Menu
The time a car takes to charge depends on several factors including the charging station power, vehicle battery state of charge(SOC), vehicle battery size, maximum power the vehicle can accept and even the weather. The previous article, how long it takes to charge an EV, discusses these factors in detail. This article will focus on battery charging curves and how the charging speed of your car varies while it is being charged.
When the vehicle is plugged into the charging station, the vehicle and station communicate. The battery management system (BMS) will control the amount of power the vehicle will accept from the charging station to protect the battery while trying to ensure optimal charging speed. This results in an EV charging curve or fast charging profile.
The charging curve of an EV represents the maximum power an electric vehicle will accept while its charging. At different states of charge, the maximum power accepted by the vehicle will change, controlling the speed of recharge.. This is particularly relevant for DC fast chargers where the power supplied by the station could exceed that of the EV. The charging curve of an actual vehicle, Hyundai Ioniq, below illustrates how the car charges under fast charging. Different vehicles have different battery charging curves. Car manufacturers keep the battery charging curve of their vehicles close to their chest. However, there are three general stages: the battery warm-up, peak charging and battery protection stages.
First, the charger starts at a little bit below the max charging speed of the car. This allows the battery to heat up and prepare it for the optimum charging conditions. This stage is relatively short.
The second stage is where the vehicle is charged at peak charging speed. The battery is charged up to about 80% of its capacity at this stage. The peak charging speed of the car is limited by its battery’s capabilities. For example, the Tesla Model 3 has a peak charging speed of 250kW so even if the Tesla was connected to a 350kW it would only reach charging speeds of 250kW at this stage. On the other hand, if the charging station power is lower than the maximum power that the vehicle can handle, for example, 50kW, the vehicle would only accept 50kW of power.
Once the battery level reaches 80%, batteries are designed to accept less power in order to protect the battery and lengthen its life. As a result, charging speeds drop significantly. It is important to note that not all cars charge the same way. Each vehicle manufacturer uses a different strategy to find the optimal balance between charging speed and battery health. However, most manufacturers advertise that the vehicle will charge from 0 to 80% in about 30 minutes when using a DC fast charger.
What does this mean for you? Firstly, if you want to charge your vehicle during a road trip then you should know that the fastest charging occurs from 0 to-80% battery levels. Charging beyond this will not only consume a lot of time, but might not be the best decision for the health of the battery. Moreover, disconnecting at 80% gives other drivers waiting in line a fair chance to charge their cars up too.
However, if you do plan to charge the vehicle fully, up to 100%, then you should plan your time accordingly.
Sign up to receive updates on electric vehicle charging tips, products, and services