Battery packs producing an output of 19.2 volts are made from 16 individual 1.2 volt cells. The cells are either nickel cadmium (NiCad) or nickel metal hydride (NiMH). The method you use to repair a 19.2 volt battery pack depends on the problem you are experiencing. If you find your battery goes dead quickly during use then you need to completely discharge it. If your battery doesn't charge up fully and isn't able to power your device properly you have dead cells which need replacing.
Repair using Full Discharge Method
Insert your fully charged 19.2 volt battery into your device. Turn on the device using the lowest power setting. You need to discharge your battery as slowly as you can.
Leave the device running until it stops. Turn it off and let the 19.2 volt battery rest for 5 minutes.
Turn on the device. It runs slowly so leave it running until it stops. Turn it off and wait five minutes.
Repeat the process until the device doesn't run. The battery is fully discharged.
Insert the battery into the battery charger. Allow it to charge until full. Usually your charger has a light that illuminates to indicate its charging and turns off once the battery is charged. The battery will take longer to charge than my may be used to. Once charged your battery is repaired.
Repair by Replacing Dead Cells
Charge your 19.2 volt battery until fully charge then remove from the charger and leave to rest for a day. This allows bad cells to lose their charge. Place the 19.2 volt battery pack on a workbench. Read the label on the battery pack to find out whether it contains NiCad or NiMH cells.
Unscrew the screws holding the battery cover in place. These are small Phillips screws so use a suitably-sized Phillips screwdriver. Remove the battery cover.
Use a voltmeter to test each cell's voltage. Place the sensor on the end of the red wire that extends from the voltmeter onto the positive terminal of the first cell. Attach the sensor on the end of the black wire onto the negative terminal of the first cell. The cell terminals are clearly labeled "+" and "-."
Read the voltmeter display. A good cell has a reading of 1.2 volts. If the reading is less than 1.1 volts then the cell is not retaining its charge so it needs replacing. Remove a bad cell by prying it out of the battery compartment using a small screwdriver. Insert the screwdriver between the battery terminal and connecter and lever the cell. Place bad cells to one side. Repeat the process on all the cells using the voltmeter. Remove bad cells and leave good cells in place.
Obtain the same number of replacement cells as bad cells you've removed. NiCad and NiMH cells are available in electronics stores. Take one of the bad cells to the store so you get the correct replacements. Insert the replacement cells into the battery compartment. Replace the battery cover using the Phillips screws and screwdriver. Put your battery on charge for half-hour. This ensures that the old and new cells charge equally. Remove the battery from the charger. Put your repaired 19.2 volt battery into your device.