Energy banks are a reality, but they are not very efficient and big. They need a cable to recharge, and therefore require a power outlet. In addition we must always monitor that they are charged to not find any surprises when we attack our devices. This is their limit. But their idea is good, it's like having an electric battery always at your fingertips. We must only make them perfect and in step with the times. let's see how the power bank will evolve in a few years ...
Think off the Grid