Hi,
Does somebody know how to model an exhausted battery in the battery charger circuit?   A huge Cap is ok?

Boby,

  Try the model in the following reference, " A PSPICE Macro-Model for
Li-Ion Batteries", Sean Gold, Battery Conference on Applications and
Advances, 1997. It is relatively easy to implement this model in Verilog-A
using table models.  It is a little more work than using a capacitor but it
is a better model of the load your charger will be driving. You might also
want to try the following source, http://www.analoghome.com/articles.html.
In the past, Steve has provided information on some of the battery models
he has published in the past.


                                                                         Best Regards,

                                                                             Sheldon