In recent years, the demand of electrical energy has
been increasing. So the renewable energy system is developed
as another choice to generate electrical energy. The renewable
energy is not available for all time, for example, solar cell
could produce power only when there is solar radiation and
wind turbine generator could produce power only when there
is an air flow. So batteries are widely used as energy storage in
renewable energy system and also in industry. When the
renewable energy system is not available, the battery is
required in order to provide power supply to load. Moreover
the advantage of battery are store net metered solar in battery
to use at peak time, save money in peak energy costs and keep
powered up during grid failed. The application of battery are
from the small-sized portable devices to the large-sized
equipment such as uninterruptible power supplies (UPS),
which is used in energy storage system to provide emergency
power to critical loads and improve power quality and
reliability of power system.
Everyone wants to keep the battery as long as possible, but the
battery must operate in environments that are conducive to
optimal battery life. Furthermore, the life of a battery may be
cut short by heavy use or unfavorable temperature condition.
The capacity of battery would also drop when the number of
cycle life is used. The battery may last shorter than what
datasheet indicates. The deterioration of battery may not occur
to all cells of battery, so the detection of dead battery cells
could be a solution to tell the user that which battery cell is a
problem.