Controlling EV Charging Schedules: Supporting the Grid and Protecting Battery Life

Uncontrolled charging is known to cause problems for the distributed power network even if only 10% of cars are powered by electric, so a charging system that prevents such problems will become necessary as they increase in popularity. Electric vehicle charging regimes that can provide the charge required by the user whilst supporting the grid and protecting battery health are required and are described here. Based on experimental tests and verified by literature, the factors that are known to shorten battery life have been quantified and the impact on battery degradation of average state of charge is analysed. Charging regimes that can lower average state of charge, thus protecting the state of health of the battery are described. It is demonstrated that delayed charging, less frequent charging and some vehicle to grid power flow for storage can prolong battery life compared with providing the same charge in an uncontrolled way. Thus grid power is supported and battery life protected by this schedule based on controlled charging. The analysis of average state of charge (SOC) as a function of cycling as well as calendar life is new and the effect on battery degradation has been found by experimental testing and verified by literature.