SA04 SiCore lithium-ion pouch cell

The SA04 SiCore lithium-ion pouch cell is a silicon-anode battery cell made by Amprius Technologies for unmanned aircraft and other weight-sensitive electric platforms. It is a cell rather than a finished pack: battery builders connect cells in series and parallel to reach the voltage and capacity needed for a flight battery on a drone, a long-endurance aircraft or a similar vehicle.

Amprius describes the SA04 as a balanced power and energy design. It is meant for applications that need good runtime but also have to deliver real current to motors during climb, hover and manoeuvres, so it sits between the high-power and the high-energy cells of the SiCore family. Silicon-anode chemistry is used to raise the energy stored per unit of mass compared with conventional graphite-anode lithium-ion cells, which translates into more flight time or more payload for the same battery weight.

The main figures are a specific energy of 315 Wh/kg and an energy density of 680 Wh/L, with a capacity of 8.9 Ah. The first number is what sets battery mass for a required mission energy; the second matters when the battery bay has a fixed volume. The maximum continuous discharge rate is 3C, which on an 8.9 Ah cell corresponds to a continuous current of about 26.7 A per cell, or proportionally more when cells are paralleled. The stated cycle life is 1400 cycles, a figure to compare against the expected number of flights over the service life of the battery.

For integration, the cell is a flat pouch with a length of 139.1 mm and a width of 52.1 mm. Pouch cells have no rigid can, so the pack designer has to provide the mechanical support, any compression, the tab connections and the thermal path, and has to pair the cells with a battery management system for balancing, protection and monitoring. The stack height of a pack therefore follows from the number of cells and from the swelling allowance chosen by the pack designer.

Typical uses are the battery packs of multirotor and fixed-wing unmanned aircraft, where energy per kilogram directly sets endurance, and other electric platforms such as high-altitude aircraft or robotics that follow the same mass constraints. Amprius supplies the SA04 under its SiCore range of silicon-anode cells and gives data on request through its catalog.