The rating marked on charge points is the maximum continuous rate of charge available to an electric vehicle from the charger.
The vehicles Battery Management System (BMS) continuously controls the rate during a charging session and dictates the rate of charge. The rate depends on a number of factors outside of the control of the charger.
The most common factors effecting the charging rate are:
- Make & Model of EV
Some models of EVs are not capable of availing of the full kW available from a charge point but can still obtain a charge suitable to its own maximum charging rate.
2. State of Charge (SOC) of battery
The rate of charging allowed by the EVs BMS reduces as the battery comes closer to fully charged in order to reduce stress on the battery pack. This reduction for most EV models starts around 50% and charge rate reduces dramatically after 80%. Fast charging is most effective up to 80% SOC.
3. Temperature of Battery
If the battery is too cold or too hot the EVs BMS will adjust the rate of charge to protect the cells of the battery. Some EVs will activate internal heaters or fans to maintain a temperature between 20 to 25 C. The main factors effecting battery temperature is the amount of driving and charging done up to the charging session.