getting quality cells for the rebuild costs more but pays off.
have a freebie drill from some handyman magazine one of our regulars dropped off.it was new but would barely do a small job on a charge.
rebuilt the pack with sanyo 1800 nicd.
been several weeks,several jobs,and lots of drilling building mods and still on the first charge.
I have an old Makita NiCad drill, maybe 25 years old that still performs. The cells are made in Japan, will self discharge after a couple of weeks, but still hold a very decent charge in the shorter term. Some of the “new” NiCads I pull from the bins will loose there charge overnight. That isn’t totally fair because the only ones I see are the ones that are thrown away.
This phrase really needs to make a comeback, ‘X or Y is goofy’.
Okay, happy to oblige… Ejected Filament is goofy. There, feel better? 
P.S. For the record, DavidEF is somewhat goofy as well.
Never run the pack beyond the first sharp drop in performance.
swap packs or take a break while it recharges.
good quality cells will last damm near forever if you follow this.
This reminds me of a joke involving Mickey Mouse, Minnie Mouse, a divorce lawyer and Goofy… but I cant tell it here.
i think thats the problem, these packs are made from no name chinese cells that they hope will last till the day after the warranty