
Your electric vehicle battery uses direct current (DC) power. However, the electricity that comes from the grid (or from an outlet) is alternating current (AC). There are two different types of charging, depending on where the electricity is converted from AC to DC. In home charging, which is AC charging, the car’s on-board charger converts the AC electricity to DC and then sends it to the battery. The on-board charger has a built in speed limit on how quickly it can do this. The maximum speed is usually around 11 kW, which means AC charging can generally add 20-40 miles per hour.
On the other hand, DC charging happens when the conversion to DC energy happens outside of the car. This is almost exclusively reserved for public charging stations, and the ones that cost quite a bit, at that. Since the electricity going into the car bypasses the on-board charging, it can refill the battery much faster. The current top speed is around 30 minutes to recharge 80%.