Hyundai IONIQ plug-in Manual page 26

Idle Mode Charging 1
While the vehicle is in the Idle mode, the
engine's power is used for charging the
battery.
Engine Braking
The engine's power is reduced for slowing
down the vehicle.
2-6 I Plug-in Hybrid Electric Vehicle (PHEV)
Charging
The deceleration energy from braking is
used for charging the battery.
Electric Mode
The battery power is used for driving
the motor, which drives the vehicle. The
engine's power is not used.
Electric Mode Charging
The engine's power is used for charging
the battery, and the motor's power is used
for driving the vehicle at the same time.
Engine Braking Charging
The engine's power is reduced for slowing
down the vehicle, and the deceleration
energy is used for charging the battery at
the same time.