1. A method for estimating a parameter of a battery system, comprising: generating an initial plurality of particles, each particle representing at least one parameter and at least one state of a battery system; generating a tuned plurality of modeled particle values by performing an iterative process a plurality of times starting with the initial plurality of particles, the iterative process comprising: propagating each of the plurality of particles through a system model configured to represent a response of the battery system to the at least one parameter and the at least one state of the battery system represented by the plurality of particles to obtain a first plurality of modeled particle values; assigning a weight to each of the plurality of modeled particle values based upon a comparison of the plurality of modeled particle values to at least one measurement of an electrical parameter of the battery system, wherein the weight represents a correlation between the modeled particle values and the at least one measurement of an electrical parameter of the battery system; generating a successive plurality of particles based upon the weight assigned to each of the plurality of modeled particle values; and repeating the iterative process using the successive plurality of particles; estimating at least one parameter of the battery system based on one or more of the tuned plurality of modeled particle values; terminating the iterative process after a desired number of iterations have been performed to generate the tuned plurality of modeled particle values.