A common technique used in battery charging algorithms is Constant Current / Constant Voltage. That is to say, initially a battery is charged by applying a constant current (which I believe is what is commonly called 'fast-charge'), up to a sensed condition, and then Constant Voltage is applied (which I believe is what is commonly called 'trickle-charging').
I envision this working (at least logically) as having (1) a Constant Current Source circuit set to the fast charge current and (2) a Voltage Regulator set to the fully charged target voltage, and switching the positive terminal of the battery between these two circuits.
What is a useful electrical model (e.g. for simulation) for a discharged rechargable battery? If it matters, I'm most interested in Lithium cell chemistry (Lithium Polymer to be more specific).
UPDATE
In order to get some more concrete feedback on this question (maybe this should be a separate question?), what does a circuit that practically / realizably implements CC/CV charging actually look like? From there, if you were to want to simulate this circuit, in SPICE or CircuitLab.com or whatever, how would you actually model the battery in that circuit?