Has anyone ever opened up a battery pack to work on it? From what I've read, the cells are in sheets, correct? If so, how many sheets, and how many cells in a sheet? What does a "brick" of cells refer to then? Any pics out there? Anyone work on a pack themselves? Having a lot of experience in smaller versions of ni-cad and ni-mh packs in series, I'm quite curious....Nobody else makes replacement sheets for the roadster, right? Are the individual cells available?