iPod Battery Technical Facts – Battery Education

Apple has shipped over 12 million iPods since their debut in October 2001. 12 million ipod users are now faced with an inevitable requirement which is: what do you do when your iPod battery dies?

Let's begin with the basics…

1. The ipod battery can be replaced by you. Go to www.Batteryship.com for detailed instructions. An ipod battery replacement can be done in just a few easy steps. iPod batteries begin at $9.99 for a 3rd gen and a mini. 4th gens, photos, video and the super capacity first gen are just a few dollars more.

2. iPod batteries last a long time, but like all batteries the longevity of a battery life depends on usage patterns. iPod batteries are made up of a lithium ion and or lithium polymer chemical compound. Etiher has a half life, a recharge cyle of between 300-500 charges. So depending on your particular usage pattern you could be using an ipod battery that is 3 years old or 18 months old.

3. iPod batteries like all batteries are rated by electrical specifications that include its volt and milliAmp hour rating. The most common voltage you will see for an iPod battery is 3.7 V. Volts as you may know is the electrical measure of energy potential. You can think of it as the pressure being exerted by all the electrons of an iPod battery's negative terminal as they try to move to the positive terminal.

Amps or A is an abbreviation of Ampere, a 19th century French scientist who was a pioneer in electricity research. Amps measure the volume of electrons passing through a wire in a one second. One Amp equals 6.25 x 1018 electrons per second.

Amp hours or Ah measures capacity. That is ultimately what we want to know about the ipod battery. Amp hours quantify how long a battery can 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 ipod batteries, a milliAmp hour (mAh) is most commonly used. Note that 1000 mAh is the same a 1 Ah. (Just as 1000mm equals 1 meter.) Note that Amp hours do not dictate the flow of electrons at any given moment. PDA batteries with a 1 Amp hour rating could deliver ½ Amp of current for 2 hours, or they could provide 2 Amps of current for ½ hour. The higher the mAh on the iPod battery the longer it will last and of course the more you will pay.

4. iPod Battery Meter. If you spend anytime in the Apple forums you will come across a common complaint that goes something like: ‘I charged my iPod for more than four hours and then when I turn it on, the battery meter says it only has about 25% (or less) charge. So I plugged it back in to charge overnight and it still says very little charge.’

The good news is is that your iPod is probably fine, fully charged, and ready to play for many uninterrupted hours. How is this possible when the ipod battery meter reads as if there is no battery charge whatsoever? Because the battery meter only approximates when you should recharge your ipod battery!

Some ipod battery meters will read empty but after about 20 minutes of use fills in the black bars to read more like the real capacity of the battery.

Since the meter is an approximation to indicate a need to recharge why then is my ipod powering down? If your battery is truly dead then buy another one and replace it yourself. If your battery is not dead then recalibrate the ipod battery meter. To re-calibrate, run the iPod until it shuts down. Recharge fully, using the AC power (mains) adapter, not a USB or Firewire port. Do not recharge until the iPod shuts down due to low battery again. This does not mean you have to leave it running for hours; use it normally, but hold off on any "top-off" recharges.

If recalibrating does not solve your problem, try resetting your iPod (method varies by model) and/or restoring it (be sure you have all of your music on your computer before doing this). Then repeat the full cycle of discharge and recharge.

5. With all that said your ipod battery will naturally degrade over time. How? Does it strictly have to do with my usage pattern? No not entirely. Contained within your ipod battery is a design and chemistry make-up that impacts your battery life far more than your usage activity and there is no amount of conditioning you can do to prevent the ultimate power loss of your pda battery.

For example we know that batteries are rated by their voltage, their mAh, and of course the chemicals contained within. These three technical facts about your battery give some insight into the actual life of (energy stored within) your battery.

But the length of time a pda battery can operate is not linear to the amount of energy stored in the battery. In fact their are four ongoing problems with all batteries that affect performance and the extended battery life of your ipod. They are: declining capacity, increasing internal resistance, elevated self-discharge, and premature voltage cut-off on discharge.

These are more complex issues that are beyond user control and are wholly contained within your ipod battery and within your device! As we will see these issues (declining capacity, increasing internal resistance, elevated self-discharge, and premature voltage cut-off on discharge) do more to cause an ipod battery Degradation and ipod power loss than your typical ipod owner could ever do.

Declining Capacity

Declining capacity is when the amount of charge a battery can hold gradually decreases due to usage, aging, and with some chemistry, lack of maintenance. iPod batteries are specified to deliver about 100 percent capacity when new but after usage and aging and lack of conditioning an ipod battery's capacity will drop. This is normal. If you are using an ipod battery (or any lithium-ion or lithium-polymer battery) when your battery's capacity reaches 60% to 70% the ipod battery will need to be replaced. Standard industry practice will warranty a battery above 80%. Below 80% typically means you have used the practical life of your ipod battery. Thus the threshold by which a battery can be returned under warranty is typically 80%.

Loss of Charge Acceptance

The loss of charge acceptance of the Li‑ion/polymer batteries is due to cell oxidation. Cell oxidation is when the cells of the battery lose their electrons. This is a normal process of the battery charge creation process. In fact every time you use your ipod battery a loss of charge acceptance occurs (the charge loss allows your battery to power your pda). Capacity loss is permanent. Li‑ion/polymer batteries cannot be restored with cycling or any other external means. The capacity loss is permanent because the metals used in the cells run for a specific time only and are being consumed during their service life.

Internal Resistance

Internal resistance, known as impedance, determines the performance and runtime of an ipod battery. It is a measure of opposition to a sinusoidal electric current. A high internal resistance curtails the flow of energy from the battery to an ipod device. The aging of the battery cells contributes, primarily, to the increase in resistance, not usage. Expect a typical life span of a Li‑ion battery to be one to three years, whether it is used or not. The internal resistance of the Li‑ion batteries cannot be improved with cycling (recharging). Cell oxidation, which causes high resistance, is non-reversible and is the ultimate cause of battery failure (energy may still be present in the battery, but it can no longer be delivered due to poor conductivity).

Elevated Self-Discharge

All batteries have an inherent self-discharge. The self-discharge on nickel-based batteries is 10 to 15 percent of its capacity in the first 24 hours after charge, followed by 10 to 15 percent every month thereafter. Li‑ion battery's self-discharges about five percent in the first 24 hours and one to two percent thereafter. At higher temperatures, the self-discharge on all battery chemistries increases. The self-discharge of a battery increases with age and usage. Once a battery exhibits high self-discharge, little can be done to reverse the effect.

Premature Voltage Cut-Off

Some ipods do not fully utilize the low-end voltage spectrum of an ipod battery. The ipod device itself cuts off before the designated end-of-discharge voltage is reached and battery power remains unused. For example, an ipod that is powered with a single-cell Li‑ion battery and is designed to cut-off at 3.7V may actually cut-off at 3.3V. Obviously the full potential of the battery and the device is lost (not utilized). Why? It could be something with elevated internal resistance and or using ipods at warm ambient temperatures. iPods that load the battery with current bursts are more receptive to premature voltage cut-off than analog equipment. High cut-off voltage is mostly equipment related, not battery.