Applicable models:

All UPSPro systems

Yes, you can add solar panels to your UPSPro system, but it is important to include a blocking or a one-directional diode in series with the positive lead of the solar panel. The solar controller will always charge the batteries using the source providing the higher voltage, so if power ever goes out to the AC battery charger, then the system will start to charge the batteries off of the solar panel voltage instead.