How to rebuild a Li-Ion battery pack

When the battery life drops significantly it's time to search for a replacement, but you will recently find out that most of notebook batteries cost almost 1/3 to 1/2 the price of the laptop at the time you will need to replace the battery. So if you want to keep your laptop but don't want to spend much money for battery replacement it's time to think about rebuild it your own, replacing each individual cell inside the pack