Mobile Geeks

What is a Mild Hybrid System?

Whenever a car company attaches the word “hybrid” onto a new car, it’s easy to have a few expectations about what that car will be like and what it might offer. We can assume, for instance, that it’ll be more fuel-efficient than a typical gas-powered car. And you can be pretty sure that the hybrid car in question will use some combination of an electric motor and a gasoline engine.

Over the last decade or so, automakers have been replacing traditionally mechanically-driven components with more efficient parts like electric power steering racks, electric brake vacuum pumps and electric water pumps.

On top of that, automakers have been adding in a ton of new infotainment options, and also driver-assist safety features like adaptive cruise control, lane keep assist, blind spot monitoring, etc. Plus, you’ve still got heated seats, heated steering wheels, and heated windshields. Needless to say, standard 12-volt electrical systems are being stretched thin; so 48-volt systems are stepping in and help accommodate the need for more onboard power.

Different manufacturers are using this 48 volt battery in different ways, the Bentley Bentayga, for example, uses the 48-volt battery to drive an electric sway bar system for better handling; the 2017 Audi SQ7 TDI it acts like an electric supercharger; and the Audi A8 & A7 Sportback are sporting a mild hybrid system.

What is a Mild Hybrid System?

The Mild Hybrid or MHEV is classified as a gasoline-electric vehicle, the mild is a reference to how much or rather how little, the car uses the electric motor.

In a full hybrid car the electric motor makes the car move, in a mild hybrid the electrical component cannot (and does not) propel the vehicle. The gas-powered engine is doing all the work, the electric motor is only assisting.

The 48-volt battery has 3 components, the electric starter generator, electrical supercharger and DC/DC converter. This final component supports the more traditional 12-volt applications in the vehicle, things like the infotainment system, wipers, seat heaters or parking brake etc.

The real benefit of the mild hybrid system is that it saves fuel by shutting off the gasoline engine when the vehicle is stopped, braking or cruising.

How do Mild Hybrids Impact the Drive?

We’re going to use the Audi A7 Sportback and A8 as our primary example since this was the first time we really noticed the mild hybrid engine having an impact on the driving experience.

Smoother Start Stop

A Smoother start-stop system is the most or actually least obvious benefit of the mild hybrid engine. In the Audi A7 Sportback where I first really came to appreciate this marriage of electrification and combustion engines, you don’t even notice that the car turned off while idling at the light.

If the driver takes his foot off the accelerator at a speed between 55 and 160 km/h (34.2 to 99.4 mph), the car can coast for up to 40 seconds with the engine off completely. During slow coasting, the start-stop phase already begins at 22 km/h (13.7 mph). And when you’re stopped at a light the stop-start feature will use the front camera to productively restart the engine as soon as the vehicle ahead starting moving.

Saves Fuel by turning off the engine while coasting

Decoupling the engine from the transmission to save fuel has been around for a years, but now the 48V system in the Audi A7 Sportback & A8 have enough juice that the engine can switch off completely for up to 40 seconds when you let off the gas, saving even more fuel and regening energy back to the battery in the boot. As soon as you get back on the accelerator the engine refires and you’re away again.

Recuperating energy when braking

When it comes to the drive, we did notice that the breaking did feel a little soft since the mild hybrid engine will use this as an opportunity to recuperate some power. This is one of the driving moments that made me curious to learn more about the mild hybrid system.

But the 48V system gives other advantages. On the Audi A8, Adaptively damped air suspension is standard with selectable ‘Comfort’ and ‘Dynamic’ modes, but you can specify something cleverer – a system that, with the help of a camera, can ‘see’ potholes, speed bumps, and so-on. Because the car knows the obstacle’s there, it can prepare itself accordingly. Rather than anti-roll bars A8s thusly equipped get an electric actuator at each corner. These actuators ‘pick-up’ individual wheels (or even lift the whole car) – stressing or relieving corners as necessary to dampen body movements.

When you look at cars are packed with tech as the A8 or the A7 Sportback when kitted out with all the bells and whistles will have five radar sensors, five cameras, 12 ultrasonic sensors and a laser scanner. In total, the A7 Sportback gets 39 driver assistance systems split into three packages: the Audi AI parking package (gradual introduction beginning 2018), the City assist package with the new crossing assist and the Tour assist package. With so many options it makes sense that the high-end cars with the most advanced technology would need a bit of extra power.

We believe that 48 Volt Systems are the future of automotive if this wasn’t enough information for you, don’t worry, we’ve got more.