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Improved battery tech for hybrid buses

Bus operator develops improved battery tech for hybrid buses

The Integrated Zero Operational Emissions project, funded by Innovate UK, brought together industrial and research partners (Alexander Dennis Ltd, Arcola Energy Ltd, ITM Power Ltd and WMG) to explore and address concerns surrounding a fuel cell hybrid bus.

Among the challenges addressed were how to manage the different requirements that fuel cell battery hybrid drive trains impose on the battery system compared with battery-only drive trains. For example, with the majority of the energy storage coming from hydrogen, this allows for lower energy capacity batteries. However, the battery system also requires higher power charge and discharge and very high cycle life as the battery is recharged from fuel cell and regenerative braking

Arcola Energy sought our expertise to select the appropriate size of battery pack needed for the vehicle and explore and identify the optimum battery cell solution. The recommended solution was Lithium Titanate technology, due to its long cycle life.

However, the team at Alexander Dennis Ltd had concerns about the performance of the cells in the buses. Using real route data, we undertook a series of validation and verification tests to ensure that the lifetime, cell performance and thermal management were suitable for this application. Although testing is ongoing, early indications show it is expected the battery chemistry selected would lead to a 7-10 times longer expected lifetime in this high power bus application than those suitable for automotive applications.

Arcola were able to validate a cell selection that perfectly suited the application, by using our specialist equipment which would have been impractical to invest in themselves. By working with us, five members of Arcola’s staff increased their skills and knowledge in the area of powertrain and thermal modelling, as well as the principles of cell performance and degradation.

The project allowed Alexander Dennis Ltd to develop new expertise in the application of battery technology to fuel cell hybrid vehicles and better understand the issues with integrating larger battery packs.

By undertaking the project both companies have been exposed to new markets in the UK and worldwide.