Amprius Technologies SiCore SA110 Cylindrical Cell

The Amprius SiCore SA110 is a cylindrical silicon-anode cell from Amprius Technologies of Fremont, California. Its dimensions of 65.0 × 18.3 mm match the round-cell format 18650, in which the first two digits give the diameter and the following ones the length in millimetres. It is intended for medium multicopters and combines silicon energy with an established round-cell format.

With 4,000 mAh and 400 Wh/kg the energy density is clearly above that of classic graphite cells in the same format. The continuous discharge current is 12 A, which is 3C; it is calculated from C-rate and capacity. If a multicopter draws more than 12 A, the current has to be spread over cells connected in parallel. The cell is quoted at 500 cycles, which for a silicon cell is a figure that allows everyday use.

Round cells are mechanically robust; the connection into a pack only arises through series and parallel wiring with cell connectors, and this step and the protection electronics (BMS) belong in a specialist workshop. For transport the cell must meet the tests of UN 38.3, spare cells are protected against short circuit, and for air travel the IATA limits of 100 and 160 Wh apply to spare batteries. In addition, IEC 62133 covers the safety of lithium cells in portable devices; whether a cell is tested to it is stated in the manufacturer's data sheet.

Wear is driven by the silicon anode: silicon expands considerably more than graphite when it takes up lithium, which limits life and makes the cycle figure depend on load. Parallel groups should consist of cells of the same capacity class. Cycle figures refer to a fixed test profile, usually to 80 % remaining capacity; cold and continuous load at the limit shorten them.