London, UK|19 Apr, 2017

Insight: Williams’ updated battery

The most obvious difference between the Season 2 and 3 Formula E cars is the twin plan front wing, which has given the car a more futuristic and dramatic appearance. However, under the skin there’s been a much more significant change, one that has made the cars faster and more efficient. 

For Season 3, Williams Advanced Engineering has introduced an updated version of its 28kW, Lithium Ion battery, which powers all 40 cars used during the races. While visually almost identical to its predecessor, the revised unit takes advantage of the lessons that have been learned over the first two seasons of Formula E and the advances in battery technology across the board.

The FIA also amended the rules for Season 3, effectively allowing 50 per cent more energy to be regenerated and put back into the battery. To take full advantage of this, certain key changes had to be made, as Paul McNamara, technical director at Williams Advanced Engineering, explains.

“We have made quite a range of small changes in three areas: the first one is the cooling system - with changes to make that more robust and make it easier for us to assemble and disassemble. We’ve also done a few things to improve the performance of the thermal interface materials and the details of how the cooling tubes link up with the cells and the bus bars.

“The second area is the bus bars themselves. In the battery, we’ve got proper bus bars dealing with the quite high currents. In terms of building up the battery those bus bars all have to be interconnected. They’ve got special joints in them so that we can disarm it and bring it down to beneath 50 volts and allow us to disassemble it. Those joints have improved so they’re more resilient to vibration and the thermal displacement going into them has improved in the battery as well.  

“And the final area has been in the detail design around supporting the cells, because the pack cells of the battery have to be supported and insulated from vibration and then connected into the bus bars. So, we’ve made quite a lot of detail changes to do that throughout. All of those things help us with making the batteries more reliable for the teams but they also help us in extracting more power and help us to put in more power.”

The knowledge gained through the tens of thousands of kilometres covered by the cars across the races and testing programmes have given the Williams Advanced Engineering technicians an enormous amount of data and experience in dealing with a situation that was previously unprecedented. While electric cars have been available for over 100 years, never before have they been subjected to the white-hot competitive environment of a single-seater racing series such as Formula E.

Having taken a bold step into the unknown, Williams Advanced Engineering has gained considerable experience of running the battery in a racing environment, which it has employed into these detail changes.

The biggest challenges are cooling and vibrations. Racing flat-out for 50 minutes builds up a level of heat that is unlike anything that will be experienced in everyday electric road car use, while the combination of bumpy city streets and stiff racing suspension, means the level of vibration is again unlike anything that would normally be experienced.

But even though these are key challenges for racing, the solutions are helping to inform how road car EV technology is developing. 

“The ability to cool the battery and do all of that in a lightweight way is the key thing,” says McNamara. “If you’re trying to make an electric car, the biggest challenge you’ve got is weight. Because by the time you’ve taken away your engine and conventional gearbox, drivetrain, fuel system, fuel tank and exhaust, the weight of all that is usually lighter than what you want to put back in terms of a battery pack. The real challenge is having parity of weight while having a decent range. So making the battery lightweight is key to that, and that’s where Formula E brings learnings to us.”

A lot of the work that Williams Advanced Engineering does in the road car arena is confidential, but two of the concepts it has been involved with have recently been made public. Both the Aston Martin RapidE all-electric concept car and the spectacular Dendrobium hyper-car, have taken the lessons Williams Advanced Engineering has learned through its work in Formula E and employed them into road cars.

It’s because of this type of work that Williams Advanced Engineering is part of a consortium that won APC (Advanced Propulsion Centre) support for its battery build facility. The project will help overcome existing supply chain gaps in the industry, as well as offering support to UK chemistry development and bridging the gap between low-volume prototype build and electric vehicle production.

This ought to help the UK to become a key player in the rapidly developing arena of battery design, development and distribution. It’s something that Formula E endorses whole-heartedly and remains one of the key aims of the championship - to help drive the development of road car technology through our racing endeavors.

But there are more potential implications for this burgeoning technology. The next challenge for Williams Advanced Engineering is to understand what the second life is for the batteries. While the units used in Season 1 and 2 are no longer suitable for racing, these batteries still contain a lot of energy and the capacity to store it over an extended period of time.

“There is a nice project we’ve got about energy storage units for homes,” says McNamara. “We have a storage unit that is being trialed in Germany and renewable energy is basically being stored in a big battery, which is then being used within the house. And that was very much influenced by Formula E.”