That's a pretty quick self-discharge. There are complaints on their site about that.
They are NiCd, so they are an older chemistry.
Any thought about going to a LiOn system? Heck, if you don't use it much, go to a corded drill.
Yep, old tech, guess I should be like Duck Dodgers and join the 21st century & upgrade to a LiOn cordless set. The set I have now has lasted me since the late 1990’s and sure has come in handy. I have the full set, drill, sawzall, circular saw and hard case.