My vacuum cleaner's Black&Decker Dustbuster battery pack (NiCd) died.
I decide to use a new D1-3S 12V-3Ah sealed acid battery (similar to those which we have in our cars, but much, much smaller. See the first picture.
Dimension of that battery is: Length 3 13/16", Width 1 11/16", Height 2".
It fits perfectly B&D battery pack compartment if you break some of the technological protrudes; see the picture.
After break them i have inserted the battery and to avoid disassemble entire machine for charging process i made connections with two wires (positive - red and negative - white) sticking out of the vacuum cleaner. now I will be able to hook it to my car's battery charger.