The automotive world may be moving toward electrification, but it will still be many years before full-on EVs become prevalent. In the meantime, automakers are developing better and more refined hybrid and plug-in hybrid vehicles. One type of hybrid that has become more common in recent years is the 48-volt mild-hybrid system. Its use has expanded the performance and efficiency of vehicles from many automakers, and has become a popular way to extract more power from a vehicle without negatively impacting fuel economy.
What is a 48-Volt Mild-Hybrid System?
Mild hybrids, also called 48-volt mild-hybrid systems, are the least electrified version of hybrid powertrains. Designs vary from model to model, but the basic concept and construction are the same. A small electric motor, which can be called an integrated starter generator (ISG), is connected to the engine and works in tandem with the internal combustion unit to provide extra power for acceleration. Automakers use 48-volt systems to boost performance, but they also come with an inherent fuel-efficiency benefit, in that they share the engine’s load in controlled scenarios, helping it save fuel. Some company, such as Volvo, employ mild-hybrid configurations with slightly different components. The Volvo ISG is 42 volts, for instance.
These systems don’t function like traditional hybrids or plug-in hybrids, in that the electric motors alone aren’t capable of powering the car on their own. Instead, the 48-volt system and ISG act as an assist for the internal combustion engine at low speeds, which includes accelerating and starting the vehicle. In vehicles such as the new Mercedes-Benz C-Class, the electric motor is sandwiched in between the engine and transmission and provides up to an additional 15 kW to the drivetrain, which is around 20 horsepower.
Like hybrid and plug-in hybrid systems, mild-hybrid systems are capable of replenishing their power stores through regenerative braking and other methods. In most cases, energy recovery takes place when the vehicle is coasting or braking.
An obvious benefit of mild-hybrid systems is the fuel economy increase that the electric motor provides. This works in a few ways, one of which is known as load point shifting, which is when the vehicle’s computers recognize a load or strain on the engine and shift some of that load to the electric motor, saving fuel. This effect is more pronounced during in-town driving, where stop-and-go traffic can place a continual strain on the engine. Automakers such as Ram are able to use mild-hybrid tech to boost fuel economy in large pickup trucks without sacrificing capability.
Improve Stop-Go Functionality
Many new vehicles offer stop-and-go engine shutoff technology to save fuel. When the vehicle is stopped, such as at a red light or stop sign, the engine shuts off to save fuel, and restarts when the driver lifts off the brake pedal or touches the accelerator. When this happens, the vehicle’s electrical functions, such as climate controls, may weaken or change over to a less functional setting until the engine restarts. Mild-hybrid systems offer a more seamless experience during this time, as the electric motor and battery power the car’s systems while the gas engine is shut down. Restart is also almost imperceptible, due to the ISG’s smoothness in place of a traditional starter.
The added price of a mild-hybrid system varies from vehicle to vehicle, but in most cases, they are less expensive than full hybrids or plug-in hybrids. This can be a big deal for buyers seeking a more fuel-efficient vehicle, as the cost of entry is lower.
Many hybrid vehicles lose valuable passenger or cargo space to accommodate battery packs and related components, but mild hybrids don’t suffer as much. Mild-hybrid systems are smaller and lighter than hybrids or plug-in hybrids, which gives them an advantage on packaging and on vehicle performance. Even with automakers figuring out how to implement batteries in ways that improve handling and weight distribution, less weight is almost always better from a performance, fuel efficiency, and handling standpoint.
Who Makes Mild Hybrids?
The number of new vehicles available with a 48-volt mild-hybrid system has grown considerably in recent years. Though the systems are most popular in the United States, their availability is global, and spans several popular makes and models.
What’s Next for Mild Hybrids?
What happens next in the world of mild hybrids is impossible to tell, but automakers such as Mercedes-Benz and Mercedes-AMG are using them to dramatically boost performance in vehicles with everything from four-cylinder commuter cars to twin-turbo V8-powered rocket ships. As the technology increases, so too does the performance of electric motors, to the point that the company now says it can create up to 201 horsepower and 236 lb-ft of torque using a mild-hybrid system. Until EVs become more affordable and more popular, mild hybrids offer a great way to get more performance and better fuel economy at the same time.
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