I just bought some 1.2v 3700maH Vapex cells complete with tabs off of eBay then soldered them together. Had to cut open the pack's casing with a small modelling saw, drop the guts out, joined all the cells up, then epoxied it back together. This was on a Swiss made 12v Bosch and that thing has been copping a belting for 15 years now. Way nicer and better balanced drill than any of the new ones I've used, just not as quick as my 18v Li-Ion Hitachi.
Had to use "Baker's Soldering Fluid" to get the zinc plated tabs on the cells to accept solder though. They were very "solderphobic" prior to that stuff
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
The cells were $5 each and for $50 I had a better than new drill.