The Audi e-tron may have solved EV range problems
Audi has invested a lot of time and money into its e-tron project, so much so it envisions that by 2025 every Audi will be either electric or hybrid. Audi’s all-electric car has been designed from the ground up to lead that change and is intended to be a groundbreaking vehicle for the Volkswagen-owned company and the automotive industry as a whole. To hit this lofty benchmark the e-tron really does have to be something special when it launches next year.
Thankfully, for Audi, that doesn’t look like it’s going to be an impossible task. It’s already invested time in building a thermoregulator for its battery to ensure it remains at a steady temperature for optimum power output, as well as building a support network for drivers across Europe and America to ensure they’re never far from a charger. But now Audi is ready to reveal the e-tron’s next secret and it’s one that could change the EV market forever – regenerative breaking, or recouperation as they call it.
Regenerative braking is no new innovation in the electric vehicle (EV) market. Some would even go as far to say it’s actually a rather mature technology, one ushered in by the advent of Kinetic Energy Recovery Systems (KERS) in Formula One nearly ten years ago. It’s in EVs and hybrid vehicles too, with cars ranging from the Toyota Prius up to the BMW i3 and Tesla Model S all utilising the technology to squeeze some extra energy back into batteries.
The difference with the e-tron’s system, compared to that of the Nissan Leaf or Jaguar iPace, is that this time the system actually makes meaningful gains. This goes beyond simple “one pedal” driving. Here Audi turns kinetic “coasting” energy back into power, even when you put your foot on the brake – something other EVs simply just allow to be lost to brake pads and heat exchange.
In short, the Audi e-tron is capable of converting potential kinetic energy into power to charge its own battery. Now, this may sound like Audi has somehow developed a perpetual motion machine, but it really does work, and it could change how people see EVs in the future.
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Audi e-tron regenerative braking: Energy saving in motion
To show off just how effective and efficient the Audi e-tron regenerative braking system is, I took a trip to the top of Pikes Peak, Colorado – a 4,302m high mountain – to drive back down it. Known for its annual hill-climb race, the Pikes Peak downhill course stretches over 16 miles with an elevation of around 2,750m, perfect for showcasing just how effective the e-tron’s regenerative braking can be.
We started our descent with the e-tron’s 700kg battery estimating a range of 105 miles with 67% remaining capacity. By the end of our 16-mile downhill journey, the e-tron had actually regained some of that capacity – to 75% – and boosted its range to 177 miles.
In reality, nobody is going to go and seek out a hill to eke out a few more miles as they drive, but it’s a great example of just how effective the regenerative braking technology seems to be.
Looking through the data of the drive itself, it was clear to see that the e-tron’s brakes were only applied five times during our descent. All other braking had come from the e-tron’s braking management system taking control and slowing our descent via engine braking, driving power back to the battery via the car’s twin motor drivetrain.
Because of this, when we reached the brake-check point around halfway down the mountain our brakes were at a low 14 degrees centigrade – nearly five times cooler than average for a car descending Pikes Peak.
So it’s clear that Audi’s technology works and works very well, even if it takes driving down a big hill to drive home just how effective it is. But how has its engineering team managed to pull so much potential out of a concept that’s already so mature? The truth seems to be something as simple as tackling the problem from a different angle.
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Audi e-tron regenerative braking: How it works
According to Dr Marko Hörter, the lead engineer for the new brake system, the e-tron’s physical brakes are only designed to be used around 10% of the time with all other braking performed via friction-based engine braking.
In other EVs, the moment you take your foot off the accelerator you’ll begin to decelerate via regenerative braking but the moment you touch the brake, you lose it as it engages the mechanical brakes. That’s not the case here. In the e-tron, even if you put your foot on the brake, it won’t engage the brake pedals unless you push hard on the pedal. Instead, it works out the best method of deceleration while maximising the amount of energy it can drive back into the battery.
As the e-tron is an electric – and therefore gearless – car, the flappy paddles either side of the steering wheel for gear changes have been modified to increase or decrease the recuperation efforts of the e-tron’s engine braking. On low, this means you can coast along and really feel no impact on speed – like in a normal car. The flip side to this is you also don’t regenerate any energy to go back into your battery. At its highest setting, it’s capable of slowing the car as effectively as gently applying the brake – all while topping up your battery.
Hörter claims this recuperative braking method is perfect for deceleration situations between 0 and 0.1g (around 0 to -0.5mph/s). When you need to decelerate faster, you’ll put your foot on the brake, at which point the car’s braking system kicks in and determines if you really need to apply the brakes or if its advanced engine braking is adequate enough for the rate of deceleration you want.
For decelerations between 0.1 and 0.3g, the engine braking kicks in, seeing the e-tron decrease the power draw to each motor and turn kinetic energy back into power for the battery. Any deceleration over 0.3g sees the hydraulic system and mechanical brakes come into play, acting exactly as you’d expect them to, with any potential energy lost to heat.
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You may feel somewhat dubious about putting your trust entirely in a braking system than the tried and tested “press pedal, get brakes” dynamic of a normal car. But, aside from the light recuperation braking of coasting, it really doesn’t feel or act differently to a normal car.
This is a key selling point for Audi and its e-tron technology. As Jaguar intended with the i-Pace, the e-tron isn’t pretending to be some expensive toy powered by electricity. It’s designed first and foremost to be a practical and usable modern motor car … that just happens to be an EV. Audi intends the final e-tron SUV to look and feel exactly like one of its petrol- or diesel-powered models, even if there’s no combustion engine under the bonnet.
From what I’ve seen of Audi’s efforts of developing the e-tron so far, including its futuristic in-car technologies like cameras for wing mirrors and the incredible 3D view camera technology for parking manoeuvres inherited from the A8, it’s clear Audi is developing a car for the future. It’s not going to be the be-all and end-all of EVs but it’s evident this is more likely to push the field of EV design and research forward than something like the Faraday Future, Byton or Fisker EMotion.
Now we just have to wait until mid-2019 to see the true fruits of Audi’s labour.
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