Surplus charging

With the cFos Charging Manager and a solar system, you can make sure that your car is (almost (*)) only charged when solar surplus power is available. Surplus = generation minus household consumption.

For this you can set up a charging rule of type "Solar". As mode select "Solar surplus". As "Start current limit" select the surplus current that the solar system should generate, from which this rule should apply.

Screenshot cFos Charging Manager Documentation - Surplus charging

Rule 2: Solar, Starting current limit: 6,5 A (6500 mA), "Solar Surplus", this activates surplus charging with the available surplus from an average feed-in of 6,5 A.

To decide if the charging rule is currently in effect, the cFos Charging Manager uses a rolling average over approximately 15 minutes for solar charging rules, so that charging is not interrupted during short-term power drops, such as those caused by passing clouds.

You can read these averages by using the virtual counter "Produced Power, Avg." for the solar charging rules in the Charging Manager, or by setting up the counter "Grid Demand, Avg." in case of surplus. If you observe these meters for a few days, you will find suitable values for the solar rules.

The surplus electricity is the electricity that would be fed into grid. To determine this, the Charging Manager must be able to measure it. The following options are available for this:

  1. Set up with a meter "Grid Demand". You install a (bidirectional) meter at the transfer point of the house connection. If this meter shows negative values, you feed in and this power is available for surplus charging. Suitable meters are, for example, Modbus meters or internal grid reference meters of your solar system.
  2. You measure your house consumption and the generation power with a suitable meter. Simple S0 meters are sufficient for this purpose. The Charging Manager then subtracts the house consumption from the generation power and makes the remaining power available for charging.

The generation power can be measured with an extra meter. Alternatively, you may be able to read the values from your solar system directly. Please refer to our list of currently supported devices.

Note: If you use meters that capture current in phases, cFos Charging Manager (especially for single or two phase charging cars) can control the charging power in phases and thus optimize it. In the case of meters that output only one power value related to the number of phases used, the Charging Manager allocates the power evenly among the phases, which leads to certain inaccuracies. In this case (and also in case of sudden heavy consumption) you should set a sufficiently high power reserve.

(*) The use of moving averages can result in a slight grid reference or feed-in in the border area.

Power reserve

The control in a power storage always tries to minimize the grid consumption and the grid injection. You can tell this to the cFos Charging Manager by setting up a meter with the role "solar storage". In this case, a discharging storage is considered a generator (the meter shows negative power values), which means that this energy is available to charge the car. However, a charging storage (the meter shows positive power values) is not considered as a consumer because the storage stops charging immediately when the charging power is used for charging the electric car. So, for meters with the role "solar storage", the cFos Charging Manager ignores its consumption.

If your electricity storage does not have a bidirectional meter, you can install an external meter. Usually bidirectional Modbus meters are recommended, but, depending on the arrangement of the meters in the installation, it may also work with several S0 meters (or other unidirectional meters), which must be checked on a case-by-case basis.