Take the dead battery pack apart and toss the cells.Take an extension cord and remove both ends (male & female) from the cord.Solder the extension cord wires to the contacts inside the battery pack.Drill a hole in the base of the pack and run the extension cord through the hole.Get a pair of battery charger alligator clamps and attach them to the other end of the cord.Important: Be sure you put the red clip on the wire that is connected to the terminal inside the old battery pack and the black clip on the terminal wire.

 Now, whenever you are working on your car, your 14.4v drill/sander etc, etc has a power supply, by simply attaching the clips to your car battery. Especially good for "on the road" repairs, etc,You don't have to worry about the battery pack going dead, or the lack of a 120v outlet on the road,you lose the "cordless" feature, but you gain a reliable tool to take along on a trip!(and you can still use the drill as a cordless by putting your other 14.4v (working) battery pack in it for "around the house" work).

 Why not just rebuild the battery pack? All it takes for most is a handful of sub-C cells, a soldering iron and a half hour (after the first one - to figure out how they are 'wired'). And yes, several of the guys here "taught" me how and it works great - unfortunately, the Porter Cable drill I did it for blew the clutch, so now I have a new Bosch drill - which isn't quite as good.And to rebuild a battery pack, you don't even need (or want, for that matter) the high-dollar fast dump high performance RC batteries, the plain vanilla's work fine.