The effect of pulsatile power loads on nickel/cadmium battery cells for mechanical circulatory support devices

A number of portable medical devices, including the implantable ventricular assist device, demand fluctuating or pulsatile power from their batteries. Therefore, a study was undertaken to determine the effects of these pulsatile discharge loads on the cycle life and operating time of rectangular prismatic nickel/cadmium battery cells. The battery cells were charge/discharge cycled at 37 degrees C using either a pulsatile discharge load of 10.0 or 11.25 W (average) or a nonpulsatile discharge load equivalent to the average of the pulsatile loads. The tests showed that the pulsatile discharged cells gave significantly less operating time throughout their cycle life, by a mean of 3 +/- 3-8 +/- 2 min on each cycle (ie, 8 +/- 8-18 +/- 5%), compared to the cells under equivalent nonpulsatile discharge loads. The tests also showed that the pulsatile discharged cells had significantly shorter cycle lives, by 61-97 cycles (11-17%), than the nonpulsatile discharged cells. The results show that, under the test conditions of this study, pulsatile discharge loads reduce the cycle lives and operating times of rectangular prismatic nickel/cadmium battery cells, compared to cells discharged under nonpulsatile loads of equivalent average power.