Laptop Batteries Key Terms

Learn more about your li-ion laptop batteries

The original laptop batteries were made of nickel cadmium (NiCd). They were quickly replaced with NiHM or nickel metal hydride batteries. Both types of batteries suffered from a memory effect issue that required batteries to be fully discharged before recharging. Lithium-ion or li-ion batteries solved this problem, as well as being lighter weight and more environmentally friendly. Since li-ion batteries come with every laptop sold, familiarizing yourself with the terminology is important.

 

Lithium-ion, or li-ion

Lithium-ion batteries are often used in consumer electronics, including laptop batteries. They are powered by a lithium ion which moves between an anode and a cathode. Their popularity is due to their high energy density, rapid charging and slow loss of charge when not in use.
Try: Learn the inner workings of lithium-ion batteries at HowStuffWorks.

Energy density, or energy-to-weight ratio

Energy density or energy-to-weight ratio is a way of measuring the capacity of a battery. Lithium-ion batteries can hold 150 watt-hours of electricity per kilogram of battery. This is far superior to the older NiHM batteries, which could only hold a maximum of 100 watt-hours per kilogram.
Try: Compare the characteristics of different battery types, including their energy density, at AllAboutBatteries.com. Look up various scientific terms, including energy density, at Wolfram Research.

Milliampere-hours (mAh)

Although battery life can be measured in watt-hours, laptop battery life is more commonly measured in milliampere-hours or mAh. If a battery was a car, voltage would be how much gas is used, and mAh would tell the size of the gas tank.
Try: Learn what the mAh rating of your battery means at Starbatteries.com.

Cells

Laptop battery packs consist of multiple cells that are wired together in series. Each individual cell contributes to the overall volume of a battery.
Try: For the more adventurous, learn how to rebuild a li-ion battery from the cells up at Electronics-lab.com. The Panasonic website explains why li-ion cells aren't usually purchased directly from distributors.

Smart battery

A smart li-ion battery has self-discharge abilities granted by a voltage monitoring circuit. Without the circuit, a li-ion battery will experience a permanent loss of capacity. Lithium-ion batteries slowly decline in capacity over their lifetime of two or three years, but smart batteries extend that life.
Try: HP laptops use lithium-ion batteries with Smart battery technology.

Protection circuit

Lithium-ion batteries are capable of bursting into fire if overcharged or overheated and can be damaged if discharged below a certain voltage. Because of this, all li-ion batteries come with a protection circuit that shuts down the battery if it is discharged below or charged above certain limits.
Try: Learn more about protection circuits at BatteryUniversity.com. Battery Facts has a diagram of a typical protection circuit on their site.

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