Resistance
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 inputs are the current, the 
voltage and a signal called Mode.  Mode determines whether current or 
voltage is the significant input.  When running direct coupled systems, 
Mode has to be set equal to one.  In a system where the voltage serves
as input to the load, Mode has to be zero and the calculations are in
reverse order.  The only parameter of the component is the resistance 
value.  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