iPod Battery Capacity

Posted on January 10, 2009 @ 3:16 am
by katie George

In my last article about the 24 Hour iPod Battery we discussed the true capability of such an iPod battery. Now however, I wanted to speak directly about the primary limitations of current battery technology that makes it difficult to truly get an iPod battery to last 24 hours given the multifaceted demands of consumers. Question: can an iPod battery power your iPod with 24 hours of music playback, a bright screen, cycling through your music files while all the while you are connecting external devices to your iPod? I do not believe so and the testimonies of thousands of iPod users support my belief. Now we must question why?

The reason why an ipod battery may not perform as specified when your average consumer is using their iPod is due to the limitations of the iPod batteries themselves, specifically the limitation of capacity. All iPod batteries including the (iPod 3rd Gen Battery, iPod Mini Battery, iPod Nano, Battery, iPod Video Battery, iPod Photo Battery, iPod 4th Gen Battery, iPod Shuffle, and iPod Classic Battery) have all been specifically designed for a battery rating that will perform a single function – to power their intended iPod Player. Battery Ratings will look very similar to:

IPOD MINI BATTERY

PART # EC003

3.7 VOLTS

550 mAh

The battery rating number that defines battery capacity in the example above is the 550 mAh (milli Amp hours). To understand, battery capacities, then we need to follow some basic electronic formulas. First however let’s define battery capacity as a reference to the total amount of energy stored within a battery. As I alluded to above battery capacity is rated in Ampere-hours (Ah).

Amp hours – or Ah – measures capacity. That is what we want to know about iPod Batteries – how long can it deliver a certain amount of charge before it runs out. As with all metric measurements, Amps can be divided into smaller (or larger) units by adding a prefix.

In the case of our example above a milliAmp hour (mAh) is most commonly used on iPod battery specs. Note that 1000 mAh is the same a 1 Ah. (Just as 1000mm equals 1 meter.) iPod batteries with a 1 Amp hour rating could deliver Amp of current for 2 hours, or they could provide 2 Amps of current for hour.

Ampere-hours (Ah) are the product of: Ah= Current X Hours to Total Discharge

The capacity is normally tested or compared with a time of 20 hours and at a temperature of 68F (20C).

Five Factors that Govern iPod Battery Capacity

Physical Size

the amount of capacity that can be stored in the casing of any battery depends on the volume and plate area of the actual battery. The more volume and plate area the more capacity you can actually store in a battery.

Temperature

capacity, energy store decreases as a battery gets colder. High temperatures also have an effect on all other aspects of your battery.

Cut off Voltage

To prevent damage to the battery and the device batteries have an internal mechanism that stops voltage called the cut-off voltage, which is tpically limited to 1.67V or 10V for a 12 Volt battery. Letting a battery self-discharge to zero destroys the battery.

Discharge rate

The rate of discharge, the rate at which a battery goes from a full charge to the cut off voltage measured in amperes. As the rate goes up, the capacity goes down.

Battery History

Deep discharging, excessive cycling, age, over charging, under charging, all reduce capacity. Note charging your battery 1 time will reduce capacity as much as 15%-20% depending on your battery’s chemistry.







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