NOVELTY - The system models a lead-acid battery in the form of a representative electrical circuit which comprises of three sub-circuits, a charging circuit, an electrochemical reaction circuit and a voltage drop circuit.. The charging circuit is (111) configured to simulate the initial charging of the battery and having a capacitor (174) configured for charging to a first voltage. The electrochemical reaction circuit (113) comprises a number of capacitors (164,166,168,170,172) configured to simulate the charging and discharging of the battery due to internal chemical reactions and configured for charging to a second voltage. A number of resistors (122,124,126,128,130,132,136,138,140,142,144) simulate the resistance of the battery.    USE - System for modelling a lead-acid battery under various operating conditions.    ADVANTAGE - The model simulates how the battery will perform under certain conditions (e.g. charging, discharging, etc.). The model is useful for determining the appropriate battery for a given application, and for maximizing performance of the battery in a selected application (e.g. hybrid electric vehicle). The battery categorization system can be implemented as a simulation model through any combination of hardware devices (e.g., circuits, MOFSETs, capacitors, resistors) or software (e.g. SPICE or other software simulation programs).    DETAILED DESCRIPTION - The voltage drop circuit (115), including a resistor (122) and kinetic capacitor (134), is configured to simulate capacitive charging and discharging of the battery and configured for charging to a third voltage; wherein the representative circuit is implemented through a computer based simulation.    INDEPENDENT CLAIMS are made for:    a) an equivalent circuit model;    b) a circuit for modelling a lead-acid battery having an RC network;    c) a method of modelling a lead-acid battery;    d) a battery characterization system;    e) a method for making an equivalent electrical circuit model of a lead-acid    battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit diagram showing the circuit for simulating a battery according to a preferred embodiment.    Charging circuit (111)    Electrochemical reaction circuit (113)    Voltage drop circuit (115)    Resistors (122,124,126,128,130,132,136,138,140,142,144)    Kinetic capacitor (134)    Capacitors (164,166,168,170,172)    Initial charging circuit capacitor (174)