Formula E Insight – The Williams Battery
Formula E recently published an interesting article on Spark-Renault SRT_01E’s battery pack developed and manufactured by Williams Advanced Engineering, a Formula 1 supplier.
As it turns out, the British company had just six months to prepare the whole system according to FIA requirements.
“In a series that is unique and groundbreaking, the most innovative component of all is Williams’ battery. Built to a specification determined by the FIA in terms of power, charge time and longevity, the work that has gone into powering the world’s first all-electric racing series could only have been performed by a company with the racing pedigree of Williams – from being awarded the tender to running on track for the first test took just six months!”
Doug Campling, the technical lead for Williams Advanced Engineering’s motorsport programs, stated:
“There are very few organisations in the world that could have done what we did in effectively six months. When you think about who else could have done it, it’s a very short list. There have been a lot of late nights! It’s hard to imagine another company that doesn’t have a racing history that would have the same ethos.”
Formula E Holdings ordered 42 racers – 40 for 10 teams (4 per team / 2 per driver), one demo and one for crash tests. To assemble them, Williams put in place a production line in the brand new ‘battery building’ that’s been erected at its headquarters in Grove, Oxfordshire.
An interesting finding for us is that battery pack performance are intentionally limited to achieve consistent output, not only across teams but also over a 2 year period (Spark-Renault SRT_01E will be used in two seasons). Total usable energy, which can be drawn from battery pack, is 28 kWh. At the moment, we don’t know who supplies lithium-ion cells. Nor do we know nominal energy for the pack. However, weight of the cells is limited to 200 kg (440 kbs), which indicates that energy density must be well over 140 Wh/kg (the minimum for 28 kWh @ 200 kg).
“Formula 1 race teams are essentially high-speed prototypers, quickly designing, testing and building new components that evolve the performance of the F1 car from race to race. However, the contract with Formula E is to produce a component that is 100 per cent consistent from one team to the next, and more over, one that is as powerful at the end of season two as it was at the start of season one.”
Okan Tur, the chief technical specialist for hybrid systems commented:
“We have more energy in the battery than the FIA allows the teams to use. FIA regulations says the cell weight has to be limited to 200kg and the output of the battery can be no more than 28kw/h, so we designed a battery with some excess stored energy levels that stayed within the FIA regulations.”
The other thing is that the Formula E racer inherits several attributes from Formula 1 racers:
While the sheer size of the Formula E battery means there’s no mistaking it for one Williams developed for its F1 programme, the knowledge flow between the programmes has been very evident. “In terms of electronic hardware architecture, it is 100 per cent the same just modified for the additional requirements of Formula E regulations,” adds Tur.
“Fire containment and suppression technology has been carried over,” says Campling, “we were able to advise on the temperature containment strategy. The structure has a built-in Faraday cage and thermal barrier, which is extremely important in Formula 1 where you have a battery and a fuel tank on top of it. We were able to demonstrate in Formula 1 that we could have a battery fire yet the temperature seen by the fuel cell was less than 70 degrees, and that we were able to pass this concept on to Dallara to build into their safety cell.”
For cooling, Williams Advanced Engineering choose active liquid cooling system as it’s the only solution that’s effective enough enough (see two blue pipes on the photos) for both high power (about 200 kW) discharge on the track and 45 minute fast charging in the pits.
“The dimensions of the battery were determined by the available space within the design of the Dallara chassis. This created a challenge for packaging and installation that needed to be overcome from the start. The next challenge was in ensuring that the battery received sufficient cooling.“Thermal management is at the core of the design because temperature defines the whole performance parameters in almost all racing cars and our battery is no different than that,” explains Tur.
Campling adds: “We had the basic architecture and we knew we could package the cells in a certain way but it would be very tight and we needed to get to a point in time where we could freeze the safety cell design as Dallara needed to manufacture the prototype and complete their safety tests.”
“There were a couple of directions we could go with more liquid cooling or more air cooling. Obviously each driver has two cars, but we needed to consider the scenario whereby if you had an issue with one car – a repairable issue – you might need to use one car and then use it again straight away. To charge the battery in 45 minutes or an hour and simultaneously cool the battery down, ready to be used again meant that we had to have a pretty effective post-conditioning system. Liquid cooling provided the best solution”
After development, one racer was crash tested (battery survived):
“When the FIA was creating the rulebook for Formula E it was decided that the battery safety cell would form part of the car’s structure, and that rather than changing batteries, for the sake of safety, the drivers would change cars instead.”
“This means that for the first time ever, a battery has been used in an FIA crash test – equivalent to the ones that F1 cars are subjected to.”
“We were required to take part in the front impact test, where the chassis and battery are mounted to a sled and crashed into a hard wall and the energy is taken out in the nose structure and also the rear impact test, where you have the battery box with the gearbox and the crash structure bolted to it, and an impact sled driven into it,” says Campling. “We were able to demonstrate that all the battery health reporting and safety functions were in place after each test and the battery could still be used if needed.”
Battery swap option? Possible, but no thanks.
“But what about changing batteries? Could it be done if the rules were written differently? “It would be quite an interesting technical challenge,” admits Campling, “we had a solution in Formula 1 that allowed the battery to be dropped out and plugged straight back in again with all the fluid and electrical solutions made and broken in a single incidence, so it is feasible for sure.”
After first shakedown tests, now everyone waits for July 3 and 4 when first official tests will take place at the Formula E home track at Donington Park, UK.
By the way, organizers had to do a series of safety tests for battery airfreight.
“UN regulation 38.3 lays out the regime that each lithium-ion battery has to fulfill in order to be allowed for air transport,” says Tur, “which includes mechanical, thermal and abuse testing and we have passed all the tests and the battery is available for certification now.”
In the end, Williams Advanced Engineering believes that racing improves the breed and we should expect higher energy density batteries thanks to Formula E. However, since the series is limited toSpark-Renault SRT_01E cars for two seasons, we don’t expect to see progress until late 2016 when the third season begins with different cars from teams.
“Campling fully endorses with this philosophy: “I think the advantage of what we’re doing is that it’s creating a groundswell of interest and a reason for accelerated development. The more public interest there is in EV vehicles in general, the more the major manufacturers with bigger budgets are going to spend on developing their products.”
“But Tur reckons there will be a more tangible legacy from the technological frontiers Formula E is pushing through.”
“There are a number of areas that Formula E will be pushing on: storage density – having more energy within the same weight – and charging times, and also the increased life. At the end of the day, with the additional power performance you can always have more life by trading the power. In these areas we will start pushing technology.
“For an example we have seen this in Formula 1. When Formula 1 started using KERS, immediately we saw power density increases in battery levels. And I believe that as we move on in the seasons we will see the FIA regulations push for improved energy densities in the batteries [in Formula E]. We will reach the point where we can very quickly charge the batteries and run long race durations.”
There’s an old saying that racing improves the breed, and Formula E is helping to improve the next generation of electric vehicles. This should mean a better quality of air – and thus life – for all of us.”