Delphi And Bosch Plan 48 Volt Mild Hybrid Systems


Bosch 48 volt mild hybrid

Imagine that there was a way to get 70% of the benefit of the plug-in hybrid systems found in Toyotas and Hondas for just 30% of the cost? If claims from Delphi and Bosch are to be believed, those are exactly the kind of results car companies can expect if they adopt the new, 48 volt electrical systems they have developed.

The new Delphi/Bosch drive systems useĀ a 48 volt lithium ion battery along with electronic controllers for the battery and hybrid powertrain, a DC/DC converter, and an electrically driven turbocharger for the vehicle’s internal combustion engine, according to Ward’s Automotive.


The watchwords in the automotive industry today are fuel economy (in the US) and emissions (in Europe). Government regulations will put enormous pressure on manufacturers to find new ways to raise gas mileage and lower carbon dioxide emissions by 2020. In the end, electric cars will probably be the solution, but they will not represent the majority of cars on the road for at least 15 years or more. In the meantime, many car makers will rely on plug-in hybrid technology to help them meet the more stringent regulations- and this new tech might play a big part.

48 volt mild hybrid batteryMary Gustanski, vice president for engineering and program management at Delphi, says the European market will be first to adopt the new 48 volt mild hybrid systems because new emissions regulations go into effect there in 2021. She thinks China, with its intractable pollution problems in its cities, won’t be far behind. When higher fuel economy standards hit the US in 2025, mild hybrids that use versions of Bosch’s thermal management systems might be in demand in America, too.

At first, says Delphi, the systems will have an inverter that steps down the voltage to 12 volts for traditional uses such as starter motors, electric windows, entertainment systems and climate control systems. But as manufacturers become more familiar with the 48 volt standard, Delphi expects more and more of them will switch over their entire electrical system to 48 volts. That will make it possible for more auxiliary systems like coolant pumps and air conditioning compressors to be powered by electricity instead of driven by the engine. Figuring out how to make the engine do less work will further boost economy and lower emissions.

The Bosch system would include a small electric motor to provide assistance to the gasoline engine under some circumstances, such as moving away from a complete stop. Bosch says the motor could also be used to power autonomous parking controlled by a smartphone app, according to Green Car Reports.

One big advantage of a 48 volt system is that it does not require expensive and heavy safety shielding the way a full plug-in or electric propulsion system does. Those systems often operate at up to 600 volts. Saving weight will be a crucial part of meeting coming regulatory standards. Delphi plans to show off its mild hybrid system, along with autonomous driving technology it has developed, at the Consumer Electronics Show in Las Vegas that begins January 5.


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  • evfan

    I think this is a day late and a dollar short. Five years ago this would have been an exciting next step to GM’s mild Saturn hybrids, but in 2015 things are different.
    I suspect these will be at the very bottom end of the market, and while they are called “hybrids” they are basically auto-stop-start systems.

    • Steve Hanley

      You may be right, but those “mild hybrid” systems did little more than turn a 12 volt generator into a 12 volt motor on occasion. 48 V has a lot more oomph.

      Still, you are correct. This is nothing more than a stop gap solution while we wait for the future to arrive. But if they offer significant improvements without the high cost of battery or full plug systems, they may serve a useful purpose.

  • Al

    This technology should have been introduced within 2 years of Toyota introducing the Prius. At this point it seems like a solution barely trying to meet the CAFE requirements. If a new presidency reverse CAFE then they will shelve it even if the additional cost to the car will be a few hundred dollars.

  • Steve Hess

    70% of the benefits of a hybrid, maybe. Certainly not 70% of the benefits of a plug-in hybrid. Those are two very different systems. I get 80MPG in my Ford Fusion plug-in. The Fusion hybrid gets 42 and the auto-start-stop gets 29. Auto-stop-start is in no way comparable to plug-in.

    From the Green Car Reports article “Delphi claims its system can offer 70 percent of the fuel-economy benefit of higher-voltage mild-hybrid systems, but at just 30 percent of the cost.”

    • evfan

      “80MPG in my Ford Fusion plug-in”
      One of the things I struggle with is understanding PHEV consumption, if you mention gasoline only. So for 80 miles your consume 1 gallon of gas and I guess 10kWh – 15kWh of electricity. Is that correct?

      • Steve Hess

        Correct. Strictly speaking it’s not really fair to compare 40 to 80. It would be $2 for the gas and about $1 for electricity (@ $0.07 / kWh). I get hourly rates for electricity and it drops down to less than $0.02 at times. It was $0.028 last night when it charged.

        • evfan

          Wow, who is your utility company? Here in California, PG&E overcharges us like crazy. I think on time of use plans, the lowest it ever gets is $0.17 per kWh.