Is there any way to replace drill batteries?
Sorry to disagree with KeithS, however there are many companies that rebuild NiCad battery packs. I'm not saying it is a great deal financially, however most common brands can be rebuilt. NiCad packs, for example, are made of several 1.5Vdc cells. the cells themselves are usually pretty uniform in size, however can differ in quality. Putting more in series makes for higher voltages, putting more in parallel gives higher AH ratings.  Beware of super discounters, look for a company that offers a good warranty and replacement policy.  An example: http://www.freedombatteryrebuilds.com  not endorsing them, just an example of re-builders.