Will the 9.6v battery work in the mini controller or no?
i dont know if you should do this, but you can and it will make the motor spin much faster than usual. I would suggest to not do this for a normal robot.
I accidentally plugged the 9.6-Volt battery pack into my new Hero 2007 Robot and as you can see in the photos I posted, it has worked very well. It does run the Vex servos and motors faster, giving the Hero 2007 its super agility and strength. The PIC micro-controller also seems to accept the extra 2.0 Volts with no complaints, but you may want to use the standard 7-Volt battery pack since it will help keep your motors and servos from wearing out their gears.
In fact, I have been able to use surplus 6.0-Volt Lead Sealed batteries with my Vex projects. Converting the standard battery holder with its form fitted plug just by soldering two leads with battery connectors to the + and - terminals of the blue battery box, gives me another renewable battery alternative. These batteries are found in discarded PC UPS systems and in Fire and Battery and emergency lighting systems and can be purchased surplus on the WEB or at your local electronic surplus store (if there is one nearby).
The Hero 2007 photo that shows the battery is located at: https://vexforum.com/gallery/index.php