battery blog

Comparison of Cobalt and Manganese as positive electrodes

Chemicals and additives help to balance the critical trade-off between high energy density, long storage time, extended cycle life and safety. High energy densities can be achieved with relative ease. For example, adding more nickel in lieu of cobalt increases the ampere/hours rating and lowers the manufacturing cost but makes the cell less safe. While a start-up company may focus on high energy density to gain quick market acceptance, safety, cycle life and storage may be compromised. Reputable manufacturers, such as Dell,IBM,Compaq,NEC,Sony,Toshiba,HP,Acer,Apple, Fujitsu,Asus and E-One Moli place high importance on safety.

Lithium-ion cells cause less harm when disposed than lead or cadmium based batteries. Among the lithium-ion battery family, the spinel is the friendliest in terms of disposal.

Charging the Li-ion battery

The lithium-ion charger is a voltage-limiting device that is similar to the lead acid Dell 310-6321 battery , Dell 310-6322 battery charger with the differences of a higher voltage per cell, tighter voltage tolerance and the absence of trickle or float charge at full charge.

Whereas the Valve Regulated Lead Acid (VRLA) offers some flexibility in terms of voltage cut off, the manufacturers of lithium-ion Dell Inspiron 9300 battery are very strict about the voltage choice. When first introduced, the charge voltage limit of the graphite system was 4.10 volts per cell. Although higher voltages deliver increased energy density, cell oxidation severely limited the service life in the early graphite cells if charged above the 4.10V/cell threshold. This effect has now been solved with chemical additives, and most new lithium-ion cells are now set to 4.20V. The tolerance on all lithium-ion batteries is a tight +/- 0.05 volts per cell.

The charge time of all lithium-ion Dell 312-0068 battery , Dell 6Y270 battery is about 3 hours at a 1C initial charge current, and the battery remains cool during charge. Full charge is attained after the voltage reaches the upper voltage threshold, and the current drops and levels off at about 3% of its nominal rating, or about 0.03C.

Increasing the charge current on a lithium-ion charger does not shorten the charge time by much. Although the voltage peak is reached quicker with higher current, the topping charge will take longer. Figure 3 shows the voltage and current signature of a charger as the lithium-ion cell passes through stage one and two.

Figure 3:  Charge stages of a Li-ion Battery.
Increasing the charge current on a lithium-ion charger does not shorten the charge time by much. Although the voltage peak is reached quicker with higher current, the topping charge will take longer.

Claims of fast charging a Li-ion Dell Inspiron 500m battery,Dell Inspiron 510m battery in one hour or less usually results in lower charge levels. Such a charger simply eliminates stage two and goes directly into ‘ready’ once the voltage threshold is reached at the end of stage one. The charge level at this point is about 70%. The topping charge typically takes twice as long as the initial charge.

No trickle charge is applied because the Li-ion is unable to absorb overcharge. Trickle charge could cause plating of metallic lithium, a condition that makes the cell unstable. Instead, a brief topping charge is applied to compensate for the small amount of self-discharge the Dell Inspiron 5100 battery , Dell 6T473 battery and its protective circuit consume.

Depending on the charger and the self-discharge of the Dell Inspiron E1505 battery , a topping charge may be implemented once every 500 hours or 20 days. Typically, the charge kicks in when the open terminal voltage drops to 4.05 volts per cell and turns off when it reaches 4.20V/cell.

Protection circuit

Commercial lithium-ion HP Pavilion DV1000 battery , HP PF723A battery packs contain redundant protection devices to assure safety under all circumstances. Typically, a solid-state switch opens if the charge voltage of any cell reaches 4.30V, and a fuse activates if the cell temperature approaches 90°C (194°F). In addition, a pressure switch in each cell permanently interrupts the charge current if a safe pressure threshold is exceeded, and internal voltage control circuits cut off the battery at low and high voltage points. Exceptions are made to prismatic and cylindrical spinel packs containing one or two cells only.

The lithium-ion is typically discharged to 3 volts per cell. The lowest 'low-voltage' power cut-off is 2.5V/cell. During prolonged storage, however, a discharge below this voltage level is possible. Manufacturers recommend a 'trickle' charge to raise such a HP Pavilion dv2000 battery , HP HSTNN-LB31 battery gradually back up into the 'acceptable' voltage window. Not all chargers are designed to apply a charge once a lithium-ion battery has dipped below 2.5V/cell.

Some batteries feature an ultra-low voltage cutoff that permanently disconnects the pack if a cell dips below 1.5 volts. This precaution is done to prohibit recharge if a battery has dwelled in an illegal voltage state. A deep discharge causes copper plating, which can lead to short circuit in the cell.
Most manufactures do not sell the lithium-ion cells by themselves but make them available in a battery pack, complete with protection circuit. This precaution is understandable when considering the danger of explosion and fire if the HP F4486B battery ,F4486A ,HP CGR-B1870AE battery is charged and discharged beyond safe limits.

A major concern arises if static electricity or a faulty charger has managed to destroy the battery's protection circuit. Such damage often causes the solid-state switches to fuse to a permanent ON position without the user's knowledge. A battery with a faulty protection circuit may function normally but will not provide the required safely. If charged beyond safe voltage limits with a poorly designed accessory charger, the battery may heat up, then bulge and in some cases vent with flame. Shorting such a HP PP2182D battery , HP 338794-001 battery , HP PP2182L battery can also be hazardous.

Analyzers for the Lithium Ion batteries

In the past, battery analyzers were used to restore batteries affected by 'memory'. With today's nickel-free batteries, memory is no longer a problem and the emphasis of an analyzer is shifting to battery performance verification, quality control and quick-test.

Conventional wisdom says that a new HP Pavilion ZT3000 battery , HP 337607-001 battery , HP 337607-003 battery always performs flawlessly. Yet many users have learned that a battery fresh from the shrink-wrap does not always meet the manufacturer's specifications. With a battery analyzer, all incoming batteries can be checked as part of a quality control procedure. In addition, warranty claims can be made if the capacity drops below the specified level at the end of the warranty period.

A typical life of a lithium-ion is 300-500 discharge/charge cycles or about three years from time of manufacturing. The loss of battery capacity occurs gradually and often without the knowledge of the user. Although fully charged, the battery eventually regresses to a point where it may hold less than half of its original capacity. The function of the battery analyzer is to identify these weak Sony VGP-BPS3 battery , Sony VGP-BPS5 battery  and "weed' them out.

A battery analyzer can also be used to troubleshoot the cause of short runtimes, some can simulate the load signature of a digital device and verify the runtime based on the available PA3107U-1BRS , PA3383U-1BRS , PA3384U-1BRS  capacity.
An important feature of modern battery analyzers is its ability to read the internal battery resistance, a test that only takes a few seconds to complete. As part of natural aging, the internal resistance of the cobalt lithium-ion gradually increases due to cell oxidation. The higher the resistance, the less energy the battery can deliver. On the manganese lithium-ion, the resistance stays low but the capacity drops.

A more reliable method of measuring the state-of-health of a battery is through quick-test methods. Cadex has developed a system that uses an inference algorithm to test battery capacities. The QuickTest™ algorithm is made battery-specific by using a trend-learning algorithm that resembles the thinking process of the human brain. QuickSort™ uses a generic matrix and services the vast pool of single cell lithium-ion A1175 , A1185 , M9324 , M8403 , M7318 for cell phones.

Summary

Lithium-ion has found a strong market niche for portable devices demanding small form-factor and light weight. The high energy cobalt version is popular for cell phones, cameras and laptop computers; the rugged but lower energy-dense manganese and phosphate variants are employed for high current applications such as power tools, medical instruments, and soon also the hybrid car and electric vehicle.

Lithium-ion has proven less favorable for a laptop that is mostly powered by AC. High heat on a fully charge A1079 , A1078 cause premature aging. Most battery chemistries suffer from this phenomenon

Recycling your Battery

Over 75 million Nickel Cadmium (NiCd) batteries were sold in the US during the year 2000. Market predictions indicate that the demand of NiCd batteries will rise six percent per year until 2003. The demand for other chemistries such as Nickel Metal Hydride (NiMH) and Lithium Ion (Li‑ion) is increasing at a more rapid pace. Where will the mountains of batteries go when spent? The answer is recycling.Dell Inspiron 630m battery

The lead acid battery has led the way in recycling. The automotive industry should be given credit in organizing ways to dispose of old car batteries. In the USA, 98 percent of all lead acid batteries are recycled. Compared to aluminum cans (65 percent), newspaper (59 percent) and glass bottles (37 percent), lead acid batteries are reclaimed very efficiently, due in part to legislation.

Only one in six households in North America recycle small rechargeable batteries. Homeowners have the lowest return ratios, but this should improve once more recycling repositories become available and better environmental awareness is emphasized.Dell Inspiron 6000 battery

The NiCd battery is one of the more hazardous batteries in terms of disposal. If used in landfills, the cadmium will eventually dissolve itself and the toxic substance will 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. Under no circumstances can batteries be incinerated as this can cause them to explode.

Although NiMH batteries are considered environmentally friendly, this chemistry is also being recycled. The main derivative is nickel, which is considered semi-toxic. NiMH also contains an electrolyte that, in large amounts, is hazardous to the environment.

If no disposal service is available in an area, individual NiMH batteries can be discarded with other household wastes. If ten or more batteries are accumulated, the user should consider disposing the batteries in a secure waste landfill.

Lithium (metal) batteries contain no toxic metals, however, there is the possibility of fire if metallic lithium is exposed to moisture while the cells are corroding. Most lithium batteries are non-rechargeable and are used by defense organizations. Cameras and other commercial products also use primary lithium batteries. For proper disposal, these batteries must be fully discharged in order to consume all metallic lithium content. Li‑ion batteries (rechargeable), on the other hand, do not contain metallic lithium and the disposal problem does not exist. Most lithium systems contain toxic and flammable electrolyte, however.

In 1994, the Rechargeable Battery Recycling Corporation (RBRC) was founded to promote the recycling of rechargeable batteries in North America. RBRC is a non-profit organization that collects batteries from consumers and businesses and sends them to Inmetco and Toxco for recycling. Inmetco specializes in recycling NiCd, but also accepts NiMH and lead-based batteries. Toxco, focuses on lithium metal and Li‑ion system. Currently only intended to recycle NiCd batteries, RBRC will expand the program to include also NiMH, Li‑ion and SLA batteries.

Programs to recycle spent batteries have been in place in Europe and Asia for many years. Sony and Sumitomo Metal in Japan have developed a technology to recycle cobalt and other precious metals from Li‑ion batteries. The rest of Asia is progressing at a slower rate. Some movements in recycling spent batteries are starting in Taiwan and China, but no significant infrastructure exists.

Battery recycling plants require batteries to be sorted according to chemistries. Some sorting is done prior to the battery arriving at the recycling plants. NiCd, NiMH, Li‑ion and lead acid are often placed in designated boxes at the collection point. Sorting batteries must be done manually, an operation that adds to the cost of recycling.

If a steady stream of sorted batteries were available at no charge, recycling would be feasible with little cost to the user. The logistics of collection, transportation and labor to sort the batteries make recycling expensive.

The recycling process starts by removing the combustible material, such as plastics and insulation using 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 easily 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. A 99.95 percent purity level of cadmium can be achieved using this method.

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. A new process is being explored, which may be more energy and cost effective. One method is dissolving the batteries with a reagent solution. The spent reagent is recycled without forming any atmospheric, liquid or solid wastes.

Who pays for the recycling of batteries in bulk? 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 that produce less valuable metals.

The highest recycling fees apply to NiCd and Li‑ion batteries because the demand for cadmium is low and Li‑ion batteries contain little retrievable metal. The recycling cost of alkaline is 33 percent lower than that of NiCd and Li‑ion because the alkaline cell contains iron. The NiMH battery yields the best return. Recycling NiMH produces enough nickel to pay for the process.

Not all countries base the cost of recycling on the battery chemistry; some put it on tonnage alone. The average cost of recycling batteries is $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 is setting 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. These subsidies are in the form of a tax added to each manufactured cell. RBRC is financed by such a scheme.