Growing interest in 48V mild hybrid vehicles

6th March 2015
Siobhan O'Gorman


Whilst showcasing its Switched-Reluctance (SR) motor-generator technology at the SAE 2015 Hybrid & Electric Vehicles Technologies Symposium, Controlled Power Technologies (CPT) witnessed an growing interest in 48V mild hybrid vehicles.

“Hybridisation at 48V provides a cost-effective near term alternative to full hybrids and pure EVs, which at present are more expensive to produce,” said Taylor Hansen, Vice President, CPT. Hansen has commercial responsibility for the company’s North American operations based in Detroit. 

“There was lots of interest from international automakers and their powertrain suppliers,” commented Hansen. “At a nominal 12V standard (14V charging at 300A) the industry is stuck with about 3kW from a motor-generator when you adjust for high current losses, which constrains the electrical power and torque available and, of equal importance, any kinetic and thermal energy recovery. However, with a nominal 48V grid (42V charging at 300A) the industry has access to approximately 12.5kW, which makes all the difference to powertrain efficiency and performance, while the DC voltage remains well below the safety critical 60V level.”

Hansen is focused on bringing to market CPT’s portfolio of electronically controlled electrical machines known as COBRA, SpeedStart and TIGERS. Each product achieves significant CO2 and NOx reduction through different applications of switched reluctance technology, which eliminates the need for permanent magnets and rare earth metals in an electrical machine.

COBRA is an electric supercharger developed for commercial vehicle and off‐highway applications capable of delivering 170l of air a second into the engine The supercharger is particularly suitable for bus and truck operations, which experience continuous stop‐start duty cycles.

SpeedStart is an advanced motor‐generator system tested continuously for more than two-and-a-half years to an industry leading 2.5 million stop‐starts. The motor-generator offers a high level of NVH refinement as well as additional 48V functionality with outstanding controllability, thermal management and robustness. Functionality includes torque assist for launch and low speed transient acceleration, optimised motorway cruise conditions with electric assist ‘load point moving’ and a leaner fuel calibration, in‐gear coast‐down, and the ability to harvest significant kinetic energy from regenerative braking.

TIGERS is a turbine integrated gas energy recovery system which provides cost‐effective energy recovery from exhaust gases with their significant mass flow rates. Consequently, the recovery system is also an effective means of supplementing or replacing an existing alternator.

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 change not seen in the industry since the 1950s when carmakers moved progressively from 6V to 12V.

“For the motorist SR technology can deliver a 30% improvement in fuel economy for a premium of less than $1,000. This is significantly less than the additional cost of high voltage hybrids, which currently can add $8,000 to the sticker price. And it’s less than one-tenth the premium for plug-in hybrids and pure electric vehicles, which currently can add up to $15,000 to the price on the forecourt,” said Hansen.

“We see rapid growth in 48V mild hybridisation and it’s easy to see why,” commented Hansen. “Compared with 200V to 600V full hybrid and battery EVs, the low voltage approach avoids the need for high cost safety features and large battery packs. Furthermore, the universal application of this technology to the more than 100 million vehicles per annum forecast to be produced from 2020 onwards, 98% of them with gasoline and diesel engines, would in the short term reduce annual CO2 emissions by 100 million tonnes globally per annum (50g/km reduction x 20,000km average annual mileage per vehicle x 100 million vehicles). And the technology is relatively easy to homologate for production, which buys the industry more time to develop lower cost pure electric and hydrogen fuel-cell vehicles”

“In frequent discussions with our customers, we see 48V mild hybridisation as a key growth area for the industry in the medium term,” said Nick Pascoe, Chief Executive, CPT. “It can cost-effectively deliver the 2.5% year-on-year reduction in fuel consumption and CO2 emissions required by legislators without loss of vehicle performance and with a manufacturing investment the industry and its customers can actually afford. It also provides the industry with a useful breathing space while it awaits a breakthrough in affordable hydrogen energy storage and distribution, and more widely available renewable energy from our national grids.”

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