Miscellaneous/Ask Isidor 051212
Isidor Buchmann, the founder and CEO of Cadex Electronics Inc., in Vancouver, BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. Award winning author of many articles and books on batteries, Mr. Buchmann has delivered technical papers around the world. Cadex Electronics is a manufacturer of advanced battery chargers, battery analyzers and PC software. He can be reached by E Mail at: [email protected]
The future battery
Compared to other advancements, the progress has only been moderate. A battery holds relatively little power, is bulky, heavy, and has a short life span. Battery power is also very expensive. The smaller the battery, the higher the cost-per-Watt becomes. Yet humanity depends on the battery as an important portable power source.
The speed at which portability and mobility is advancing hinges much on the battery. So important is this energy source that engineers design handheld devices around the battery, rather than the other way around. With each incremental improvement of the battery, the doors swing open for new products and enhanced applications. It is the virtue of the battery that provides us with the freedom of being disconnected from home and office. The better the battery gets, the greater our mobility and freedom will become.
The improved runtime of new portable devices is not credited to higher energy-dense batteries alone. Much improvement has been made in reducing the power consumption of portable devices. Some of these advancements are, however, counteracted with the demand for faster processing time of laptop computers and quicker data transmission of cellular phones.
The electric vehicle has failed to become the accepted mode of transportation because of the battery. Short distances between recharging and a limited service life of the battery are to blame. Consumers demand a battery that will last for the life of the vehicle but battery manufactures are hesitant to provide the mandatory 8 to 10-year warranty.
Battery research is proceeding at a steady pace. The average annual gain in capacity is typically 6%. In comparison, microelectronics has done much better.
Gordon Moore made his famous observation in 1965 when he predicted that the growth in the number of transistors per integrated circuit would double every two years. Through Intel’s relentless technological advances, Moore’s Law (www.intel.com/research/silicon/moreslaw.htm) has been maintained and is being carried into the 21st century. Such advances would shrink a heavy-duty car battery to size of a coin, had this been possible for batteries.
Will the fuel cell replace the battery?
More than 2,000 organizations throughout the world are actively involved in fuel cell development. There is a good reason for this — it’s a great concept. And yet, since its invention in 1839 by Sir William Grove, the fuel cell has made little impact in our daily lives so far. In comparison, the internal combustion engine, a development that began at about the same time as the fuel cell, has far broader use.
The fuel cell was used in the Gemini space program in the 1960s, followed by trial runs in buses and cars during the 1990s. One of the main obstacles is high energy cost. The cost-per-Watt. must be reduced by a factor of ten to become competitive with other sources, such as the internal combustion engine.
The improvements of the fuel cell during the last 10 years have been moderate. Attempts to mass-produce have failed, even though four public fuel cell companies in North American have raised over a billion dollars in public stock offerings from 1999 through 2001. Unlike other investments that paid early dividends from product sale, returns on fuel cells lie years ahead. Today, 45% of the money raised by the four fuel cell companies is lost.
Fuel cell advocates are promoting a technology that is intended to replace the battery but the opposite is occurring in mobile and portable applications. The fuel cell has a defined power band in which it operates efficiently. Outside this band, the fuel cell loses effectiveness. Sluggish start-up when cold and limited loading are other limitations. Until resolved, the fuel cell will serve as the generator to charge the batteries that do the driving.
There are also problems with the longevity of the stack. The membranes, the core of the engine, degenerate too quickly. The replacement of the stack is a major expense. Until these problems can be resolved, the fuel cell will be reserved for specialty applications, such as providing power (and water) for space vehicles and submarines. Here, no combustion is possible and toxic exhausts cannot be tolerated.
Experts believe that the fuel cell, as we know it today, would only be implemented in vehicles if the supply of fossil fuel is exhausted or if mandated by law due to environmental concerns. Comments have been made that the fuel cell may never become the engine of choice for mass-produced cars. This is in line with the notion that the steam engine of the 1800s was never intended to propel airplanes.
Continuous improvements in the fuel cell are being made but the results are slower than with other technologies. Eventually, the fuel cell will find important niche markets that dwell outside the domain of the polluting internal combustion engine. Should a major break-through occur and the fuel cell does become an alternative power source, the world would become a cleaner place and humanity would be thankful for it.
What is the ultimate miracle battery?
The ultimate miracle battery is nowhere in sight and the battery remains the ‘weak link’ for the foreseeable future. As long as the battery is based on an electro-chemical process, limitations of power density and short life expectancy must be taken into account. We must adapt to this constraint and design the equipment around it.
People want an inexhaustible pool of energy in a small package that is cheap, safe and clean. A radical turn will be needed to satisfy the unquenchable thirst for portable and mobile power. It is anyone’s guess whether a superior electro-chemical battery, an improved fuel cell, a futuristic atomic fusion battery or some other groundbreaking energy storage device will fulfill this dream. For many, this break will not come in ones lifetime.
References: The Roethle Group, Inc, USA
Remote control (RC) racing enthusiasts have experimented with all imaginable methods to maximize battery performance. One technique that seems to work reasonably well is zapping Nickel-cadmium cells with a very high pulse current. Zapping is said to increase the cell Voltage by 20 to 40mV when measured under a 30A load. This would increase the cell Voltage from 1.25V to about 1.28V. (Note that industry tends to rate Nickel-cadmium at 1.25V whereas the consumer market has adapted 1.20V. It is simply a preference of rating). According to experts, the Voltage gain is stable; only a small drop is observed with usage and age.
During the race, the motor draws 30A from a 7.50V battery (6 cells connected in series). This calculates to over 225W or about a quarter HP of power. The race lasts for roughly four minutes. By raising the cell Voltage by say 30mV from 7.50Vto 7.68V per pack, an extra 5W can be drawn. Although small, this reserve power may be detrimental to the winning team.
According to experts, zapping works only reliably with Nickel-cadmium cells. Nickel-metal-hydride has been tried but the results are inconclusive. The zapping process is done with a 47,000mF capacitor charged to 90V. Best results are achieved if the battery is cycled twice after treatment, then zapped again. Once in service, zapping will no longer improve the cell’s performance. Neither does zapping regenerate a cell that has become weak.
Companies specializing in zapping batteries use top quality Japanese-made Nickel-cadmium cells. The cells are normally sub-C and are handpicked at the factory. pecially labeled, the cells arrive in a discharged state with an open cell Voltages of 1.11 to 1.12V. If below 1.06V, the cell is suspect and zapping does not work well. A low Voltage may hint at elevated self-discharge or chemical deficiencies. The 1.1V is produced through the electro-chemical potential of the Nickel-cadmium cell. This Voltage is present even with no charge. Applying a load would cause the open terminal Voltage to collapse. There are no apparent side effects to zapping, however the battery manufacturers remain non-committal. No scientific explanation is available and only little is known on the longevity of the cells after treatment.
Technological advancements regularly take off soon after a major breakthrough has occurred. Not so with electricity. Electrical power was discovered circa 1600 AD (or earlier). At that time, no one knew what to do with it other than create sparks and experiment with twitching frog legs. Metal plating by means of electrolysis only began in the 1800s. But soon after, a primary battery powered the first electric light using charcoal electrodes. Once the relationship with magnetism was discovered in the mid 1800s, generators were invented that were able to produce a steady flow of electricity. Motors followed that enabled mechanical movement and the Edison light bulb appeared to conquer darkness.
The invention of the electronic vacuum tube in the early 1900s was the significant next step towards high technology, enabling frequency oscillators, signal amplifications and digital switching. This led to radio broadcasting in the 1920s and enabled the first operational digital computer (ENIAC) in 1946. The discovery of the transistor in 1947 paved the way to the integrated circuit ten years later. Finally, the microprocessor ushered in the Information Age and revolutionized the way we live.
While large primary batteries have been around for 200 years, the sealed Nickel-cadmium, as we know it today, is only as old as the transistor (1947). In the meantime, batteries have become a very important energy source and demand is growing steadily.
In the year 2000, the total battery energy consumed globally by laptops and mobile phones is estimated at 2,500 mega Watts. Let’s make some power comparison with various transportation modes.
Battery power and the Boeing 747 jumbo jet
Travelers experience the exhilarating take-off of a jumbo jet. Fully loaded at 400 tons, the Boeing 747 requires 90 mega-Watts (MW) of energy to get airborne. This relates to 120,000 horsepower (hp). The energy consumption during cruising is reduced to half, or 45MW (60,000hp). The global battery power consumed by mobile phones and laptops could keep 56 Boeing 747s in the air.
The mighty Queen Mary, an 81,000-ton ocean liner stretching over 300 meters (1000 ft) in length, was propelled by four steam turbines producing 160,000hp. The energy consumed globally by mobile phones and laptops could power 20 Queen Mary ships, with 3000 passengers and crew aboard, traveling at a speed of 28.5 knots (52 km/hr). The Queen Mary was launched in 1934 and is now a museum in Long Beach, California.
A 275hp (200kW) motor powers an SUV or large car. The average family home is wired to draw 20kW. A large vehicle has enough power to provide electrical energy for 10 houses and satisfy peak current requirements. This is substantial when considering that most vehicles carry only the driver.
An active person requires 3500 calories per day to stay fit, which relates to 4kW (1 food calorie = 1.16 Watt-hour). If traveling on foot, a person covers about 40 km per day (25 miles). In Figure 1 we compare energy per passenger-kilometer for a loaded Boeing 747, the retired Queen Mary ocean liner, a gas-guzzling SUV and a fit person on foot.
How are newer battery chemistries faring?
Lithium-ion is the winner for portable applications. Among the most popular Lithium-ion are the 18650 cylindrical cells and a variety of prismatic cells in a metal package.
Lithium-ion-polymer serves well when the cell geometry must be less than 4mm or when specialty packs are required. High power Lithium-ion-polymer pouch cells allow convenient stacking to create a powerful and compact battery pack with optimum space allocation. There is a price premium, however. Lithium-ion-polymer cost about 10% more than Lithium-ion without gaining extra capacity. Some room allocation for swelling must to be considered when stacking pouch cells.
Lithium-ion is being tested in medical instruments and hybrid cars with mixed results. Short service life and high price are major hurdles. These markets will continue to be served by the more rugged and lower-cost lead and nickel-based batteries.
There are no new battery chemistries on the horizon that will replace the classic Lead-acid for automotive and wheeled-mobility markets. Lead-acid is mature and the manufacturing costs are low. The spiral wound Lead-acid, a technology similar to the ValveRegulated Lead-acid (VRLA) and the absorbent glass mat (AGM) are gradually replacing the flooded car battery on high-end applications. Again, there is a price premium on these more advanced batteries but the longer service life will pay back the investment.
Q: How is the Right Battery Chosen for Industrial Applications?
A: Choosing the right battery for industrial applications
Industrial applications have unique power needs and the choice of battery is important. While consumer products demand high energy density to obtain slim and elegant designs, industry focuses on durability and reliability. Industrial batteries are commonly bulkier than those used in consumer products but achieve a longer service life.
Batteries are electro-chemical devices that convert higher-level active materials into an alternate state during discharge. The speed of such transaction determines the load characteristics of a battery. Also referred to as concentration polarization, the nickel and lithium-based batteries are superior to lead-based batteries in reaction speed. This attribute reflects in good load characteristics.
Discharge loads range from a low and steady current flow of a flashlight to intermittent high current bursts in a power tool, to sharp current pulses on digital communications equipment, laptops and cameras. In this paper we evaluate how the various battery chemistries perform in a given application.
What’s the best battery for video cameras?
Nickel-cadmium batteries continue to power a large percentage of professional cameras. This battery provided reliable service and performs well at low temperature. Nickel-cadmium is one of the most enduring batteries in terms of service life but has only moderate energy density and needs a periodic full discharge.
The need for longer runtimes is causing a switch to Nickel-metal-hydride. This battery offers up to 50% more energy than Nickel-cadmium. However, the high current spikes drawn by digital cameras have a negative affect and the Nickel-metal hydride battery suffers from short service life.
There is a trend towards Lithium-ion. Among rechargeables, this chemistry has the highest energy density and is lightweight. A steep price tag and the inability to provide high currents are negatives.
The 18650 cylindrical Lithium-ion cell offers the most economical power source. “18” defines the cell’s diameter in millimeters and “650” the length. No other Lithium-ion cell, including prismatic or polymer types, offers a similar low cost-per-Watt ratio.
Over the years, several cell versions of 18650 cells with different Ah ratings have emerged, ranging from 1.8Ah to well above 2Ah. The cells with moderate capacities offer better temperature performance, enable higher currents and provide a longer service life than the souped up versions.
The typical 18650 for industrial use is rated at 2Ah at 3.60 Volts. Four cells are connected in series to obtain the roughly 15 Volts needed for the cameras. Paralleling the cells increases the current handling by about 2A per cell. Three cells in parallel would provide about 6A of continuous power. Four cells in series and three in parallel is a practical limit for the 18650 system.
Lithium-ion requires a protection circuit to provide safe operations under all circumstances. Each cell in series is protected against Voltage peaks and dips. In addition, the protection circuit limits each cell to a current about 2A. Even if paralleled, the current of a Lithium-ion pack is not high enough to drive digital cameras requiring 10 to 15A peak current. Tests conducted at Cadex Electronics have shown that the 18650 allows short current peaks above the 2A/cell limit. This would allow the use of Lithium-ion on digital cameras, provided the current bursts are limited to only a few seconds.
What’s the best battery for still cameras?
The power requirement of a professional digital camera is sporadic in nature. Much battery power is needed to take snapshots, some with a powerful flash. To view the photo, the backlit color display draws additional power. Transmitting a high-resolution image over the air depletes another portion of the energy reserve.
Most non-professional cameras use a primary Lithium battery. This battery type provides the highest energy density but cannot be recharged. This is a major drawback for professional use. Rechargeable batteries are the answer and Lithium-ion fits the bill but faces similar challenges to the video cameras.
What is the best battery for medical devices?
One of the most energy-hungry portable medical devices is the heart defibrillator. The battery draws in excess of 10 Amperes during preparation stages. Several shocks may be needed to get the patient’s heart going again. The battery must not hamper the best possible patient care.
Most defibrillators are powered by Nickel-cadmium. Nickel-metal hydride is also being used but there is concern of short service life. In a recent study, however, it was observed that a defibrillator battery cycles far less than expected. Instead of the anticipated 200cycles after two years of seemingly heavy use, less than 60 cycles had been delivered on the battery examined. ‘Smart’ battery technology makes such information possible. With fewer cycles needed, the switch to higher energy-dense batteries becomes a practical alternative.
Sealed Lead-acid batteries are often used to power defibrillators intended for standby mode. Although bulky and heavy, the Lead-acid has a low self-discharge and can be kept in prolonged ready mode without the need to recharge. Lead-acid performs well on high current spurts. During the rest periods the battery disperses the depleted acid concentrations back into the electrode plate. Lead-acid would not be suitable for a sustained high load.
The medical industry is moving towards Lithium-ion. The robust and economical 18650 cells make this possible. The short but high current spurts needed for defibrillators are still a challenge. Paralleling the cells and adding current-limiting circuits that allow short spikes of high current will help overcome this hurdle.
What is the best battery for power tools?
Power tools require up to 50 Amperes of current and operate in an unfriendly environment. The tool must perform at sub zero temperatures and endure in high heat. The batteries must also withstand shock and vibration.
Most power tools are equipped with Nickel-cadmium batteries. Nickel-metal hydride has been tried with limited success. Longevity is a problem but new designs have improved. Lithium-ion is too delicate and could not provide the high Amperage. Lead-acid is too bulky and lacks persistent power delivery. The power tool has simply no suitable alternatives to the rugged and hard-working Nickel-cadmium.
In an attempt to pack more energy into power tools, the battery Voltage is increased. Because of heavy current and application at low temperatures, cell matching is important. Cell matching becomes more critical as the number of cell connected in series increases. A weak cell holds less capacity and is discharged more quickly than the strong ones. This imbalance causes cell reversal on the weak cell if the battery is discharged at high current below 1V/cell. An electrical short occurs in the weak cell if exposed to reverse current and the pack needs to be replaced. The higher the battery Voltage, the more likely will a weak cell get damaged.
The sealed Lead-acid battery is designed with a low over-Voltage potential to prohibit the battery from reaching its gas-generating state during charge. This prevents water depletion of the sealed system. Consequently, these batteries will never get fully charged and some sulfation will develop over time.
Finding the ideal charge Voltage threshold is critical and any level is a compromise. A Voltage limit above 2.40 Volts per cell produces good battery performance but shortens the service life due to grid corrosion on the positive plate. The corrosion is permanent. A Voltage below the 2.40V/cell threshold strains the battery less but the capacity is low and sulfation sets in over time on the negative plate.
Driven by diverse applications, two sealed Lead-acid types have emerged. They are the sealed lead-acid (SLA), and the valve regulated Lead-acid (VRLA). Technically, both batteries are the same. Engineers may argue that the word ‘sealed Lead-acid’ is a misnomer because no Lead-acid battery can be totally sealed.
The SLA has a typical capacity range of 0.2Ah to 30Ah and powers personal UPS units, local emergency lighting and wheelchairs. The VRLA battery is used for large stationary applications for power backup. We are looking at methods to restore and prolong these two battery systems separately.
The sealed Lead-acid (SLA)
SLA batteries with mild sulfation can be restored but the work is time consuming and the results are mixed. Reasonably good results are achieved by applying a charge on top of a charge. This is done by fully charging an SLA battery, then removing it for a 24 to 48 hour rest period and applying a charge again The process is repeated several times and the capacity is checked with a final full discharge and recharge.
Another method of improving performance is by applying an equalizing charge, in which the charge Voltage threshold is increased by about 100mV, typically from 2.40V to 2.50V. This procedure should last no longer than one to two hours and must be carried out at moderate room temperature. A careless equalize charge could cause the cells to heat up and induce venting due to excessive pressure. Observe the battery during the service.
The cylindrical SLA, made by Hawker and sold under the Cyclone name, requires slightly higher Voltages to reverse sulfation. An adjustable power supply works best for the service. Set the current limit to the lowest practical setting and observe the battery Voltage and temperature during charge. Initially, the cell Voltage may rise to 5V, absorbing only a small amount of current. In about two hours, the small charging current converts the large sulfate crystals back into active material. The internal cell resistance decreases and the cell starts to clamp the Voltage. At around 2.30V, the cell accepts charge. If the sulfation is advanced, this remedy does not work and the cell needs replacing.
Sealed Lead-acid batteries are commonly rated at a 20-hour discharge. Even at such a slow rate, a capacity of 100% is difficult to achieve. For practical reasons, most battery analyzers use a 5-hour discharge when servicing these batteries. This produces 80% to 90% of the rated capacity. SLA batteries are normally overrated and manufacturers are aware of this practice.
Cycling an SLA on a battery analyzer may provide capacity readings that decrease with each additional cycle. A battery may start off at a marginal 88%, then go to 86%, 84% and 83%. This phenomenon can be corrected by increasing the charge Voltage threshold from 2.40V to 2.45V and perhaps even 2.50V. Always consider the manufacturer’s recommended settings. Cyclone batteries require slightly higher Voltage settings than the plastic version.
Avoid setting the charge Voltage threshold too high. In an extreme case, the limiting Voltage may never be reached, especially when charging at elevated temperatures. The battery continues charging at full current and the pack gets hot. Heat lowers the battery Voltage and works against a further Voltage raise. If no temperature sensing is available to terminate the charge, a thermal runaway can be the result.
The recovery rate of SLA batteries is a low 15%. Other than reverse sulfation, there is little one can do to improve SLA. Because the SLA has a relatively short cycle life, many fail due to wear-out.
Valve regulated Lead-acid (VRLA)
The charge Voltage setting on VRLA is generally lower than SLA. Heat is a killer of VRLA. Many stationary batteries are kept in shelters with no air conditioning. Every 8°C (15°F) rise in temperature cuts the battery life in half. A VRLA battery, which would last for 10 years at 25°C (77°F), will only be good for 5 years if operated at 33°C (95°F). Once damaged by heat, no remedy exists to improve capacity.
The cell Voltages of a VRLA battery must be harmonized as close as possible. Applying an equalizing charge every 6 months brings all cells to similar Voltage levels. This is done by increasing the cell voltage to 2.50V/cell for about 2 hours. During the service, the battery must be kept cool and careful observation is needed. Limit cell venting. Most VRLA vent at 0.3 Bar (5 psi). Not only does escaping hydrogen deplete the electrolyte, it is highly flammable.
Water permeation, or loss of electrolyte, is a concern with sealed Lead-acid batteries. Adding water may help to restore capacity but a long-term fix is uncertain. The battery becomes unreliable and requires high maintenance.
Always store Lead-acid in a charged condition. Never let the open cell Voltage drop much below 2.10V. Apply a topping charge every six months or when recommended.
· Avoid repeated deep discharges. Charge more often or use a larger battery.
Prevent sulfation and grid corrosion by choosing the correct charge and float Voltages.
Avoid operating Lead-acid at elevated ambient temperatures.
( January 2004) Non-Correctable Battery Problems. Some rechargeable batteries can be restored through external means, such as applying a full discharge.
(October ,2003)Recycling batteries
Modern batteries are often promoted on their environmental qualities. Lithium-based batteries fall into this category. While Nickel-cadmium presents an environmental problem on careless disposal, this chemistry continues to hold an important position among rechargeable batteries. Power tools are almost exclusively powered by Nickel-cadmium. Lead-acid batteries continue to service designated market niches and these batteries also need to be disposed of in a proper manner. Lithium-ion would simply be too fragile to replace many of these older, but environmentally unfriendly, battery chemistries.
Our quest for portability and mobility is steadily growing, so is the demand for batteries. Where will the mountains of batteries go when spent? The answer is recycling.
The lead acid battery has led the way in recycling. The automotive industry should be given credit in organizing ways to dispose of spent car batteries. In the USA, 98% of all lead acid batteries are recycled. In comparison, only one in six households in North America recycle batteries.
Careless disposal of Nickel-cadmium is hazardous to the environment. If used in landfills, the cadmium will eventually dissolve itself and the toxic substance can seep into the water supply, causing serious health problems. Our oceans are already beginning to show traces of cadmium (along with aspirin, penicillin and antidepressants) but the source of the contamination is unknown.
Although Nickel-metal-hydride is considered environmentally friendly, this chemistry is also being recycled. The main derivative is nickel, which is considered semi-toxic. Nickel-metal-hydride also contains electrolyte that, in large amounts, is hazardous. If no disposal service is available in an area, individual Nickel-metal-hydride batteries can be discarded with other household wastes. If ten or more batteries are accumulated, the user should consider disposing of these packs in a secure waste landfill.
Lithium (metal) batteries contain no toxic metals, however, there is the possibility of fire if the metallic lithium is exposed to moisture while the cells are corroding. Most lithium batteries are non-rechargeable and are used in cameras, hearing aids and defense applications. For proper disposal, the batteries must first be fully discharged to consume the metallic lithium content.
Lithiumion batteries used for cell phones and laptops do not contain metallic lithium and the disposal problem does not exist. Most lithium systems contain toxic and flammable electrolyte.
In 1994, the Rechargeable Battery Recycling Corporation (RBRC) was founded to promote recycling of rechargeable batteries in North America. RBRC is a non-profit organization that collects batteries from consumers and businesses and sends them to recycling organizations. Inmetco and Toxco are among the best-known recycling companies in North America
Europe and Asia have had programs to recycle spent batteries for many years. Sony and Sumitomo Metal in Japan have developed a technology to recycle cobalt and other precious metals from spent Lithiumion batteries.
Battery recycling plants require that the batteries be sorted according to chemistries. Some sorting must be done prior to the battery arriving at the recycling plants. Nickel-cadmium, Nickel-metal-hydride, Lithiumion and lead acid are placed in designated boxes at the collection point. Battery recyclers claim that if a steady stream of batteries, sorted by chemistry, were available at no charge, recycling would be profitable. But preparation and transportation add to the cost.
The recycling process starts by removing the combustible material, such as plastics and insulation, with a gas fired thermal oxidizer. Gases from the thermal oxidizer are sent to the plant's scrubber where they are neutralized to remove pollutants. The process leaves the clean, naked cells, which contain valuable metal content.
The cells are then chopped into small pieces, which are heated until the metal liquefies. Non-metallic substances are burned off; leaving a black slag on top that is removed with a slag arm. The different alloys settle according to their weights and are skimmed off like cream from raw milk.
Cadmium is relatively light and vaporizes at high temperatures. In a process that appears like a pan boiling over, a fan blows the cadmium vapor into a large tube, which is cooled with water mist. This causes the vapors to condense and produces cadmium that is 99.95 percent pure.
Some recyclers do not separate the metals on site but pour the liquid metals directly into what the industry refers to as `pigs' (65 pounds) or `hogs' (2000 pounds). The pigs and hogs are then shipped to metal recovery plants. Here, the material is used to produce nickel, chromium and iron re-melt alloy for the manufacturing of stainless steel and other high-end products.
Current battery recycling methods requires a high amount of energy. It takes six to ten times the amount of energy to reclaim metals from recycled batteries than it would through other means.
Who pays for the recycling of batteries? Participating countries impose their own rules in making recycling feasible. In North America, some recycling plants bill on weight. The rates vary according to chemistry. Systems that yield high metal retrieval rates are priced lower than those, which produce less valuable metals.
Nickel-metal-hydride yields the best return. It produces enough nickel to pay for the process. The highest recycling fees apply to Nickel-cadmium and Lithiumion because the demand for cadmium is low and Lithiumion contains little retrievable metal.
Not all countries base the cost of recycling on the battery chemistry; some put it on tonnage alone. The flat cost to recycle batteries is about $1,000 to $2,000US per ton. Europe hopes to achieve a cost per ton of $300US. Ideally, this would include transportation, however, moving the goods is expected to double the overall cost. For this reason, Europe sets up several smaller processing locations in strategic geographic locations.
Significant subsidies are sill required from manufacturers, agencies and governments to support the battery recycling programs. This funding is in the form of a tax added to each manufactured cell. RBRC is financed by such a scheme.
Important: Under no circumstances should batteries be incinerated as this can cause explosion. If skin is exposed to electrolyte, flush with water immediately. If eye exposure occurs, flush with water for 15 minutes and consult a physician immediately.
(September,03)Storing and priming of batteries Batteries are perishable products that start deteriorating right from the moment they leave the factory.
(August,03) Q: What is the 'smart' battery
(July,03) What is a `smart' battery? The battery has the inherit problem of not being able to communicate with the user. Neither weight, color, nor size provides an indication of the battery's state-of-charge (SoC) and state-of-health (SoH). The user is at the mercy of the battery.
The purpose of a battery is to store energy and release it at the appropriate time in a controlled manner.
(May 2003)Q: What are considerations for discharging at high and low temperature. Batteries function best at room temperature. Operating batteries at an elevated temperature dramatically shortens their life.
Not just a concept to provide greater information about battery charge conditions, Electrochemical Impedance Spectroscopy (EIS) now provides data to show superior performance. The electrochemical characteristics of a battery are determined by applying an AC potential at varying frequencies and measuring the current response of the electrochemical cell. Written by our Expert, Isidor Buchmann
(July 2002) Q: What are the chraracteristics of Nickel-based batteries, its dominance and the future?
(May 2002) Q: What’s the best battery?
Battery novices often brag about phantom battery systems that offer very high energy densities, deliver 1000 charge/discharge cycles and are paper-thin. These attributes are indeed achievable but not on the same battery pack.
A certain battery may be designed for small size and long runtime, but this pack has a limited cycle life. Another battery may be built for durability but is big and bulky. A third pack may have high energy density and long durability but is too expensive for the commercial consumer.
Battery manufacturers are aware of customer needs and offer packs that best suit the application. The cell phone industry is an example of this clever adaptation. Here, small size and high energy density reign in favor of longevity. Short service life is not an issue because a device is replaced before the battery fails.
Let’s briefly examine various battery designs. A prismatic Nickel-metal-hydride battery is made for slim geometry. Its energy density is a meager 60Wh/kg and the cycle count is limited to around 300. In comparison, a cylindrical Nickel-metal-hydride offers 80Wh/kg and higher. Still, the cycle count is moderate to low. High durability Nickel-metal-hydride for industrial use and electric vehicles is packaged in large cylindrical cells. Surprisingly, the energy density on these cells is a modest 70Wh/kg.
Similarly, Lithium-ion batteries for defense applications are being produced that far exceed the energy density of the commercial equivalent. These super-high capacity Lithium-ion batteries are not approved for the commercial market for safety reasons.
Let’s examine the strength and limitations of today’s popular battery systems. Although energy density is paramount, other viral attributes are service life, load characteristics, maintenance requirements, self-discharge and operational costs. Since Nickel-cadmium remains a standard against which batteries are compared, we evaluate alternative chemistries against this classic battery type.
· Nickel-cadmium — mature but has moderate energy density. Nickel-cadmium is used where long life, high discharge rate and a extended temperature range are important. Main applications are two-way radios, biomedical equipment and power tools. Nickel-cadmium contains toxic metals.
· Nickel-metal-hydride — has a higher energy density compared to Nickel-cadmium at the expense of reduced cycle life. There are no toxic metals. Applications include mobile phones and laptop computers.
· Lead-acid — most economical for larger power applications where weight is of little concern. This battery is the preferred choice for hospital equipment, wheelchairs, emergency lighting and UPS systems.
· Lithium-ion — fastest growing battery system; offers high-energy density and low weight. Protection circuits are needed to limit Voltage and current for safety reasons. Applications include notebook computers and cell phones.
· Lithium-ion-polymer — Similar to Lithium-ion, this system enables slim geometry and simple packaging at the expense of higher cost per Watt/hours. Main applications are cell phones.
· 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.
Table 1 on page 13 summarizes the characteristics of the common batteries. The figures are based on average ratings at time of publication. Note that Nickel-cadmium has the shortest charge time, delivers the highest load current and offers the lowest overall cost-per-cycle but needs regular maintenance.
In subsequent columns I will describe the strength and limitation of each chemistry in more detail. We will also examine charging techniques and explore methods to get the most of these batteries.
Table 1: Characteristics of commonly used rechargeable batteries.
Nickel- Nickel-metal- Lead-acid Lithiumion Lithiumion- Rusable
cadmium hydride polymer Alkaline
Gravimetric Energy Density 45-80 60-120 30-50 110-160 100-130 80(initial) (Wh/kg)
Internal Resistance (includes 100 to 2001 00 to 3001 <1001 150 to 2501 200 to 3001 200 to 20001
peripheral circuits) in mW 6V pack 6V pack 12V pack 7.2V pack 7.2V pack 6V pack
Cycle Life 15002 300 to 5002,3 200 to 3002 300 to 5003 300 to 500 503
(to 80% of initial capacity) (to 50% capacity)
Fast Charge Time 1h typical 2 to 4h 8 to 16h 2 to 4h 2 to 4h 2 to 3h
Overcharge Tolerance moderate low high very low low moderate
Self-discharge/Month 20%4 30%4 5% 10%5 ~10%5 0.3%
Cell Voltage (nominal) 1.25V6 1.25V6 2V 3.6V 3.6V 1.5V
Load Current peak 20C 5C 5C7 >2C >2C 0.5C
best result 1C 0.5C or lower 0.2C 1C or lower 1C or lower 0.2C or lower
Operating Temperature8 -40 to -20 to -20 to -20 to 0 to 0 to
(discharge only) 60°C 60°C 60°C 60°C 60°C 65°C
Maintenance Requirement 30 to 60 days 60 to 90 days 3 to 6 months9 not required not required. not required
Typical Battery Cost10 $50 $60 $25 $100 $100 $5
(US$, reference only) (7.2V) (7.2V) (6V) (7.2V) (7.2V) (9V)
Cost per Cycle (US$)11 $0.04 $0.12 $0.10 $0.14 $0.29 $0.10-0.50
Commercial use since 1950 1990 1970 1991 1999 1992
1 Internal resistance of a battery pack varies with cell rating, type of protection circuit and number of cells. Protection circuit of Lithiumion and Lithium-ion-polymer adds about 100mW.
2 Cycle life is based on a battery receiving regular maintenance. Failing to apply periodic full discharge cycles may reduce the cycle life by a factor of three.
3 Cycle life is based on the depth of discharge. Shallow discharges provide more cycles than deep discharges.
4 The discharge is highest immediately after charge, and then tapers off. The capacity of Nickel-cadmium decreases 10% in the first 24h, then declines about 10% every 30 days thereafter. Self-discharge increases with higher temperature.
5. Internal protection circuits typically consume 3% of the stored energy per month.
6 1.25V is the open cell Voltage. 1.2V is commonly used as a method of rating.
7 Capable of high current pulses.
8 Applies to discharge only; charge temperature range is more confined.
9 Maintenance may be in the form of ‘equalizing’ or ‘topping’ charge.
10 Cost of battery for commercially available portable devices.
11 Derived from the battery price divided by cycle life. Does not include the cost of electricity and chargers.
(April 2002) Q: When was the battery invented?
One of the most important discoveries in the last 400 years has been electricity. You may ask, “Has electricity been around that long?” The answer is yes, and perhaps much longer. But electricity only became useful in the late 1800s.
The earliest methods of generating electricity were by creating a static charge. Alessandro Volta (1745-1827) invented the so-called “electric pistol” by which an electrical wire was placed in a jar filled with methane gas. By sending an electrical spark through the wire, the jar would explode.
Volta then thought of using this invention to provide long distance communications, albeit only one Boolean bit. An iron wire supported by wooden poles was to be strung from Como to Milan, Italy. At the receiving end, the wire would terminate in a jar filled with methane gas. On command, an electrical spark would be sent by wire that would cause a detonation to signal a coded event. This communications link was never built.
The next stage of generating electricity was through electrolysis. Volta discovered in 1800 that a continuous flow of electrical force was possible when using certain fluids as conductors to promote a chemical reaction between metals. Volta discovered further that the Voltage would increase when Voltaic cells were stacked. This led to the invention of the battery.
No longer were experiments limited to a brief display of sparks that lasted a fraction of a second. A seemingly endless stream of electric current was now available.
At this time, France was approaching the height of scientific advancements and new ideas were welcomed with open arms to support the political agenda. By invitation, Volta addressed the Institute of France in a series of lectures in which Napoleon Bonaparte was present. Napoleon himself helped with the experiments, drawing sparks from the battery, melting a steel wire, discharging an electric pistol and decomposing water into its elements. New discoveries were made when Sir Humphry Davy installed the largest and most powerful electric battery in the vaults of the Royal Institution of London. He connected the battery to charcoal electrodes and produced the first electric light. As reported by witnesses, his Voltaic arc lamp produced “the most brilliant ascending arch of light ever seen.” In 1802, Dr. William Cruickshank designed the first electric battery capable of mass production. Cruickshank arranged square sheets of copper soldered at their ends, intermixed with sheets of zinc of equal size. These sheets were placed into a long rectangular wooden box that was sealed with cement. Grooves in the box held the metal plates in position. The box was filled with an electrolyte of brine, or watered down acid.
Until now, all batteries were primary cells, meaning that they could not be recharged. In 1859, the French physicist Gaston Planté invented the first rechargeable battery. This secondary battery was based on Lead-acid chemistry, a system that is still used today.
The third method of generating electricity was discovered relatively late — electricity through magnetism. In 1820, André-Marie Ampère (1775-1836) had noticed that wires carrying an electric current were at times attracted to one another, while at other times they were repelled. In 1831, Michael Faraday (1791-1867) demonstrated how a copper disc was able to provide a constant flow of electricity when revolved in a strong magnetic field. Faraday and his research team succeeded in generating an endless electrical force as long as the movement between a coil and magnet continued.
In 1899, Waldmar Jungner from Sweden invented the Nickel-cadmium battery. In 1947, Neumann succeeded in completely sealing the cell. These advances led to the modern sealed Nickel-cadmium battery.
Research of the NiMH system started in the 1970s, but the metal hydride alloys were unstable in the cell environment. New hydride alloys were developed in the 1980s that improved the stability. NiMH became commercially available in the 1990s.
The first primary Lithium batteries appeared in early 1970s. Attempts to develop rechargeable lithium batteries followed in the 1980s but failed due to safety problems. Because of the inherent instability of lithium metal, especially during charging, research shifted to a non-metallic lithium battery using lithium ions. Although slightly lower in energy density than lithium metal, the Lithium ion is safe, provided certain precautions are met when charging and discharging. In 1991, the Sony Corporation commercialized the first Lithium-ion battery.
As awkward and unreliable the early batteries may have been, our descendants may one day look at today’s technology in a similar way to how we view our predecessors’ clumsy experiments of 200 years ago. History of Battery Development
The 88-page first edition book appeared in 1997 and covered such topics as the memory effect of Nickel-cadmium batteries and how to restore them. Some readers commented that I favored the Nickel-cadmium over the Nickel-metal-hydride. Perhaps this observation is valid and I have taken note. Having been active in the mobile radio industry for many years, much emphasis is placed on battery longevity, a quality that is true of the Nickel-cadmium. Today’s battery users prefer small size and maximum runtime. Longevity is less important, especially in the consumer market.
The second edition Batteries in a Portable World was published in 2001. With 18 Chapters and 300 pages, this book has been extended to answer most questions battery users would ask. Much emphasis is placed on new battery technologies and their field applications.
In May 2001, I created the Battery Information Website www.buchmann.ca and made the contents of the book available to everyone. New battery articles have also been added. A search engine helps the readers in finding issues of interest.
Out of sheer curiosity, I did a statistical analysis at the end of the year to find out which battery topics are being requested most often. The five winning chapters are:
Number 1. Getting the Most from your Batteries Chapter 10
Number 2. Proper Charge Methods Chapter 4
Number 3. Internal Battery Resistance Chapter 9
Number 4. Choosing the Right Battery Chapter 8
Number 5. The ‘Smart’ Battery Chapter 7
With “Getting the Most from your Batteries” as first choice, it is evident that people want good runtime and dependable service. “Proper Charge Methods” is also very much in the hearts of the battery users. A surprise was “Internal Battery Resistance” in third position. This subject is of growing concern with digital equipment that puts high demands on the battery. A seemingly good battery often fails to deliver the heavy current bursts because of elevated internal resistance caused by aging and high cycle count.
Batteries in a Portable World is written for the non-engineer. It addresses the use of the battery in the hands of the general public, far removed from the protected test lab environment of the manufacturer. Some information contained in this book was obtained through tests performed in Cadex laboratories; other knowledge was gathered by simply talking to diverse groups of battery users. Not all views and opinions expressed in the book are based on scientific facts. Rather, they follow opinions of the general public, who use batteries. Some difference of opinion with the reader cannot be avoided. I will accept the blame for any discrepancies, if justified.
The monthly columns, which will appear in Batteries Digest Newsletter, will be based on the book, Batteries in a Portable World. I will address such issues as the choice of battery chemistries, physical battery packs, charge and discharge methods, runtime concerns, the ‘smart’ battery, internal battery resistance and much more. I hope you will find these columns helpful.
About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decade