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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:

  1. Approximately two hours between charges.

  2. 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.

  3.  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:

  1. They are light weight and have very good energy-to-weight ratios,

  2. They have long life spans, and can last for several hundreds (or even thousands) of re-charges.

  3. Do not suffer from the 'memory effect'

  4. 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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