During fast charging, the vehicle is charged with the maximum power that the vehicle and house allow. Any energy source is used here, so the system could potentially be drawing power from the home storage system to charge your vehicle.
During PV-optimized charging, SMA EV Charger charges the vehicle with the energy mix saved in the Sunny Portal (slider). Charging of battery prior to optional loads checkmark decides whether the battery or OPTIONAL load is supplied with the surplus solar power initially. Depending on how the slider is set, energy from the home storage system or utility grid can also be used to charge the vehicle.
During forecast-based charging, surplus solar energy is initially used for achieving the charging target configured in the SMA Energy app. If not enough of this energy is available for achieving the charging target, the home storage system is used. Once the home storage system is used up, the energy is drawn from the utility grid.