From The Solar - EcoFlow DELTA 3 Plus Manual

Please connect the power station's AC input port to a wall outlet using the
provided AC charging cable.
The input port supports a maximum charging power of 1500W, and the
charging speed can be set in the EcoFlow app.

From the Solar

The XT60i input port(s) of the power station supports both solar charging and
car charging.
Here is a basic guiding principle that helps you check your setup, when
connecting your solar panel(s) to charge the power station:
1. Connect this port to solar panel(s) using an
Charging Cable (sold separately).
2. Please make sure that the total Voc (open circuit voltage) of the solar
panel(s) is within 60V, and the total Isc (short circuit current) is within 15A to
avoid product damage.
3. For series or parallel connection, please refer to the solar panel's manual for
more details.
EcoFlow Solar to XT60i