Lithium ion batteries are meant for long term use but eventually they also die down or stop holding their charge very well. This is not very convenient as these batteries are for the most part used in laptops which are relied on for use during travel. At times when electrical sockets are unavailable the users are relying solely on the batteries to power their device. Replacement batteries are quite expensive but an old one can be restored.
Power down the computer and take out the battery. This battery will be used again so be careful with it. The battery will be located on the back of the laptop or one of the sides. This is easier seen by flipping the laptop over.
Open the battery casing in order to expose the set of batteries. These should say 1600 milliamp and 3.7 volts on them. If not purchase the version that you do have.
Use the soldering gun to heat up and unsolder the dead batteries' wires. Note the polarity and placement of the batteries relative to the wires. Remove the old lithium ion batteries from the casing.
Arrange the brand new six lithium ion batteries within the open battery casing. Use the soldering gun to solder the wires into the exact same places as the previous batteries. Close the battery casing by snapping it shut and insert it into the back of the laptop.
Place the battery casing with the now-replaced batteries back into the laptop and leave for over 18 hours to charge. The laptop will charge the batteries as it did with the originals. Turn the laptop on after fully charged to see whether the new batteries work.
To improve the life of your batteries store them in a cold place such as a refrigerator when not in use. The main block size battery which powers your laptop includes the smaller Lithium ion batteries within it. The laptop battery specifications such as 4-cell or 6-cell stand for the amount of the smaller batteries which are contained inside the main block size battery. Laptop batteries can be restored for a fraction of a price of an actual new laptop battery. The rechargeable batteries are not very expensive but work is involved in the restoration.
Safety glasses should be worn during soldering to protect your eyes.