Makita batteries are used in a wide variety of cordless tools including drills, saws and screwdrivers. After they no longer hold a charge, Makita batteries can be restored to work like new. Within the Makita battery pack is a chain of smaller rechargeable batteries. If even one of these batteries stops functioning, it will affect how your entire battery pack charges. Restoring a Makita battery pack can be done with a few simple tools.
Unscrew the Makita battery pack to reveal the inside smaller rechargeable battery cells.
Write down how the cells are placed into the battery casing and which cells are soldered together, taking particular note of the cell polarity. You will want to make sure that you maintain the correct polarity positions during reassembly.
Use the battery tester to determine which cells have gone bad. Mark these cells for replacement.
Determine what type of rechargeable battery cells are being used in the pack. Nickel cadmium (Nicad) and nickel metal hydride (NiMH) are the most common.
Purchase new matching cells at a local electronics or hardware store. Only replace size "C" Nicad batteries with the same type of battery. The Makita battery pack should not be restored by mixing Nicad, lithium and NiMH batteries within the chain.
De-solder the first "bad" cell and remove it from the chain. Re-solder a new battery cell into the chain taking care to match the polarity position of the original battery.
Repeat this process with all other "bad" battery cells to fully restore the Makita battery pack.
Using your diagram, replace the battery cells back into the Makita battery casing and screw it closed.
Set the fully restored Makita battery pack on the charger overnight.