“Racing improves the breed,” is one of the most time-honored phrases in motorsports. Many new ideas got tried on race cars first before they were incorporated into road cars — electronic fuel injection, disc brakes, overhead camshafts, to name just a few. Formula E features battery-electric open-wheel race cars that compete on racing circuits laid out on city streets. All the cars use a 28 kWh battery supplied by Williams Advanced Engineering, a subsidiary of the Williams Formula One enterprise. The lessons learned from the first two Formula E seasons have taught Williams engineers how to make a better EV battery for road cars.
Racing flat out for 50 minutes builds up a tremendous heat, more than would ever be experienced in an ordinary electric car in daily use. Also, the combination of bumpy city streets and stiff racing suspension means the level of vibration is far higher than any passenger car would normally experience. To address those concerns, Williams Advanced Engineering has many modifications that will make a regular EV battery more robust and reliable. Paul McNamara, technical director at Williams Advanced Engineering, explains the changes:
“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.”
To make things more complicated, the FIA has approved a rule change for season three that allows 50% more energy to be regenerated and put back into the battery during braking. That means even more heat that the drivetrain must cope with.
“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.”
The lessons learned in Formula E will result in a better, more reliable EV battery for road cars in coming years. This is one instance in which racing really is improving the breed.
Source: Electric Cars Report
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