I Just wondered if this was normal. I had been crawling round at city traffic speed for a good mile or two and the hv battery had got low.
As i touched the accelerator to gently induce the motor the engine started vibrating at a guessed 2000rpm. It was like a small diesel engine lol. It would stop and cut out if i braked/regenned. But the second i touched the accelerator it started vibrating again. Once the battery was topped up this didn't happen again.
I think the battery is low, not flat.
I have not had this with the C-HR, but I had this with my previous Auris. The engine (ICE) is started to charge the battery.
It will be running at a resonance frequency which resembles a diesel. It can be annoing.