TP760: Li-Ion battery dead - can I put NiMH cells inside?

[CYBERYOGI =CO=Windler]

The Li-Ion battery of my IBM Thinkpad 760XD (FRU P/N 29H9232, ASM P/N 29H9032) almost died half a year ago (in April?). I use the laptop only every few months, so it wasn't continuously charged. When powered on, it displayed flashing 0% charge for 18 seconds or so, then the battery icon disappeared from the LCD and stayed gone when I powered it off and on again. After waiting some hours with mains disconnected the icon re-appeared, but did always the same after 18 seconds. I repeated this several times and finally gave up. I used my 760EL wreck without drives for charge tests if anything goes wrong.

I now (October) have first time after months tried to charge it again (hope it won't explode). The LCD showed non-flashing 0% for some minutes and now it surprisingly indeed seems to charge.

However I do not really trust into this old battery any more and expect it to die soon anyway. A new Li-Ion battery is absurdly expensive, and I calculated that modern NiMH of the same size would have more capacity than the ancient Li-Ion pack. I don't want to experiment with charging individual cells with a power supply, nor I want to solder new Li-Ion cells into it, because such things can make them explode like fireworks rockets and infest the whole apartment with severely poisonous smoke and residues (containing cobalt, hydrofluoric acid and plenty of other really malicious chemicals).

-Can I replace the contents of the Li-Ion battery pack with modern NiMH cells?

What is inside an original NiMH battery packs for the Thinkpad 760 series? Does it contain a complex charger circuit (like with Li-Ion) or just a bunch of bare cells? How are they wired? Without a charger PCB 16 Mignon/AA cells would fit into the case, those would provide 9.6V when 2 groups of 8 in series are wired parallel. With 2600mAh per cell it would provide 5200mAh, which is more than the 3000mAh of the original lithium. So far it needs a charger circuit, can I make my own? I guess that even battery holders may fit inside the case to make the NiMH cells replaceable. I also own a 2nd specimen of the Li-Ion battery pack, which is completely dead.

Has anybody ever done such an upgrade before?