As in all things solar energy-driven, the science is meant to work with a strong and natural light source. Solar-powered devices operate under full sunlight.
Particularly phones require quite a bit of energy and the chance to test your charger may only be possible in some cases.
You can give it a go and try to power up a phone or small (5volt) USB device – have fun experimenting with different light settings!
But don’t be discouraged if you can’t get optimal conditions to power a phone. Your recipient child will have plenty of time to wait for a full sunny day, to make the science come alive and keep experimenting with the best conditions!
Tip: Different phone types require different energy inputs [e.g. iPhone is harder to power up than Android]