To do this, you can specify in the battery storage settings the state of charge (SoC) down to which the battery storage may be discharged. In the wallbox settings, you should keep the solar power percentage at 100%, as any difference would otherwise be drawn from the battery storage. You should also avoid using the “Lässig” and “Always charge” charging modes, as these allow battery discharging.
Additionally, you should not use the "SoC plan".