observed: large systems take up too much system memory

proposed: don't make separate copies of objects until absolutely necessary.

instead of making copies and tracking all objects as individuals, just reference the same copy of identical objects. for example: when making a module, rather than copying the cell 96 or 128 times, just reference the same cell until there are differences. Ditto for modules - if all the modules in a string are identical, just reference the same module rather than making cheap copies until needed. in other words only create as many objects, the minimum, as needed to describe the characteristics and condition of the system.

issues:

• requires caching of the references somewhere. for example: the cells that reference the cell object could be cached in the modules in a cached_cells field as a dictionary. Instead, an easier way is to just keep the lists the same, and put the reference you want in there. see my 1st comment below
• requires tracking of cell changes in object (eg cell) characteristics like temperature, shunt and series resistance, etc.

also profiling to demonstrate this is an improvement over current methods is required.