Nica
If you get the 9.6v-24v charger (about $25-$35) just make an adapter from the charger to your battery. It's a Black and Decker Firestorm. It's a very fast charger. Recharge as soon as the tool starts getting tired.
It will send a high current pulse, check voltage and, if needed, another high current pulse, sense, etc. to reform the battery. Once the computer (yes) senses the pack is accepting a charge it switches to charge mode, periodically stopping to check voltage.
As the battery approaches full charge the lessening change in voltages between charge cycles clues the charger to what the final voltage will be.
In the reform mode (I'm assuming here - it may not be exactly like this) it shorts the battery briefly between pulses. At the Houston Post (RIP) we built a reformer for individual 1.25v cells. It applied a high current pulse, then shorted the terminals. This cycled about 1/1000 sec pulse, 1/500 sec short, about 5 mins to 30 mins, however long it took to reform the cell. That's when 1.25v C sub-miniature cells were $5-10
apiece. (Back before

)
The indicator LEDs will indicate a pack that can't be reformed. I usually hang on to these for a while. Remove the ni-cads (dispose of properly - don't throw 'em in Dougster's Swamp

) inside and you have a case to use as an adapter. Ask friends, etc. for a bad battery pack you can cannibalize. Wire from the empty battery case to your (old/bad) charger case and you will be set up. I did this for a friend with a Makita drill. When needed just slide the adapter case into the charger. The charger itself remains unmodified. You can also use a broken tool as a battery holder while charging.
Dewalt may have the same type charger available but it will be more expensive. I haven't tried, but I think (at least for the older post style battery) you only have to remove one "bump" near the base of the post to fit a Dewalt battery to a B and D. B and D makes Dewalt.
Ted