Abstract: There are described apparatus for detecting the presence of a defective cell in a lead-acid storage battery. The apparatus is included as a part of a larger apparatus for analyzing the condition of the battery and its suitability for further use in automobile lighting, starting, and ignition applications. The apparatus measures the terminal potential of the battery when it is subject to a constant resistance load. If that potential is found to increase more than a predetermined amount during a time interval following the application of the load, the battery is known to have at least one defective cell.

Abstract: Apparatus for automatically testing automotive-type, lead acid storage batteries are disclosed in which three separate tests are made and the results thereof compared to predetermined standards in a specified order to maximize the information obtained about the battery. The three tests measure (1) whether the battery meets its cold cranking rating by drawing a predetermined load current therefrom for a predetermined period of time and determining whether the battery terminal voltage is above a specified level at the end of that period, (2) whether the battery terminal voltage is above another specified level at the end of a predetermined period of time following the completion of the first test, and (3) whether the internal resistance is acceptably low. If the battery passes the first test, it is known to be acceptable. If the battery fails the first test and passes the second test, it is known to be unacceptable. If the battery fails the first and second tests, the third test is performed.