Battery Technology – Page 4 – Battery Education

Understanding Battery Life – Part 3

In my previous two installments of Understanding Battery Life we reviewed what battery life means; how battery life is measured; what factors determine and impact battery life; when do batteries begin to lose life; and how the internal battery design limits the overall capability of the battery. In part 3 of Understanding Battery Life I want to look at two aspects of battery usage that reduces battery life and they are: individual usage patterns and internal technical factors.

Individual Usage Patterns

Using your battery, even only once, will initiate battery degradation. Battery degradation the eventual loss of battery life begins when a user activates their battery (even only once). Furthermore once battery degradation begins there is no stopping it! Activating a battery can be done by charging a battery, connecting a battery to a device, opening a battery or any other actions that would chemically activate the battery! The reason why is because connecting a device for example to a battery creates a closed pathway through which current and the electrons flow through the device to the positive electrode. At the same time, an electrochemical reaction takes place inside the batteries to replenish the electrons. The effect is an electrochemical process that creates electrical energy.

Beyond that first cause in battery degradation there is very little a person can do to speed up the degradation except for the following: use the battery. That is a long-winded way of saying that if you use you will lose it!

I do not mean to say never use your battery – that is not the point – in fact how silly would it be to buy a battery and never use it! The fact of the matter is is that if you were to buy a battery and store it for say 5 years there is a good chance that it would not perform to spec for you because of its age.

If you buy a battery to use in your PDA or other mobile device then of course use it but be aware that by using your battery you are consuming its natural life. The battery was made to be used, to be consumed, and to power your device. So, what we as battery users complain about (short battery life) is not a necessarily a bad battery or a problematic battery (not including potential battery defects) but simply the designed life cycle of the battery.

Before we move to the internal technical factors that affect battery life it is well to point out that using your battery as the primary source for powering your device’s accessories will deplete your batteries capacity faster.

Internal Technical Factors

As pointed out above a battery over time degrades and eventually stops working, this is no surprise, but why this occurs is really a fascinating yet technical process. The reasons are complex issues that are way beyond user control and are wholly contained within your 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 Battery Degradation and Power Loss than your typical portable device 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’s a lack of maintenance. PDA batteries, for example, are specified to deliver about 100 percent capacity when new but after usage and aging a pda battery's capacity will drop. This is normal. If you are using a pda 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 battery a loss of charge acceptance occurs (the charge loss allows your battery to power your device by delivering electrical current to your device). 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 device. The aging of the battery cells contributes, primarily, to the increase in resistance, not usage. 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 in the following months of use. 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 devices like PDAs do not fully utilize the low-end voltage spectrum of a battery. The PDA device itself, for example cuts off before the designated end-of-discharge voltage is reached and battery power remains unused. For example, a PDA 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 fully utilized). Why? It could be something with elevated internal resistance and or PDA operations at warm ambient temperatures. PDAs 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.

Concluding Remarks

Now to conclude this 3 part series of Understanding Battery Life lets recap. In part 1 of the series we looked at look at what battery life means; how battery life is measured; what factors determine battery life; and finally when do batteries begin to lose life. In part 2 we looked at the internal design of batteries as their designed potential. Finally in this article we looked at how individual usage patterns and internal technical factors ultimately cause batteries to fail.

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

Understanding Battery Life – Part 2

In my previous installment of Understanding Battery Life we reviewed what battery life means; how battery life is measured; what factors determine and impact battery life; and finally when do batteries begin to lose life. In part 2 of Understanding Battery Life we will look at a battery’s internal design. A battery design is an important foundation on understanding battery life because of the fact that a battery is a consumable product (a batteries internal chemical is consumed upon activation) and that this consumption shortens the batteries life over time. Therefore to know what the maximum potential of a battery is (the starting point) before the battery is ever consumed is good because once a battery is used even once a battery begins a gradual degradation to the point of no longer being able to power a device (typically about 80% of the batteries capacity – less than 80% capacity is often times too low for a device to recognize the battery).

Initial Technical Ratings

The initial technical ratings of a battery are the specs (the technology) that define the battery. They are represented in most battery websites as the voltage, mAh (battery amperage/capacity), and battery chemistry. There is much that can be written, and has been written, about each of these factors individually; however, what is key to know about the battery’s technical specs is that they were all decided upon prior to the production of the battery and predestined to operate at specific power levels. Knowing this allows the buyer and seller of a battery to understand in advance how the battery will perform, thus disclosing upfront the capability of the battery.

A battery’s design is a compilation of several required parameters.

Battery Voltage
Battery Current
Battery Capacity
Battery Chemistry
Battery Temperature
Battery Protection Circuitry
Battery Smart Technology

Before we begin I want to note that Battery Protection Circuitry and Battery Smart Technology require minimal battery usage and although critical components of battery design it is not germane to battery life in great quantity and therefore will not be discussed in this article. I do have more info available on my blog which can be accessed from the links at the end of this article.

Battery Voltage

Critical to battery design is to know how much voltage is required? Voltage is the electrical measure of energy. To know the voltage requirements we need to know the upper and lower voltage range (nominal range).

Battery Current

The second critical key component to battery design is the battery’s current requirements. PDAs, MP3s and other portable devices, for the most part, utilize a constant power discharge to operate. This means that the amount of current will increase as the battery discharges electricity in order to maintain constant power. So we will need to ultimately know the maximum current required. This is important since knowing the max current requirement will influence the necessary protection of chemistry, circuitry, wire, and capacity amongst others. Again we must know the current requirement over the entire nominal voltage range of the battery including start-up currents, surges (intermittent transient pulses). One other important aspect to know about current requirements is the inert current drain of the device. Devices, even when powered down, require small amounts of current to power memory, switches and component leakage.

Battery Capacity

The third key component to know of internal battery design is the necessary battery capacity and runtime. This will define the overall physical size of the battery. Capacity and runtime is measured in Amperes.

Battery Chemistry

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. Lithium 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.

Battery Temperature

Ambient operational temperatures are also important because the internal heat of the battery compartment will dramatically affect the life of a battery. Usage and storage patterns are external effect that will also affect battery life and are the responsibility of a user (for example do not leave your device in a hot car with the windows rolled up, or take your device into a sauna).

In my next segment on Understanding Battery Life we will look at two other aspects of battery life and that is how individual usage and internal technical factors affect battery life.

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

Understanding Battery Life – Part 1

Mobile Computing users (people that use laptops, PDAs, and Smartphones) have one thing in common and that is they all use batteries to power their device. When considering a battery purchase most mobile computing users seek to find the answer to one of the following questions if not all (questions of which relate to the battery); the questions are: What does the life of the battery mean? How is battery life measured? What factors determine battery life? When does the battery begin to lose life? What factors shorten battery life? Is it better to buy a long life battery?

In part 1 of this article series I will look at the meaning of battery life; how battery life is measured; what factors determine battery life and finally when do batteries begin to lose life.

What does the life of the battery mean?

Battery life is the term that is often used when we speak about how long a battery can last (other terms we often use when speaking about battery life is battery capacity, battery runtime, battery mAh, battery milliamp rating, and battery playtime). All these terms speak about the life of the battery – how long the battery will power my PDA (or other mobile computing device) before I have to recharge.

How is battery life measured?

Battery life or is a measurement of capacity. What is Battery Capacity? Battery capacity is a reference to the total amount of energy stored within a battery. Battery capacity is rated in Ampere-hours (AH), which is the product of:

AH= Current X Hours to Total Discharge

What factors determine battery life?

The duration of the battery charge is governed by five factors including:

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, or energy stored, 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 typically 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.

When does the battery begin to lose life?

A battery begins to lose life the very moment is used. Let’s clarify a little more so that we are clear with what that technically means! A new battery is NOT: a battery that was charged, connected to a device, been opened from its wrapping or chemically activated in any way. Now be very careful with 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. Why?

Inside the battery itself is a system designed to produce a chemical reaction. The chemical reaction is designed for a single purpose: to create an electron flow (i.e. electricity) by which the device is powered. 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.

One note is that a battery only need be connected to a device or have its connectors touched to effectively create a closed circuit for the chemical to potentially activate, at which point of course the battery life will begin to deplete.

In part 2 of the article on Battery life we will look at the factors that shorten the battery life and whether it is better to buy a long life battery or a lesser capacity battery.

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.

Dissecting A Smart Battery – Part 3

In my first two articles of the series Dissecting A Smart Battery I discussed the specialized hardware contained in the smart battery including the connector, the fuse, the charge and discharge FETs, the cell pack, and the the sense resistor (RSENSE). In my final article of the series “Dissecting A Smart Battery” I would like discuss some of the other important hardware features contained in a smart battery.

As we have done in the first two parts of Dissecting A Smart Battery let’s recap the specialized hardware we have talked about. Included in the smart battery are the following specialized hardware:

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 or firmware for the fuel-gauge IC.

The Primary and Secondary Protection IC

Integrated Power Management Circuits protects against over-voltage, and under-voltage conditions and they maximize battery life between charges, minimize charging times, and improve overall battery life. Batteries for PDAs, MP3s, Digital Cameras, and Laptops for example have designed within them integrated power management circuits that insure that the deliverance of reliable power is properly managed. Without these power management integrated circuits even fine tuned handhelds will exhibit problems such as over-voltage, and under-voltage conditions. Incidentally, overcharging is potentially a very dangerous problem. Overcharging is the state of charging a battery beyond its electrical capacity, which can lead to a battery explosion, leakage, or irreversible damage to the battery. It may also cause damage to the charger or device in which the overcharged battery is later used.

An integrated circuit in general is a miniaturized electronic circuit. An electrical circuit is a network that has a closed loop, giving a return path for current. The goals of integrated circuits are multifaceted, for example when designing for signal processing integrated circuits apply a predefined operation on potential differences (measured in volts) or currents (measured in amperes). For batteries the use of integrated circuits with the goal of power management is integrated battery management which include voltage regulation and charging functions. Power management integrated circuits offer other key benefits as well including maximizing battery life between charges, minimize charging times, and improve battery life. The other critical aspect of power management integrated circuits is their functioning design to detect and monitor voltage levels in batteries. When certain parameter thresholds are exceeded or dangerous conditions exist, these “supervisory circuits” react through a programmable logic design to protect the monitored system and correct problems as programmed. Supervisory circuits are known by a variety of names, including battery monitors, power supply monitors, supply supervisory circuits and reset circuits. They perform critical functions including power-on-reset (POR) protection to ensure that processors always start at the same address during power-up. Without POR, even well-functioning systems can exhibit problems during power-up, power-down, over-voltage, and under-voltage conditions.

The Fuel-gauge IC

We may all be familiar with the battery charge indicator on our device. The little blinking light or bar meter indicator that let’s us know when we need to recharge our battery. But did you know that the calculation of the remaining battery capacity (power) is performed within the battery and that calculation is transmitted to the device from within the battery to the device through the connector. The calculation of remaining battery capacity is performed by the fuel-gauge integrated circuit. The fuel-gauge stores cell characteristics and application parameters used in the calculations within the on-chip EEPROM (which we will discuss shortly). The available capacity registers report a conservative estimate of the amount of charge that can be removed given the current temperature, discharge rate, stored charge and application parameters. Capacity estimation is then reported in mAh remaining and percentage of full charge.

The Thermistor

A thermistor is a temperature-sensing element. The thermistor is used to determine starting temperature and prevent charging if the battery temperature is too low or too high. The battery charger also uses the thermistor as an external thermal sense that provides input to temperature sense for the fuel gauge.

The PC Board

All the components that we have discussed throughout the series on Dissecting A Smart Battery (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) is at one point within the battery connected to a PC Board. The PC Board or printed circuit board is used to mechanically support and electrically connectthe aforementioned specialized hardware using conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate.

The EEPROM

Lastly I want to discuss the EEPROM, which stands for the electrically erasable programmable read only memory of the smart battery. It is a reference in effect to the user programmable integrated circuits memory devices which retain stored information in the absence of electrical power and in which the information may be altered electrically.

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

Dissecting A Smart Battery – Part 2

In part 1 of Dissecting A Smart Battery I mentioned that smart batteries have contained within them specialized hardware that when working in concert provides the power necessary to run a device such as a PDA, digital camera, or ipod player. Continuing the dissection of a smart battery this article of the series will look at the smart battery’s fuse, charge and discharge FETs , the cell pack, and the sense resistor (RSENSE) to discover what role they each play within the smart battery.

Before we begin let’s just recap some of the specialized hardware within the smart battery:

1. the connector
2. the fuse
3. the charge and discharge FETs
4. the cell pack
5. the sense resistor (RSENSE)
6. the primary and secondary protection ICs
7. the fuel-gauge IC
8. the thermistor
9. the pc board
10. the EEPROM or firmware for the fuel-gauge IC.
11. and the SMBus

The Smart Battery Fuse

When we discuss fuses in relation to electronics we are speaking directly of a fusible link that is responsible for protecting the device from over current. Fusible links have a metal wire that melts when heated to a predetermined electric current rating. When melted the electrical circuit is opened and thereby protecting the circuit from an over-current condition. The obvious concern here is the selection of the fuse – an improperly selected fuse will not protect from over-current conditions and the result will be a fire or damage due to a short circuits.

In a smart battery a typical fuse has three-terminal components that limit current flow based on the temperature, current, and or power across the heating wire. Besides temperature ratings other important factors when selecting the proper fuse to work with each smart battery is hold current, trip current, maximum battery voltage, and fuse size.

The Smart Battery’s FET (field effect transistor)

Smart batteries must have a series FET (field effect transistor) switch to open and protect the battery’s cells. A FET is a transistor that uses an electric field to control the conductivity of a particular 'channel' in a semiconductor material. FETs at times are used as voltage-controlled resistors. As such field effect transistors are chosen based upon their designed ability to dissipate on demand power.

The Smart Battery’s Cell Pack

The battery cell can be thought of as the holding area of the battery’s chemical. The battery cell pack is critical to the overall capability of the smart battery. Cell packs have to be designed and integrated based upon the vitals of the battery including chemistry type (Li-ion, Li-po, NICD, NIMH, etc.) cycle life, storage-capacity loss, shelf life, impedance, capacity at different rates of discharge and temperature, and mechanical and environmental requirements. It is critical to say the least.

The Smart Battery’s Sense Resistor

The final specialized hardware I want to review in this article is the sense resistor (RSENSE). In electronics, sense, is generally referred to the task of producing the correct voltage. Current not temperered will cause damage so sense resistors need to be integrated in order to control power and temperature.

In my next article on the dissection of a smart battery I will cover secondary protection ICs, the fuel-gauge IC, the thermistor, the pc board, and the EEPROM.

Dissecting A Smart Battery – Part 1

Smart Batteries – they are used in PDAs, MP3s, MP4s, Laptops, Cell Phones, Smartphones, DVD players, and other electronic devices. When we buy new batteries we want them to work. We really don’t care how they work just as long as the do. But since PDA Batteries are a unique interest for me and since pda batteries are smart batteries I’m going to dig a little deeper to discover what lies within PDA batteries. So follow along as I dissect a pda battery to learn what it is made of!

Contained within a smart battery is specialized hardware. Hardware that has a specific purpose: to deliver calculated and on demand current as well as predicted information.

This specialized hardware includes:

But what are each of these components and what do they do? Let’s find out?

The connector is a device that joins electric circuits together. Most battery packs require more than one connector. The main battery connector is both the mechanical and electrical part that interfaces the battery to the PDA or other electronic device. If you have ever installed a battery in your PDA then you probably have plugged your battery in by plugging/snapping in the main battery connector to the device’s PC board. Features that have to be considered when selecting a connector of a particular battery is operating temperature (range/limits) since high capacity batteries discharge excessive heat – having a connector that can withstand such temperature extremes will prevent a short circuit. Connectors also have to proper pin assignments so that current and performance capacity can be met and short-circuit thresholds are predetermined. Pin orientation within the connector has to be designed in order to fit the device. If it doesn’t well you won’t be able to connect the battery to the PDA or other electronic device. Finally the connectors has to be handle time-varying current therefore the ratio of the phasor voltage across the element to the phasor current through the element (otherwise known as impedance) has to be preset or else expect connector to not function in the way it was supposed to!

In the next article of this series I will cover the smart battery’s fuse, charge and discharge FETs , the cell pack, and the sense resistor (RSENSE). The article after the next will cover the primary and secondary protection ICs, the fuel-gauge IC, the thermistor, the pc board, the EEPROM, and the SMBus.

What is Inside A Smart Battery?

If you have a PDA, MP3, MP4, Laptop, Cell Phone, Smartphone, DVD players, or other electronic device then more likely then not the battery within your device is a high capacity smart battery pack. What is a high capacity smart battery pack? A high capacity smart battery pack is a complex battery system designed to power high tech electronic devices.

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:

In addition to the above advanced chip components, I mentioned that information flows from these components to another advanced component of the smart battery and that is the smart battery’s System Management Bus (SMBus) control – a two-wire interface through which simple power-related chips can communicate with rest of the system. Typically a SMBus uses I2C as its backbone so that multiple chips can be connected to the bus. The SMBus allows a device to transfer manufacturer information, transfers model or part number to and from the device and battery, save its state for a suspend event, report different types of errors, accept control parameters and return its status.

All in all the smart battery is a highly specialized battery that functions within its intended design. Used outside its design the smart battery really won’t work too well!

Batteries – One Size Does Not Fit All

I have a Palm Zire 72 and a Palm m505 PDA. If I buy a Palm Zire 72 Battery that is 3.7 volts can I plug it into a Palm m505 and have that battery power both devices as needed?

In a nut shell the question above seeks to ascertain if all 3.7 volt batteries are the same?

The quick answer is no – all 3.7 volt batteries are “not” the same – and a battery specifically designed for a Palm Zire 72 will not be compatible with a Palm m505 PDA.

Let me explain.

It is true that all batteries share similar components and share common electrical measurements. But just because all batteries have some common components and measurements does not mean at all that you can interchange batteries with various devices even if the technical ratings are the same. Note that a component is something tangible and a measurement is intangible – a result of an action contained within the battery system.

Quick Review: What is a Battery and how does it work?

A battery in its most basic definition is a device that converts chemical energy into electrical energy. Batteries have two electrodes, an anode (the negative end) and a cathode (the positive end). Collectively the anode and the cathode are called the electrodes. What is positve and what is the negative terminal? It would be great to simply say that the anode is negative and the cathode is positive, however, that is not always the case. Somtimes the opposite is true depending on battery technology.

In between the battery’s two electrodes 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). This battery consisting of two electrodes is called a voltaic cell.

Electrical measurements that can be gleaned from battery operations inclued the measurements of:

Volts – or V – is the electrical measure of battery’s energy potential. For example you can think of energy potential as the pressure being exerted by all the electrons of a PDA Battery’s negative terminal as they try to move to the positive terminal.

Amps – or A – which is a measure of the volume of electrons passing through a wire in a one second. One Amp equals 6.25 x 1018 electrons per second.

Watts: Volts x Amps = Watts. Watts are important because a watt represents the electrical energy spent by a battery (power generator) and used by an electrical device. Watts in effect is the measure of the amount of work done by certain amperage (amount) of electric current at a certain pressure or voltage.

Now beyond that basic review of the common components and measurements of batteries begins the radical differences between batteries. If you have a PDA, MP3, MP4, Laptop, Cell Phone, Smartphone, DVD players, or other electronic devices then more likely then not the battery within your device is a high capacity smart battery pack.

What is a high capacity smart battery pack? A high capacity smart battery pack is a complex battery system designed to power high tech electronic devices.

To construct a smart battery the battery manufacturer must carefully plan the internal battery design environment by considering the:

• design parameters
• current requirements
• capacity and runtime requirements
• temperature requirements
• safety requirements
• ambient operational/non-operational temperatures

As a design for a smart battery pack is considered manufacturers must evaluate the differences in components in relation to their design environment. Proper component evaluation and specification selection based on the intended application will determine the ultimate performance of the entire battery.

To give you an example of why smart batteries are carefully designed consider a PDA that when turned on explodes (don’t think it can’t happen) thankfully it occurs very rarely. To be a more reassuring the US Consumer Product Safety Commission has noted that 339 battery-related overheating incidents have occurred since 2003. Since conservative estimates puts the sale and use of devices containing smart batteries in excess of 100 million battery related devices during the same period makes the 339 incidents reported by the Saftey Commission at .000003% (a very small percent) of all battery related devices on the market. What is preventing more battery related fires -reliable and safe design under worst-case conditions is especially critical when designing with lithium based batteries. Specifically over-voltage and under-voltage of the cells and over-current of the battery pack.

Now with all this said I can tell you again, almost emphatically, that not all batteries are the same. From battery to battery the internal design will be different depending on the device the battery was specifically built to work within.