Laptops are made for portability and ease of use, so the battery is one of the most essential components, providing power when away from a wall outlet. Here we will look at how a laptop battery works.
The most laptop batteries use Lithium-Ion technology, or Li-ion. They are so-named because the movement of lithium-ions from a negative to a positive electrode as they travel through a non-aqueous electrolyte. This discharges the battery and releases the energy to power the laptop components.
The inside of a Lithium-Ion laptop battery consists of an anode made from carbon, a cathode made of metal oxide, and an electrolyte, which is a lithium salt in an organic solvent. The reaction is contained within multiple “cells” inside the battery. Batteries with larger capacities (and longer battery life) usually contain more cells. Some very large Toshiba laptop batteries can contain up to 12 cells. Some Sony laptop batteries contain as few as 3 Cells due to the ultra portable design of some of their machines. These will provide less battery life, but will keep the machine small and lightweight.
There are a number of chips in most batteries to control the charge and discharge, as well as a number of safety features. Many batteries have a chip which shuts down the battery in the event of extreme overheating to avoid a potentially dangerous situation.
Charging the battery essentially works in the reverse of discharge. The power coming in through the AC adapter and the charging circuit actually provides a higher voltage than the battery’s normal operating voltage. This causes the lithium ions to move from the positive to the negative electrode and they are deposited in a porous material and stored for later use.
The outside of the battery is usually constructed of rigid plastic or metal, depending on the laptop model. The outer case usually incorporates vents to allow heat to escape, as heat can be very damaging to a battery. Most laptop batteries are color matched to the plastics of the notebook for aesthetic reasons.
The one disadvantage of Lithium-Ion batteries is that they tend to lose capacity over time. This is caused by deposits that form in the electrolyte of the battery. This begins to inhibit the battery’s operation and results in less charging capacity. Once the capacity gets low enough, the battery should be replaced.
While Lithium-Ion laptop batteries are currently the most popular, newer technologies such as lithium-polymer are stretching the boundaries of current laptop battery design. As laptop batteries continue to evolve, engineers will undoubtedly be able to provide more power, longer battery life, and reduced charge times to improve the portability of the laptop computer.