If you're battery pack contains NiCad or NiMH cells then fixing it is moderately easy.
Battery packs contain individual cells that are wired in series to produce the required voltage needed. Battery packs may consist of four main types of cells: nickel cadmium (NiCad), nickel metal hydride (NiMH), lithium polymer (LiPo) and lithium ion (Li-ion). If yyour battery goes dead or doesn't charge properly you need to fix it. However, LiPo and Li-ion battery packs contain power surge breakers to prevent overcharging, because if they are overcharged the battery pack can catch fire or explode. For this reason you need to get LiPo and Li-ion packs fixed professionally, but if you have a NiCad or NiMH battery pack then it's moderately easy to fix it.
Instructions
1. Check the type of cells in the battery pack. It's clearly marked on the label attached to the pack.
2. Put your NiCad or NiMH battery pack on charge and leave it charging until it's full. Remove from the charger and leave to stand overnight. This is to allow bad cells in the battery pack to lose their charge. Not all cells go bad at the same time, so you may find that you only need to replace one or two cells to fix your battery pack.
3. Put your battery pack on a workbench. Check how the battery cover is fixed on. Usually it has several small screws, sometimes it has clips. If it has screws, remove the screws using a suitably-sized screwdriver. If it has clips, insert a small flat-head screwdriver under the clip and twist the screwdriver to release the clip. Remove the battery pack cover to reveal the cells. The number of cells depends on the output voltage of the pack. For example, if the output voltage is 9.6 volts then it has eight cells; both NiCad and NiMH cells produce 1.2 volts.
4. Check the voltage from each cell with a voltmeter. Attach the prong on the end of the red wire from the voltmeter onto the positive terminal of the first cell in the pack. Attach the prong on the end of the black wire from the voltmeter onto the negative terminal of the first cell. The positive and negative terminals are labeled "+" and "-."
5. Read the voltage from the cells on the voltmeter display. Good cells have retained their charge and the voltage reads between 1.1 volts and 1.2 volts. Bad cells rapidly lose their charge so the voltage is lower than 1.1 volts. If the voltage is less than 1.1 volts you need to replace the cell. Make a mark on the cell so you remember which ones are bad.
6. Remove bad cells from the battery pack. Cells may push into the battery compartment, or they may be soldered. If they push in then simply use a flat-head screwdriver to lift out each bad cell. If they are soldered in place, heat a soldering iron. Touch the end of the soldering iron onto a cell terminal and let the solder melt. As soon as it melts remove the soldering iron and quickly lift the cell away from the battery terminal using a flat-head screwdriver. Repeat the process until all the bad cells are removed. Turn off the soldering iron.
7. Count how many bad cells you have so you know how many replacements to buy. Take a bad cell along to the store so you get the correct replacements.
8. Put the new cells into the battery pack. If they need to be soldered, heat a soldering iron. Put the cells into the battery compartment. Put the end of the soldering iron onto a cell terminal and introduce the solder. Let a small amount of solder melt so it fuses the cell terminal onto the connector in the battery compartment. Remove the soldering iron and solder. Repeat the process until you have soldered all the cells in place. Turn off the soldering iron.
9. Replace the battery pack cover.
10. Put your battery on charge for a short time; half an hour is fine. This equalizes the charge in the battery pack. Remove the battery pack from the charger.
Tags: battery pack, soldering iron, battery pack, NiCad NiMH, battery compartment, cell terminal, flat-head screwdriver