Cell phone batteries demystified

By Aloysius Choong
16/05/2002

If you are always on the move, a vehicle charger like this will keep your phone going.

Different flavors

Nickel cadmium
Nickel cadmium batteries are the cheapest, but hold a number of drawbacks. The technology has been around for many years, and such batteries have the smallest capacity.

You may have heard of the term "memory effect", also called voltage depression. NiCad batteries are prone to this problem, meaning that if you do not fully discharge the battery before you recharge each time, gradually the capacity of the battery will be reduced.

Another key issue with NiCad batteries is that the chemicals contained within are not environmentally friendly. It is difficult to dispose of cadmium-rich waste. Because of these disadvantages, we hardly see NiCad batteries in mobile phones anymore.

Nickel-metal hydride
Nickel-metal hydride batteries are much more common than NiCad ones these days, especially in lower-end mobile phones. That's partly because NiMH batteries have a larger capacity.

NiMH batteries are also non-toxic and are therefore more environmentally friendly. They also are less susceptible to memory effect. NiMH batteries only need to be fully discharged every week or two.

A disadvantage of NiMH batteries is that its durability is suspect. After a few hundred charge cycles, the battery may not be able to give the extra power needed for making calls.

Lithium-ion
Lithium-ion batteries have excellent capacity for their size and weight. They also do not have many of the problems that other battery types do. Like NiMH, Li-ion ones are non-toxic. Li-ion batteries are also said to be immune to memory effect.

Li-ion batteries are also less durable than other battery types. As they are more costly than NiMH ones, Li-ion batteries are most commonly used in higher-end phones.

Lithium-polymer
Lithium-polymer batteries are very similar to Lithium-ion ones. The difference between the two is that Li-Po batteries can be molded in different shapes, unlike Li-ion which is confined to a rectangular shape. Being a recent technology, Lithium-polymer batteries are the most expensive of the battery types listed here.

Battery types explained