Lightweight
composite solutions

TRB has been working on a project to develop safe and robust battery enclosures. This collaborative project has focused on the production of battery boxes and modules for a new fleet of electric buses that are being rolled out in the USA, supporting the drive towards more sustainable transportation.

Key facts

• Lightweight and robust battery enclosures
• Carbon fibre composite
• Additional layers to prevent electrical conductivity and electromagnetic radiation
• Partnership contributing to all stages of product development

Challenge
Enclosures for battery cells on buses restrict the natural expansion that occurs as cells are used and recharged over their lifetime. The project requirement was to produce panels – one top, one bottom, plus 16 or 30 endplates for each enclosure – that would create a lightweight, compact, robust and electrically-isolated container to meet the tight space requirements of the bus. Weight was the most important driver for this particular application; the battery enclosures needed to be lightweight, but still robust and capable of withstanding impact.

Solution
The partnership kickstarted with a number of brainstorming sessions to further develop an initial concept and come up with innovative design ideas that would fit all of the technical specifications. A composite was chosen for the panels, comprising layers of high specification carbon fibre pre-preg – carbon fibre impregnated with resin – plus additional layers to prevent both electrical conductivity and electromagnetic radiation. The enclosure dimensions were limited to approximately 1.8 by 0.8 m, and around 0.3 m high but, thanks to the low mass of the material, the final product met the target of around 12 kg for the base and top panels – 500 kg for the overall battery enclosure.

Putting innovation into action
TRB contributed to all stages of the product’s development, and constant communication with the customer was key to driving the success of the project. Devising a suitable material for the application that was light, durable, cost-effective to produce, and easy to manufacture at the required high volumes was crucial.

Prototypes of the enclosures were manufactured after an initial cycle of six months of concept development, followed by a further six months of process development; this process was repeated once more to reach the final design. The products are currently going through rigorous quality and safety checks, with prototypes already fitted on a few buses in a limited test area of the USA.

In time, the battery packs will be retrofitted onto buses, replacing the engine – or parts of the engine – and upgrading them to either fully electric or hybrid vehicles, drastically reducing their carbon footprint and contributing to a more sustainable transportation infrastructure.