I attacked the "bad" Sony battery pack with a Dremel-powered cutoff disk. It
was stuffed with five huge prism cells, each measuring 3 x 7/8 x 1/4. At least
two of them appeared to have excessively low voltage.

I have no intention of trying to restore or replace these cells, especially as
they aren't interconnected in the way you'd expect.

The question remains... As nicads and NiMH cells are charged by constant
current (theoretically, anyway), what would cause the total post-charge
voltage to hit nearly eight volts?