Kia Motors will introduce its first 48V diesel mild-hybrid powertrain in the second half of 2018. The new “EcoDynamics+” powertrain supplements acceleration with electric power from an additional 48-volt battery and extends combustion engine ‘off time’ using a new Mild-Hybrid Starter-Generator unit.
The Kia Sportage will be the first model to offer the new EcoDynamics+ diesel mild-hybrid powertrain later in 2018. The new third-generation Kia Ceed will be the second among a range of Kia models to offer the new powertrain from 2019.
The EcoDynamics+ diesel mild-hybrid system is paired with Kia’s Selective Catalytic Reduction (SCR) active emissions control technology, reducing CO2 emissions by up to 4% on the new Worldwide harmonized Light vehicles Test Procedure (WLTP), and up to 7% on the New European Driving Cycle (NEDC). The roll-out of diesel mild-hybrid technology will contribute to the brand’s global efforts to improve whole-fleet fuel efficiency.
Kia’s mild-hybrid technology features a compact 0.46 kWh 48-volt lithium-ion battery and a new Mild-Hybrid Starter-Generator (MHSG). By electronically controlling the MHSG using the inverter, the system switches seamlessly between two modes: “motor” and “generator”. Connected by a belt to the diesel engine’s crankshaft, under acceleration the MHSG provides up to 10kW of electric power assistance to the powertrain in motor mode, reducing engine load and emissions. In generator mode, the system harvests kinetic energy from the vehicle during in-gear deceleration and braking and uses the power to recharge the batteries.
In motor mode the battery is discharged under acceleration, providing additional torque to the engine for a slight boost in performance under hard acceleration, or to reduce engine load during light acceleration. Under deceleration, or when driving downhill or towards a junction, the MHSG switches to generator mode, recuperating energy from the crankshaft to recharge the battery on-the-go.
The system is controlled by an advanced Electronic Control Unit (ECU), which calculates the most efficient use of the available energy, and adjusts accordingly, taking into account the amount of charge remaining in the car’s batteries.
Battery power can also be used to provide a new Moving Stop & Start function. If the battery has sufficient charge, the combustion engine turns off automatically during in-gear deceleration and braking. The MHSG can then seamlessly re-ignite the engine—in any situation—if the driver presses the throttle pedal.
The compact nature of the technology means that integrating the EcoDynamics+ mild-hybrid system into existing vehicle architecture is relatively straightforward. Depending on vehicle, the 48V battery will be located beneath the boot floor, minimizing the impact on vehicle practicality. Because the MHSG integrates directly with the engine, driving the crankshaft via a belt, there is little need to repackage the engine bay.
The 48V battery’s DC/DC converter enables the new battery to connect to the vehicle’s on-board power supply, leading to a significant reduction in the size of the 12V battery required to power the car’s ancillary electronics. The adoption of the MHSG also means the conventional starter motor can be downsized and used primarily for cold starts at low temperatures. Charge from the 48V battery helps to start the engine in most conditions.
Kia’s EcoDynamics+ diesel mild-hybrid powertrain is compatible with both manual and automatic transmissions, and could be adapted for front-, rear- and all-wheel drivetrain layouts. The powertrain will also be adapted for use in gasoline engines.
The 48V mild-hybrid powertrain is the first new technology to be launched as part of Kia’s wider powertrain electrification strategy. The introduction of the new 48-volt powertrain marks Kia as the first manufacturer to offer consumers hybrid, plug-in hybrid, battery-electric and 48-volt technology across its model line-up. Kia plans to launch 16 advanced powertrain vehicles by 2025, including five new hybrids, five plug-in hybrids, five battery-electric vehicles and—in 2020—a new fuel-cell electric vehicle.