In addition to the 2.0-liter CRDi 48V diesel powertrain introduced in the New Tucson in 2018, Hyundai Motor has now combined its efficient and responsive 48V mild hybrid technology with the 100 kW/136-PS 1.6-liter CRDi diesel engine.

The technology comprises a 48-volt battery, a Mild Hybrid Starter Generator (MHSG) and LDC converter (Low Voltage DC/DC). In addition to the 48V electrical system, the vehicle is equipped with the conventional 12V electrical system, which is connected via the DC/DC converter to the 48V system. Thus, parts of the energy stored in the 48V battery system can also be used to stabilize the 12V on-board power supply.

The 0.44 kWh 48V lithium-ion battery, which supplies the mild hybrid system with electric energy, is located beneath the rear luggage compartment, while the MHSG is mounted to the combustion engine. A belt connects the MHSG to the crankshaft of the internal combustion engine. The MHSG generates kinetic energy from recuperation of up to 12 kW and 55Nm of torque at the MHSG shaft.

The system was developed at Hyundai’s European Technical Center in Germany and Hyundai’s R&D Center in Namyang, Korea. It will be available in combination with more engines in the future.

Hyundai’s Mild Hybrid technology as used with the New Tucson improves the powertrain’s fuel economy and CO₂ emissions by up to 11% (NEDC 2.0) depending on the vehicle specification. As an additional benefit, the system supports the internal combustion engine, compensating with power during the different stages of driving, and helps lead to a faster and smoother engine start.

The mild hybrid system has particular advantages in city traffic, with the MHSG supporting the combustion engine when re-starting after traffic stops. This action supports a faster and smoother engine start with supplemental torque, drawing on energy from the 48V battery.

As a result of the earlier and faster delivery of torque, the engine start can be anticipated by 0.2 seconds. The conventional 12V starter is only used for the initial starting operation if the engine oil is still cold and a higher starting torque is required.

The MHSG assists the combustion engine during take-off by compensating with torque and power.

Under acceleration, the MHSG supports the combustion engine with compensatory 4 to 12 kW of power, depending on the battery system’s state of charge and the degree of accelerator input from the driver. Once the required speed is reached, the MHSG shifts to neutral mode, delivering no power.

At a constant speed, the MHSG either is at idle or acts as a generator charging the 48V battery, depending on the battery state of charge.

In active braking or overrun phases, the rotating crankshaft powers the MHSG, which then acts as a generator with a maximum recuperation output of 10 to 12 kW. The generator converts the kinetic braking energy into electricity, and feeds it back into the 48V battery. In these phases, the combustion engine remains switched on and clutch kept closed to be able to transfer the power from the wheels over the transmission and the engine to the MHSG.

When coasting at low speeds, the start-stop function already activates at 30 km/h. Under deceleration between 30 and 0 km/h, and with the clutch disengaged, the engine is switched off completely.

With the additional mild hybrid powertrain for its best-selling model in Europe, Hyundai is further expanding its electrification strategy.