[JesseK]

Move the battery away from the pole, slightly -- definitely do not put it right up against the pole. Put it level with or just slightly below the traction wheel in terms of vertical positioning. This change in center of mass creates a pivot point at the traction wheel. That pivot point will then create a moment at whatever contact is on the opposite side of the pole. If that contact point is higher than the traction wheel, it then acts as a pivot to create a moment on the traction wheel itself, thereby increasing the wheel's force to the pole (i.e. traction). Note that this will also increase the friction on 'zip ties' or whatever other locking mechanism you use, so design accordingly.

The very first prototype one of my students made was exactly like this, yet didn't lose traction. It was a 4-4.5 second bot due to the excess friction though.