Energy surplus

Say energy plants produce energy that is stored in massive city sized batteries, and cities get their energy from these batteries.  You can extend these "battery" plants indefinitely, limited only by how much space they take up and how energy they store in that space.  You can extend this to island batteries, battery complexes in remote parts of the world, and space battery stations.  Any type of energy can go in, so solar, hydro, coal, gas, and nuclear can all add to storage. 

What would be wrong with this system?  What would make it innefficient?  What amount of energy would be wasted in energy transportation, storage life, and redistribution of energy (a middleman instead of directly from the plant).  How long could you keep surplus battery energy?  Could you store enough to offset any losses in efficiency? 

The battery plants are located next to power plants, while cities draw energy from the battery plants through regular power lines.  When the batteries are at a certain percentage, power drain is routed to the power plants directly.  Or, plants provide to the city and excess energy to surplus storage.  The batteries store energy from already existing plants, and are used like silos when needed.  The use of windmills and solar energy to help generate energy means that these forms of power can be used for energy storage to be used later, rather than  a city having to actually rely on solar energy primarily. 

There would be no "over air" transmission of energy.  Space satellites would gather solar energy and store it in batteries, while nearby stations can hook up and drain its energy.  

On Earth, battery stations would still rely on local plants, but excess energy not used by the city would be stored, just as any resource is stored, such as oil or food.  There needs to be an efficient means of converting stored energy to useable energy.