Rechargeable Batteries Can Only Be Charged 300-500 Times – Part 1

A charge-discharge cycle involves draining or using your battery to where there is for all intensive purposes, no charge left, and then subsequently charging the battery with a power adapter to 100% capacity. This process of charging and discharging (charge cycling) can only be done between 300-500 times. The question that we want to address is why? Why is it that lithium batteries can only be charged less than 500 times? Why does a battery over time degrade and eventually stops working and what if any does the reduction of the battery's active material and subsequent causes of chemical changes effect battery degredation?

In my last article I explained how that the simple task of charging a battery is far from easy. For example I examined how a battery, a device that converts chemical energy into electrical energy, has two internal electrodes – an anode (the negative end) and a cathode (the positive end), and that between the two electrodes runs an electrical current caused primarily from a voltage differential between the anode and cathode. We learned that batteries are made up of plates of reactive chemicals (Li-ion, Li-po, NIMH, NICD) separated by an electrolyte barrier (which can be either be in a liquid, solid, or gel state), and subsequently polarized so all the electrons gather on one side. We looked at how electricity is produced through a chemical change inside the battery system. We also learned that batteries require electricity to produce electricity and that the introduction of electricity involves replenishing the electrons in the lithium chemical and this chemical process is called intercalation, which, is the joining of a molecule between two other molecules. So without question charging a battery is anything but easy.

One other thing we learned that has helped shape this article is that a charge-discharge cycle involves draining or using your battery to where there is for all intensive purposes, no charge left, and then subsequently charging the battery with a power adapter to 100% capacity. This process of charging and discharging (charge cycling) can only be done between 300-500 times. The question that we want to address is why is it that lithium batteries can only be charged less than 500 times?

Battery Degradation and Power Loss

A battery over time degrades and eventually stops working, this is no surprise, but why this occurs is really a fascinating yet technical process. These reasons are complex issues that are way beyond user control and are wholly contained within your battery and within your device! These technical processes are a result of the reduction of the battery’s active material and subsequent causes of chemical changes. The chemical changes that I write of are:

Declining capacity  – when the amount of charge a battery can hold gradually decreases due to usage, aging, and with some chemistry, lack of maintenance.

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 discharge 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, 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).

All batteries have an inherent elevated 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 chemistry 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 utilized).

Now that we have looked at how the chemical changes in a battery effect battery degradation and power loss and contribute to the eventual total loss of the battery I will, in my next article, discuss why battery degradation occurs in the first place.

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

How Many Times Can I Charge My Battery?

500 million lithium batteries are in use today. A very big number indeed and the chances that you are one of them are quite high. You could have a laptop, PDA, MP3 or even a cell-phone, all of which more likely than not has a lithium ion or a lithium polymer chemical based battery system. If so then one question that you will have eventually is how many times will I be able to charge the battery before it is effectively dead? Is it 300 times, 400 times, or 500 times? The answer is between 300-500 times.

500 million lithium batteries are in use today. A very big number indeed and the chances that you are one of them are quite high. You could have a laptop, PDA, MP3 or even a cell-phone, all of which more likely than not has a lithium ion or a lithium polymer chemical based battery system. If so then one question that you will have eventually is how many times will I be able to charge the battery before it is effectively dead?  Is it 300 times, 400 times, or 500 times? The answer is between 300-500 times.

But what does that answer mean? As this article will explain the charge cycle is quite complex and involves the replenishment of electrons. In order to get a beginning understanding of what actually is taking place during a charge and discharge cycle we need to understand: what a battery is, how it works, what it produces, and finally what happens when you charge and discharge.

What is a Battery?

As I have written in other articles a battery 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 be in a liquid, solid, or gel state). This battery consisting of two electrodes is called a voltaic cell. Most batteries today are advance forms of the voltaic cells and have additional technology packed into the battery casing to support the overall system and its connected  device. These controls include the connector, fuse, charge and discharge FETs, the cell pack, the sense resistor (RSENSE), the primary and secondary protection ICs, the fuel-gauge IC thermistor, pc board, and the EEPROM or firmware for the fuel-gauge IC.

How Does a Battery Work and What Does It Produce?

We know that the result of a battery converting chemical energy into electrical energy allows us to turn on our laptop, PDA, MP3 or even a cell-phone. But how does the conversion process take place? As stated above the batteries we use today are variable changes of the voltaic pile. In addition to the controls I listed above today’s batteries are made up of plates of reactive chemicals (Li-ion, Li-po, NIMH, NICD) separated by an electrolyte barrier (which can be either be in a liquid, solid, or gel state), and subsequently polarized so all the electrons gather on one side. The system was designed to separate both positive and negative electrons. Then after separation an electron exchange occurs and a current of electron flow moves electrons to and from the anode and cathode. Simultaneously an electrochemical reaction takes place inside the battery to replenish the electrons. The effect is a chemical process that creates electrochemical energy.

Now the electrochemical reaction that is taking place is a chemical change that is necessary in order to create electricity. One factor that needs to be understood is that electricity is the flow of electrons. Specifically, electricity is a property of subatomic particles which couples to electromagnetic fields and causes attractive and repulsive forces between them. This repulsive force between the subatomic particles creates an electric current; the flow of electric charge transports energy from one atom to another. This electrical current is measured in amperes, where 1 ampere is the flow of 62,000,000,000,000,000,000 electrons per second!

Electricity therefore is a created energy source. All electricity in fact is a created source made or converted from coal, natural gas, oil, nuclear power, wind, heat, sun, water, biomass and or other chemicals. In batteries today electricity is created by two chemicals in a solution for example: {a Solution of Lithium hexaflourophosphate (LiPF6) – a mixture of Organic Solvents: [Ethylene Carbonate (EC) + DiEthyl Carbonate (DMC) + DiEthyl Carbonate (DEC) + Ethyl Acetate (EA)]}

Charging and Discharging Your Battery

Charge cycling a battery means to completely discharge (or drain) a battery’s created electricity to where there is a charge of less than a 1% capacity remaining. At this point the power to the device will cease and your device will power off. Then after the power is off you recharge the battery to 100% capacity using a power adapter either from a wall socket for example. Regardless of how you charge the battery that process of discharging and charging represents one complete charge cycle.

I noted above that an electrochemical reaction takes place inside the battery to replenish the electrons. The effect is a chemical process that creates electrical energy (electrochemical energy). Lithium is used, amongst other chemicals, as a battery anode material due to its high electrochemical potential. 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.

Charging lithium can be thought of as the introduction of ions or movement of chemistry. To move the lithium chemistry (lithium-ion, lithium polymer, lithium iron phosphate, etc) you have to have a minimum voltage applied to the lithium. Most battery cells are charged to 4.2 volts with relative safe workings at about 3.8 volts. Anything less than 3.3 volts will not be enough to charge or move the chemistry. One thing to note here is that volts are an algorithmic measurement of current. So in a sense to create current through your battery you have to introduce current into your battery’s lithium .

Introducing current into your lithium is called intercalation. Intercalation is the joining of a molecule (or molecule group) between two other molecules (or groups). When it comes to charging your battery you are in effect pushing ions in and out of solid lithium compounds. These compounds have minuscule spaces between the crystallized planes for small ions, such as lithium, to insert themselves from a force of current. In effect ionizing the lithium loads the crystal planes to the point where they are forced into a current flow. The current flow is then channeled back and forth from anode to cathode and thereby creating an electrical flow to power on your device. Again this can done 300-500 times. In my next article we will look at why batteries have limited charge cycles.

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

Lithium Ion Batteries Are Sensitive to Heat

Over 15 million students are enrolled in fall college classes across the United States according to a US Census Bureau study in 2004. Using that number as a base it can be projected that the fall of 2008 should see a slight up-tick in college enrollees. Interestingly the number of college students that are going to college with laptop computers have increased by 28% compared to 42% of college students in 2004. This means that nearly 70% of enrolled students are using laptop computers. In real numbers that represents 10,500,000 laptop computers.

Now listen up college students – your laptop battery is more than likely a Li-ion battery and if it is then there is a natural tendency to keep your laptop plugged into a wall outlet when you are close to one. You may also find that you are actually “plugged” in to a wall outlet more than you are not and there in lies a problem. When your laptop is plugged into a wall outlet your battery heats up big time and heat and lithium do not mix well together.

Hold on! You have to charge battery. Yes that is true, but you do not have to keep your laptop plugged into a wall outlet for the entire school year! But won’t that reduce my battery life if I’m constantly powered from the battery?

Your battery will diminish in capacity – the ability to charge and power your laptop. That is a fact and a natural consequence of batteries today. This diminishing power performance is called battery degradation and power loss. I have written on this topic before and you can read about it on my blog but on a high level a battery over time degrades and eventually stops working, this is no surprise, and it occurs due to the following technical processes: declining capacity, increasing internal resistance, elevated self-discharge, premature voltage cut-off on discharge.

So should you constantly keep your battery charged at 100% capacity? No you should not. Why? To answer that question let’s look at what is occurring when you charge a battery. When charging your battery you are forcing electrical current into a battery cell from a charger. The force of electrical current causes temperature increases.

Now it is true that contained within your laptop battery are integrated power management circuits that are designed to protect against over-voltage and under-voltage conditions that increase heat in the battery but one factor of how well a battery is being protected during a charge depends on the ratio of the heating rate versus the dissipation rate. If the heating rate is higher then the dissipation rate then thermal runaway will occur (leaking, smoking, gas venting, flames).

Now don’t go into panic mode since the integrated circuits are really good at keeping the heating rate lower than the dissipation rate and you are in extremely minimal danger of thermal runaway occurring.  But the practice of keeping your battery charged continuously can negatively affect your battery’s longevity. So charge your battery and then run your laptop on battery power until you have to charge it again.

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

Digital Memory Effect on Batteries

Have you ever wished that you had an extra 20 minutes of battery life left in your portable device? How about an hour! A real difference exists between the life of your battery and the displayed battery charge meter on your device? How big of a difference? How often does it occur? Why does it occur? What can be done? In this article we will look at these questions and learn about what you can do to reduce power waste and maximize your battery life.

Help my batteries dead and I can’t power on!  The cultural expression of a “dead battery” is the habitual practice that occurs in place of the more technically appropriate reason of 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. Declining capacity is inherent in the ultimate design of a battery – due to limitations with technology -  you could consider it the natural side effect or wear and tear of the battery (other wear and tear aspects includes increasing internal resistance, elevated self-discharge, and premature voltage cut-off on discharge).

But there is a real problem with declining capacity and that is the capacity that is measured by your device and displayed to you on your battery charge meter is not always correct. Your device could be reading a digital imprint instead of the actual hardware that transmits capacity back to the device. The digital imprint (digital memory effect) causes your device to use the incorrect reading as its base measuring capacity. This action results in forcing a premature voltage cut-off on discharge, which is when a device does not fully utilize the low-end voltage spectrum leaving unused power in the battery. Another fancy word for leaving unused power in your battery is “waste”. Let’s find out what can you can do reduce power waste and maximize battery life by looking at:

  • What is the Digital Memory Effect?
  • What Can Be Done To Correct the Digital Memory Effect?

What is the Digital Memory Effect?

The digital memory effect is a failure mode (see my article series on Battery Failure Mode and Effects Analysis) whose effect results in the transmission of improper calibrations of the battery’s fuel gauge to a device.

Now let’s unpack that answer to discover its real meaning. 

First we must distinguish between memory effect and digital memory effect. A memory effect is the concept that was derived from cyclic memory. Cyclic memory is the thought that a battery could “remember” how much energy was used up on previous discharges. Cyclic memory only affects nickel-cadmium batteries.  Since we are strictly focused on lithium ion and lithium polymer chemistries I don’t want to get into the chemical change that occurs at the molecular level (crystal growth and concealment of active electrolyte material) but simply will state that the memory effect is the common term people use when there is a voltage depression problem with a battery. Voltage depression causes the inaccurate measurement and subsequent unnecessary charging of a battery.

Inaccurate measurement of capacity is the only similarity between memory effect and digital memory effect since digital memory effect has nothing to do with molecular chemical change. Instead digital memory effect is the improper calibration and reading by the device and the battery’s fuel gauge.

More specifically, inside a battery (or more correctly stated smart battery) is specialized hardware that provides calculated on demand current as well as predicted information to and from the device and 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 or firmware for the fuel-gauge IC.

In addition to the above advanced chip components information flows from these components to the device through the System Management Bus (SMBus) control – a two-wire interface through which simple power-related chips can communicate with rest of the system. 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.

Now with that back drop of information we can address the digital memory effect. As alluded to above the fuel gauge integrated circuitry calculates remaining battery capacity (power) and transmits that calculation to the device operating system through the SMBus connectors. The fuel gauge also stores present cell capacity characteristics and application parameters within the on-chip EEPROM (electrically erasable programmable read only memory). The calculated capacity registers 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 capacity remaining and percentage of full charge to the device.

But sometimes the reported information is not correct. The incorrect report of capacity remaining and percentage is caused by the fuel gauge not recalibrating its circuitry automatically. The digital memory effect is then a false reading for maximum capacity and thus results in lower battery run time.

What Can Be Done To Correct the Digital Memory Effect?

To correct the digital memory effect and properly recalibrate the fuel gauge circuitry simply do a full cycle discharge/recharge every several dozen charges. There is no real hard number. If you have never done a complete discharge then do so now. By performing a complete discharge you will cause a manual reset of the fuel gauge circuitry and will eliminate the digital memory effect.

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

Battery Safety Guidelines

Have you ever held a battery before? Did you know that a battery though relatively safe can act and operate like a mini bomb? Don’t worry your next battery more than likely will not explode on you if handled correctly. In fact in excess of 100 million battery related devices have been bought by consumer since 2003 (that is a conservative number). So the 339 incidents report by the Consumer Product Safety Commission represent .000003 (a very small percent) of all battery related devices on the market. So the likelihood of your next battery exploding is highly unlikely. However if you ever use a battery or plan on using a battery you should know how to handle and maintain basic battery safety guidelines.  In fact as a general rule of thumb battery packs have to be:

  • Batteries have to be stored safely
  • Batteries have to be charged correctly
  • Batteries have to be protected from unexpected damage
  • Batteries have to be handled safely

Batteries have to be stored safely

Batteries can be stored both indoors and outdoors as long as batteries are kept in cool conditions without direct sun light on the battery or battery storage box or container. Batteries should be stored in a dry location with low humidity, and a temperature range of –20°C to +30°C. Batteries can be stored for a long time however the longer the storage time is the faster the acceleration of the battery’s self-discharge which can lead to the deactivation of the batteries. To minimize the deactivation effect, store battery packs in a temperature range of +10°C to +30°C.  Also if a battery has been stored for a long period of time please note that the deactivation of the batteries may have led to decreased capacity. To recover batteries in this state simply repeat several cycles of fully charging and discharging. Also when storing packs for more than 6 months be sure to charge the battery at least once every 6 months to prevent leakage and deterioration in performance due to self-discharging.

Batteries have to be charged correctly

Batteries must be charged correctly. This means you need to charge your battery with a charger that has the specified voltage and current to correctly charge your battery. You should never attempt reverse charging, since charging a battery with the polarity reversed can cause a reversal in battery polarity, causing gas pressure inside of the battery to rise, which can lead to leakage of the batteries in the pack. Also avoid overcharging. Repeated overcharging can lead to deterioration in pack performance and the battery pack may get over heated. Also note that battery charging efficiency drops at temperatures above 40°C.

Batteries have to be protected from unexpected damage

Batteries, understandably should have some basic protection everyday damage. For example the battery terminals [(+) connector and/or (-) connector] should never be touched or connected to metal wires, necklaces, or chains. Batteries should not be dropped since dropping a  battery will cause the battery to malfunction or puncture. Also batteries should not be twisted or bent. Since any such forced movement will cause the battery to fail.

Batteries have to be handled safely

Furthermore batteries should never be disassembled. Batteries should never be used if an abnormality is detected such as foul odor, deformation, discoloration, bubbling and so on. Battery cells, such as Li-ion or Li-polymer cells should never be reused after removing from the chemistry from the battery pack. Also never touch any liquid coming out of the battery if there is an electrolyte leakage. Also batteries and water should never mix. Once water or moisture gets onto the battery, the battery has the potential to malfunction. In addition never store batteries in hot temperatures 140 degrees Fahrenheit or more. Furthermore do not put batteries into a fire, do not crush, puncture, or nail a battery. Finally never solder directly onto the battery casing or terminals.

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

Battery Failure Mode and Effects Analysis Part 3

In part 1 and 2 of the article series Battery Failure Mode and Effects Analysis we identified that a battery mode and effects analysis is a procedure for identifying and understanding potential failure modes in a battery system. We found that a battery mode and effects analysis contains four main steps or phases including:

  • Battery Mode Pre-work – explained in part 1
  • Battery Failure Severity – explained in part 2
  • Battery Failure Occurrence – explained in part 2
  • Battery Failure Detection

Now in part 3 of Battery Failure Mode and Effects Analysis I will address Battery Failure Detection and wrap with a summary of the article series.

Battery Failure Detection

Battery failure detection is method of inspection that is used when examining failure modes within a battery system. The method of detecting a battery failure begins with a review of existing system controls that are designed to prevent failure modes. Next comes testing, analysis, and monitoring failures. The purpose of which is to understand why a particular mode is failing. When a failure mode occurs, a detection number that represents the likelihood of detecting a failure mode, is subsequently assigned, and after a series of detections the total number of detection numbers are collected and added together to give a total score of battery failure modes; the lower the detection number is the better the overall battery system design schema.

Remember as in all of the three previous articles it has been noted that the purpose of a battery failure mode and effects analysis is to identify and understand potential failure modes in a battery system. The reason why this is so important is that customers, who provide cash-flow (the lifeblood of a company), must be satisfied. Satisfaction as it relates to batteries is the lowest possible cost while still maintaining the best possible battery product. Thus insuring the lowest possible detection number is critically important to insuring the maximum potential of a company involved in battery design, manufacturing and sales.

Battery Failure Mode and Effects Analysis Summary

Over the last three articles we looked a battery failure mode and effects analysis and learned how helpful this procedure is for analyzing potential failure modes in a battery system. Discovering potential defects in a battery design or manufacturing process is extremely helpful in controlling business expenses and losses as well helping to make more efficient the overall battery development project. A battery failure mode and effects analysis is also closely associated with six sigma methodologies and is a proactive tool for reducing errors, reducing expenses, and increasing profits. Now you could probably find a failure mode and analysis software online or you can build a custom template (that would be my preference) to suit your individual needs. Regardless, simply integrating a battery failure mode and effects analysis into your battery design process, battery manufacturing process, and battery sales process is a valuable tool in helping providing the best possible product to customers.

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

Battery Failure Mode and Effects Analysis Part 2

A battery mode and effects analysis is a procedure for identifying and understanding potential failure modes in the internal system of a battery. But how do you perform this procedure? In part 1 of this article series we look at the valuable pre-work that lays the ground work for identifying potential problems. In this next portion of the series we learn how to measure failed battery's mode severity and occurrence. To recap we found that a mode and effects analysis contains four main steps or phases including:

  • Battery Mode Pre-work – explained in part 1
  • Battery Failure Severity
  • Battery Failure Occurrence
  • Battery Failure Detection

Battery Failure Severity

Identifying battery failure severity includes an assessment and subsequent severity rating or score of all failed modes and their effects – both direct and indirect. To assess all potential malfunctioning modes in a battery system it is important to notate the battery's designed performance specifications. Knowing upfront how the battery should perform under designed specifications proves to be extremely helpful when determining every potential botched mode.

Potential mode malfunctions could include degradation, warping, incompatibility, misuse or abuse, erroneous algorithms, excessive voltage, improper operating conditions, faulty or weak internal system hardware etc. In addition failing modes have a direct and indirect relationship with an effect. For example the causality of a failed mode could be an electrical short-circuiting, corrosion or deformation.

The causality thus is what needs to be rated with regard to severity. More to the point, each failed mode has a failing effect on the function of the battery system. The effect is user perceived. If the battery user experiences "x" failure effect then the severity of the effect can be rated from 1 to 10 (a severity rating of 10 is the most extreme and is typically reserved for injury to a user).

One note on severity ratings is that there could be a consequential effect of the failed battery on interfacing systems. In another words an improperly performing battery may or may not be wholly contained within its own system. Depending on the severity of the malfunction the effect may go well beyond the battery's system. Conversely and just as important in identifying the cause of the failed battery is the direct and indirect effect of the interfacing system – whereas the interfacing system could be the root cause of a malfunctioning battery.

Battery Failure Mode Occurrence

The next phase of a mode and effects analysis is the occurrence pattern of the failed battery. Simply enough – the occurrence pattern assesses how frequent a failure occurs. Since batteries that fail are looked upon as weak design it is important to know the type, effect, and frequency of a failed battery. This way a design change can be made and money can be saved.

To measure a frequency of a failing mode you can review similar product failure occurrences, processes, or datasheet (if previous examples are available) can be used. Or if previous examples are not available then a trial and error process could be conducted. Why is this important – because if a failed battery is ever rated in the 8-10 zone then you can bet someone is losing life, limb, and or property somewhere. And obviously you would not want to many occurrences at that level of severity.

In part 3 of our article series Battery Failure Mode and Effects Analysis I will wrap up with the final phase which is Battery Failure Detection.

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

Battery Failure Mode and Effects Analysis Part 1

Have you ever wondered “why” your battery stops working? All batteries fail at one point or another and more importantly all batteries fail – due to different reasons. Specifically, two identical batteries that come from the same manufacturing batch, with the same identical voltage, capacity, and chemistry fail (or stop working) at different times. Why? To understand why batteries fail I will walk through the steps of a battery mode and effects analysis to discover modes of battery failure and the effects of the battery failure.

A battery mode and effects analysis is a procedure for identifying and understanding potential failure modes in a battery system. A battery mode and effects analysis contains four main steps or phases:

  • Battery Mode Pre-work
  • Battery Failure Severity
  • Battery Failure Occurrence
  • Battery Failure Detection

Battery Mode Pre-work

The Battery Mode Pre-work is an essential preliminary component to a battery mode and effects analysis and often times the one component that gets the least attention. It is a way of “starting smart” in the identification of battery failures. As an example, battery failures are often caused by shared interfaces. If an engineer, focused on a single facet of the battery’s micro or macro system, glosses over the effectiveness and efficiency of interfacing components when designing, compiling and assembling a battery’s system, then the failure rate and severity could dramatically increase regardless of how “correct” the engineer’s portion of the system is working. A really good case study on shared interface failures is the battery interface with the device’s operating system. The inefficiency of the operating system’s software in a device can under or over utilize the maximum capacity and voltage of a battery and thus subsequently degrade the battery faster then normal. At the consumer level they would just say the battery is bad or “sucks” when in fact it is the device’s software that is the culprit of faster than normal battery degradation.

Thus careful attention to a battery’s mode pre-work is well advised. Battery mode pre-work includes a complete and detailed description of the battery’s system, the battery’s function, the battery’s intended uses, and the probable unintended uses.

In part 2 of Battery Failure Mode and Effects Analysis I will address Battery Failure Severity and Battery Failure Occurrence.

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

Seal Lead Acid Batteries

Seal Lead Acid batteries have a long history of industrial use and date back to 1859. Lead acid batteries are used commonly in a multitude of industries including aviation, telecommunications, medical equipment, electronics, solar power, garden equipment, and automobile engines. In addition lead acid batteries are surprisingly one of the most environmentally friendly resources on the free market and are actually “greener” then soft drink cans, beer cans, newspapers, glass bottles, and tires. What exactly are lead acid batteries? Who uses them? And what are the real benefits of seal lead acid batteries?

What Are Seal Lead Acid Batteries Made of?

All lead acid batteries contain a chemical soup, ingredient compounds that react with lead sheets inside the body of the battery. For example one possible chemical ingredient list could include an electrolyte sulfuric acid (H2SO4), lead (Pb), lead oxide (PbO), lead sulfate (PbSO4), arsenic (As), calcium (Ca), and tin (Sn). Besides the chemical ingredients the battery body includes a high integrity terminal seal, resealable safety vent, a plastic internal container, positive and negative plates, lead grids, a highly retentive separator, all surrounded by a metal can enclosure.

One final component of a seal lead acid battery are the lead wires. Lead wires are typically stranded copper wires with insulation (red and black color coding). Lead wires lengths vary depending upon application. Standard lengths are about 9 inches, but again you can have shorter or longer lengths depending on your specific need. The ends of the leads are dipped in wax, which, is removed prior to use. Wire gauges (the diameter of the wire) are based on battery type and the American Wire Gauge specifications which are calculated with the formula D(AWG)=.005·92((36-AWG)/39) inch. For example:

  • D lead acid batteries could have 18 AWG
  • DT lead acid batteries could have 16 AWG
  • X lead acid batteries could have 16 AWG
  • E lead acid batteries could have 14 AWG
  • J lead acid batteries could have 14 AWG
  • B C lead acid batteries could have 12 AWG

One final note and that is lead wires can be soldered or come as braided copper straps if your application is vibration proned so that your leads would not come lose even under the most extreme environment.

What Are the Benefits of Seal Lead Acid Batteries?

Benefits of Seal Lead Acid Batteries especially those that have a lead-tin chemical base include:

  • Power Density — per unit weight, lead-tin products offers greater volumetric power.
  • Cycle Life – seal lead-tin batteries can have between 200-300 cycle-lifes.
  • Float Life – seal lead batteries can have a standby life of up to 15 years.
  • High Stable Voltage Delivery – low internal resistance allows for high stable voltage delivery; and a flat discharge allows for a fast discharge and recharge period which allows for greater application flexibility.
  • Temperature Range – is substantial. Typically seal lead acid batteries can operate as low as -60 degrees Celsius to +80 degrees Celcius and as an additional component also has an Atmospheric pressure range of – Vacuum to 8 atmospheres.
  • Rugged Construction – seal lead acid batteries have a strong external construction which means they have a high tolerance to shock and vibration.

What I also find simply fascinating is that seal lead acid batteries are an environmental success! Lead-acid batteries are the environmental success story of our time. More than 97 percent of all battery lead is recycled. This ia almost twice as much as aluminum soft drink and beer cans, newspapers, glass bottles and tires. In fact lead-acid batteries are the most recycled consumer product of our time.

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

What Materials Are Used To Make A Battery?

One billion batteries! Considering that we are a mobile society it does make sense that batteries are ubiquitous and the likelihood that you yourself have bought a battery before is quite high. Indeed the buying of batteries is a daily and regular occurrence. Conservatively speaking billions of batteries are bought each year. Out of my own curiosity and perhaps your own, I have thought about the vast amount of raw material that must be used to go into the making of a battery, and thought that I would share my findings.

Building a battery requires certain components and their associated raw materials which ultimately affect the price of batteries. The basic battery components include:

• The Battery Casing
• The Battery Chemistry
• The Battery’s electrolyte
• The Battery’s specialized hardware

The Battery Casing

The purpose of a battery casing is for enclosing and hermetically sealing a battery body which converts chemical energy into electrical energy in order to generate current to power an electronic device. Battery casing is manufactured in layers. The casing layers are developed from various raw materials and can include one or two, for example, polyethylene terephthalate layers, a polymer layer, and a polypropylene layer. Another example may be a casing with layers of carbonized plastic.

The Battery Chemistry

As noted above a battery is a device that converts chemical energy into electrical energy. To convert chemical energy into electrical energy the battery must contain the chemical base to allow conversion to occur. Types of common chemicals used in batteries on the market today are:

1. Nickel-cadmium batteries were first invented in 1899 and are a mature energy type with moderate energy density. Nickel-cadmium is used in batteries where long life, high discharge rate and extended temperature range is important. The main applications for nickel-cadium batteries are for two-way radios, biomedical equipment and power tools.

2. Nickel-metal-hydride batteries has a higher energy density compared to nickel-cadmium but at the expense of severely reduced cycle life. Applications include mobile phones and laptop computers not much needs to be talked about here since nickel-metal hydride batteries are not too commonly used anymore for your portable consumer.

3. Lead-acid batteries are the most economical portable power source for larger power applications where weight is of little concern. Lead-acid is the preferred choice for hospital equipment, wheelchairs, emergency lighting and UPS systems. The most common place where most of us find lead-acid batteries are in our personal vehicles. Automobiles, light trucks and vans almost always use a 12-volt, six cell, and negative grounded, lead acid automotive battery used to start gasoline or diesel engines. You will find lead-acid batteries in motorcycles, boats, snowmobiles, jet skis, farm tractors, lawn and garden tractors, SUVs, etc.

4. Lithium-ion batteries are widely used today since they offer significant benefits for portable consumers. Lithium is the lightest of all metals, it has the greatest electrochemical potential, and the largest energy density for its weight.The load characteristics of lithium are reasonably good in terms of discharge.The high cell voltage of 3.6 volts allows battery pack designs with only one cell versus three (less costly and compact). Lithium ion is a low maintenance battery with no memory and no scheduled cycling being required to prolong the battery's life. And finally Lithium-ion cells cause little harm when disposed.

5. Lithium-ion-polymer batteries are very similar to lithium-ion, but with an even far more slimmer geometry and simple packaging but of course with a higher cost per watt/hours. Main applications are cell phones and PDAs. The lithium-polymer differentiates itself from the conventional battery in the type of electrolyte used (a plastic-like film that does not conduct electricity but allows ion exchange – electrically charged atoms or groups of atoms). The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolyte. 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). Lithium polymer can be formed and shaped in any way imagined. Commercial lithium-polymer batteries are hybrid cells that contain gelled electrolyte to enhance conductivity. Gelled electrolyte added to the lithium-ion-polymer replaces the porous separator. The gelled electrolyte is simply added to enhance ion conductivity. Capacity is slightly less than that of the standard lithium-ion battery. Lithium-ion-polymer finds its market niche in wafer-thin geometries, such as PDA batteries. Lithium ion also offers improved safety – more resistant to overcharge; less chance for electrolyte leakage.

6. Reusable Alkaline – Its limited cycle life and low load current is compensated by long shelf life, making this battery ideal for portable entertainment devices and flashlights. Great batteries if you want to store on demand power for a emergencies.

The Battery’s Electrolyte

The actual conversion of chemical energy into electrochemical energy can only be done if an electron flow passes between two electrodes, an anode (the negative end) and a cathode (the positive end). The battery’s electrical current (electron flow) runs from one electrode to another through a conductive chemical called an electrolyte solution.

A basic electrolyte solution is a chemical compound (salt, acid, or base) that when dissolved in a solvent forms a solution that becomes an ionic conductor of electricity. In the battery cell the electrolyte solution is the conducting medium in which the flow of electric current between the electrodes takes place by the migrating electrons.

Since the 1970 it has been known that adding salts to polymers can enable the polymer to conduct lithium ion. This material thus can serve as an electrolyte in lithium batteries. Lithium solid polymer electrolyte batteries, when given full measure to the capacity for miniaturization of a fully solid state battery can have the highest specific energy and specific power of any rechargeable technology.

Some of the benefits that lithium solid polymer electrolytes include:

• ease of manufacturing
• immunity from leakage
• suppression of lithium dendrite formation
• elimination of volatile organic liquids
• mechanical flexibility.

The Battery’s Specialized Hardware

A battery consists of more then the casing, electrolyte, and the chemical. It requires some very specialized hardware, especially when we speak directly about a smart battery. Your typical smart battery may have a multitude of hardware componenets that when working in tandem not merely create electrical power and transfer it to a particular device but additionally sends data packets of information to the device so that the device can actually gauge the battery (at least in theory). Some of the common hardware features in a smart battery include:

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.

Until next time – Dan Hagopian www.BatteryShip.com
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