Firstly, prismatic cells. These cells have the highest specific energy of all three types we are looking at today, and features the same internal layout as that of a pouch cell - albeit with additional layers of packaging. The main drawback to the prismatic cells I researched was the maximum voltage for a given capacity. Our target capacity of ~ 6.5kWh would have resulted in a maximum voltage of 131.2V, which is far too low, as the maximum current this particular cell could sustain is 150A, giving us a maximum power output of 19.68kW. Even if we could justify using this cell to the design judges, we would be at a significant disadvantage in the dynamic events.

The next cell type to look at is that of pouch cells. While pouch cells contain many similarities to prismatic cells, they are much more difficult to package, as they cannot bear any weight and are also more vulnerable to piercing of the outer material. However, they are much more suitable to a regenerative braking system, as they can sustain higher burst charge currents than the cylindrical cells we have been using for the last few years. While the majority of commercially available pouch cells were unsuitable for use due to their lower maximum voltage for a given capacity, one cell from Hong Kong manufacturer 'Electric Power' seemed to fit all our criteria, with a similar maximum voltage and capacity to a like-for-like cylindrical cell configuration.

The final cell type I am looking at today is cylindrical cells. UH Racing currently uses the Murata 18650 cells in their accumulator, due to their excellent voltage characteristics, energy capacity and the fact they are used in the Energus Li1x5pVTC6T modules, which has five cells in parallel and allows for temperature monitoring.

The main challenges of this cell type are for the integration of the regenerative braking system and cooling, as a cylindrical cell configuration is only suitable for air cooling. One piece of feedback we got at FSUK 2022 was to try and integrate a water-cooling system for both the inverters and accumulator, as running two separate systems is added complexity and an additional point of failure.