You can tell when your Power+ is charging from the sun when the single light on the top blinks. A singular blink means that your Power+ is charging slowly (but surely), two consecutive blinks means it is charging faster already and thrice means it is charging optimally. If this light blinks 8 times in a row when in the sun, it means that it is fully charged. That’s good news because you can now charge your devices most efficiently!
You can place the Power+ with its solar panel towards the sun or hold it under a strong lamp to check if the light is blinking and functioning properly.