Charging station for electric vehicles
Optimization in details
The optimized charging modes ensure efficient charging processes and allow you to control the charging of the electric vehicle. Three charging modes are available:
Green charging mode, in which almost exclusively self-generated energy is used.
Fast charging mode, in which the vehicle is charged as quickly as possible using all available resources.
Smart charging, in which the charging process is optimized based on self-consumption and tariffs. Individual settings are possible so that the charged vehicle is available when needed while being charged as cost-effectively as possible.
For all charging modes, you can set whether energy from the battery (power storage system) should be used to charge the electric vehicle.
Charging modes
Green Charging
Ideally, in green charging mode, the electric vehicle is only charged with PV excess. However, strict adherence to the PV excess curve can lead to interruptions during the charging session, especially on cloudy days. To ensure a stable charging session, the vehicle is charged as long as the predicted charging self-sufficiency rate is above 90% and the charging current limit can be exceeded. This depends on the minimum charging current and the charging phases (1-phase, 3-phase) of the connected vehicle. As a result, the proportion of PV power that is charged into the vehicle for each charging session is at least 90% in green charging mode.
In the scenario displayed in graph 1, it is cloudy from around 5 p.m. till 6:30 p.m., so that not enough PV power can be produced to continue charging the vehicle. The algorithm of the optimization feature “Smart EV Charging” decides, taking into account the activated setting for charging with energy from the battery, that charging of the vehicle can be continued during this period by discharging the battery and a small amount of electricity from the public grid, thus preventing an interruption of the charging session, as shown in graph 2.
Fast charging
In fast charging mode the vehicle is charged as quickly as possible using all available resources. This means that in addition to the self-produced PV power from the photovoltaic system, the energy requirement is covered by discharging the battery (power storage system) and consumption from the grid, as shown in graph 3. The energy resources that guarantee the fastest charging session are selected. The charging current limit can be manually set to 6-16 A/phase in the ViCare app.
Please note that the charging current limitation reduces the charging power of your electric vehicle. Reducing this limit can result in your vehicle no longer charging. Set a value that is higher than the minimum charging current of the vehicle.
Smart charging
Smart charging combines personal needs with complex data analysis to fully automatically optimize vehicle charging. In addition to self-consumption optimization, tariff-based optimization is available in smart charging and can be activated in ViCare. These optimization features work hand in hand. In addition to dynamic and time-based electricity prices as well as available PV excess — if a photovoltaic system is part of the system — Energy Management also takes into account the individual settings stored for smart charging. Based on forecasts, the charging process is intelligently planned to achieve the most economical and efficient charging session.
To save costs with tariff-based optimization, an active dynamic or time-based electricity tariff must be stored and the “Dynamic Assistant” subscription must be active in ViCare.
Each time the electric vehicle is newly connected to the charging station, a new optimization cycle begins. The more precise the information provided in the following individual settings, the better the charging process can be optimized and costs can be saved.
Charging levels: Based on the specified plug-in charge level and the desired target charge level, Energy Management precisely analyzes and plans the required amount of energy.
Charging time window: By specifying the charging time window, Energy Management knows how many hours the vehicle is expected to remain connected to the charging station. Three charging strategies are derived from the available time period: balanced charging, time-saving charging and cost-saving charging.
In the scenario shown in graph 5, a dynamic tariff is available. In the individual settings for smart charging, “balanced charging” was defined with a charging time window of 13 hours and a desired target charge level of 23 kWh. When deciding how to proceed, Energy Management takes into account not only these settings, but also the expected PV electricity production (self-consumption optimization) and the expected electricity prices (tariff-based optimization). The vehicle is connected to the charging station at 4:00 p.m. and charged using available PV excess. Due to the high electricity price in the first half of the charging time window and sufficient time buffer until the target charging time, Energy Management decides not to draw the remaining energy required to reach the target charge level from the public power grid, but instead to pause charging. Charging resumes from midnight, when electricity prices are lower. This allows the greatest possible savings potential to be achieved.
In the scenario shown in graph 6, no photovoltaic system is part of the system, or no self-generated energy is available due to weather conditions. For this reason, the entire charging process of the vehicle starts only from midnight at a lower electricity price, instead of immediately after the vehicle is connected to the charging station at 4:00 p.m. This allows charging to take place at the lowest electricity price.
If the “time-saving charging” strategy is selected with a charging time window of, for example, 6 hours, protection against price peaks may not be possible because the available time buffer is too short to significantly shift charging. In this case, the charging process is optimized based on tariffs, but the resulting cost savings may be low.
Overload protection
Without overload protection
The value of the maximum grid connection current has been exceeded and the house connection capacity has been overloaded.
With overload protection
The Viessmann Energy Management overload protection starts automatically and protects your house connection from overloading. If necessary, the charging power of the electric vehicle is dynamically reduced so that the charging session is carried out with the maximum possible power. At the same time, exceeding the maximum grid connection current is prevented to avoid tripping circuit breakers.︎
Note: The overload protection protects your house connection and optimizes the charging session, but does not replace general safety precautions such as circuit breakers against system damage caused by excessive currents.
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