Why is my car not charging on 'surplus only'?

Limitations of the IEC 61851-1 standard

The standardised communication protocol between the EV and charging station (IEC 61851-1) defined a minimum charging current of 6 A before an EV is allowed to start charging. This means that there is a minimum required power before your vehicle can start charging. In case of a single phase installation this is 1.4 kW and 4.1 kW for a three phase installation. This is quite a large consumption for a PV installation and unfortunately we cannot change this. 


Workarounds to optimise for solar consumption:

1) Smart charging schedules

In this scenario we will optimise the consumption of your solar production throughout the day. This means we will import additional power from the grid, if necessary, to allow your vehicle to charge. A downside of this method is that additional solar production will not flow into the vehicle once the charging schedule has finished.


2) Minimum surplus percentage

In the Smappee app, you can choose to reduce the minimum percentage of surplus necessary to start charging. For example, if you set this to 50%, charging will start when there is a surplus of 690 W (single-phase) or 2070 W (three-phase). The other half of the power required to start charging will come from the grid.



In the example below the sun only needs to provide 30% of the minimal charging speed, the rest (70%) will be provided by the Grid.

In a monophase setup this means, the car will start charging as soon as there is 1.8A export. (+- 414w)

In a 3 phase setup this means, the car will start charging as soon as there is 5.4A export. (+- 1242w)




3) Adapting your charging cable

Another possible workaround is to detach 2 phases in a three phase installation. Our recommended approach is to detach the desired phases from the charging cable as depicted in the picture below.image.png

This decreases the minimum required power to 6 A * 230 V * # connected phases. Decreasing this required power increases the likelihood that you have enough solar production to start charging your car. A drawback of this approach is that you decrease the maximum charging speed of your vehicle. In most cases this is actually negligible because most EVs are only able to charge 16 A on 3 fases (11 kW) while they can still charge 32 A on a single fase (7.3 kW).