FRANKFURT (Reuters) - Carmakers squeezed between carbon emissions cuts and falling sales of fuel-efficient diesels have used the Frankfurt auto show to spotlight a future generation of electric cars that will largely come too late to help them out of their bind.

FILE PHOTO: Dieter Zetsche, CEO of Mercedes car maker Daimler AG presents the new Mercedes S-class models during the Frankfurt Motor Show (IAA) in Frankfurt, Germany September 12, 2017. REUTERS/Kai Pfaffenbach/File Photo

But elsewhere at the show, suppliers like Valeo and Delphi are lifting the lid on a quicker fix: affordable 48-volt hybrids.

These “mild” hybrids, which add some electric power to existing petrol models without a costly redesign, are now being deployed without fanfare by brands from VW to Volvo.

It is diesel's disgrace and decline, executives and analysts say, that has finally set the stage for mass electrification. While diesel pollution problems became notorious with the Volkswagen VOWG_p.DE test-cheating scandal, the subsequent shift to petrol is bloating carbon dioxide (CO2) emissions, making the next round of European Union goals harder to meet.

“Our view is that 48 volts on a gasoline engine is an alternative to diesel,” said Karin Thorn, vice president for vehicle propulsion at Volvo. “If and when the diesel market is dropping, something else needs to take its place.”

Diesels are stalling already, in fact - and weaker second-hand values suggest the slump can only accelerate.

An attention-grabbing pledge by the Swedish carmaker to “electrify” its entire range by 2019, initially hailed as a bold step, now looks more like an industry-wide reality.

PSA Group, which had previously seen no need for 48V hybrids, now plans to introduce them “across the board” in response to diesel’s faster-than-expected decline, the Peugeot maker’s programs chief Patrice Lucas told Reuters.

By quadrupling the 12-volt standard in conventional car electrics and allowing a beefed up starter motor to feed extra power to the drivetrain, complementing the combustion engine, carmakers can transform petrol cars into mild hybrids without redesigning the vehicle’s architecture and factory tooling.

ENABLING TECHNOLOGY

The motor delivers a noticeable torque boost and recovers braking energy to recharge a battery - smaller and cheaper than those required by electric cars or “full” hybrids such as Toyota’s Prius, which typically run at 100-300 volts. Total manufacturing cost comes in 500-1,000 euros ($600-$1,200) below an equivalent diesel.

“It’s the most interesting enabling technology and will comfortably replace diesel,” said Evercore ISI analyst Arndt Ellinghorst. “It can do the job and it’s already cheaper - you don’t have to be an early adopter to buy one.”

By 2020, the brokerage expects 48V cars to outpace European sales of full hybrids, including plug-ins that can be recharged with a cable and driven in electric-only mode. By 2025, it predicts, they will equip 55 percent of all cars sold.

The technology is surfacing first in luxury cars such as the Mercedes S-Class on show at the Frankfurt event - which runs until Sunday - before trickling down to the mass market, chiefly in Europe and China.

Volkswagen’s next Golf, a benchmark in compact cars, will arrive with 48V electrics in 2019, and other models will follow, development chief Frank Welsch told Reuters.

“The technology has a lot of potential and will make hybrids more affordable for the masses,” Welsch said. Renault, Japanese affiliate Nissan and Hyundai are among other mass car manufacturers with 48V in the pipeline.

In 2021, the key EU emissions goal drops to 95 grammes of CO2 per kilometer from its current 130 grammes - a challenge exacerbated by the replacement of standard lab tests with on-the-road “real driving emissions” measurements.

DIESEL HEADACHE

Despite incentives, neither battery technology nor charging infrastructure is ready for the mass electric-car uptake required to put a dent in average emissions by then.

The headache is compounded by the decline of diesels, which emit 15-20 percent less CO2 than petrol alternatives. Fortunately, 48V hybrids deliver savings in the same bracket.

Their simplicity also lets carmakers adjust their fleet emissions on shorter lead times than typically required to redevelop a drivetrain, which may help to avoid stiff EU fines of 95 euros per excess gramme of CO2, per vehicle sold.

Among suppliers, Valeo stands to benefit most with a 40 percent share of mild-hybrid orders, Citi analysts predict. Continental and Delphi are also well positioned.

Paris-based Valeo expects some carmakers to effect more abrupt U-turns than PSA’s - in some cases installing 48V systems without waiting for model facelifts. Innovation director Guillaume Devauchelle declined to name names.

“These solutions will become market standards,” Devauchelle said, adding that tougher rules on nitrogen oxide (NOx) pollution from diesels would deepen their cost disadvantage.

Later 48V hybrids will squeeze out more efficiency by shifting the electric motor lower down the transmission, below the engine. Valeo has electrified Magna’s Getrag gearboxes and GKN differentials.

“What automakers are finding is they need more than just advanced combustion engines to reach the fleet average reductions,” said Mary Gustanski, Delphi’s engineering boss.

The supplier is combining 48V hybrids with cylinder deactivation that cuts engine capacity when less power is required, for additional savings. The system is in development with one European and one Chinese carmaker, Gustanstki said.

The coming profusion of 48V cars should outsell pricier, higher-voltage hybrid incumbents such as the Prius, as market projections show - a prospect Toyota takes in its stride.

Thanks to a quarter-century of hybrid investments, the Japanese carmaker can meet future CO2 targets with ease, global planning chief Didier Leroy said in Frankfurt.

“We’re in a different position,” Leroy said. “We don’t have to rush to find a temporary solution - we don’t need to develop 48V to be competitive.”