Following-up - I'm not as good a tinkerer as you are, githerfixed... What is the plastic cap, under which I would find the screws to disassemble the battery unit?
I'm attaching a picture of the battery unit, labelled with "1" and "2".
1 (of which there are four on each side of the battery unit) appears to be some kind of a weather cap over what, if I were building such a thing, would be where I'd put the screws. Is that where I need to find the screws you located? How did you get those weather caps out/off?
2 is a hard rubber wrapper which runs longitudinally all the way around the battery unit. It provides the non-slip, non-scratch surface which presses against the bicycle top tube. It can be partly pried up at various points, and at the bottom it has four snaps (two on each side) which can be easily lifted out of their matching anchor points in the hard plastic case on both sides of the battery. Are the screws which you found located somewhere underneath this hard rubber wrapper? If so, at what point, and how did you lift the wrapper enough to avoid tearing it? It sort-of looks like it was stretched over the whole battery unit, and with age I'm concerned about trying to stretch it back as I imagine it would tear.
Thanks again!
Jay