A+ Essentials Tutorial

2.0 Laptop and Portable Devices

2.1 Identify the fundamental principles of using laptops and portable devices

  • Power and electrical input devices (e.g. auto-switching and fixed-input power supplies, batteries)

Batteries are at the heart of laptop computers. They provide required power to operate a laptop when the laptop is not connected to the mains. There are primarily 3 types of batteries. These are:

  • Nickel Cadmium (NiCad) batteries
  • Nickel-Metal Hydride (NiMH) batteries, and
  • Li-Ion batteries (Lithium-ion)

NiCad batteries are hardly used these days in laptop computers. The following are the important properties of NiCad batteries:

  • Approximately two hours between charges.
  • Battery life decreases with each charge based on the 'memory effect'. As a result, it requires special care for charging of the NiCad batteries. It is recommended to let the NiCad battery to discharge completely before recharging it.
  • If the battery charges too long under unfavorable conditions (heat), it can explode.

Nickel-Metal Hydride (NiMH) batteries, unlike NiCad batteries do not suffer from "memory effect" to the extent as that of NiCad batteries. NiMH batteries last longer between charges than NiCad.

Li-ion batteries are being widely used in laptop computers. The advantages of Li-ion batteries are given below:

  • They are light weight and have very good energy-to-weight ratios,
  • They have long life spans, and can last for several hundreds (or even thousands) of re-charges.
  • Do not suffer from the 'memory effect'
  • These batteries can be charged randomly, and won't overheat if overcharged.

Typically, a laptop battery provides power for about 2 to 5 hours. If additional power is required, having a secondary battery is recommended. Laptop batteries last for about 1 to 5 years depending on the usage pattern.

lithium polymer batteries (Li-poly) are rechargeable batteries are also being used recently in laptops. The advantages of Li-poly include light weight, non-flammable substance, and longer life.

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