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48-Volts and beyond: Hybrid changes and DTC tips

Tuesday, January 1, 2019 - 09:00
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When will we see 48 volts?

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Forty-eight-volt vehicles have already been appearing in Europe in fair numbers due to the higher price of fuel there. As for models made in/imported into the USA, Mercedes has launched 48-volt system in their CLS 450 model (Figure 10) for American roads this year. In addition, select Dodge Ram 5.7 liter V-8 Hemi, Dodge Ram 3.6 liter V-6 and Jeep Wrangler 3.6 liter V-6 models for 2019 have adopted a belt driven 48-volt motor generator system called E-Torque.

Figre 10 - This 2019 Mercedes CLS 450’s MG (Motor Generator) is a 48-volt stop start unit located between the engine and transmission. The unit is large, heavy and contains the typical features of a higher voltage full hybrid’s MG – such as a resolver to sense torque and direction.

Dodge/Jeep E-Torque 48-volt system explained

The E-Torque system uses two major serviceable assemblies each containing non-serviceable main subassemblies/components.

  1. Battery Pack – PPU (Power Pack Unit)

HV Battery, HV Battery Control Module and DC-DC Converter

Dodge’s 48-volt Li-Ion battery pack contains a BPCM (Battery Pack Control Module) that is an integral part of the complete PPU (Power Pack Unit, Figure 11). The PPU’s Li-Ion battery pack is an air-cooled unit containing 12 4-volt Li-Ion cells. The BPCM monitors for current, temperature, voltage and internal resistance of the pack the same as any HEV/EV’s battery control module. The BPCM also controls the charging and discharging of the battery pack. The BPCM’s HV battery self-diagnostics include SoC (State of Charge) and SoH (State of Health). SoH is based on the rise in calculated internal resistance and decrease in capacity. Battery end of life is generally defined as a 20 percent decrease in the 48-volt battery system capacity or 25 percent power degradation. The unit contains a DC-DC converter, which is, of course, any hybrid vehicle’s solid-state version of a conventional 12-volt alternator. The BPCM communicates on and manages a special CAN bus called a CAN-ePT data network. The CAN-ePT is a private bus network used only in the e-Torque system with e-Torque components.

(Image courtesy of FCA) Figure 11 - The Dodge Ram e-Torque PPU (Power Pack Unit) mounts at the back of the cab and is an all in one battery pack / DC-DC converter that is air cooled and contains the BPCM (Battery Pack Control Module). Care MUST be taken to remove the underhood 12-volt battery’s negative cable first. Then verify the lack of 12-volts at the PPU before removing the 12-volt cable from the unit (6) for safety’s sake. Then the 48-volt cable can be removed. (5) A common ground for both voltage levels is next to the PPU. (4)
  1. Belt driven MGU (Motor Generator Unit)

Motor/Generator, Inverter and Main Hybrid ECU

The MGU mounts on the front of the engine (Figure 12) and contains the HCP (Hybrid Control Processor) which is the major smarts for the entire e-Torque system. The HCP serves as an electronic controller for the E-Torque system as well as an inverter module to change the MGU’s internal 3-phase AC to 48 volts of DC power. The HCP commands the PPU to close the HV battery pack’s contacts via a bus message. The HCP also serves the important job of sending the PPU a message to go into a cell balancing mode when the BPCM indicates there is an imbalance. The MGU also serves as the starter motor to crank the engine as well as the generator for the vehicle. E-Torque systems also utilize a stop/start strategy that interfaces with several other modules on the vehicle such as the HVAC, ABS and TCM.  In addition to electrical generation and gas engine stop/start duties the MGU handles regen braking and engine low end torque boost with 130 ft. lbs. of additional torque.

(Image courtesy of FCA) Figure 12 - The Dodge Ram e-Torque MGU (Motor Generator Unit) contains the system’s HCP (Hybrid Control Processor). For all practical purposes this entire assembly does the job (using generic terms) of and engine’s starter motor, generator (for 48-volt electrical production and regenerative braking), inverter and hybrid ECU. Dodge service information recommends getting a helper to assist in removing the unit. It is HEAVY!

HCP Flashing Precaution:
The HCP is flash programmable and is sensitive to cold temperature during module flashing. The HCP will need to be flashed when the vehicle is at room temperature. Failure to flash the module at room temperature can cause the flash procedure to not complete, resulting in an unnecessary component replacement.

BPCM Flashing Precaution:

The ignition state needs to be transitioned to OFF for at least 30 seconds and then transitioned to RUN prior to flashing the BPCM. This allows the PPU’s contactors to be commanded open. If the ignition state is cycled too fast, a precondition warning may occur which could prevent the flash programming procedure from completing.

48-volt future – big or small?

According to the EPA, a fleet of 11 million 48-volt mild hybrids would benefit consumers and increase the nation’s air quality by saving over 4 billion gallons of fuel over the life of those vehicles. That’s a very good thing no matter how you state it. Will we see 11 million new 48-volt micro hybrids or will the American fleet hit some other number...lower or higher? Mary Gustanski, senior vice president and chief technology officer for Delphi Technologies gave some interesting insights into that question as she predicted some directions where electrification is likely to be heading while speaking at the 2018 AAPEX show in Las Vegas. Significantly lower costs for 48-volt systems are a big plus but higher voltage system prices have started coming down. Adding into that mix are the variables of governmental policies regarding required MPG increases/relaxations along with EPA restrictions on PM (Particulate Matter) and NOx (diesel emissions) for the diesel option some OEMs take. This leads us to the opinion that the only thing we can really bank on is more electrification and continuing changes in technologies. To that end Motor Age will be keeping you informed and ready for whatever new technology comes into your service bay!    

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