Eli5: How does a power bank charge a device until it dies, wouldn’t equilibrium be reached?

Question

Eli5: How does a power bank charge a device until it dies, wouldn’t equilibrium be reached?

In: 551

Answer 1

Imagine you fill a bucket with water from another bucket.
The bucket below does not care how much is in the one you are pouring from.

Equilibrium states are only reached if the device can also charge back the power bank. This is however not the case here.