Small thread bump; I've got a 5300 with a dead battery I'd like to rebuild but want the case intact. Found a thread on the top of a google search but most of the attached images are gone by now. Maybe something will help you in there, certainly given me some ideas.
I didn't see any logic board inside my 5300 dead battery pack. Just a few bits (thermistor, fuse, and what looks like a 2 prong eprom?) behind the contacts)
I plan to test with some 2KmAH AA cells first, and then try out higher capacity. (2500mAH)