Disable screen dimming when pluged in topic

I use the Nexus 7 (running lollipop) in the car, with torque.

I have setted up the "stay awake" option when charging in the devs options.
When I turn the car off, the tablet should go to sleep in the shortest delay possible, so I set the screen timout to 15 seconds.
Only problem is that the screen "dims" automatically after a couple of seconds. Even if I set the screen timout to 30 mins. it still dims after 30 min., which is more than anoying.

Is there an option I could change or a command I could use to disable the dimming alltogether?

Thanks!