Types of laptop batteries
There are three main types of laptop batteries: Nickel-Cadmium (Ni-Cd), Nickel Metal Hydride (Ni-MH), and Lithium Ion (Li-ion).
This type of battery must be fully discharged and then fully recharged every few weeks. If you do not do this, it will quickly lose battery life due to what is called memory effect. This means that if you do not discharge your Ni-Cd battery completely, it will only charge up to the percentage of last charge. So if you only discharge it down to 25%, it will begin to only be able to charge up to 75%. It will only be able to charge at 100% if you discharge it all the way (100%).
Nickel Metal Hydride (Ni-MH)
Ni-MH batteries are similar to Ni-Cd batteries although they are not as prone to the "memory effect" and have more capacity to charge (so they will allow your laptop to run longer).
Lithium Ion (Li-ion)
Li-ion batteries do not have problems with memory effect, but Li-ion batteries will lose effectiveness if they are overcharged or left in full charge without use. For example, if you rarely use the battery and keep the laptop plugged in, the battery will lose effectiveness. There can also be problems if the battery is fully charged and then not used, then charged again.
What should you do to keep your battery healthy?
1) Battery packs should be charged for 12 hours when you first get them. Laptop batteries are completely discharged at the time of purchase, and need a full charge before their first use.
2) For daily use, charge the battery to full, then run it on battery power only until it is completely out if using Ni-Cd or Ni-MH batteries (to prevent the "memory effect") or mostly out for Li-ion (to prevent overcharging).
3) Do not leave your battery inactive for extended periods of time. Even if you use AC power most of the time, use the battery periodically to keep it in good condition. Unplug your AC adapter when the computer is not in use to prevent overcharging.
If you do not use your laptop for extended periods of time (a week or more), remove the battery pack from the laptop. Store batteries in a cool, dry place away from heat and metal objects. Batteries left idle for extended periods of time will self-discharge. Remember that they will need to be charged again before using them.
Do not expose the battery to high heat. Permanent damage will result if the battery is stored in temperatures above 110º F. Do not leave your battery in your car in the summer.
Most batteries can be recycled. Don't just throw them away—they contain a lot of toxic substances. The University of Michigan has an active battery recycling program. Batteries can be recycled in Desktop Support Services (2026 Shapiro) or in Distribution and Supply (17 Hatcher North).