How Long will My iPod Video Play?

By Dan Hagopian

Is it true the ipod video (fifth gen ipod) will hold a charge for up to 20 hours? Let's see!

First of all the legal fine print on Apple's iPod page explicitly refers to the 60 Gb iPod Video only being able to play (hold a charge in the battery) up to 20 hours. I would bet with all of its legal woes on the horizon this claim from Apple that the "new iPod boasts up to 20 hours of battery life, five hours more than before" is legally valid in a controlled test environment.

But consumers don't live in a controlled test environment, which is why I would not be surprised if your new ipod video (fifth gen ipod) will NOT hold a charge for 20 hours.

The legal keyword here is "up to". So even if the battery lasts an hour Apple is legally covered!

On the new 5th Generation iPod battery performance has to now be measured with: music playback, photo playback, and video playback (on iPod screen or through a TV).

Apple claims that the new 30GB iPod will play music for 14 hours, photo and music slideshows for 3 hours, and iPod on-screen video for 2 hours. In a iLounge test they found that the new iPod Video played music for 15 hours and 30 minutes, photo slideshows for 2 hours and 32 minutes, on-iPod video for 2 hours and 10 minutes, and iPod-to-TV video for 3 hours and 10 minutes.

Apple also claims that the new 60GB iPod will play music for 20 hours, photo and music slideshows for 4 hours, and video for 3 hours. Again in In a iLounge test they found that the new iPod Video played music for 19 hours, 50 minutes, but exceeded Apple’s photo and video claims, playing a music photo slideshow for 4 hours, 47 minutes, iPod-screen video for 3 hours, 23 minutes, and on-TV video for a hefty 5 hours and 24 minutes.

But everyone may experience slightly different battery life play times. For example here is a situation from a user quoted from the Apple fourms:

"It is clear that when you use the click wheel a lot, you assume that your battery life gets smaller quickly. I had a problem with my ipod 5G 30Gb battery life : Firstly, I charged it (as soon as i received it) until the plug icon appeared on the screen (1h 30mn) . Then I listened music 'til it was fully discharged. The battery life was approximately 8hrs. Then, this battery life decreased to 5hrs last day. I called Applecare ; the guy told me to restore my ipod, then to let it discharge fully, and to refill it for 4 hrs even if the plug icon appear on the ipod screen. After that, I synchronized ipod to itunes and let it play allnight long to see the battery life now. It played music with default settings during 15hrs 'til it shut down. These are the Apple specifications for that ipod. My problem wasn't the battery, but the battery life calibration, which has not been done as it should."

The reality is all batteries including batteries designed specifically for iPods (regardless of generation) have a certain amount of capacity and once the full amount of the capacity has been used then your battery will stop working. This is the normal function of battery designs.

In fact consider this taken from Apple iPod Warranty Care: "Your one year warranty includes replacement coverage for a defective battery. You can extend your coverage to two years with AppleCare Protection Plan. During the second year, Apple will replace the battery if it drops below 50% of its original capacity. If it is out of warranty, Apple offers a battery replacement for $59, plus $6.95 shipping. Apple disposes your battery in an environmentally-friendly manner." So basically Apple is correctly telling you that your battery will die with time and use. No questions about that; and that Apple is telling you that your battery replacement plan will cost you a total of $59, plus $6.95 shipping. Folks: Before you pay that amount go to BatteryShip.com and replace your battery for far less!

The admittance by Apple that your ipod battery will dies is based on real limitations of the battery's internal design.

Before I discuss the limitations of the battery's internal design there are external limitations that reduce the playtime of your iPod Video - personal usage. Yes running your iPod Video, even under normal usage, will reduce your iPod Video's playtime. Personal usage has way too many variables to describe here but in short - the way you use your iPod will determine, in part, how long your iPod battery will last.

Now on to the techincal internal battery design limitations...

Battery Capacity

The more the better (and more expensive), however there are a number technical limiations that force the iPod Video battery to cap off at where it is at.

A key requirement to know is the necessary battery capacity and runtime. This will define the overall physical size of the battery. Apple chose to ignore this rule and due to its desire to make the iPod as small as possible forced battery manufacturers to comply to the physical space limitations first instead of the runtime specifications. It traded capacity for space.

Capacity and runtime is measured in Amperes. 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. The electrical current is measured in amperes, where 1 ampere is the flow of 62,000,000,000,000,000,000 electrons per second!

Amp hours - or Ah - measures capacity. Amp hours is what is ultimately important to consumers as it is the capacity or amp hours that tells us how long we can expect a battery to deliver a charge before it runs out. As with all metric measurements, Amps can be divided into smaller (or larger) units by adding a prefix, in this case by adding an "m" to the amp hour we are renaming the amp hour to milli amp hour: mAh; (1Ah = 1000 mAh).

In addition when we consider the design capacity we must determine the chemical needed to insure that the necessary runtime will be met. Lithium is used because of its electrochemical properties. Lithium is part of the alkali family of metals a group of highly reactive metals. Li reacts steadily with water. In addition the per unit volume of lithium packs the greatest energy density and weight available for this grouping of reactive metals.

iPod batteries that have a chemistry design of either lithium ion or lithium polymer will over time regardless of usage will experience power loss to the point of non-functioning. In fact 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 ipod battery.

Here is another situation from a user quoted from the Apple fourms:

"Recently, my iPod battery didnt seem to be lasting anywheres near 18 hours, so I tested it, and after about 4 hours the meter was still 3/4 of the way full, so i did the math and figure it was fine. My question is though, is it normal for the iPod to loose quite a bit of battery power without turning it on, because i lost about 1/8 of the life without using it for the past two days."

The reason why this occurred is due to elevated self-discharge as we will see below but let's first continue on our discussion.

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 an ipod battery can operate is not linear to the amount of energy stored in the battery.

In fact their are four ongoing problems with your ipod battery that affects 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 ipod itself! 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 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 a pda 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 pda 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 a 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 ipod). 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 a 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 a pda 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/polymer 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, a 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 iPod operations 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.

So to sum up will your iPod Video play up to 20 hours - yes. Will it play for 20 hours straight - more than likely - no. So what do you do - accept it or don't buy the iPod.