Patent ID: 6362598
Filing Date: 2002-03-26
Classification: G01R

Abstract:
A method for determining state of charge and loading capacity of an electrical storage battery comprising:measuring current, voltage and temperature of the battery; comparing the measured values with corresponding values generated by a circuit of the storage battery; varying i) selected parameters of components in the circuit and ii) selected state variables such that the measured values are matched and the state of charge and the loading capacity are calculated from adjusted parameters and state variables, wherein the circuit comprises 1) an internal resistor Ri, 2) a parallel circuit comprising a Warburg impedance Wp for diffusion processes in active material in the battery, 3) an element D having a diode characteristic curve and containing kinetic dependencies of the battery, and 4) a Warburg impedance We which represents acid diffusion in the storage battery and, optionally, a constant voltage source Uo, the Warburg impedance Wp containing resistors which depend on current direction and voltage, the diode characteristic curve having a forward direction for currents in a discharge direction of the storage battery, and the Warburg impedances We and Wp containing a capacitor C with which at least one series circuit comprising a resistor R and a further capacitor C is connected in parallel, the further capacitor C optionally having further respective series circuits comprising a resistor and a capacitor connected in parallel, and the constant voltage source Uo depending on present electrolyte concentration, and wherein mean voltage Uâˆ’We across the capacitors of the electrolyte Warburg impedance We derives a measure of the state of charge, and calculating the loading capacity of the storage battery from the state-of-charge and parameter values.