P50B (21700) cylindrical rechargeable battery cell

The Molicel INR-21700-P50B is a cylindrical rechargeable lithium-ion cell in the 21700 format, made by Molicel as a power cell with low impedance. It stores electrical energy for use inside a battery assembly, and the maker lists drones and eVTOLs among its applications, together with racing motorcycles and high-performance electric cars.

The P50B belongs to Molicel's power cell series, which is built around a high ratio of discharge power to energy. Typical capacity is 5.0 Ah at a nominal voltage of 3.6 V, which is about 18 Wh per cell. The maker gives a gravimetric energy density of 260 Wh/kg and a volumetric energy density of 714 Wh/L. Low internal resistance means less heat is produced for a given current, which matters in a multirotor or eVTOL pack where cooling space is limited.

Current ratings define how the cell can be loaded. The charge current listed is 5 A, and the discharge current listed is 60 A. For pack design, these figures translate directly into the number of cells in parallel needed to meet the peak and continuous current of the propulsion system, with the pack designer responsible for thermal checks at that load.

The cell is cylindrical with a maximum diameter of 21.55 mm and a maximum height of 70.15 mm, and a maximum weight of 71 g. These tolerances should be used for holder and busbar design, including spacing for cooling. As a cell, it has no protection electronics, connector or housing: the battery management system, cell interconnection, fusing and cooling are all provided by the pack builder, and the pack voltage follows from the series count.

The maker provides test reports and certificates (UL, UN and IEC) and a safety data sheet and datasheet on its product page. Typical applications are battery packs for uncrewed aircraft and eVTOL demonstrators, high-power tools and other equipment that needs short bursts of high current from a compact cell.