1. An apparatus for estimating resistance characteristics of a battery based on a battery voltage variation pattern, comprising: a data storing manager for obtaining and storing battery voltage, current and temperature data from a voltage sensor, a current sensor and a temperature sensor, which are coupled to a battery, whenever a resistance characteristic is estimated; an open circuit voltage calculator for calculating a battery open circuit voltage from a battery voltage variation pattern measured at the present and in the past; a weighted mean resistance calculator for calculating a battery resistance parameter from a battery current and a difference between the battery open circuit voltage and a battery voltage, and calculating a weighted mean resistance from battery resistance parameters calculated at the present and in the past; a weighted mean resistance convergence calculator for calculating a weighed mean resistance convergence value by repeatedly calculating a weighted mean sequence using the weighted mean resistance as an initial condition; and a resistance characteristic estimator for estimating a battery resistance from the weighted mean resistance convergence value.