When supercars breed

The Formula E Spark-Renault racing car is far from a French fancy: sharing DNA with both the McLaren P1 and the Jaguar C-X75 makes it automotive aristocracy. Ross Ringham visited Formula E battery maker Williams Advanced Engineering to talk cells, safety and a six month schedule.  

A pair of track-prepped Jaguar C-X75s crouch in pens, bare carbon fibre skins as incongruous against the gleaming polished floor as Darth Vader in a dentist’s chair. They’re sat on the ground floor of a new 3,800sq m facility built to house consultancy Williams Advanced Engineering, and they glower out at the summer sunlight shafting through the walls of glass that frame the empty workshop. All menacing muscular lines and bristling flanks, they’re like black bulls awaiting a matador, stripped and ready for action. 

In contrast, the glossy blue model sat the other side of the double doors is a heavyweight champ in an Armani suit, street smarts smartened up for public presentation.

Hang on: that’s three C-X75s within touching distance. Three.

This is the supercar that made headlines in 2010 when it debuted at the Paris motor show with gas turbines married to electric hub motors, encased in the sort of smooth lines and flowing haunches that Shakira, Beyonce and JLo combined couldn’t match. They were destined to be 200mph+ technological triumphs disguised as £1million objects of desire, but never made the production line (a decision that must have felt, says Top Gear magazine, “like strangling a puppy”).

Only a mere handful of test mules ever saw the light of day, including the snorting, fire breathing track animals here. They really work – albeit with the turbines dropped in favour of a 1.6 litre, four cylinder internal combustion engine that’s both supercharged and turbocharged, and the electric motors brought inboard and reduced to two.

It is Williams engineering expertise that underpins the C-X75’s aerodynamics, carbon composite manufacturing and space age hybrid tech, which includes batteries influenced directly by the company’s F1 programme. Something very similar to those batteries now nestles under the sinuous rear fairing of the Formula E Spark-Renault racing car, providing the juice to power an electric motor borrowed from the momentous McLaren P1 hypercar. It’s becoming pretty clear that Formula E teams have got their hands on a powertrain that is something special.

The world’s best shed

“With the C-X75, the brief was to build something with the performance of a Bugatti Veyron, the carbon emissions of a Toyota Prius, and the electric range of a Chevrolet Volt,” says James Francis, communications manager at Williams, as we lope across the organisation’s Oxfordshire complex, from the F1 facility on one side of the site to the engineering consultancy on the other. We pass two buildings that house wind tunnels; enormous, square structures that look like industrial units. One is used by the eponymous F1 team – within strict limits – and the other is an older facility that is rented out to customers such as, until very recently, Caterham F1. The current client list is a closely held secret, like much else at Williams.

The new engineering block that we’re heading to was opened just a few weeks ago by British Prime Minister David Cameron, and stands as a statement of intent by the business. Through Williams Advanced Engineering, the company has been exploring ways to monetise its decades of engineering expertise with varying degrees of success. The Jaguar concept was one foray; another was its flywheel business, which has since been sold to GKN; and there is a relationship with Nismo which explains the presence of brace of Nissan GTRs parked around the back.

The latest venture of the consultancy arm – that can be disclosed, anyway – is the Formula E tie up. The batteries for the electric racing cars are assembled on site here, in a single-storey lightweight structure behind the impressive flagship facility. It’s like the world’s best shed. Inside, eight full time technicians package the battery components into large black boxes. I watch through the window – I’m not allowed into the building in case I see too much. Presumably I’d then be shot. It’s a quiet spot, and many of the staff are away as a result of the F1 summer shutdown. No witnesses. Gulp.

As we head back into the main building and upstairs to the offices, Francis describes the C-X75 project arc: “Jaguar approached us when the car was already designed – we had to squeeze in real-world systems without disrupting the sleek form of the original concept.” That experience would prove mighty handy when it came to Formula E.

Formula E battery assembly process courtesy Williams

Box of secrets

Not much is known about the Spark-Renault batteries and Williams isn’t doing much talking. They are packed away in sealed, structural “safety cells” and supplied to the teams as finished units. Why all the secrecy?

“A lot of the technology is sitting in the C-X75 downstairs, and a lot of the learning,” explains Gary Ekerold, who leads the company’s Formula E battery programme. We’re sat in a meeting room on the first floor, above the workshops of the ground level. “But we’ve been developing this technology since 2009, first of all with our KERS programme in F1. That is our commercial advantage, and we’re guarded about that.”

In fact, elsewhere Williams has described the link between its F1 and Formula E battery tech as particularly close: “In terms of electronic hardware architecture, it is 100% the same, just modified for the additional requirements of Formula E regulations.”

Given that F1 rival McLaren is closely involved in building the Spark-Renault too, closed lips come as no surprise. “There is no info whatsoever,” says Craig Scarborough, a noted motorsports journalist and technical illustrator, on what is known about the battery technology used in any of today’s F1 regenerative systems, until recently known as KERS. These capture kinetic energy lost through braking and heat emanating from the internal combustion engine; the energy is stored in batteries and released to boost overall power. “Pictures of the batteries and control electronics do not exist; any images released preseason bear no relation to what’s actually on the cars.”

Something very similar to the Formula E batteries is shortly to appear in a commercial setting, too, probably in some form of road car tie up. All in all, it means details are sparse and will remain so.

Here’s what we do know about the Formula E energy source:

  • headline specifications are 30kWh and 200kW
  • cell architecture is almost identical to that used in the Williams F1 programme and the Jaguar C-X75
  • the cells weigh 200kg on their own and, according to the SAE, are liquid-cooled lithium-polymer pouch cells
  • the battery is designed to be fully charged in under an hour at the track, though it can be replenished much faster
  • it can recharge at 200kW to accommodate the needs of the regenerative braking system
  • it is designed to deliver full power for just three 57s laps in a row
  • it is cooled with a patent-pending thermal management system that uses dielectric oil
  • the safety cell is a structural component, built by Dallara from carbon fibre and aluminium honeycomb; battery cells included, the unit weighs in at around 320kg, about 40% of the total weight of the car
  • 45 units have been built at the new production plant

Terminal velocity

The Formula E battery development process was something of a race itself. “An OEM was looking at the design and delivery of the battery,” explains Okan Tur, technical lead at Williams and the man whose brainchild the battery is. “But their decision was not to continue with that, so we were approached to see if we were interested.”

They were, but lagged the other consortium partners – namely, McLaren and Dallara, led by Spark Racing Technology and advised by Renault – by six months. “The biggest constraint we were faced with was that the car was already designed,” Tur says. “We were given a design and told – ‘please, do everything within this box’.”

Formula E battery safety cell courtesy of Williams

Echoes of the C-X75. With that project, of course, Williams had proved it could take the slinky shape of a customer’s car and translate its headline specifications into something that actually works – although replicating that process with a single-seater race car was significantly more challenging.

“An open wheel racing is car is fundamentally quite different in its structure to a normal car,” says Ekerold. “In a normal car, you have a large platform on which the body sits.” Commonly, batteries are spread out along the floor, to aid weight distribution and fit around other components more fluently. Ekerold goes on: “In an open wheel car you don’t have that floor space.”

“Integrating the electric powertrain was quite challenging,” said Theo Gauzin, technical director at Spark, in a recent interview. “The SRT_01E is a very compact single-seater, hence the challenge to fit this equipment.”

The “box” that Williams had to design to was the safety cell, a protective case for the battery and a structural component of the car. The driver’s monocoque survival pod is bolted to the front of it, and the gearbox, motor and suspension attached to the rear. That meant that exploring battery swap concepts was never an option for the Williams team, although the compressed schedule would have ruled out such ideas in any case.

Venturi Spark-Renault Formula E powertrain with rear fairing removed

“In May 2013, we delivered concept work and bid,” Tur says of the fast-track process. The contract was won in June; by the end of the year, the first prototype had been produced and was undergoing testing. That’s six months to go from paper to a state-of-the-art, fully working energy source. Not bad. A phased approach to track testing began in February this year, with the final full scale version tested in May – just weeks later, the first batteries were delivered to teams at Donington Park.

The speed of the process required a multi-faceted approach to design, and Tur is not a bad choice for such a tight, technical programme. With long brown hair tied up in a ponytail and a wiry, compact frame, he looks more like a guitarist from a rock band than an electronics engineer, but he has spent his whole career designing electric cars and propulsion systems. He notched up a Master’s degree at Istanbul Technical Univeristy in his native Turkey before heading to Blighty, where his CV includes a stint at Mercedes, working on the first F1 KERS technologies in 2008 and 2009, and leading on hybrid programmes for Jaguar Land Rover. In his three years at Williams, he’s already put his name to the battery packs for the C-X75. This is a chap who knows his onions. Or cells.

“We started with the concept level design phase – selecting the cell chemistry,” Tur explains. “We looked at the specification and the timeframe. We weren’t free to do indepth testing, but we’ve been designing batteries for some time, so we understand the different cell chemistries. We made a sensible decision, selected a chemistry, and then started looking for off the shelf cells.”

While waiting on cell samples, Tur made a start on other aspects of the battery, including structural, electrical and thermal modelling, making extensive use of computer aided engineering simulation. The parallel workflows were, Tur remarks dryly, “sufficiently challenging.”

Also challenging was heat – or more accurately, cooling. “We had performance targets to meet, which required significant thermal management,” he says. The solution is a new system that is patent pending. Both configuration and composition are utterly secret: “All I’m willing to say is that it is a liquid system with dielectric oil.” 

Battery performance was dictated by requirements set out by the FIA and series organiser FEH. “This application was more about energy than power,” says Tur. “The challenge for us was in delivering enough energy within the voltage and power range specifications given to us. When we started, the regulations said that, including regenerative braking, the maximum energy used on a single car has to be limited to 30kWh. As we progressed the design, the regulations were adapted. Regen became free – teams can use as much energy as they capture under the standard FIA efficiency rules. Pure battery energy is now limited to 28kWh.”

The inclusion of regenerative braking has meant that the battery needed to be capable of charging at 200kW, although the trackside charging target is an hour. “In theory, it takes as much time to recharge as it does to empty it, so 20 minutes,” Gauzin went on to say in the aforementioned article. “However, we’d rather work with a recharging time of between an hour and 90 minutes.”

“We easily achieved that,” says Tur. “At our facilities, we recharged the battery in half an hour.”

Donington test day two charging cable top of battery

Assault on battery

Problems with batteries plagued teams over the first couple of public test days, leading to replacement units being fitted and lots of Williams staff rushing around with laptops and worried expressions. But according to Tur and Ekerold, nothing was unearthed that was completely unexpected.

“We tested this battery for three months,” says Ekerold. “Then we go and give it to 10 race teams, where you’ve got engineers who aren’t as experienced in electrical activity as our guys are and racing drivers who are looking for every competitive advantage. There are some clever guys in those teams who are looking for ways that they can do things slightly different – and we give them a battery to do what they like with. All of a sudden you start getting faults that you think, hang on a minute, we haven’t seen that sequence of events.”

Teams pushing parts to the limit won’t have come as a complete surprise to South African Ekerold, whose dad Jon was a champion motorcycle racer and who has spent years heading up two wheeled racing teams himself. But the situation wasn’t helped by a gulf of difference between the circuits the battery has been prepared for and the circuit at which team testing has taken place. Ekerold explains: “This battery has been designed to deliver power at 200kW for three 57s laps. That is the qualifying criteria. Then we go to a circuit like Donington Park – that’s one and a half minutes long. Drivers think – ‘we’ll do three laps, that’s what you told us.’ But three laps around Donington is four and a half minutes. All of a sudden you’re running at nearly 50% outside what the battery was ever designed to do.”

There were also teething problems with the new battery cooling system, which has been tweaked as a result. Ekerold goes on: “We had some minor technical issues, but you’d expect that at a test. F1 has been around for 50 years; they go to their first test and they have engine problems. That is why motor racing is important to technological advancement, because it is a test bed that puts the product under the most extreme circumstances. Did we have any major issues? No.”

Ekerold points out that the private simulation days ran without hitch. “When we went to the race sims, where there were very controlled periods for free practice, qualifying and then the race, the dynamics of the battery changed tremendously,” he asserts. “Put the issues we saw at the first two tests in the context of a race weekend for which the batteries are designed and a lot of those issues fundamentally disappear. We had a race simulation this week. Battery failures? None.”

The F word

One of the teams most affected by battery issues at the public tests was perversely the source of the most glowing review of the safety aspects of the battery. An engineer at the team told me how impressed he was with the multiple protection features built into the high voltage system. All teams had to undergo bespoke training, too, before they could get hands on the batteries. It’s a stance that has been driven through the series from the very beginning.

“The FIA has safety at the top of its agenda, and we support that,” says Ekerold. “All the learning that we’ve generated over the last five years with KERS we bring to the Formula E series.”   

As much work has gone into safety as into every other aspect of the battery design – in particular, to avoid any chance of fire. One of the Virgin Racing cars caught light at the public tests, but the issue turned out to be with the 12V auxiliary battery and Ekerold is keen to stress the Williams package wasn’t involved in any way. “The 12V system and the high voltage system are totally different,” he says. “Every racing car in the world has a 12V battery in it; that’s not unique to electric cars. We’re not sure of the reason for the fire, but it was car-related rather than battery-related. It had nothing to do with our system and our battery. Safety is at the forefront of our minds.”

The battery has also been subjected to – well, a battery of tests to earn its place. Tur says: “We had to go through full FIA crash tests, standard tests defined by UN, and our own state of the art safety tests.”

To ensure the battery would survive the worst that close quarters track action could throw at it, Williams got involved with the design of the safety cell, the box in which the battery sits. “The external dimensions were predetermined,” Ekerold explains. “But we had a lot of learning in safety cell manufacture from our KERS system that we wanted to help Dallara introduce. Our battery is the first to ever go through an FIA crash test. We passed it first time.”

Marrying top F1 teams

Williams will field a support team of eight at every race to ensure the batteries are kept in tip top condition and to ensure every team gets identical equipment. “We do not foresee any degradation in terms of power performance,” says Tur. “There will naturally be some degradation in terms of capacity, but we have some excess energy in the battery.” That means that teams should be able to extract as much performance from the car in London next year as they can in Beijing next month.

“We’re focused on delivering the best product for Spark,” says Ekerold. For its part, Spark is happy with how things have gone thus far. “We couldn’t have found a better partner,” says Gouzin.

For now, the battery shed is quiet, with the limited production run of 45 units completed. But development is already underway for next season. Williams has the ability to supply the entire powertrain (and indeed, to build an entire car) and it’s already looking at how to improve performance for subsequent iterations.

“There’s talk that in year two, teams can look at everything from the bulkhead backwards – battery, electric motors, even the rear suspension is free from year two,” says Ekerold. That means that the Williams offering will need to be competitive both in terms of cost and performance, to turn as many teams as possible into season two clients. He isn’t worried: “The teams are sensible. In the interests of controlling costs and making sure this is sustainable, it will be a phased step. No one wants to redesign the world.”

The world can wait: Tur is itching to have a go at the entire powertrain. “If were designing our own car, with a blank piece of paper, we would have gone with a different type of solution – probably,” he says. Because the safety cell is a structural component, “it is not the lightest thing we could have designed.”

Ekerold puts it another way: “People always ask these questions: could it be lighter? Could it be faster? Could it hold more energy? All of the answers are: yes; maybe; no. It depends on the confines of the regulations. There are a very specific set of regulations that were set for us and we designed for those regulations. If those regulations didn’t exist, could we design something that was lighter, faster, holds more energy? Probably. But that wasn’t the objective of the design scope.”

While the regulations may appear to be little conservative compared to where the boundaries of available technology lie, the approach does mean that Formula E will offer room for leaps of engineering innovation instead of the mantra of “marginal gains” common in other sports. “There are progressive targets, starting immediately next season, with bigger steps in 2016 and 2018,” says Tur.

What is far from conservative is the pace at which everything has materialised. Let’s not forget: 12 months ago, there was no car, no drivers, no confirmed calendar, no completed list of teams and no HQ at Donington Park. Today, the series is flesh and blood and gearing up for the first race. The engineering and logistical challenges have been phenomenal – and they have been met.

And then there’s the impressive roster of names behind the new series. “This programme has three different partners involved: McLaren, Dallara, and us,” Ekerold concludes. “I can’t think of another example of two top F1 teams working together.”

McLaren, Williams and Jaguar, the P1 and the C-X75: what an epic family tree. 

C-X75 and GTR at Williams Advanced Engineering courtesy Williams

All images courtesy of Williams, unless otherwise indicated.

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