DeWalt have been producing battery operated power tools since about 1992. Most new DeWalt batteries use lithium ion, or Li-ion, cells as they produce higher voltage so fewer cells are needed to power the tool, making the battery pack much lighter. Old DeWalt battery packs contained nickel cadmium, or NiCad, cells which after time fail to retain their charge, so you find the power tool goes dead quickly even though you have just charged it. However, there's no need to dispose of NiCad batteries, you can quickly and cheaply refurbish your old DeWalt battery.
Put the old DeWalt battery that needs refurbishing on a work surface. Read the label on the base or side of the battery to determine the output voltage. Most old DeWalt NiCad battery packs are either 12 volts or 14.4 volts.
Divide the output voltage marked on the old DeWalt battery pack by 1.2. This tells you the number of replacement cells you need to buy as each NiCad cell produces 1.2 volts. For example DeWalt 14.4 volt battery has 12 cells as 14.4 divided by 1.2 equals 12.
Get the number of replacement cells you need to refurbish the old DeWalt battery pack from an electrical supplier so if your battery pack is 14.4 volts get 12, or if its 12 volts, get 10. NiCad cells are widely available and relatively inexpensive.
Use a small Phillips screwdriver to unscrew the six screws holding the battery pack cover in place. Once removed the cover lifts off and you find the individual cells inside.
Determine how the cells are fixed in the Dewalt battery pack. The cells sometimes click into place, others have soldered tabs. If they click in place, use a screwdriver to pry them out. If they are soldered you need to heat a soldering iron. Put the end of the soldering iron on the tab and battery terminal. Allow the solder to melt. Pry the cell from the battery compartment as soon as the solder melts then remove the soldering iron. Repeat the process until you remove all the cells. Turn off the soldering iron.
Put the 10 or 12 NiCad cells in a clear plastic bag and put them to one side. You need to recycle NiCad batteries in a battery recycling facility; they must not be disposed of in your regular trash. You can find advice on battery disposal by clicking the link in the resources section.
Put the replacement NiCad cells into the empty battery pack. Ensure you insert them correctly so the cell terminals line up with the correct connectors in the battery pack. Each cell is labelled "+" at one end and "-" at the other. The small protruding metal part on top of the cell is the positive terminal and the flat surface on the bottom of the cell is the negative terminal. Look on the inside of the battery pack and you see a diagram showing which way the cells need to be fitted. It's marked "+" for positive and "-" for negative. Getting it wrong doesn't damage the cells and it's not dangerous, but the battery pack won't work.
Push the cells into place using your fingers, if they fit using this method, or heat a soldering iron if they are soldered. Touch the end of the soldering iron onto the tab and battery terminal. Introduce some solder and let it melt. Remove the soldering iron and solder as soon as it melts. Let the solder harden then repeat the process on the other tabs. Turn off the soldering once all the cells are soldered in place.
Put the cover on the battery pack. Put the six Phillips screws into the holes and then tighten the screws using the Phillips screwdriver. Put your refurbished DeWalt battery pack into the device it powers.