To meet these requirements, Grayson proposed the BTMS M2-600V DC, a compact module providing active cooling, passive cooling and active heating in a single integrated package. The unit’s dimensions – 1340 mm in length, 554 mm in width and 421 mm in height – allowed for it to be installed within PAK-PCE’s rooftop height envelope, while still offering the internal volume necessary for the compressor, heat exchangers, electric heater, pump and header tank.

Thermally, the BTMS M2 was well aligned with the NesoBus battery’s needs. At an outside temperature of 40°C, with a coolant outlet temperature of 25°C and a flow rate of 40 L/min, Grayson’s M2 delivers up to 10 kW of cooling capacity. On the heating side, the BTMS offers integrated water heating capacities of 3.6 kW, providing enough energy to support battery warming and thermal stability in low ambient conditions.

The system is designed to work with a 50/50 glycol–water mixture, in line with PAK-PCE’s coolant specification, and incorporates an integrated brushless coolant pump and header tank. This integrated approach simplifies system layout on the vehicle and gives engineers a well-defined thermal module with known pressure and flow characteristics, making it easier to validate the complete battery cooling loop.

Electrically, the BTMS M2 operates from a 600 VDC high-voltage supply for the compressor and heater, matching the preferred supply architecture of the NesoBus. A 24V DC supply powers the pump and brushless fans and supports control functions. Communication is via CAN J1939, allowing PAK-PCE’s control system to monitor temperatures and control setpoints.

Grayson’s engineering team worked closely with PAK-PCE from the project start in November 2020 through prototype build, calibration and testing. The first BTMS unit for the NesoBus was supplied in June 2021, enabling the customer to move from development into pre-series testing and, subsequently, serial production.