If a CH200 or PS200 is hooked up to both solar and ac power supplies, which power supply does the device use?

The CH200 or PS200 will pull power only from the source with the highest voltage at that moment. For example, the regulator will take the 20 W input from the 24 Vdc wall transformer rather than from the 18 V 50 W solar panel—even during the day. If the power goes out, the 50 W solar panel will charge during the day with no charging at night.