STATE OF CHARGE INDICATORS FOR ALKALINE BATTERIES

The work described has been divided into two major categories: Pulse Techniques and Phase Techniques. For the pulse techniques, a load was connected to a test cell through an appropriate switch so that the current was suddenly increased from zero to the required value. These values changed from C/2 to 100C on 4 Amp-Hr cells. The parameters being studied were displayed onAN OSCILLOSCOPE AND A PHOTOGRAPHIC RECORD MADE. Results of the transient peak height measurements have been inconsistent. The height shows a somewhat random variation although there is a general decrease in transient peak height with decreasing capacity. The ohmic resistance shows a capacity dependence. The double layer capacitance varied with state of charge but the lack of reproducibility of the measurements caused errors in predicting the state of charge that were too large to be acceptable. Two successive refinements in the apparatus failed to reduce this error appreciably. The phase techniques rely on the measurement of the shift in phase between the cell voltage and current. It appears that with the phase method a battery would have to be tested cell by cell. With the resistance method an entire battery could be checked with one measurement by bringing all cell terminals to a common multi-pin connector on the battery. (Author)