PV surplus charging with the Victron EV Charging Station

How Auto mode works

In Auto mode the charging station regulates the charging current by the available surplus. It only starts once there is enough surplus for the minimum current, then follows the sun up to the configured maximum current.

With three-phase charging the minimum is 6 A per phase, around 4.1 kW. If the surplus is below that, charging does not start. If you often want to charge with less sun, you can charge single-phase: then around 1.4 kW is enough.

House battery first, then the car

The setting "Start charging at backup battery SoC" defines from which state of charge of the house battery the car may charge at all in Auto mode. From the factory it is often at 90 %. We lowered it to 80 %: the car gets power earlier on sunny days and the house battery is still well filled.

The second limit "Stop charging at backup battery SoC, if Off Grid" applies only during a grid outage and then protects the backup reserve.

AutoStart: the moment after plugging in

With AutoStart enabled the charging station starts charging immediately after plugging in, in whatever mode is currently set. If it is on manual at 16 A, the car draws full power for a moment, also from the battery or the grid, until a controller changes the mode. To avoid that, switch AutoStart off and let the controller decide.

Two cars, one charging station

If two cars share one charging station, the controller needs a way to tell which car is plugged in. In our case Gridzilla reads the Tesla's state of charge and position through the Tesla API: if it is plugged in within a few metres of our charging station, it is charged by plan. Any other car gets solar surplus only.

Checklist

• Use Auto mode for pure surplus charging.
• Plan on at least 4.1 kW of surplus for three-phase charging.
• Choose the house battery start SoC deliberately, e.g. 80 %.
• Switch AutoStart off if a controller is to take over the start.