MacBook Pro charging compatibility

It will take FAR longer with a power source that is only HALF the standard capability (and likely lower Top Voltage capability as well.) Those sorts of Power Sources can sometimes be used to keep it from going completely dead.

You MIGHT be able to charge it overnight if you shut it down. But it could take longer than just one night to charge that way.

You could probably use the 30 watt charge cube, but expect very slow charging, or possibly for the battery percentage to actually decrease if doing CPU/GPU intensive tasks.