Copy Paste from the F10 manual:
Originally Posted by bfv
I thought battery will charge when you drive in city as city driving requires frequent braking/deceleration.
The energy of motion of the vehicle is converted to electrical energy while coasting. The vehicle battery is partially charged and fuel consumption can be lowered.
So what is coasting -- When approaching a red light, take your foot off
the accelerator and coast to a halt in the highest applicable gear. On a downhill slope, take your foot off the accelerator and coast in a suitable gear.
2011 535ix | Black Sapphire/Black Dakota/Dark Wood| P1 | P2 | Sports | Convenience | Cold Weather | Shift Paddle