Process for monitoring the residual charge and capacity of a battery

Abstract

Process for monitoring the residual charge and the capacity of a battery, where at least two voltage-current measurements have been carried out on the load-carrying battery. The current load of the battery selected here should be greater than 30% of the nominal capacity per hour, e.g. for a 100 Ah battery, at least 30 amperes. The initial voltage-current measurement is taken at an initial time for an initial load condition of the battery. A second voltage-current measurement is carried out at a second time for a second load condition of the battery. It is essential here that the load condition of the battery has changed because of the current that has been drawn. The current-voltage measurements produce an initial measuring point and a second measuring point. The two measuring points set an interpolation line and determine the point of intersection with a limiting voltage level (U,). This point of intersection is marked by a so-called limiting current (I,). The limiting voltage level is decided from the minimum voltage required by the connected consumers in order for them to operate fault-free. The limiting voltage level is therefore stipulated for the technical layout of the battery system and is known. Furthermore, fault-free operation of the connected consumers requires a minimum operating current (I,), which is also specified and known as a design parameter of the battery system. The difference between the determined limiting current I,and the minimum operating current I,is determined and recorded. This difference is a dimension for the residual charge of the battery that is still available and in accordance with the invention is here designated as the limiting current reserve.