In that respect electricity isn't like water...

The extra voltage will be given to the motor, the ESC doesn't care how much cells you hook up to it (as long as it's within specs) it's the motor at the receiving end that will have to convert the energy into motion, and into heat, as the wires will be too thin, and will heat up to the point of destruction.

But you don't have to take my word for it, just go ahead and try!

Make sure to post the results here.

Regards, Jan.