Makita drill battery packs contain individual cells wired in series so they produce the correct voltage to operate your power tool. For example, a 9.6V Makita drill battery(Makita battery for 193176-1 ) contains eight 1.2-volt cells. The problem is that not all the cells go dead at the same time, but as the makita drill battery keeps going dead quickly after it's been charged, batteries get disposed of when all they need is fixing.
Charge your makita drill battery pack(MAKITA BML240 battery) until it's fully charged. Remove the makita drill battery pack from the charger and leave it for 8 to 12 hours. This allows bad makita drill battery cells to lose their charge while good makita drill battery cells retain their charge.
Remove the cover from the makita drill battery pack. It usually has six to eight small Phillips screws holding the cover in place so use a suitably sized Phillips screwdriver to remove the screws. Once removed you see the individual cells.
Get a voltmeter. Start at the top of the makita drill battery pack( Makita 193158-3 drill battery) as you need to get a system in place to test each cell. Put the sensor on the end of the red wire that's attached to the voltmeter onto the positive cell terminal. Put the senor on the end of the black wire that's attached to the voltmeter onto the negative cell terminal. The cell terminals are labeled '+' and '-.'
Read the voltmeter display. If it reads between 1.1 and 1.2 volts, the cell is good. If it reads below 1.1 volts, replace the cell. Put on mark on the cell using a marker pen so you know which cells need replacing.
Replace the process for each cell in the pack using the voltmeter as before. Mark bad cells.
Remove the cells you marked as bad. Insert a small flat-head screwdriver into the cell compartment and lever the cell out.
Make a note of the type of cell you have removed from the power drill makita drill battery pack as you need to get replacements that are exactly the same. The type of cell is clearly marked down the side and is likely to read 'NiCad,' meaning nickel cadmium, or 'NiMH,' meaning nickel metal hydride.
Get replacement cells to replace the cells you've removed from the makita drill battery pack. They are widely available from electrical outlets. It's helpful to take along one of the cells so you can be certain of the getting the same type.
Insert the replacement cells into the cell compartments. Simple push them into place using your fingers.
Replace the power drill makita drill battery cover. Insert the screws into the screw holes on the cover and tighten using a Phillips screwdriver.
Put your fixed makita drill battery pack on charge for about half an hour. This lets all the cells charge equally. Remove from the charger and insert the makita drill battery into your power tool and it's ready for use.