Amprius Technologies SiCore SA03 Pouch Cell

The Amprius SiCore SA03 is a silicon-anode pouch cell from Amprius Technologies. The company, based in Fremont, California and founded in 2008, develops silicon-anode cells for manned and unmanned aviation. The SA03 is intended for fixed-wing drones, which fly long and steadily and whose range depends on energy per kilogram.

The capacity of 11,800 mAh says little about flight time on its own; what counts is energy density, which is 400 Wh/kg, or 875 Wh/l by volume. At 1C the continuous discharge current is 11.8 A, a value calculated from C-rate and capacity. That suits the cruise of a fixed-wing aircraft, which draws little current, but leaves little reserve for take-off, climb or gusts. The cell measures 139.5 × 52.5 mm in length and width, and the manufacturer quotes 300 cycles.

As a lithium cell the SA03 must pass the tests of UN 38.3 for transport, and because pouch cells are sensitive to pressure, spare cells should be packed protected against short circuit and pressure. A specialist workshop with suitable test and protection equipment assembles it into a flight pack. For air travel, the IATA limits of 100 and 160 Wh apply to spare lithium-ion batteries; a pack adds up the energy of its cells.

When choosing, remember that silicon anodes trade cycle life for energy. 300 cycles suit missions where every flight counts, less so daily training. Cycle figures refer to a fixed test profile, usually counted to 80 % remaining capacity; cold and high currents shorten them. Pouch cells swell slightly in service and need room and even support in the fuselage.