There are other options. I repacked the battery pack on my 14.4volt ryobi and chanded from NiCad to NiMH.You can even get them pre packed in the right layout for many drills. I just bought the right number of SubC cells and soldered them together so they looke like the old one. Just make sure it is not the charger at fault
Thanks for the info Ian.
I will look into this again.
At one time I found the proper Lithium Ion batteries that would fit the pack (I think they were either 18350 or 18340), and a charge-controller board (needed to prevent overheating and overcharging, as the chemistry of these batts is more volatile than NiCd or NiMh but has greater energy density), but I need to find out if the factory charger that came with the drill is sound, and can charge the Lithium Ion chemistry at the proper current without causing problems (like a fire).
I am well versed in the Lithium Ion NCR, ICR and IMR chemistry batteries since I use them in my own electronics hobby projects (lots of items are 5v USB-powered nowadays and 18650 batteries do well with a nominal 4.7v DC), but rebuilding a battery pack requires finesse and if a new charger is needed or some other MacGuyver solution, the whole project has the potential to exceed the cost of a newer, cheaper pre-made drill kit, since Ideally you'd want 2 battery packs...
I struggle with this often, because I despise the throw-away nature of the way lots of things are manufactured, and when the cost of a proper rebuild, which
nearly always guarantees my ability to keep things alive & working for a very long time since I can DIY any future repairs after the rebuild, when the cost exceeds the price of new, once you factor in your time and effort, in addition to the parts, sometimes it seems hopeless.
However, when I have done this type of life-extension-of & DIY for things, it always teaches me something, and advances my confidence to fix things, for which I am always proud of these projects, and of course as you probably know well, sometimes our failures teach us more than our successes.