Rechargeable batteries for power tools sometimes will no longer charge but often these can be easily restored back to life with this simple method.
Step 1: The Problem
The problem: You have a drill or other power tool with rechargeable batteries but one of the batteries is completely dead and when you plug it into the recharger unit it won't recharge at all. The manufacturers would tell you that you need to buy a new battery. When you look into it you find that the cost a new battery is so high that you may as well just buy a new drill that comes with a couple of new batteries. Well all is not lost!
Step 2: The Method
A friend in the UK told me about this method to revive a dead drill battery many years ago and I have used it successfully a number of times since. Basically, it seems that when a battery becomes completely discharged the charger unit effectively does not recognise that a battery has been inserted. This method puts enough charge into the battery so that it is not recognised by the charger and it gets recharged.
I take the dead Dewalt battery and a good fully-charged battery and place them side by side. I then use a couple of pairs of scissors to connect the terminals together (plus to plus and negative to negative). I keep them connected for a minute or so and by then the dead battery has sufficient charge to be fully recharged by the charger unit. Of course you can use two pieces of wire or something else to connect the batteries together but I have found scissors work well when doing it by yourself with only one pair of hands. Although I have Dewalt battery I have used this method to fix other makes when the battery will not charge. So, in future, if you have a dead Nicd power tool battery try this first before buying new.