Two Vex battery questions

First: What type of plug do the Vex batteries use?
Second: Can you use other (non-Vex) batteries with more/less mAh, as long as it’s a 7.2V and a Ni-Cd(for the robot), or 9.6V and a Ni-Cd (for the transmitter)?

I know somweone that uses a battery with more mAh and the robot works fine. The positive effect of this is that the battery lasts longer.

Yes - Think of the stored current (the thing measured in mAh (milliAmperehours) like stored water and the voltage like water pressure. The equipment attached to the water-tank (the equipment attached to the battery) is designed to operate at a certain pressure (voltage). How long the equipment operates depends both on how much water (current) is stored and on how much of that water can be supplied at any given moment at the required pressure.

I also suggest you use duracell Ni-Mh batteries, because they have 2400-2650 mAh and have a 15 minute charger. There is an battery that comes with the starter kit that lets you put normal AA batteries in, like the Ni-Mh batteries from duracell.

btw i buy the duracells from costco.

The batteries use hobby RC battery connectors as described by Radio Shack on their website. Check out this link.

Always check out the FAQ Sections, your questions where answered there. See Batteries / Charger.