Volkswagen Ag

Vb Autobatterie Gmbh

Dieter Ubermeier

Eberhard Meissner

Karsten Michels

Helmut Laig-Horstebrock

Uwe Dierker

In a process for determining the state of charge and the peak current loadability of batteries in the currentless pauses before and after a loading phase the no-load voltages U.sub.01 and U.sub.02 are measured. From them, with allowance for battery-specific parameters, especially the time curve of the no-load voltage, the true battery rest voltages U.sub.001 and U.sub.002 are computed. During the loading phase the converted current quantity q is measured and from the relationship U.sub.002 -U.sub.001 =C.sub.1 .multidot.q/Q.sub.0 the acid capacity Q.sub.0 of the battery is found. The relative state of charge SOC.sub.1 is determined from a curve of the rest voltage U.sub.00 linearized by the formula SOC.sub.1 =U.sub.002 /C.sub.1 -C.sub.2 as a function of the state of charge of the battery from which the absolute state of charge is calculated as SOC.sub.1 .multidot.Q.sub.0. From the internal resistance R.sub.1, a preassigned temperature and the last determined state of charge, a rest voltage is predicted for a later time from which, with the current necessary for starting the engine known, a pronouncement can be derived concerning the starting capacity of the battery.

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Hannover, Germany

Dieter Ubermeier