How does a tablet automatically power on when a power source is connected? Please imagine a car situation where you have an Android tablet:

http://content.worldcarfans.co/2014/11/24/thumbnails/24486128385597.hl2.jpg

And the following working rules (as expected in most cases):


If the car is OFF, tablet is OFF;
If the car is ON, tablet is ON (automatically);


I have been reading about enabling auto power on mode when the charger is connected: most tablets have the playlpm, lpm, or a specific file that displays the battery charging animation.
The trick is to overwrite these files and force a boot.

Furthermore, I have also checked and tested Tasker, where I was able to achieve this behavior only when USB is connected.

However, I would like to know if there's anyway we can do it if the tablet has no battery attached on it. 

Would this same approach work?
I managed to solve this situation only by removing the battery.

Turns out that most tablet's automatically power on when they're directly connected to an external power source.