TABLE OF CONTENTS Small, metal foil lead-acid batteries have been used in aerospace applications for some time, particularly where high currents for a short period are required. In the last few years Bolder Technologies Corporation has concentrated on developing this technology and combining traditional lead-acid cell chemistry with a much improved mechanical construction. This gives very large plate surface areas combined with unique end connectors that provide very low impedance connections between the plates and the outside world.
The design of a 1.2 Ah metal foil lead-acid cell of 23 mm (0.9 inch) diameter and 72 mm (2.8 inch) length is shown in Figure 5.2. Two layers of coated lead foil and separator are wrapped round a central insulating core so that alternate layers of the lead foil protrude from either end of the coil. The 0.05 mm thick lead foil has 0.08 mm of active lead oxide on each side, with the lead foil layers being separated by 0.2 mm of glass microfibre. This results in flexible plates only 0.25 mm thick, and provides a large surface area which allows more of the active material to be used in the charge/discharge processes. There are also short path lengths to the battery terminals which are cast onto the full length of the exposed ends of the spirally wrapped cell. This construction has resulted in a cell of extremely low impedance, of the order of 0.5m ? for the 5 Ah, 2V cell, with the capability of both providing...
