Solar Charging and Battery Priority

Battery priority decides how far the station may draw a house battery down to keep a vehicle charging. It is part of ECO+ mode and is controlled by two thresholds, Stop SoC and Start SoC. Available from firmware 2.3.81 on all station models.

Requirements

Battery priority is evaluated only when all of the following hold:

• ECO+ mode is active. With ECO+ off, battery priority has no effect at all.
• The station detects a battery on the installation. Without a detected battery there is nothing for the function to protect.
• Firmware 2.3.81 or newer.

Stop SoC and Start SoC

The two values are not two conditions on the same event. They are the two halves of a hysteresis, and each one is evaluated in a different state:

• Stop SoC — the battery state of charge at which the station pauses vehicle charging. At or below this level the battery is no longer drawn down for the vehicle. While charging is running, this is the only threshold that is evaluated.
• Start SoC — evaluated only while such a pause is active. Charging resumes once the battery has recovered to this level.

While the station is charging, Start SoC has no effect. The only question asked during a running session is whether the battery has reached Stop SoC.

What this means during a session

With battery priority active, a negative surplus — that is, import from the grid — is deliberately ignored and bridged from the battery instead. The session continues until Stop SoC is reached.

Two consequences that are easy to misread, both with Stop SoC at 60 % and Start SoC at 95 %:

• A cloud passes while the battery is at 90 %. Charging continues without interruption. That 90 % is below the Start SoC of 95 % does not matter, because no pause is active.
• Evening, battery at 90 %. The session is not ended. The station keeps charging from the battery until it reaches 60 %, and pauses only then. The battery is not held at 90 %.

Choosing the two values

• Start SoC must be higher than Stop SoC. The configuration interface does not enforce this. If Start SoC is set at or below Stop SoC, the resume condition is already satisfied the moment the station pauses, and the station alternates between pausing and charging.
• A high Start SoC means a long pause. At 95 %, charging resumes only once the battery is practically full. That is the intended behaviour — the battery has priority — but it is a longer wait than a resume threshold just above Stop SoC would give.