What is Inside My iPod Battery?

The iPod is the fastest selling music player, selling over 100,000,000 iPods in the last 5 years! In fact just in the last 3 months of 2006 Apple sold 21 million iPod players. So it is no real surprise that 48% Apple’s $7.1 billion in revenue is comprised of iPod sales. Wow quite an accomplishment!

There is downside to this and that is the 100 million people who bought an iPod will at one point or another need to have their iPod battery replaced. The good news about replacing your iPod battery is that iPod battery replacements can be done relatively easily and cost right around $10. iPod battery replacements kits come with tools and you can find your iPod’s battery online or at retailer’s like www.Batteryship.com.

However since so many people have purchased an iPod and since the demand for iPod batteries is quite high it is my curiosity to take a quick peek inside the iPod battery to find out what inside makes it work!

All iPod Batteries will ultimately fail, stop working, and cease to operate, and or otherwise end their useful life. It is the nature of the ipod battery’s design. iPod battery’s are designed to power iPods for a specific amount of time and are also designed with a certain number of battery charge cycles before the battery will not hold enough charge to power your iPod.

But let’s take a step back for just a moment and look at how iPod batteries work and why? First of all iPod batteries are in effect a device that converts chemical energy into electrical energy. iPod batteries have two electrodes, an anode and a cathode and running in between the two nodes runs an electrical current caused primarily from a voltage differential between the anode and cathode. The voltage runs through a chemical called an electrolyte (which can be either liquid or solid).

The most common cause of battery failure is not really a battery failure but normal internal battery wear or use. This is technically classified as declining capacity, increasing internal resistance, elevated self-discharge, and or premature voltage cut-off on discharge. Of these normal battery wear and tear factors the most common is declining capaicty caused by the creation and transfer of chemical energy into electrical energy.

The chemical used to create electrical energy is lithium polymer. Lithium polymer is used as a battery anode material in dry cells and storage batteries. In fact the energy of some lithium-based cells can be five times greater than an equivalent-sized lead-acid cell and three times greater than alkaline batteries. Lithium cells often have a starting voltage of 3.0 V. This means that batteries can be lighter in weight, have lower per-use costs, and have higher and more stable voltage profiles. Some specific benefits of the lithium polymer chemical includes:

  • Lithium polymer chemistry uses a plastic-like electrolyte film that does not conduct electricity but allows ion exchange – electrically charged atoms or groups of atoms.
  • The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile geometry.
  • Cell thickness measures as little as one millimeter (0.039 inches).
  • Can be formed and shaped in any way imagined.
  • Lithium polymer offers a safer design – it is more resistant to overcharge; and is less prone to electrolyte leakage.

In addition to the iPod battery’s cell chemistry there are other specific hardware components that makeup the iPod battery and that together, working in concert with the battery cell that allow the iPod battery to push electrical current to your iPod.  These specialized hardware components include:

  • the iPod battery connector
  • the iPod battery fuse
  • the iPod battery charge and discharge FETs
  • the iPod battery cell pack
  • the iPod battery sense resistor
  • the iPod battery primary and secondary protection ICs
  • the iPod battery fuel-gauge IC
  • the iPod battery thermistor
  • the iPod battery pc board

Until next time, Dan Hagopian – www.batteryship.com
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