Are 48 Volt Systems the Future of Automotive?

by Nicole on February 24, 2018

As the automotive industry makes plans for its all-electric future, the reality is that this dream is further away than it may appear.

For the last seven decades or so, 12-volt batteries have been the standard. But now that vehicles have an increasing number of electrical components and are relying on hybrid drive systems, it appears that carmakers are turning away from this norm.

The road to the 48 Volt battery has been a long one, the 12-volt system emerged in the 1950s and in the 1990s the industry briefly considered a 42 Volt system. Adding in this extra component is simpler than the drive train on a full hybrid like a Prius and it’s less expensive than we find on a full electric like a Telsa. This new electrical architecture keeps up with the power-hungry tech our cars now need while enabling the use a lower cost hybrid system.

Moving forward, it’s likely that the 48-volt system will be seen in what’s called a mild hybrid system, which is said to offer 70 percent of the benefit of a full hybrid car at 30 percent of the cost. Projections now suggest that 48-volt mild hybrids could take 14 percent of market share in terms of global new vehicle sales in 2025, and gas or diesel-only engines will only have 65 percent market share.

Different mild-hybrid setups work in different ways. One example, Suzuki’s SHVS (Smart Hybrid Vehicle by Suzuki) system, incorporates a ‘starter generator’ and a relatively small 0.37kWh (kilowatt hour) battery pack. The generator’s built-in motor can be called on to assist the engine during hard acceleration, as well as allowing the car’s stop-start system to bring the engine back to life more smoothly, thanks to a belt-drive system.

At the other end of the scale, all versions of the latest Audi A8 and A7 Sportback feature a mild-hybrid setup, although its operating effect is more far-reaching than that of Suzuki’s system. Dubbed MHEV (mild hybrid electric vehicle), the Audi system is underpinned by a 48-volt electrical system and the greater power this provides the starter generator enables the car’s engine to be turned off for up to 40 seconds when coasting, automatically restarting when acceleration is called for. This is said to offer greater fuel-economy savings than the conventional stop-start of previous models.

Not every mild-hybrid system is focused on fuel-efficiency, though. Ferrari’s flagship hypercar, the LaFerrari, uses its mild-hybrid system to boost the engine’s prodigious power, as part of an electrical network that supports a number of the car’s auxiliary systems.

48 Volt enabling e-charger for faster acceleration

A four-cylinder car with a turbocharger has the performance of a V6 without a turbo. But there’s lag here, those tenths of a second while the turbo spools up to 100,000-200,000 rpm and forces more and more air into the engine. Virtually every review describes turbo lag as “barely noticeable,” which really means “noticeable” when you want to pass on a two-lane road, or get over the railroad tracks when the signal lights start blinking.

Enter the electric turbocharger / electric supercharger, or e-charger. Rather than wait for exhaust gases to eventually bring the impeller up to speed, an electric motor makes it happen more quickly so that the lag is truly barely noticeable. This, too, requires a 48-volt system.

Why 48 volts?

Settling on this level hold the electrical system under the 60-volt safety threshold of what is considered to be high voltage, where power cables must be orange and special connectors, which cost 10X more would be required, said Robert Buchmeier at ZF, which is a major automotive industry supplier. ZF has an integrated starter generator, the iSG48 for mild hybrid systems, which is why I reached out to gain a deeper perspective on the technology.

As a new component being introduced to the car, the 48-volt system has a great deal of potential to enable other technologies. There are several technologies that might be further supported by the 48V technology, in the driveline as well as in the chassis, but also in other vehicle domains. Buchmeier explains ‘The active chassis systems such as electric power steering, active rear axle steering, active damping systems or electromechanical roll control, as well as more powerful additional starters, electrically-assisted turbochargers, electric valve timing adjustment of the combustion engine or – one step further – electromechanically-actuated inlet and outlet valves of the combustion engine.’

Will 48 volt battery be the new standard for automotive?

Back in the 90s the 42-volt system fizzled out over concerns about the cost of dual systems, as well as practical matters such as switch contacts arcing, requiring costlier spring-loaded switches to reduce wear.

Between then and now, there is more concern about the environment, and more car components have gone electrical. Cars with lane keep assist and lane centering assist, and self-driving cars shortly, need electric not hydraulic power assist.

The intelligence packed into today’s modern car needs more power and the flexibility of how the 48 volt system can be used means we’ll be seeing more not less of it.