Industry embraces 48V supply in the aim of bringing down emissions
Keynote speaker Florian Kühnlenz, responsible for series development of low voltage energy systems at Volkswagen AG, set the scene with a presentation of the electric and electronic architecture requirements of dual voltage power supplies in vehicles at 12 volts and 48 volts; with initial steps already having been taken for the adoption of the proposed LV148 standard suggested by Audi, BMW, Daimler, Porsche and Volkswagen.
Kühnlenz outlook is that the introduction of a second voltage at 48 volts addresses new challenges for automotive electrical and electronic systems, but that most issues have now been identified with preliminary solutions already developed for introduction during the ramp-up to the 95g/km CO2 requirement by 2020. The displacement of high wattage loads to a more efficient 48 volt network is expected to be the next step in the development of a new generation of low voltage mild hybrid vehicles.
“Other global carmakers will have to decide whether they want to embrace 48 volts,” says Paul Bloore, product validation manager for the hybrid product group of Controlled Power Technologies (CPT), a British technology company and a strong proponent of the 48V system. Commenting on the need expressed by tier one suppliers for an international standard when introducing low voltage hybrids and their note of caution should this not happen, he added that “it makes sense to have a common global standard, because 48V hybrids are currently the most cost-effective way of meeting stringent CO2 emissions being introduced in 2020, compounded potentially by a shift from the current NEDC test to the more aggressive WLTP test, with further 25 per cent reductions anticipated in 2025 and 2030.". According to Bloore, a consensus of global forecasts suggests that 48V hybrids will soon come to dominate the market. "A common international 48V standard would be a smart move," he said.
Salah Benhassine a specialist in electromagnetic compatibility (EMC) at PSA Peugeot Citroën set out the French carmaker’s approach to 48V mild hybridisation by focusing on one of the specific technical challenges. He similarly concluded that collaboration between automotive industry and suppliers is essential.
Robert Eriksson, senior technical leader for electric propulsion architecture at Volvo Cars, concluded that there were several opportunities for building scalable and modular solutions with different attributes in the mild hybrid category, commenting on the recuperation possibilities with expanded 48V architecture, thereby achieving the goal of less than 95g/km of CO2 levels after 2020.
Ulf Stenzel, lead engineer for new battery technologies, hybrid and electric powertrain systems at AVL GmbH, which is heavily involved with CPT and the European Advanced Lead-Acid Battery Consortium (EALABC) in the development of the ‘LC Super Hybrid’ gasoline powertrain, discussed the development by Hyundai and Kia of a 48V mild hybrid diesel powertrain, commenting that its combination with an electric supercharger offered ‘realistic potential in terms of performance increase and further fuel consumption reduction.’
The EU goal is to introduce the WLTP by 2017 if possible and no later than 2020 to coincide with the 95g/km requirement. The WLTP defines a global harmonised standard for determining the levels of pollutants and CO2 emissions, fuel or energy consumption, and electric range from passenger cars and light-duty commercial vehicles – therefore it becomes even more important for the industry to agree beforehand a global electrical standard for the 48V mild hybridisation of its vehicles.
One of the issues for the industry to confront in moving away from the NEDC test is that the WLTP typically halves the measurement of CO2 reduction gained from first generation stop-start systems, which characteristically reduce CO2 emissions on the NEDC by 5 per cent. This reduces to 2.5 per cent when measuring the same vehicle on the WLTP.