I have found that some very old NiCd batteries go high-resistance if left for years. I've managed to get some life into some of them by gradual charge/discharge cycles.
Pushing current into a high resistance needs more volts (I used 30V) but do use a series resistor of maybe 1k Ohm to protect the bettery/charger.
Discharge into a reasonable load (not a screwdriver).
As I said, I've had _some_ success with this, but if you don't revive a dead battery, it won't be a great loss.
Regards
Edwin Spector edwin.spector.att.com