Mild hybrid 48V systems driving lower CO2 emissions

“Mild hybrid” 48V vehicles are coming of age, with the technology now ready for mass production.

In 2011, at the 15th Automobil Elektronik Kongress in Ludwigsburg, Audi, BMW, Daimler, Porsche and VW made the ground-breaking announcement that they would instigate a 48V standard known as LV148 for their vehicles’ on-board power networks – a sea-change not seen in the industry since the 1950s when carmakers moved progressively from 6V to 12V.

Among the first to develop practical technical solutions is UK-based environmental award winner, Controlled Power Technologies (CPT). It is upbeat about the response the company’s switched-reluctance (SR) motor-generator technology received during the International SAE 2015 Hybrid & Electric Vehicles Symposium held in Los Angeles in February 2-15. With three core products – COBRA, SpeedStart and TIGERS – CPT’s SR technology can be applied for torque assist as well as energy recovery applications.

Automotive Industries (AI) asked Nick Pascoe co-founder and chief executive of CPT, why mild hybrid vehicles are becoming more popular.

Pascoe: The technology enables the car makers to cost-effectively meet ever more stringent CO2 and NOx emission requirements and produce vehicles at a price that motorists can afford. It also buys the industry valuable time to achieve the long-awaited chemistry breakthrough for more affordable batteries able to store significantly more energy for pure electric vehicles … or a comparable cost-effective breakthrough with hydrogen fuel-cell electric vehicles.

The first 48V mild hybrids will be introduced by European premium car manufactures from 2016 onwards, quickly followed by the volume car makers. The influx of mild hybrid vehicles will continue to gain market share and possibly peak circa 2028 when the penetration in the premium sector will have reached 80-90%.

AI: Tell us about the role CPT plays in the European Advanced Lead-Acid Battery Consortium (EALABC).

Pascoe: CPT is a developer of switched-reluctance motor-generator technology, so we’re agnostic when it comes to batteries, and can work with any chemistry. Through EALABC we work closely with many international automotive companies. A technology developer like CPT provides the EALABC with the means to demonstrate its advanced lead-carbon battery technology to vehicle manufacturers.

Switched-reluctance motor-generators and the latest lead-carbon battery technologies are complementary. With the new battery chemistry breakthroughs being particularly suited to the high rate partial state-of-charge (HRPSoC) requirements of a low voltage mild hybrid vehicle, it also offers a more cost effective option for mass market application. Both technologies are now ready for high volume series production.

AI asked Taylor Hansen VP CPT, how well CPT technology has been received in the United States.

Hansen: We’re seeing rapidly growing interest in low voltage mild hybrid vehicles as demonstrated by the significant response whenever we showcase our switched-reluctance motor-generator technology.

AI then asked Alastair Muncey CPT’s lead engineer responsible for the SpeedStart motor-generator technology, how it is a first step towards 48V hybridization.

Muncey: As part of the Front End Accessory Drive (FEAD), SpeedStart not only replaces the alternator, but also has the potential to eliminate a conventional starter motor once the belt technology is able to cope with low temperate engine starts at – 30o C. Already, belt technology companies such as Mubea are getting close to achieving this goal.

AI: What are some of the critical design elements that were kept in mind when developing SpeedStart?

Muncey: SpeedStart is a sealed plug-and-play unit with fully integrated control and power electronics. Not only does this avoid any ingress of foreign material, but being a liquid cooled electrical machine its thermal management is of a high order.

AI: How does SpeedStart help vehicle manufacturers increase efficiency of their mild hybrid vehicles?

Muncey: A small family car with a mass of approximately 3,300lb (1,500kg) that brakes from 62mph (100km/h) to 50mph (80km/h) in two seconds needs to be shedding energy at an average rate of 104kW per second. At 48V, SpeedStart can harvest almost 10% of this kinetic energy. This recuperated energy can be temporarily stored in the battery until the next acceleration event, when SpeedStart can provide torque assist through the FEAD belt directly to the engine