System for Determining Battery Parameters

A difference voltmeter (DVM) is used in a battery testing apparatus for determining values of open-circuit voltage, self-discharge, self-discharge rate and internal resistance of batteries. A reference voltage Vref is generated. A difference OCV relative to Vref is determined at times t1 and t2 as ΔOCV1 and ΔOCV2. The SD for a battery is determined as (ΔOCV2−ΔOCV1), and the SDR is determined as SD/(t2−t1). The IR of a battery is determined by measuring voltage at two levels of direct current and calculating IR as equal to (ΔV2−ΔV1)/(I2−I1). The smaller FSR of the DVM allows a more accurate measurement of OCV, which allows the time for determining the SDR to be reduced.