Diversity gives pack balance
Williams Advanced Engineering has developed a battery pack that combines different types of batteries to balance out the needs of peak and sustained power (writes Nick Flaherty).
The first version of the Adaptive MultiChem design combines lithium-ion nickel, manganese, cobalt (NMC) pouch cells to provide high energy density, and NMC cylindrical cells to provide high power density.
This is made possible by using separate bidirectional DC-DC converter designs for the different cell formats. That allows the charge and discharge profiles to be optimised for the different cells. This approach would also allow different battery cell chemistries to be used, although Williams has not yet developed such a system.
The demonstration unit has a total stored energy of 60 kWh and a core weight of 345 kg. This provides a peak power of 550 kW in a 20 s pulse as well as a continuous power of 170 kW.
A key part of the design is the thermal management. This is different for pouch cells, which are mounted horizontally compared to the cylindrical cells, which are mounted vertically.
The module uses an exoskeleton with a single composite preform of carbon fibre re-inforced polymer. This ‘223’ material can be used with additive manufacturing processes to generate complex shapes that incorporate the battery cooling system.