CompTIA A+® Certification All-In-One For Dummies®, 2nd Edition

7.2. Looking at Laptop Batteries

Laptop computers ship with a battery that can be removed or replaced at any time. The battery acts as the primary source of power for the laptop and all its components. The battery maintains its charge, or is recharged, by an AC adapter that plugs the laptop into the wall. The following sections outline everything you need to know about portable-computer batteries for the A+ exam.

7.2.1. Different types of batteries

It is important to understand that a laptop computer has two types of batteries: a main battery and a CMOS battery.

• Main battery: This battery supplies power to the laptop and its components. A laptop is designed to work with one of four types of main batteries:

  • Alkaline: Typically found in palmtop computers; the same battery type you find in calculators.

  • NiCad (nickel-cadmium): Typically found in laptop computers; very heavy. NiCad batteries, which are fairly inexpensive, typically need to be recharged after three or four hours of use.

  • Li-Ion (lithium-ion): Has a lot more battery charge time than a NiCad battery. A Li-Ion battery is also more expensive than a NiCad battery.

  • NiMH (nickel-metal hydride): Environmentally friendly because they do not contain toxic materials. They are the same weight as NiCad batteries but are more expensive and don't last as long as a Li-Ion battery.

• CMOS battery: Just like a desktop computer, a laptop computer has a CMOS battery that is responsible for holding a charge to CMOS RAM so the CMOS configuration ...