I have one of these??in my kit and use it to monitor the voltage from my power banks/USB trigger cables so I can ensure that it has stabilized before turning on /plugging in.? It measures the current and charge (mA-hours) also and it even allows setting voltage and current limits although I have not used that feature until I can put an oscilloscope on it and understand the system's behavior going into and recovering from a fault.? The load resistors and clip leads are handy additions.
Plugging the cable into the power source first, then into a radio, should be a safe process as long as a reliable connection is made to avoid power (and voltage) cycling due to intermittent contacts.
73, Don N2VGU
Donald S Brant Jr