Battery
by Jurgen Eckstein 1990

	This component simulates the performance of a lead-acid storage
battery.  It is designed to operate in conjunction with a solar
cell array and a regulator.  The only input of the component is the current.
The battery may consist of several cells connected in series and parallel
to satisfy the voltage and current requirements of the load.  The output 
voltages VD and VC are the voltage limits on discharge and charge for
possible use in the charge controllers.  To avoid battery damage, the
battery must be protected from overcharge and deep discharge.  Charging the
battery to too high a voltage causes gassing which reduces the charging 
efficiency and there is a danger of explosion from the generated Hydrogen
and Oxygen gases.  VC and VD have to be provided by the user for a single
cell.  Data are available in battery handbooks or can be obtained from the
manufacturer.  Sample input and output are included in the source code.

REF: Detailed Modeling of Photovoltaic System Components (Masters Thesis)
     Solar Energy Laboratory  University of Wisconsin at Madison