I presume you are not aware of a setting where you can stop the petrol engine recharging the battery above and beyond the 15-20% minimum?
No! 😂
However by design of a self charging hybrid, it will charge the battery and deplete it again over “x” distance and keep recharging and depleting the battery again over the course of a journey. Depending on the journey, the battery is charged by the engine, braking and regeneration or a mixture of all 3. A PHEV is still basically a hybrid but, with a much greater electric only range.
IMHO, the Tucson is missing a mode. That said all manufacturers do things differently, BMW for example doesn’t have any user selectable modes, as the car decides. Toyota on the otherhand has 4 modes –
EV (electric vehicle) mode – the default mode.
HV (hybrid vehicle) mode.
Auto HV/EV mode.
Charging mode.
HEV mode on the Tucson doesn’t charge the battery, as Charge mode would on the Rav4/Across, however, I’m interest how HV mode uses the battery on say the Across @Oscarmax and whether it hovers battery charge level around the point, it was switche to HV mode?