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

So someone explain this to me, I have a power bank that will lose charge if accidentally left on. So tell me, if it’s not plugged into any device, where does the power go?