Updated Mercedes S-class to get 48V mild hybrid tech

Mercedes-Benz is poised to launch a major electrification onslaught with a switch to 48V systems that will allow the installation of mild hybrid assistance on almost its entire range over the next few years.

The first application will be a new M256-designated straight-six petrol engine that will be introduced in next year’s facelift of the S-Class and includes an electrical motor attached directly to the crankshaft. This can act as both an alternator and a starter – allowing the engine to fire up in just a fraction of a second – but it will also be able to add assistance and harvest electricity through regenerative braking.

This new straight-six will progressively replace the V6 engines throughout the Mercedes range. Although we have no statistics about the petrol engine yet, we’re told the electric motor can add up to 19hp of assistance and harvest up to 20hp during regeneration, delivering immediate economy gains of between 10-15 percent.

Unlike Mercedes’ high-voltage hybrid systems, there is no way of disconnecting the motor from the engine, so it can’t operate under electric-only power, but the relatively small capacity of the 0.9kWh 48V battery effectively rules this out anyway.

It seems likely that cars fitted with this electrical assistance system won’t carry hybrid branding, although Mercedes has confirmed the 48V setup will in effect replace all of its non-plug-in hybrids.

The new six-cylinder petrol engine is based on the same architecture as the OM654 four-cylinder diesel that made its debut in the new E-class. Mercedes driveline engineering boss Jürgen Schenk said it will be joined by a diesel equivalent using the same integrated starter/generator later.

A four-cylinder petrol version with a less advanced belt-driven starter/generator will also be launched next year. That will mean all Mercedes cars using longitudinally mounted engines will have some form of mild hybrid assistance shortly afterwards.

The process of developing more powerful hybrid systems is also ongoing. Mercedes will launch a 350 e version of the GLE Coupé internationally, which will use the same underpinnings as the E 350 e. In addition, the S 500 hybrid is set to get a new battery pack next year. This increases capacity from 8.7kWh to 13.5kWh while retaining the same dimensions and 120kg weight and it will increase electric-only range to around 30 miles.

Jochen Strenkert, Mercedes’ head of plug-in hybrid powertrains, said it’s likely the same battery pack will be used to create a plug-in version of the diesel-powered S 300 hybrid.