iPhone Battery: Lithium Ion Vs Nickel Cadmium


Although Lithium Ion batteries are presently the norm for small portable devices like the iPhone, Nickel cadmium once ruled the mobile industry. So what makes the Lithium Ion battery better suited for the iPhone? The Lithium Ion battery has a much higher energy and power density than the Nickel Cadmium battery. This makes it ideal for small portable devices like the iPhone. A one cell nickel cadmium battery (NiCad for short) rates at 1.25 volts, whereas a one cell lithium ion battery rates at 3.6 volts. This means that it would take three NiCad cells connected in series to match the voltage rating of a Lithium Ion battery. This makes for a smaller and lighter weight battery which is ideal for the iPhone.

The Lithium-ion iPhone battery does not suffer from the infamous “memory affect” that has plagued NiCad batteries. The memory affect refers to the loss of capacity in a NiCad battery if the battery is repeatedly recharged without being allowed to fully discharge. When this happens, the battery seems to develop a memory for a smaller capacity. Fortunately, lithium-ion batteries do not suffer from the “memory effect”.

There are two major drawbacks to Lithium Ion batteries. First, lithium Ion batteries are fragile. Each Lithuim-Ion battery has a protection circuit built in to ensure safe operation. This protection circuit ensures that the voltage of the battery does not drop too low during discharge or peak too high during charging. Either voltage extreme can seriously damage the battery, making  this protection circuit a necessity.  Unfortunately, this protections circuit adds to the cost of the battery, and is a component that is susceptible to damage during impact. This makes the iPhone battery another fragile component in the iPhone that can be damaged during a drop or fall.

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