Over time the rechargeable batteries in your Makita 14.4 will wear down and eventually not hold a full charge. Take the time to repair your Makita 14.4 battery pack instead of throwing it away and purchasing a new one. A chain of smaller battery cells rests within the Makita 14.4 battery pack. When one of these cells goes bad, it will impact the charging capacity of the entire battery pack.
Locate the screws on the Makita 14.4 battery case. Use a screwdriver to open the case and set the screws aside for later reassembly. Note that some cases come with an internal spring that tends to pop out when the case is opened.
Note how the batteries are set within the case. This will assist with later reassembly. Take particular note of the polarity in terms of how the individual battery cells are soldered together.
Determine the size and type of battery cells within the pack. Size C and size A rechargeable batteries are the most common sizes. The types of batteries are most likely Nickel Metal Hydride (nimh) or Nickel Cadmium (nicad)., depending on the age of your Makita 14.4-volt tool.
Use a battery tester on each battery cell in the Makita 14.4-volt battery pack. Mark each cell that is bad and needs replacement.
Purchase replacement rechargeable batteries at a hardware or electronics shop. Make sure that they are a similar size and type of rechargeable battery. Do not use non-rechargeable batteries. Do not mix types or sizes of batteries within the chain. If the battery was a size C nimh rechargeable battery, replace it with a size C nimh rechargeable battery. Again, this will depend on the age of your Makita 14.4-volt rechargeable tool.
Remove the first bad battery cell from the chain using a soldering gun. Replace the bad battery with a new rechargeable cell. Re-solder the new cell into the chain in the same polarity as the original battery. Repeat this process for all other damaged cells in the Makita 14.4-volt battery pack.
Place the chain of battery cells back into the Makita 14.4 battery pack casing. Use the screwdriver to close the case.
Charge the Makita 14.4 battery with the battery charger overnight.