Method and device for checking a storage battery

Abstract

A battery of series-connected storage cells is checked by:Measuring the transient elementary open-circuit voltage at the terminals of each storage cell;Comparing the said elementary voltages with the average transient voltage of the said storage cells (i.e. with the total transient open-circuit voltage divided by the number of storage cells). The battery is rejected if the difference between the said average transient voltage and one of the said elementary transient voltage becomes greater than a predetermined threshold.BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to a method and a device for checking a storage battery, more particularly a lead acid storage battery, charged and filled with electrolyte, this checking being effected in principle when the battery comes off the production line.2. Description of the Prior ArtKnown means which are used at present for detecting electrical defects which have not been detected during checks made at intermediate stages of production are of two types:Firstly, devices for measuring the voltage of the batteries at the end of the forming and charging phase enable the rejection of the battery whose-end-of charge voltage is lower than a predetermined thereshold; andSecondly, rapid discharge devices require the rejection of batteries whose voltage is insufficient after a few seconds of discharge.These means are generally completely insufficient for detecting small or medium internal short-circuits and even large short circuits, which can be detected by conventional checking methods only after long storage or service periods.Preferred embodiments of the present invention enable electrical defects such as short circuits to be detected after charging ie; during battery finishing operations.SUMMARY OF THE INVENTIONThe present invention provides a method of checking a battery of series connected storage cells, comprising the following operations:An elementary transient open circuit voltage is measured at the terminals of each storage cell (ie;The said elementary voltages are compared with the average transient voltages of the said storage cells (ie with the total transient open circuit voltage devided by the number of storage cells);The battery is rejected if the difference between the said average transient voltage and one of the said elementary transient voltages is greater than a predetermined threshold.In the method according to the invention, the transient voltage of a storage cell to be tested is compared, not with that of a standard storage cell, but with the average transient voltage of all the cells of the battery to which it belongs; thus in each battery, the average theoretical cell is assimilated to a normal reference cell.The existence of an electric defect in a storage cell results in a difference in transient voltage which is greater in proportion the magnitude of the threshold value is chosen as a function of the least defect which it is necessary to detect.The measurement of transient voltages in an open circuit can be effected continuously or at predetermined instants in a period counted from the end of charging and ranging from a few tens of minutes to ten or so hours, a period of about one hour being preferable.The invention also provides a device enabling the implementing of the above method.Embodiments of the invention are described by way of example with reference to the accompanying drawings:

Description

Claims

1. A method of checking a lead battery of series connected storage cells at the end of the battery production line, comprising the following steps, in order:

fully charging said lead battery at the end of battery production;

measuring an elementary transient open circuit voltage at the terminals of each storage cell in a time period from the end of charging which ranges from a few tens of minutes to about ten hours;

comparing said elementary voltages with the average transient voltages of said storage cells; and

rejecting the battery if the difference between said average transient voltage and one of said elementary transient voltages is greater than a predetermined threshold.

2. The method according to claim 1, wherein said point in time is about one hour.

3. The method according to claim 1, wherein said measuring step comprises taking point measurements.

4. A device for checking a fully charged lead battery of series connected storage cells at the end of the battery production line, wherein during a time period counted from the end of charging and ranging from a few tens of minutes to about ten hours, the elementary transient open circuit voltage at the terminals of each storage cell is measured and wherein said elementary voltages are compared with the average transient voltages of the storage cells, said device comprising:

means for measuring an elementary transient open circuit voltage at the terminals of each storage cell;

means for comparing said elementary voltages with the average transient voltage of said storage cells; and

means for providing a rejection signal for the battery if the difference between the average transient voltage and one of said elementary transient voltages is greater than a predetermined threshold.