P45B (21700) cylindrical rechargeable battery cell

The Molicel P45B (21700), listed by the maker as INR-21700-P45B (Low impedance), is a cylindrical rechargeable lithium-ion battery cell for high-power battery packs. It belongs to Molicel's Power Cell series and is a battery cell in the 21700 format, supplied for assembly into packs by cell and pack manufacturers rather than as a finished battery.

Molicel lists the cell for drones and eVTOL aircraft, together with two-wheeled motorcycle racing and hyper EVs and racing sports cars. For an airframe designer this places the P45B among cells chosen where a pack has to deliver high current from a small, light package, such as the propulsion batteries of multirotors, VTOL transition phases and other electric aircraft.

The headline figures describe a high-rate cell. Nominal voltage is 3.6 V and typical capacity is 4.5 Ah, which corresponds to roughly 16 Wh stored in each cell. The maker gives a charge current of 4.5 A and a discharge current of 45 A. The discharge figure equals ten times the capacity, so a pack built from these cells can supply high peak power without a large number of cells in parallel. Energy density is 242 Wh/kg gravimetric and 643 Wh/L volumetric, which sets the pack mass and volume that a given energy requirement will need before housing, busbars and cooling are added.

Mechanical data matter for pack layout. Maximum diameter is 21.6 mm and maximum height is 70.2 mm, with a maximum weight of 69 g. The maximum dimensions, not nominal ones, should be used for holder pitch, spacing between cells and the clearance of the pack enclosure. At 69 g per cell, the cell mass of a pack is easy to estimate from the series and parallel count.

The cell has no integrated electronics, connectors or housing. Series and parallel connection, current collection, protection, balancing, temperature monitoring and thermal management are defined by the battery-system design, and the integrator is responsible for keeping the pack within the current and temperature limits in Molicel's datasheet. The datasheet is available from Molicel on request through a download form, and the maker also invites enquiries about continuous discharge and charge rates for a single cell in a specific application.

The product page lists test reports and certificates for the cell under the headings UL, UN, IEC and SDS. Buyers should obtain the individual documents from the maker, since pack-level transport and safety approvals depend on the finished assembly as well as on the cell.

Typical uses are propulsion and auxiliary power packs for drones and eVTOL aircraft, as well as electric motorcycles and high-performance electric vehicles, where the combination of a 45 A discharge rating, a 21700 form factor and a mass of 69 g is the main selection criterion.