[Chris is me]

I really don't want to come across as attacking in your first post - I'm just trying to help. But... the main difficulty I think you guys are going to run into is that it's against the rules to start robot design before the build season starts. Besides that, we aren't even sure what size the robots will be yet, which game piece we're using, how we will interact with them, if the field will have any obstacles, etc. I'm not saying it's useless to be thinking about this stuff before Kickoff, but just know that you can't get a jump ahead of anyone by doing "pre-design" or pre-building.

Lots of teams do CAD before the season, in the form of design exercises or practice, including our team. But using any design made before the season starts without changing it is illegal. It's okay to come up with an idea for a drive base and then CAD it, but you can't use that design when the season starts without changing it in some way. On 2791 we usually come up with a concept, then change details once the game comes out (e.g. the size of the frame, exact gearbox layout, etc).

As for a good place for the battery, you want it as low as you can and in a place that you can reasonably get to. It is more important that the main breaker be easy to access than it is for the battery to be, but you still don't want students to have trouble changing it fairly quickly. Stowing the battery vertically in some sort of custom box is a good way to save on space and to make removal easy. Put it off to one side if you have a heavy manipulator on the other side, otherwise try to bring it a little closer to the center.

We don't usually decide exactly where the battery goes before we have an idea of where our manipulator is going to be. We don't want to put it somewhere, and then make students have to reach in / out / around a bunch of parts just to get a hold of it.