Phase switching makes sense in order to optimally utilise the output of a PV system. A wallbox signals to the electric car the maximum current (per phase) that can be used for charging. For technical reasons, it is not possible to signal less than 6 A charging current to the car. However, the car may fall below this value, for example when the battery is almost full. In the case of three-phase charging, the wallbox can therefore not signal any lower power than 3 × 6 A × 230 V = 4.14 kW to the car. However, this is more than many PV systems deliver, especially in the winter months. With single-phase charging, the minimum power that the wallbox can signal to the car is 1 × 6 A × 230 V = 1.38 kW. Many solar systems can supply this power even in winter or when it is very cloudy. It therefore makes sense to charge the car with only one phase when the solar power is low if you do not want to draw any more power from the grid.
The cFos Power Brain Wallbox Solar has an additional single-phase contactor and therefore offers the option of switching between single-phase and three-phase charging in the settings. You can set the wallbox to three-phase during the season when the solar system is providing enough power and to single-phase during the rest of the year. The setting only becomes active the next time the charging plug is unplugged. Phase switching allows you to optimise the use of your solar power. The cFos Power Brain Wallbox controls the charging current in such a way that as little grid power as possible is drawn from the grid and as little is fed into the grid as possible, so that all the solar energy ends up in your car without any additional purchase.
Automatic phase switching:
The idea of switching phases automatically depending on the solar power is an obvious one. On one day, you could charge single-phase in the morning and switch to three-phase when there is enough power around midday, and then switch back to single-phase in the afternoon.
Unfortunately, there are some cars that do not support automatic phase switching and could be damaged. We offer automatic phase switching for the cFos Power Brain Solar Wallboxes (from firmware version 1.24.0). However, before activating it, you must confirm to us that you are using it at your own risk and that we are not liable for any damage. In any case, manual phase switching (see below) is a prerequisite for automatic phase switching.
Switching between single-phase and three-phase charging can cause problems in some cars. The car initialises its charging unit in a "safe" state if the charging plug is not plugged in, as it cannot know whether single-phase or three-phase charging will be used during the next charging process. If the charging plug is plugged in, some cars assume that the number of phases used will not change. If three-phase charging is used and then phases are switched off, the car could assume that there is a power failure on the switched-off phases. If single-phase charging is used and then phases are added, the car could have short-circuited unused phases, causing a maximum short-circuit current to flow when the phases are connected - with damage to the charging unit installed in the car, the wallbox and/or the domestic installation! To avoid this, the cFos Power Brain Wallbox only changes phase utilisation when the charging plug is unplugged. However, if you know that your car is designed for this, you can also enable phase switching when the charging plug is plugged in. When switching phases while plugged in, charging is stopped if necessary, the contactor is switched off and the voltage level of the CP control line is set to a value close to 0 V for 120 seconds. This should signal to the car that the charging plug is unplugged and thus cause the car to reinitialise its charging unit. Whether this works depends on the car. For example, there could be a mechanical sensor on the car's charging socket that detects that the charging plug is not unplugged and therefore the car could not initialise the charging unit. You can find out from your car manufacturer whether phase switching is permitted with your car when it is plugged in. Please ask them whether you have to pull the plug for phase detection or whether charging only has to be interrupted (and if so, for how long). Please note your exact car model designation and year of manufacture. You can activate the switching of the number of phases when plugged in at your own risk. In this case, we are not liable for any damage caused by phase switching when plugged in. If in doubt, leave phase switching in the unplugged state.
To give you an indication, we will try to give car models where the phase change works or does not work. This is for information purposes only. Only your car manufacturer can make a binding statement here. If your car allows phase switching when plugged in, we would be pleased to receive feedback and list the model here accordingly.
If you want to test the phase changeover with the car plugged in(at your own risk!), we recommend that you first test whether the changeover from three-phase to single-phase works without any problems and only then test whether the changeover from single-phase to three-phase also works.
Have you successfully tried phase switching with your vehicle and the cFos Power Brain Wallbox? Then please let us know so that we can expand the list of compatible vehicles.