If no battery is connected, the CH100 voltage depends on the charging source. If a solar panel is connected, the voltage could vary from zero (dark sky above the solar panel) to approximately 14 V, depending on the temperature. If the CH100 is powered by an ac wall transformer and no battery is connected, the voltage would also be approximately 14 V.
Note: The battery also acts as a line filter, and Campbell Scientific does not recommend running the charger without a battery plugged in.