Prismatic Sealed Ni-Cd Battery For Aircraft Power

Prismatic sealed Ni-Cd batteries in the capacity range of 5-100 Ali have been providing reliable power for space use for several decades. The application of that technology to terrestrial and aircraft power use has been hindered in the past due to limited charging rate capabilities and high cost driven by the stringent need to balance the active materials and the electrolyte distribution in the cell. Recent developments in fiber structured electrodes and in rapid recombination technologies have led to the introduction of an economical maintenance free prismatic sealed Ni-Cd cells in the capacity range of 5-100 Ali. The cells feature starved electrolyte though the active areas during discharge, including the separator, are essentially fully wet. The cells which are sealed at negative internal pressure incorporate special plates for oxygen recombination during over charge. This allows for rapid charging without pressure build-up. Currents as high as 2C rate can be sustained throughout charging Thus, typical charging tunes are below 30 minutes. Vented Ni-Cd batteries of the sintered plate design have been the battery of choice for aircraft power for over 30 years. This battery features high power capability at a wide temperature range coupled with, if properly maintained, long life. However, this battery requires frequent maintenance. This maintenance consists of water toping, and often, cell shorting, to recover its capacity. The frequency of the maintenance intervals depends upon the duty profile, charging tune and voltage, and the temperature of operation. Typical maintenance frequency for aircraft batteries is I to 6 months. The sealed FNC cells do not require such conditioning. Data will be presented and discussed to illustrate and expound this attribute. The optimized pore structure of the fiber electrode results in better utilization of the active material and improved power capabilities per unit weight. The actual power capability of a given battery depends on the total electrode area, which for a given volume depends upon the plate thickness. Power capabilities of several sealed FNC cells will be presented in comparison to other technologies. The highest power 45 ampere hour cells will deliver an in rush peak power current of 2700 ampere. This translates to a peak power in excess of 400 watts per lb.