While the automotive world is focused on lithium ion batteries that can power a car for 200, 300, or more miles, some companies are focusing on so-called mild hybrids. Those are cars that use a 48 volt system. Instead of an electric motor integrated with the transmission, most of them employ an alternator that can double as an electric motor to help move a car forward from rest. The first few hundred feet after a dead stop contribute a disproportionate amount of carbon dioxide emissions, compared to operating at a steady rate of speed on the highway.
Christian Schaefer, global director of advanced electrical and electronic architectures at Delphi, told a conference for engineers at the Frankfurt auto show last fall, “From our experience and our discussions with European OEMs, we have seen between 7 and 10 percent reductions in CO2 emissions from the current test fleet with today’s 48-volt alternators, which have a nominal power of between 10 and 12 kW. For the next generation with up to 20 kW, we expect that we could increase the CO2 reduction to 15%.”
The principal reason to consider a mild hybrid system is because it can provide a significant decrease in emissions for about 1/4 to 1/3 the cost of a full hybrid system. 48 volt systems have other potential benefits as well. Many of the auxiliary systems on today’s cars — from stop/start and infotainment systems to power steering and coolant pumps — can operate on 48 volt electrical systems. Air conditioning compressors can be powered by electricity as well. That means the conventional internal combustion engine needs to do less work to run all those peripherals.
Many manufacturers like Audi and Volvo are incorporating electric turbochargers into their cars as well. They can spool up to operating speed much quicker than a turbo can, which improves performance without increasing emissions. Finally, electronically adjustable suspensions are coming to many new cars. They can be operated efficiently using 48 volt power without putting extra demands on the engine.
One of the vital components to all those electrical accessories are ultracapcitors. A battery stores electricity through a chemical reaction. While it can produce high power, the chemistry takes time to respond to demands. An ultracapacitor can deliver high power and accept a high rate of charge in a much shorter time, making it ideal for active suspensions, regenerative braking systems, and stop/start technology.
Maxwell Technologies is a leader in making ultracapacitors for automotive uses. General Motors recently selected a stop/start system manufactured by Continental Automotive Systems that uses Maxwell ultracapacitors for its 2016 2016 ATS and CTS sedans and ATS coupes. Maxwell ultracapacitors are already in use in over a million Citroen and Peugeot automobiles and have proven to give long, troublefree service in demanding applications.
As autonomous driving technology becomes more common, additional uses for ultracapacitors from Maxwell Technologies will be found. Such systems will rely on the high degree of reliability that Maxwell products are known for.