Hi,  @Simon70 
Thank you for your post on our business forum.

Unfortunately, the SP9030 only supports connection to a single solar panel. Below is the product interface diagram for your reference:

We do not recommend connecting additional solar panels to this unit. Should any device damage occur as a result of such operation, it may affect the validity of your product warranty. 
 

If you are looking for a solar system that supports two solar panels, we would like to recommend the VIGI SP18090:Specifications - VIGI SP18090 | VIGI Intelligent Solar Power Supply System | TP-Link

We would also like to note that the charging efficiency of solar panels is affected by a number of factors, including installation angle, the intensity of direct sunlight, among others. Therefore, switching to a dual-panel system may not necessarily resolve your current issue. For guidance on adjusting and installing the solar panel system to maximize charging efficiency, please refer to the following guide:How to install the VIGI Solar Panel system | TP-Link