Check the charger first, do you have a multimeter? Check the power supply, put one lead inside the plug and the other to the outside. Match it to the label for voltage, I imagine it will be 14v-18v but probably will be unregulated so it will probably read higher. If it's good, plug it in and test the leads that would touch the battery, should be more than 12v.
If both of those are good you should try to shock the battery. If you have a 14v power supply, probably up to 18v hook it up to the battery, making sure to get the polarity right. Leave it on for about 10 mins (since it has a partial charge), watch it DO NOT LEAVE IT UNATTENDED. If you overcharge it with this method it will burst and could ignite or blow up(literally). Then plug it into the charger, it should now accept the charge.
You can also check the drill by hooking up a battery/power supply to the leads inside the drill, this will definitely tell you if the drill is working. 6v to 14v would be fine and not cause any damage. More voltage would work but could cause excess RPM/heat, it should easily be able to handle 24v but no sense in pushing it.
If both of those are good you should try to shock the battery. If you have a 14v power supply, probably up to 18v hook it up to the battery, making sure to get the polarity right. Leave it on for about 10 mins (since it has a partial charge), watch it DO NOT LEAVE IT UNATTENDED. If you overcharge it with this method it will burst and could ignite or blow up(literally). Then plug it into the charger, it should now accept the charge.
You can also check the drill by hooking up a battery/power supply to the leads inside the drill, this will definitely tell you if the drill is working. 6v to 14v would be fine and not cause any damage. More voltage would work but could cause excess RPM/heat, it should easily be able to handle 24v but no sense in pushing it.

