After all the talk of electric trucks and whether they are feasible at this time, a new concept is now joining the discussion, electric mild hybridisation.
At the spring meeting of the Technology and Maintenance Council of the American Trucking Associations, what Diesel Workshop’s US Correspondent, Steve Sturgess, found the most interesting was an Eaton roll out of upcoming fuel economy technologies, including a 48-volt architecture to support electric mild hybridisation in regional and long-haul sleeper applications.
According to Dr Mihai Dorobantu, Eaton’s director of technology planning, diesel-electric hybrids are going to be niche applications for the next 10 years for urban applications with no real long-haul solution using today’s infrastructure. To compete with diesel, electrics need 500-700 miles (800-1100km) on one half hour charge. That would demand charging at over 100-150 amps and is not realistic. If charging at greater than one kW, we need a high voltage solution, he said, such as 48-volt for long haul charging that reduces wiring demands.
So Eaton is developing a 48-volt mild hybrid solution, especially valuable in sleeper operations which offers a two-three per cent fuel saving while driving and provides an electrical solution for hotel loads. It also has the potential for additional savings for stop-start engine controls.
This 48-volt generation is through electric regenerative braking system. This is achieved through a transmission-mounted motor/generator at the PTO opening which also has an aircon compressor. It can be driven electrically or mechanically through coasting or engine deceleration. It would be close to the battery pack so eliminates wiring up to the front engine-mounted alternator. And 48 volts can drive power steering in engine off, coast mode. The 48-volt system can be realised with battery management, so it uses today’s regular four-battery system with a suitable controller, still providing 12-volt supply for trailers and lighting for instance.