Patent ID: 7567085

Claim:
A battery diagnostic system configured to: measure the characteristic of a storage battery system ( 3 ) comprising a plurality of storage batteries; diagnose an aging status of the storage battery system, and manage history data relating to the characteristics of the storage battery system ( 3 ), the system comprising: a main processor unit MPU ( 1 ) configured to: control a storage battery cell to be measured, control an amplifier of an automatic scaling circuit ( 7 ), control the generation of a AC constant current (Is) applied to the storage battery cell, obtaining waveforms of an impedance voltage (Vis) and the AC constant current (Is) when the AC constant current (Is) is generated, determine measurement data including a terminal voltage (VD), current (I), and temperature (t) of the storage battery cell, and calculate internal impedance of the storage battery cell using the AC constant current (Is) and the impedance voltage (Vis); and a constant current source ( 5 ) configured to generate the AC constant current (Is) applied to the storage battery cell, wherein the constant current source ( 5 ) is configured to turn on and off according under control of the MPU ( 1 ), wherein a frequency of the constant current source ( 5 ) is determined by the MPU ( 1 ); an A/D converter ( 6 ) connected to the constant current source ( 5 ) and the automatic scaling circuit ( 7 ), the A/D converter configured to convert each signal output from the constant current source ( 5 ) and the automatic scaling circuit ( 7 ) into a digital signal; and a communication port ( 8 ) configured to transmit the measurement data determined by the MPU ( 1 ) to a computer; wherein the automatic scaling circuit ( 7 ) comprises: a plurality of operational amplifiers ( 50 ) having different amplifying gains; and a signal selector ( 51 ) connected to output ends of the plurality of operational amplifiers ( 50 ) and configured to select one of the plurality of operational amplifiers ( 50 ) and automatically scale a size of the impedance voltage (Vis) obtained when the AC constant current (Is) is generated.