I have a Skil drill that uses the 144bat pack. The standard charger is apparently designed to die if the battery is dead, mine did. Is it possible to build a high quality battery charger for this battery pack?
You can buy a new drill and batteries for what it would cost in time and money to fix the one you have.
You're on the right track. Just hook your cells in series until you have about 8v or more, and hook them to a 7805 +5v regulator. This will limit the voltage to 5v, but won't be terribly efficient. This will only work if your cells can provide enough voltage under the load your phone will put on them to keep the regulator at 5v. You may need more cells in parallel to increase the current.
i would check your charger with a different battery, if you haven't already, odds are the charger is still good. NiCD batteries won't accept a charge when they go bad, but that shouldn't destroy the charger also. you would have to be an electrical engineer to build a charger that would charge these batteries correctly, too high a rate of charge or milliamps will overheat the batteries and destroy them, and so would overcharging
