April 2007 – Battery Education

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
Copyright © BatteryEducation.com. All rights reserved.

Common Causes of Battery Failure – Part 2

All batteries will ultimately fail, stop working, and cease to operate, and or otherwise end their useful life. It is the reality of a consumable product. But sometimes batteries can warp, bubble, and even explode! Batteries can also fail due to incompatible designs or improperly selected hardware, and batteries can fail due to customer misuse or abuse.

According to the U.S. Consumer Product Safety Commission each year deaths, injuries and property damage from consumer product incidents cost U.S. taxpayers more than $700 billion annually. This cost includes over 15,000 different types of products that pose a risk of fire, electrical, chemical, or mechanical hazard or products that can injure children (cribs, toys, etc.). Batteries by their nature are 1 out of the 15,000 products the CPSC monitors because of the increased implementation of battery chemistries that pack higher energy in smaller packages. Batteries with lithium ion and lithium metal polymer chemistry are thinner, smaller, and lighter weight and contain more energy than traditional rechargeable batteries. These battery chemistries are excellent choices for small electronic devices that require higher capacities and specialized hardware to safeguard the battery from doing anything other than performing as expected within the device.

It is true that sometimes batteries can warp, bubble, and even explode. It is also true that batteries can fail. According to the U.S. Consumer Product Safety Commission there have been 339 battery-related overheating incidents tracked. 339 overheating cases sounds like a lot but when compared to the well over 100,000,000 battery related devices that have been bought by consumer since 2003 it represents a very small percentage (.000003) of all battery related devices on the market.

The reason why overheating occurs in batteries to the point of warping, bubbling, or exploding is due to one of the following reasons:

1. Improperly Selected Hardware – from the connector, the fuse, the charge and discharge FETs, the cell pack, the sense resistor, the primary and secondary protection ICs, the fuel-gauge IC, the thermistor, or the pc board

2. Uncontrolled Manufacturing Processes – including badly run production facilities which lead to cell short circuits, leaks, unreliable connections, sealing quality, mechanical weakness, and contamination.

Batteries can also fail due to customer misuse or abuse. Battery abuse can happen in a variety of ways however all types of battery abuse fall under one of the following categories including altitude simulation, thermal cycling, shock, external short circuit, impact, overcharge, forced discharge.

Finally batteries can fail due to consumer misuse. Misuse is different then abuse because battery abuse is intentional consumer disruption of the battery and battery misuse is unintentional consumer misuse of a battery. For example one common misuse of a battery is trying to use a camera battery rated and designed for a specific camera model, but used for an entirely different camera. It may sound funny but it has happened. Why because consumer’s think that just because the physical footprint, the voltage and the capacities are the same that the battery will work in multiple devices. This is a fallacy that happens frequently. To avoid this type of misuse, only use a battery that is specifically designed for the device model you have and do not battery swap.

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

Common Causes of Battery Failure – Part 1

All batteries will ultimately fail, stop working, and cease to operate, and or otherwise end their useful life. It is the reality of a consumable product. The cost to operate a replacement battery in your device, however, is relatively cheap so it is not a catastrophe when batteries stop working (although certainly an inconvenience). Yet when batteries do fail have you ever wondered why? In my next series I will look more closely at the common causes of battery failure including:

Batteries degrade and lose the ability to power a device
Batteries can warp or bubble
Batteries can explode
Batteries can have incompatible designs
Batteries can have improperly selected hardware
Batteries can be misused or abused

Battery degradation and power loss is the normal result of internal battery use. Technically battery degradation and power loss includes declining capacity, increasing internal resistance, elevated self-discharge, and premature voltage cut-off on discharge. I have written about each of these points in depth in another article at our Battery Education blog so please see that blog for more info, but what is important to get across is the fact that battery degradation and power loss is real! Much like gravity it exists regardless if we believe that it does not!

Furthermore battery degradation and power loss begins when one of the following occurs: when the battery is charged, when the battery is connected to a device (the device does not have to be turned on), when a battery is opened, or when a battery is chemically activated in any way. Any assumption you may have where a battery could still be considered new even after it was charged, connected to a device, been opened or chemically activated in any way is faulty. Why because inside the battery itself, a chemical reaction is produced the moment any of the aforementioned factors occur to begin electron flow. The chemical reaction is purposely designed to create electron flow (i.e. electricity). The electron flow is measured (or moves at speeds) in amperes, where 1 ampere is the flow of 62,000,000,000,000,000,000 electrons per second! Therefore once the chemical is activated and the flow of electrons takes place, even for a second, then the loss of power and battery degradation begins and there is no stopping it. Once battery degradation begins a battery is considered used and its natural life will deplete in a matter of time.

In part 2 of the series I will look at some of the other reasons why batteries fail including batteries that warp, bubble, explode, and batteries that have incompatible designs or improperly selected hardware.

Until next time, Dan Hagopian – www.batteryship.com
Copyright © BatteryEducation.com. All rights reserved.

Lithium ion Batteries Explode?

"A cellphone exploded in his living room last year, causing up to $100,000 in damages. Ortega and his family had to live in a trailer for a few months while their house in California was fixed" as reported in the Chicago Tribune back in 2006. Without question the impact that the fire had on this family is devastating but what is alarming about that fire is that through the fire and insurance investigation the cause was found to be due to a cell phone's lithium-ion battery failure and subsequent spontaneous combustion. What? How is that possible?

If you have a PDA, MP3, MP4, Laptop, Cell Phone, Smartphone, DVD player, or other electronic device then more likely then not the battery within your device is a high capacity smart battery pack (the chemical base being lithium ion). What is a high capacity smart battery pack? A high capacity smart battery pack is a complex battery system designed to power high tech consumer electronic products.

What differentiates smart batteries from standard batteries is the specialized hardware that provides calculated on demand current as well as predicted information.

This specialized hardware includes:

the connector
the fuse
the charge and discharge FETs
the cell pack
the sense resistor (RSENSE)
the primary and secondary protection ICs
the fuel-gauge IC
the thermistor
the pc board
the EEPROM

Each of these components working in concert allows electrical current to be created, controlled, and transferred to your individual electronic device on demand. Your battery in effect was purposely designed to be an energy dense power pack, which used within its properly designed purpose you can feel comfortable that your battery will not explode.

How can I say that you will “feel comfortable” because statistically your battery will not explode or even become defective! The report about the fire at the Ortega’s family house is one of 339 battery-related overheating incidents tracked by the Consumer Product Safety Commission since 2003. 339 overheating cases sounds like a lot but when compared to the well over 100,000,000 battery related devices that have been bought by consumer since 2003 it represents a very small percentage (.000003) of all battery related devices on the market.

However when smart batteries do explode, bubble, or warp the cause is due to an internal cell short that may cause the battery to overheat and explode, posing a potential hazard to consumers.

To isolate the ultimate cause of the short circuit a study of every aspect of the smart battery development and customer use must be considered including:

the specialized each of the hardware components
the cell design
the manufacturing processes
battery operation in extreme conditions
intentional battery abuse
unintentional abuse through the use of the battery in any device, product, and or in any conceivable manner other than what the battery was specifically designed to be used for and in

So yes it is possible to have high capacity smart battery pack explode and cause unexpected damage but as we have seen it is very unlikely considering the sheer quantity of lithium ion based batteries on the market.