Makita has been making power tools for almost a century, although cordless tools are a relatively recent innovation. Makita makes 18-volt batteries using nickel cadmium (NiCad), nickel metal hydride (NiMH) and, more recently, lithium ion (Li-ion) cells. The chemical composition of Li-ion cells and the requirement that power-surge breakers be fitted into battery packs means that the battery is best rebuilt by professionals. However, rebuilding an 18-volt Makita battery containing NiCad or NiMH cells is a moderately easy task and is much less expensive than purchasing a new battery pack.
Check the label on the outer casing of the 18-volt Makita battery to find out whether it contains NiCad or NiMH cells. It's best to rebuild a battery using the correct type of cell as the milli-amp hours (mAh) produced is different and may affect the operation of your device.
Purchase 15 NiCad or NiMH cells, depending on the type currently in your 18-volt Makita battery. Each NiCad or NiMH cell produces 1.2 volts so 18 divided by 1.2 equals 15. The cells are available in most electrical stores.
Unscrew the cover from your 18-volt Makita battery. Makita battery covers are held in place using small Phillips screws, so use a suitably-sized screwdriver. The number of screws varies, depending on the type of battery as Makita make four types of 18-volt NiCad and NiMH batteries.
Heat a soldering iron. Makita cells are soldered in place to give a more secure connection. Place the end of the soldering iron on a cell terminal and let the solder melt. It's best to start at the top of the battery pack and work down so you have a system in place.
Once the solder melts remove the soldering and quickly use a small screwdriver to lever out the cell before the solder solidifies.
Repeat the process by touching all the cell terminals using the soldering iron and levering the cell from the battery compartment. Once the cells are removed, turn off the soldering iron.
Put the cells to one side. Insert the replacement cells into the battery compartment.
Heat a soldering iron. Start at the top of the battery pack and work down. Put the end of the soldering iron and some solder on a cell terminal and let it melt. Remove the soldering iron and solder as soon as the solder melts. Let it harden then move onto the next terminal. Repeat the process until all the terminals are soldered in place. Turn off the soldering iron.
Put the cover on the Makita battery. Use a Phillips screwdriver to screw in the screws.
Connect the battery to your Makita charger. Charge for a short while: half-hour is fine. This just ensures the batteries are charged to the same level.
Place the old cells in a plastic bag while the battery is charging. You need to dispose of NiCad or NiMH cells in a recycling depot. They must not be placed in your regular trash bin. Disconnect the battery from the charger after 30 minutes.