EV solar charging with Victron ESS

The problem

The sun is out and the wallbox is in its solar mode, yet the car hardly charges, or it charges from the home battery instead of the sun. Behind a Victron ESS, this is common.

Why the wallbox waits

A wallbox's solar mode usually decides from one reading: the power flowing out to the grid at the meter.

A Victron ESS uses solar power for the house first and then charges the home battery. Power goes to the grid only when the battery is full or charging at its maximum rate. While the battery takes the surplus, the meter shows little or no export, so the wallbox keeps waiting.

Two controllers on one grid connection

Owners also report the ESS and the wallbox reacting to each other. The ESS treats a charging car as a house load and can cover it from the battery. When the wallbox slows down, the inverter briefly exports, which the wallbox reads as surplus, so it speeds up again.

What Phaeton does

Phaeton works with your Victron system and sets the charger's current itself, so only one controller decides.

• Its Auto mode reads solar production, house use, grid power and the home battery from your Victron system, and runs the same two algorithms as a Victron EV Charging Station: Battery-powered and Feed-in.
• Battery-powered watches the home battery, not only the grid meter. Solar power going into the battery counts as surplus, so the car can start charging while the battery is still taking it.
• While the car charges, Auto follows that surplus, so the car gets solar power the home battery would otherwise take.

How Battery-powered charges

With the default settings of a Victron EV Charging Station:

• Charging starts when the home battery is at 90% or more and not discharging, at least 100 W of solar is left after the house's own use, and little or no power comes from the grid.
• With the home battery at 99% or more, the car can also start charging without a solar surplus, from the battery or the grid.
• Charging starts at the minimum current: at the usual 6 A, about 1.4 kW on one phase or 4.1 kW on three.
• Auto then raises the current by 1 A every 15 seconds, and lowers it by 1 A when the home battery discharges more than 400 W or the grid supplies more than 400 W for several seconds. Below 80%, the home battery must keep charging at 100 W or more, or Auto lowers the current.
• With too little solar at the minimum current, charging stops after a minute. If the setting Use battery or grid power is on (the default for new installations), it keeps charging at the minimum for up to 30 minutes before it stops.
• Without up-to-date Victron data, Auto holds the charging current, and it stops charging after two minutes without data.

What you need

• A Victron system with a GX device. Phaeton runs on the GX or on another always-on Linux computer.
• Solar production that the GX measures: Victron solar chargers, or PV inverters the GX shows, except on a generator input. Solar power the GX does not measure is not counted.
• The home battery's state of charge and power on the GX.
• Modbus TCP switched on in the GX, unless Phaeton connects to the GX over MQTT.
• The charger wired where the Victron system counts it as house use, not ahead of the grid meter.
• A supported charger that takes its current from an energy management system rather than its own solar mode.
• Auto selected on Phaeton's Charging page, with the Auto mode Battery-powered or Controlled by the Victron GX in Settings. Controlled by the Victron GX charges the same way until the GX takes over. Feed-in waits for export to the grid, much like a wallbox's solar mode.

Victron GX setupCharger settings per model

What differs per charger

These charger features matter for solar charging. The Supported chargers page lists each model's limits.

• Automatic switching between one and three phases (Alfen, go-e and KEBA), where the installation and charger are set up for it and Multiple relay charging is on, with Auto mode phase set to One or three phases: with a smaller surplus, Auto charges on one phase from about 1.4 kW. Without it, charging on three phases draws about 4.1 kW or more.
• Control through the manufacturer cloud (Zaptec): a cloud or internet outage can prevent control, including stopping.

Next steps

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