Author: BatteryEducation

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.

Buying Batteries: How To Buy A Battery?

We buy batteries first because we need them and then secondly we buy them at the cheapest possible price. Considering that 75% of the world’s batteries are made by Chinese manufacturers, regardless of brand then it makes sense to buy the cheapest battery available knowing full well that I will have to buy another replacement battery sooner rather than later. But who cares as long as it is cheap (buy cheap – buy often)! However if I wanted to make a better battery purchase what considerations would I have to factor? In other words how do I buy a battery that gives me the best value for my dollar?

Swap-meet shopping (that brings back childhood memories) is the ultimate in buying cheap gems. But can I buy a battery at swap-meet prices and be satisfied because I bought the best battery, the longest lasting battery, the best price battery? Buying a battery is not as easy as it first may seem. Most people believe that if you bought an iPod Nano, for example, you would need to buy your battery replacement directly from Apple. Savvy battery shoppers know there is a cheaper and better way of getting their battery replacement. Incidentally Apple does not manufacturer batteries directly – they outsource them to Chinese manufacturers and then affix their own private label to the batteries. Take the private label off and their just like the ones sold by other retailers.

Now before you go out and by your next battery replacement you do need to know a few things including:

  • My Device’s Battery
  • Battery Chemistry, Battery Voltage, and Battery Capacity
  • Battery Price

My Device’s Battery

Your device, be it a PDA, Laptop, iPod, MP3, Camera, Barcode Scanner, Twoway Radio (or any other device) will have a battery that was manufactured  specifically for it. Typically the battery part number will be listed directly on the battery label. The battery part number is often times different from the device’s model number. For example a 167648 battery part number fits the iPAQ 3600 PDA. Interestingly enough the 167648 also fits the IPAQ H3600, IPAQ H3135, IPAQ H3150, IPAQ H3630, H3635, IPAQ H3650, IPAQ H3660, IPAQ H3670, IPAQ H3760, and the IPAQ H3765. In addition to this the 167648 also has alternative or compatible part numbers that is associated with including: COMPAQ DLP 305590, COMPAQ 305590, COMPAQ 3S619-001. This type of numbering sequences within the realm of electronics is quite common as each number though relating to the same device is different due to batch manufacturing, marketing procedures and business management processes. But the same battery, in this case, the 167648 fits with all the numbers above.

In order to buy the right type of battery for your device you must first and foremost know your deice model number. That is actually the best. So if you know you have an iPAQ 3600 then the best way to locate the iPAQ H3630 battery is to search with that model number. If you know your device’s battery part number then that is even better, but at the bare minimum you need to know that you need a battery for an IPAQ H3630. Once you have that information then you can consider the battery’s chemistry, the battery’s voltage, and the battery’s capacity.

Battery Chemistry, Battery Voltage, and Battery Capacity

Next when buying your replacement battery you need to know the battery’s technical ratings. The technical ratings include the battery’s chemistry, the battery’s voltage, and the battery’s capacity. This will get slightly technical but we will go slow and keep the tech lingo at a surface level only.

To begin with a battery is a device that converts chemical energy into electrical energy. The basic design of a battery includes two electrodes, an anode and a cathode. 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. To convert chemical energy into electrical energy the battery must contain the chemical base. Common battery chemicals in use today are: Nickel-cadmium batteries, Nickel-metal-hydride batteries, Lead-acid batteries, Lithium-ion batteries, Lithium-ion-polymer batteries, Reusable Alkaline batteries. Choosing your battery’s chemistry is typically not an option since your device’s design was specific to one chemical or another. But it is still good to know what type of chemical is used in your battery.

The other feature that is also not optional to change is your battery’s voltage. Battery voltage is an electrical measure of energy potential. Voltage can be thought of as the amount of "pressure" of electrons that pass from a negative connector to a positive connector. Voltage can also be defined as the Electrical Potential difference – a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force. In the fields of electronics the electrical potential difference is the amount of work per charge needed to move electric charge from the second point to the first, or equivalently, the amount of work that unit charge flowing from the first point to the second can perform. Actually voltage is strictly a mathematical product of V= I x R; where V=Voltage, I=Current, R=Resistance. Another words a measurement.

Voltage depending on the type of battery can be measured and is listed on the battery at 3.6V, 2.7V, 7.4V, 14.4V for example. What makes buying a battery difficult, especially when trying to match up the replacement battery’s voltage with your current battery’s voltage is the measurement of nominal voltage. FYI there are a number of different types of voltage including: Float Voltage, Nominal Voltage, Charge Voltage, and Discharge Voltage.

In the case of nominal voltage a device that requires a 3.7V battery will work with a 3.6V battery. But a 12V battery would not do the trick. Another words small voltage deviations are ok – just not big ones.

The final technical rating requirement you will need to know is the battery’s 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 Amperes (commonly "Amps"). Thinking about this another way battery capacity of AH is a measurement of the quantity of the number of electrons passing through a given wire per second. In a single Ampere there are 62,000,000,000,000,000,000 electrons per second! More Amps, More electrons, More current! More is better! So if your existing battery is say 1000 mAh (1 Ah) and your replacement battery 1800 mAh (1.8 Ah) then the 1800 mAh battery offers a higher battery capacity which means your device will run longer. The bigger the capacity the longer your device will run.

Battery Prices

When buying your battery replacement price is something to consider. When considering your price you need to match and compare the technical ratings, the retailers warranty, the retailer’s level of service, the overall value of the retailer. Reading retailers testimonials are good to do as well. Factor in shipping costs and the availability at the retailer for your battery replacement.

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

Recycling Seal Lead Acid Batteries

Seal Lead Acid batteries have a long history of being 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. Indeed lead-acid batteries are an environmental success story of our time. More than 97 percent of all battery lead is recycled. This is 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. How are lead acid batteries recycled and reused in brand new batteries. What is the recycling process of lead acid batteries? Let’s find out.

Lead acid batteries are transported via trucks to recycling centers. Once at recycling centers batteries are broken apart in a hammermill, which is a machine that hammers the battery into pieces. At its most basic level a hammermill is a steel drum that contains a cross-shaped rotor. On the rotors are mounted hammers that pivot when the rotor spins. When the rotor spins the hammers swing and when the battery fed into the drum the batteries broken into pieces.

Once broken the batteries components are separated into 3 categories:

Plastics

Broken pieces of polypropylene plastic are collected, washed, blown dry and sent to a plastic recycler. At the plastic recycler the broken pieces of polypropylene are melted at the plastics correct melting point (or glass transition temperature (Tg), which is the temperature at which a polymer changes from hard and brittle to soft and pliable). Then the molten plastic is passed through a machine called an extruder that shapes the molten plastic into pellets which are then sold back to battery manufacturers to begin the new battery’s manufacturing process.

Lead

The lead acid batteries lead grids, lead oxide and other lead parts are cleaned and then heated to 621.5 degrees Fahrenheit – leads melting point. After the lead reaches its melting point the molten lead is poured into ingot molds. The leads impurities, known as dross, floats to the top and subsequently scraped away and then the ingots sit there thill they are cooled. After cooling the ingots are sold back to manufacturers for use in new lead plate production.

Electrolyte – Sulfuric Acid

Spent battery acid can be neutralized using an industrial grade baking soda compound. After neutralization the acid turns into water, treated, cleaned to meet clean water standards, and then released into the public sewer system. Or another option would be to convert spent battery acid into sodium sulfate, which is used in laundry detergent, glass and textile manufacturing. Considering that a typical battery recycling plant recovers 10,000 tons of lead, about 4000 tons of sulphuric acid, and can produce about 6000 tons of sodium sulphate – there is definitely some merit into this conversion process.

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
Copyright © BatteryEducation.com. All rights reserved.

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
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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
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