How much energy can be stored in a battery?
No, since batteries store energy, not power.  Your question makes no sense since the units are wrong.  It is like asking what percent interest your wallet holds.

Batteries store energy.  Power is energy per time.  This also means that energy can be expressed as power times time, like the kiloWatt-hours used to express the electric energy your house consumes during a billing period.  Another common measure of energy is the Joule.  A Watt (a unit of power) is one Joule per second.  A kiloWatt-hour is therefore 3.6 MJ.

Batteries are usually rated in units of current times time.  This does not directly tell you how much energy the battery can store, but can be a more useful value in deciding how long a circuit will run from a battery.  For example, a car battery might be rated for 50 Ah.  That means in theory it could source 50 A continously for 1 hour and then go dead.  In practise it's never that simple, and there are various factors that effect battery capacity (the current*time rating), like temperature rate of discharge, previous history, etc.