When people wanted something roomier than a station wagon but not as commercial-looking as a van, the auto industry gave us minivans. Then when people wanted something sportier than minivans but not as workmanlike as pickup…
Reports from the Energy Storage Research Program at DOE have found that “every year roughly one-million usable lithium-ion batteries are sent for recycling”. Knowing when to replace a battery is an ongoing concern and date-stamping serves as only a partial and imperfect solution. It is important to understand and acknowledge the fact that batteries do not fail suddenly, but rather they follow a predicted decline in capacity losing performance over time. Battery life is governed by usage, not time.
A new battery is rated at a nominal capacity of 100%. As the battery ages, the reserve capacity drops and the battery eventually needs replacing when the reserve capacity falls below a certain level to be defined depending on the application of a battery-powered medical device.
Nickel-based batteries provide about three-years of service; Li-on five. Storage characteristics have also improved. However, under-usage in healthcare is more common than ever, and bio-medical technicians have discovered that many medical batteries that are recycled still have a capacity of above 90%, leading to millions of unchecked batteries being discarded every year.
The date-stamping approach to batteries has several serious flaws:
It does not detect a damaged or prematurely faded battery. Batteries that are used regularly may fade before the expiry date listed on the stamp.
Through this approach, it is also often neglected that even batteries held in storage and are not in use, lose capacity over time.
It is a costly procedure as it does not allow for full battery service life to be used, resulting in most batteries in this system being replaced after less than half of their useful life is still intact. Li-on batteries, for example, often last 2-3 times longer than the date stamp mandates, but also have higher purchase prices making premature disposal even more costly.
By replacing the arguably outdated approach to battery replacement, with a greener, more reliable approach, the future of battery management in healthcare will be increasingly optimized.
Batteries achieve the desired operating voltage by connecting several cells in series; each cell adds its voltage potential to derive at the total terminal voltage. Some packs may consist of a combination of series and parallel connections. Laptop batteries commonly have four 3.6V Li-ion cells in series to achieve a nominal voltage 14.4V and two in parallel to boost the capacity from 2,400mAh to 4,800mAh. Such a configuration is called 4s2p, meaning four cells in series and two in parallel.
It is important to use the same battery type with equal voltage and capacity (Ah) and never to mix different makes and sizes. A weaker cell would cause an imbalance, as a battery is only as strong as the weakest link in the chain.
Single Cell Applications
The single-cell configuration is the simplest battery pack; the cell does not need matching and the protection circuit on a small Li-ion cell can be kept simple. Typical examples are mobile phones and tablets with one 3.60V Li-ion cell. Other uses of a single cell are wall clocks, which typically use a 1.5V alkaline cell, wristwatches and memory backup, most of which are very low power applications.
Series Connection
Portable equipment needing higher voltages use battery packs with two or more cells connected in series.
Figure 2: Series connection of four cells (4s).
Adding cells in a string increases the voltage; the capacity remains the same.
High voltage batteries keep the conductor size small. Cordless power tools run on 12V and 18V batteries; high-end models use 24V and 36V. Most e-bikes come with 36V Li-ion, some are 48V. The car industry wanted to increase the starter battery from 12V (14V) to 36V, better known as 42V, by placing 18 lead acid cells in series.
Some mild hybrid cars run on 48V Li-ion and use DC-DC conversion to 12V for the electrical system.
Parallel Connection
If higher currents are needed and larger cells are not available or do not fit the design constraint, one or more cells can be connected in parallel. Most battery chemistries allow parallel configurations with little side effect.
Figure 4: Parallel connection of four cells (4p).
With parallel cells, capacity in Ah and runtime increases while the voltage stays the same.
Series/parallel Connection
The series/parallel configuration shown in Figure 6 enables design flexibility and achieves the desired voltage and current ratings with a standard cell size. The total power is the product of voltage-times-current; four 3.6V (nominal) cells multiplied by 3,400mAh produce 12.24Wh. Four 18650 Energy Cells of 3,400mAh each can be connected in series and parallel as shown to get 7.2V nominal and 12.24Wh. The slim cell allows flexible pack design but a protection circuit is needed.
Figure 6: Series/ parallel connection of four cells (2s2p).
This configuration provides maximum design flexibility. Paralleling the cells helps in voltage management.
Safety devices in Series and Parallel Connection
Positive Temperature Coefficient Switches (PTC) and Charge Interrupt Devices (CID) protect the battery from overcurrent and excessive pressure. While recommended for safety in a smaller 2- or 3-cell pack with serial and parallel configuration, these protection devices are often being omitted in larger multi-cell batteries, such as those for power tool.
Simple Guidelines for Using Household Primary Batteries
- Keep the battery contacts clean. A four-cell configuration has eight contacts and each contact adds resistance (cell to holder and holder to next cell).
- Never mix batteries; replace all cells when weak. The overall performance is only as good as the weakest link in the chain.
- Observe polarity. A reversed cell subtracts rather than adds to the cell voltage.
- Remove batteries from the equipment when no longer in use to prevent leakage and corrosion. This is especially important with zinc-carbon primary cells.
- Do not store loose cells in a metal box. Place individual cells in small plastic bags to prevent an electrical short. Do not carry loose cells in your pockets.
- Keep batteries away from small children. In addition to being a choking hazard, the current-flow of the battery can ulcerate the stomach wall if swallowed. The battery can also rupture and cause poisoning.
- Do not recharge non-rechargeable batteries; hydrogen buildup can lead to an explosion. ·Perform experimental charging only under supervision.
Simple Guidelines for Using Secondary Batteries
- Observe polarity when charging a secondary cell. Reversed polarity can cause an electrical short, leading to a hazardous condition.
- Remove fully charged batteries from the charger. A consumer charger may not apply the correct trickle charge when fully charged and the cell can overheat.
- Charge only at room temperature.
LiFePO4 chemistry lithium cells have become popular for a range of applications in recent years due to being one of the most robust and long-lasting battery chemistries available. They will last ten years or more if cared for correctly. Please take a moment to read these tips to ensure you get the longest service from your battery investment.
Tip 1: Never over charge/discharge a cell!
The most common causes for premature failure of LiFePO4 cells are overcharging and over-discharging. Even a single occurrence can cause permanent damage to the cell, and such misuse voids the warranty. A Battery protection System is required to ensure it is not possible for any cell in your pack to go outside its nominal operating voltage range,
In the case of LiFePO4 chemistry, the absolute maximum is 4.2V per cell, though it is recommended that you charge to 3.5-3.6V per cell, there is less than 1% extra capacity between 3.5V and 4.2V.
Over charging causes heating within a cell and prolonged or extreme overcharging has the potential to cause a fire. EV Works Takes no responsibility for any damages caused as a result of a battery fire.
Over charging may occur as a result of.
- Lack of a suitable battery protection system
- Faulty of infective battery protection system
- incorrect installation of the battery protection system
At the other end of the scale, over-discharging can also cause cell damage. The BMS must disconnect the load if any cells are approaching empty (less than 2.5V). Cells may suffer mild damage below 2.0V, but are usually recoverable. However, cells which get driven to negative voltages are damaged beyond recovery.
On 12v batteries the use of a low voltage cutoff takes the place of the BMS by preventing the overall battery voltage going under 11.5v no cell damage should occur. On the other end charging to no more than 14.2v no cell should be overcharged.
Tip 2: Clean your terminals before installation
The terminals on top of the batteries are made from aluminium and copper, which over time builds up an oxide layer when exposed to air. Before installing your cell interconnectors and BMS modules, clean the battery terminals thoroughly with a wire brush to remove oxidation. If using bare copper cell interconnectors, these should be cleaned too. Removing the oxide layer will greatly improve conduction and reduce heat buildup at the terminal. (In extreme cases, heat buildup on terminals due to poor conduction has been known to melt the plastic around the terminals and damage BMS modules!)
Tip 3: Use the right terminal mounting hardware
Winston cells using M8 terminals (90Ah and up) should use 20mm long bolts. Cells with M6 terminals (60Ah and under) should use 15mm bolts. If in doubt, measure the thread depth in your cells and ensure that the bolts will get close to but not hit the bottom of the hole. From top to bottom you should have a spring washer, flat washer then the cell interconnector.
A week or so after installation, check that all your terminal bolts are still tight. Loose terminal bolts can cause high-resistance connections, robbing your EV of power and causing undue heat generation.
Tip 4: Charge frequently and shallower cycles
With lithium batteries, you will get longer cell life if you avoid very deep discharges. We recommend sticking to 70-80% DoD (Depth of Discharge) maximum except in emergencies.
Swollen Cells
Swelling will only occur if a cell has been over-discharged or in some cases overcharged. Swelling does not necessarily mean the cell is no longer usable though it will likely lose
Eco-conscious drivers are buying hybrid cars and other fuel-efficient vehicles for their lower emissions. The combination of a smaller gasoline engine for power, an electric motor for fuel economy and the promise of so-called green driving have proven to be successful incentives for consumers looking to save money on fuel and do their part to help out the environment. But increased awareness about the environmental impact vehicles and vehicle parts have on the Earth has led drivers to shift their concern from fuel efficiency to something else entirely — hybrid car batteries.
The batteries in hybrid cars are responsible for the better fuel economy that’s become central to the technology. They power the electric motor, which typically propels a hybrid car at lower speeds. This puts less pressure on the gasoline engine and stretches out the amount of fuel a vehicle burns in between trips to the gas station.
But the chemical material that makes up all car batteries, whether it’s a conventional car or a hybrid, is typically toxic. Currently, there are far fewer hybrid cars on the road than conventional cars; however, concerns have been raised that if the number of hybrid cars increase, landfills will soon overflow with toxic batteries that are full of corrosive and carcinogenic materials.
There are three major types of batteries that companies use or are considering for use in hybrid cars: lead-acid, nickel-metal hydride (NiMH) and lithium-ion (Li-ion). By far, lead-acid is considered the most toxic of the three, and on top of that it’s also extremely heavy, reducing some of the fuel efficiency gains from the electric motor. Lead-acid is becoming less of a contender in the hybrid car battery market and is being replaced by nickel-metal hydride. Nickel is less toxic than lead, but it’s not without its own problems — it’s potentially carcinogenic and the mining process is considered hazardous. Since they’re the least toxic, many consider lithium-ion batteries to be the next step for hybrid car batteries. In fact, car companies are investing millions of dollars in research for a working hybrid car battery that uses the same kind of power currently found in laptops and MP3 players.
TOPICS:Battery TechnologyCarbon DioxideGreen TechnologyMITSustainability
By DAVID L. CHANDLER, MIT NEWS OFFICE SEPTEMBER 22, 2018
This scanning electron microscope image shows the carbon cathode of a carbon-dioxide-based battery made by MIT researchers, after the battery was discharged. It shows the buildup of carbon compounds on the surface, composed of carbonate material that could be derived from power plant emissions, compared to the original pristine surface (inset). Courtesy of the researchers
New lithium-based battery could make use of greenhouse gas before it ever gets into the atmosphere.
A new type of battery developed by researchers at MIT could be made partly from carbon dioxide captured from power plants. Rather than attempting to convert carbon dioxide to specialized chemicals using metal catalysts, which is currently highly challenging, this battery could continuously convert carbon dioxide into a solid mineral carbonate as it discharges.
While still based on early-stage research and far from commercial deployment, the new battery formulation could open up new avenues for tailoring electrochemical carbon dioxide conversion reactions, which may ultimately help reduce the emission of the greenhouse gas to the atmosphere.
The battery is made from lithium metal, carbon, and an electrolyte that the researchers designed. The findings are described today in the journal Joule, in a paper by assistant professor of mechanical engineering Betar Gallant, doctoral student Aliza Khurram, and postdoc Mingfu He.
Currently, power plants equipped with carbon capture systems generally use up to 30 percent of the electricity they generate just to power the capture, release, and storage of carbon dioxide. Anything that can reduce the cost of that capture process, or that can result in an end product that has value, could significantly change the economics of such systems, the researchers say.
However, “carbon dioxide is not very reactive,” Gallant explains, so “trying to find new reaction pathways is important.” Generally, the only way to get carbon dioxide to exhibit significant activity under electrochemical conditions is with large energy inputs in the form of high voltages, which can be an expensive and inefficient process. Ideally, the gas would undergo reactions that produce something worthwhile, such as a useful chemical or a fuel. However, efforts at electrochemical conversion, usually conducted in water, remain hindered by high energy inputs and poor selectivity of the chemicals produced.
Gallant and her co-workers, whose expertise has to do with nonaqueous (not water-based) electrochemical reactions such as those that underlie lithium-based batteries, looked into whether carbon-dioxide-capture chemistry could be put to use to make carbon-dioxide-loaded electrolytes — one of the three essential parts of a battery — where the captured gas could then be used during the discharge of the battery to provide a power output.
This approach is different from releasing the carbon dioxide back to the gas phase for long-term storage, as is now used in carbon capture and sequestration, or CCS. That field generally looks at ways of capturing carbon dioxide from a power plant through a chemical absorption process and then either storing it in underground formations or chemically altering it into a fuel or a chemical feedstock.
Instead, this team developed a new approach that could potentially be used right in the power plant waste stream to make material for one of the main components of a battery.
While interest has grown recently in the development of lithium-carbon-dioxide batteries, which use the gas as a reactant during discharge, the low reactivity of carbon dioxide has typically required the use of metal catalysts. Not only are these expensive, but their function remains poorly understood, and reactions are difficult to control.
By incorporating the gas in a liquid state, however, Gallant and her co-workers found a way to achieve electrochemical carbon dioxide conversion using only a carbon electrode. The key is to preactivate the carbon dioxide by incorporating it into an amine solution.
“What we’ve shown for the first time is that this technique activates the carbon dioxide for more facile electrochemistry,” Gallant says. “These two chemistries — aqueous amines and nonaqueous battery electrolytes — are not normally used together, but we found that their combination imparts new and interesting behaviors that can increase the discharge voltage and allow for sustained conversion of carbon dioxide.”
They showed through a series of experiments that this approach does work, and can produce a lithium-carbon dioxide battery with voltage and capacity that are competitive with that of state-of-the-art lithium-gas batteries. Moreover, the amine acts as a molecular promoter that is not consumed in the reaction.
The key was developing the right electrolyte system, Khurram explains. In this initial proof-of-concept study, they decided to use a nonaqueous electrolyte because it would limit the available reaction pathways and therefore make it easier to characterize the reaction and determine its viability. The amine material they chose is currently used for CCS applications, but had not previously been applied to batteries.
This early system has not yet been optimized and will require further development, the researchers say. For one thing, the cycle life of the battery is limited to 10 charge-discharge cycles, so more research is needed to improve rechargeability and prevent degradation of the cell components. “Lithium-carbon dioxide batteries are years away” as a viable product, Gallant says, as this research covers just one of several needed advances to make them practical.
But the concept offers great potential, according to Gallant. Carbon capture is widely considered essential to meeting worldwide goals for reducing greenhouse gas emissions, but there are not yet proven, long-term ways of disposing of or using all the resulting carbon dioxide. Underground geological disposal is still the leading contender, but this approach remains somewhat unproven and may be limited in how much it can accommodate. It also requires extra energy for drilling and pumping.
The researchers are also investigating the possibility of developing a continuous-operation version of the process, which would use a steady stream of carbon dioxide under pressure with the amine material, rather than a preloaded supply the material, thus allowing it to deliver a steady power output as long as the battery is supplied with carbon dioxide. Ultimately, they hope to make this into an integrated system that will carry out both the capture of carbon dioxide from a power plant’s emissions stream, and its conversion into an electrochemical material that could then be used in batteries. “It’s one way to sequester it as a useful product,” Gallant says.
“It was interesting that Gallant and co-workers cleverly combined the prior knowledge from two different areas, metal-gas battery electrochemistry and carbon-dioxide capture chemistry, and succeeded in increasing both the energy density of the battery and the efficiency of the carbon-dioxide capture,” says Kisuk Kang, a professor at Seoul National University in South Korea, who was not associated with this research.
“Even though more precise understanding of the product formation from carbon dioxide may be needed in the future, this kind of interdisciplinary approach is very exciting and often offers unexpected results, as the authors elegantly demonstrated here,” Kang adds.
MIT’s Department of Mechanical Engineering provided support for the project.
Publication: Aliza Khurram, et al., “Tailoring the Discharge Reaction in Li-CO2 Batteries through Incorporation of CO2 Capture Chemistry,” Joule, 2018; doi:10.1016/j.joule.2018.09.002
Imagine having access to a battery, which has the potential to power your phone for five continuous days, or enable an electric vehicle to drive more than 1000km without needing to “refuel.” Monash University researchers are on the brink of commercializing the world’s most efficient lithium-sulfur (Li-S) battery, which could outperform current market leaders by more than four times, and power Australia and other global markets well into the future. Dr. Mahdokht Shaibani from Monash University’s Department of Mechanical and Aerospace Engineering led an international research team that developed an ultra-high capacity Li-S battery that has better performance and less environmental impact than current lithium-ion products.
The researchers have an approved filed patent (PCT/AU 2019/051239) for their manufacturing process, and prototype cells have been successfully fabricated by German R&D partners Fraunhofer Institute for Material and Beam Technology.
Associate Professor Matthew Hill, Dr. Mahdokht Shaibani and Professor Mainak Majumder. Credit: Monash University
Some of the world’s largest manufacturers of lithium batteries in China and Europe have expressed interest in upscaling production, with further testing to take place in Australia in early 2020.
The study was published in Science Advances today (Saturday, January 4, 2020) — the first research on Li-S batteries to feature in this prestigious international publication.
Professor Mainak Majumder said this development was a breakthrough for Australian industry and could transform the way phones, cars, computers, and solar grids are manufactured in the future.
“Successful fabrication and implementation of Li-S batteries in cars and grids will capture a more significant part of the estimated $213 billion value chain of Australian lithium, and will revolutionize the Australian vehicle market and provide all Australians with a cleaner and more reliable energy market,” Professor Majumder said.
“Our research team has received more than $2.5 million in funding from government and international industry partners to trial this battery technology in cars and grids from this year, which we’re most excited about.”
Using the same materials in standard lithium-ion batteries, researchers reconfigured the design of sulfur cathodes so they could accommodate higher stress loads without a drop in overall capacity or performance.
Inspired by unique bridging architecture first recorded in processing detergent powders in the 1970s, the team engineered a method that created bonds between particles to accommodate stress and deliver a level of stability not seen in any battery to date.
Attractive performance, along with lower manufacturing costs, abundant supply of material, ease of processing and reduced environmental footprint make this new battery design attractive for future real-world applications, according to Associate Professor Matthew Hill.
“This approach not only favors high-performance metrics and long cycle life, but is also simple and extremely low-cost to manufacture, using water-based processes, and can lead to significant reductions in environmentally hazardous waste,” Associate Professor Hill said.
According to the Environmental Protection Agency, billions of batteries find their way into landfills every year.
These batteries contain toxic substances which can then leech into the earth and water supplies. Fortunately, this negative impact on the environment can be avoided by battery recycling.
Did you know that you can recycle lithium batteries? You can, and it’s easier than you might think. Keep reading to learn more about the only safe way to get rid of old batteries.
Why Recycle Batteries
Before we go any further, let’s take a quick look at why it’s important to recycle batteries. When you understand why you’re doing something, you’re more likely to continue doing it.
Here are some of the reasons why you should be recycling old batteries:
- Conserves natural resources
- Reduces the amount of waste in landfills
- Prevents pollution created by the collection of raw materials
- Creates new jobs in the recycling and manufacturing industries
- Saves energy
- Avoids polluting the environment and groundwater supplies
Many of these benefits come from the fact that metals such as aluminum, nickel, and copper can all be harvested from old batteries. These can then be used in other ways and new metals don’t have to be taken from the earth.
What to Do Before Taking in Batteries
Before you take your batteries somewhere to recycle them, there are a few things you’ll want to do.
First and foremost, you need to keep your batteries out of your regular trash and recycling bin. Lithium batteries can cause sparks, even if they’re completely dead. This is why you want to avoid putting them with other recyclables.
To prevent them from sparking, cover the terminals or ends with electrical tape. It’s a good idea to get into the habit of doing this as soon as a battery is removed so it won’t cause any problems.
The other thing you want to do before you pack up your old batteries to recycle is to call ahead. You want to make sure the place you’re taking them accepts the type of battery you have so you don’t waste a trip out there.
You also need to ask about fees. Some places will charge a fee to recycle batteries for you whereas other places do it for free. Asking in advance will help you avoid an unpleasant surprise.
Where to Recycle Batteries
Recycling lithium batteries is as easy as finding a place that will take them. Here are a few resources you can use to recycle lithium batteries:
Recycling Center
One of the best places to take your batteries to where there’s a good chance they’ll take them is a local recycling center. Not every recycling center takes every type of battery, so this is one you’ll definitely want to call before going.
A quick search online should allow you to find several recycling centers near you so you can find one that will take your old batteries.
Household Hazardous Waste Center
If you’re unfortunate enough to not have a recycling center near you that will take your lithium batteries, you should be able to find a household hazardous waste center.
This will require another online query which should lead you to the right place that will definitely take your old batteries.
Scrap Yards
To make your trip worth it, you may consider taking your old batteries to a scrap yard. Many of these locations will purchase them from you because they can remove the metals from them and make a profit.
This is particularly great for hobbyists who have several large batteries lying around that are in need of recycling.
Scrap yards don’t often take alkaline batteries, so if you also have some smaller batteries saved up from various electronics, you’ll have to visit a couple of places to get rid of all of your batteries at once.
Local Library or Community Center
Sometimes, a city or local community will have a battery drive or else a specific location where you can drop off batteries to be recycled for you. Ask at your local library or community center for more information about this.
In most cases, they primarily take smaller household batteries and other used electronics rather than larger batteries. For this reason, you’ll want to double-check that your larger vehicle batteries will be accepted.
Because of how close these places generally are to you compared to recycling centers, this can be the most convenient option.
Electronic and Hardware Stores
Here are some stores that may accept batteries for recycling:
- Staples
- Best Buy
- Home Depot
- Lowes
As you can imagine, hardware stores are more likely to accept larger batteries since they sell them for tools and smaller vehicles.
Electronic stores may only accept smaller batteries used in cell phones and other electronics, so you’ll definitely want to ask before taking them there.
It’s also important to keep in mind that not every store location offers this service. Call ahead and ask about the specific types of batteries you’re looking to recycle before showing up with them.
There might be a battery explosion when internal electrical parts short-circuit, when mechanical issues occur after a fall or an accident, or when they is installation error. All of these failures happen when one side of the battery is heated up and cannot lower down the high temperature fast enough, creating a continuous reaction that generates more and more heat. This kind of snowball process is usually termed as thermal runaway.
Introduction
The process can occur in just milliseconds. This has attracted much attention from the press. But it turns out that not all batteries are equally likely to fail. Any energy storage device carries a risk, as demonstrated in the latest moment on 15th March 2017, involving a pair of headphones exploding on a plane. Many batteries come along with a safety risk, and battery manufacturers are supposed to meet safety requirements.
Even though Lithium-ion batteries are safe, there are millions of customers using then so failures are bound to occur. A one-in-200,000 mechanical failure that happened in 2006 caused a recall of close to six million lithium-ion packs (Battery University).
Specialists of the lithium-ion batteries comment that on rare occasion microscopic metal particles may touch with other parts of the battery cell, causing a short circuit with in the cell.
So why do people and businesses still use them?
Lithium-ion batteries are super-efficient. They keep large capacity of energy in a small space and can keep electronic gadgets working for a long time. Li-ion power cells are also ranked highly in technology. The earliest rechargeable lithium-ion batteries were made for Handy-cams 25 years ago, and now there are many battery suppliers around the globe.
But unlike most advanced technologies, they get volatile with time. This is mainly due to the fact that we want higher-capacitydable batteries in small packages at affor prices. The symptoms may be the similar as they explode but a lot of other factors might be contributing to lithium-ion’s explosions.
These include;
Production Flaws
With all these exploding batteries, the first diagnosis is something must be wrong with the ways the battery is manufactured. Many people might think like that, but Samsung Note 7 issue illustrates that pinpointing the key flaw is not very easy. The initial recall involved devices that had batteries made by Samsung, the ones that did not have enough room between the battery’s protective pouch and electrodes. The squeeze tilted the electrodes in some batteries, leading them to short-circuit. But once the devices were recalled, replacing them with safer batteries from another firm had different issues. Many were not wrapped well, while others had ragged edges inside that caused damage to the main separator. That also caused short circuiting, but for entirely different reasons.
User-Supplied Damage
Even if a device is designed well, continuous dropping and subjecting it to long-term wear and tear can cause damage to the volatile energy source. The best way to tell if your battery is damaged is if it looks all swollen—evidence that the chemicals inside the battery are producing too much gas. That swelling also creates its own stress with the battery housing, which could result to a rupture. Unfortunately, a lot of devices today have a sealed-in battery, and taking the device apart to inspect it involves nullifying the warranty. If the external package of any device appears to be pushing apart or feels abnormally hot to the touch, it’s best to be careful and bring it in for inspection.
Battery Design Flow
Most of today’s devices are designed to be as slim, light, and sleek as possible in order to go with the trend. That can cause stress on an otherwise well-built battery, especially a high-capacity cell packed into a tiny body. Pressure from the hardware surrounding the battery can lead to damage to the electrodes and lead to short circuiting. Insufficient venting or thermal management can lead the flammable electrolyte inside the battery to heat up. Once it gets hot, chemical reactions can cause it to heat up even more and spiral out of control. It’s a situation called thermal runaway that often ends in an explosion or fire.
Industry Pressure and Competition
Companies make billions of profits when they save a small amount on each battery. As a result, many lithium-ion battery manufacturers do shortcuts in order to price their cells at affordable prices. The materials may not meet the required quality, causing damage in the already-thin separator. This situation was likely a major cause of the hoverboard fires: The first models on the market were expensive, and their popularity bred knockoffs with cheap prices and even cheaper internals. Crowd funding and low-priced components have democratized the consumer-electronics industry, but savings often come at the expense of safety.
Even though exploding batteries sound scary, they’re actually quite rare. Himax is committed to supply safer lithium batteries to its customers by using LiFePO4 cells in a variety of applications. LiFePO4 is a more stable and safer cathode material.
The hybrid car is not new – Ferdinand Porsche designed the series-hybrid vehicle in 1898. Called the Lohner-Porsche carriage, the hybrid function served as an electrical transmission rather than power boost. With Mr. Porsche in the driver’s seat, the car broke several Austrian speed records, including the Exelberg Rally in 1901. Another example of an early hybrid was the 1915 Woods Motor Vehicle built in Chicago. The car used a four-cylinder internal combustion engine and an electric motor. Below 15 mph (25 km/h), the electric motor propelled the vehicle; at higher speeds, the gasoline engine kicked in to take the vehicle up to a top speed of 35 mph (55 km/h). As part of the Federal Clean Car Incentive Program, Victor Wouk installed a hybrid drive train in a 1972 GM Buick Skylark but the EPA canceled the program in 1976. Meanwhile, Honda and Toyota have made strong headways by commercializing attractive and fuel-efficient hybrid cars.
The hybrid electric vehicle (HEV) conserves fuel by using an electric motor that assists the internal-combustion engine (IC) on acceleration and harnesses kinetic energy during breaking. Furthermore, the IC motor turns off at stops and during slow travel. When full power is required, both the IC engine and the electric motors engage simultaneously to get maximum boost. This power-sharing scheme offers two advantages; it calls for a smaller IC engine and improves acceleration because the electric motor has excellent torque characteristics.
Most HEVs use a mechanical drive train from the IC engine to the wheels. In this respect, the HEV is similar to an ordinary vehicle with crankshaft, clutch and transmission, with the difference of having an electric motor and a battery. This design is known as a parallel configuration. Most up-and-coming plug-in HEVs use the serial configuration in which the wheels are powered by one or several electric motors. Instead of a mechanical link, the IC engine energizes a generator to produce electricity for the motor(s). Similar to a laptop or a cell phone, the driver plugs the car into the AC outlet for an overnight charge. The typical driving range with a full charge is 20 miles or 32 km. On long trips, the IC engine engages to provide continuous power for the electric motors.
What’s the best battery for the hybrid car?
The early HEV models used lead acid batteries because there was no alternative. Today, Honda and Toyota employ nickel-metal-hydride (NiMH). This chemistry is lighter and environmentally friendlier than lead-based systems. The battery consists of cylindrical cells that are connected in series to attain several hundred volts. The cell strings are suspended in mid air to allow air-cooling. Figure 1 shows a demonstration pack of an early Toyota hybrid car battery.
Figure 1: Nickel-metal-hydride battery of a Toyota hybrid car.
The cells (orange color) are supported to allow forced air-cooling. The battery is placed behind the back seat.
Courtesy of the Toyota Museum, Nagaya, Japan
One of the critical battery requirements for hybrid applications is longevity. Rechargeable batteries for consumer products typically last for two to three years. This short service life is no major drawback with cell phones, laptops and digital cameras because the devices get obsolete quickly. At $2,000 to $3,000 per battery pack, the replacement cost of an HEV battery would constitute a major expense.
Most batteries for HEV are guaranteed for eight years. To meet this long service life, the cells are optimized for longevity and not size and weight, as is the case with portable applications. Since the battery runs on wheels, the increased weight and size is not too critical.
A NiMH for an HEV can be charged and discharged 1,000 times if done at an 80% depth-of-discharge. In a hybrid vehicle, a full discharge occurs seldom except if the owner lives on a mountain and requires all available battery power to commute home. Such a routine would add stress to the battery and the life would be shortened. In most other application, the hybrid car only uses 10% of the rated battery capacity. This allows thousands of charge/discharge cycles. Batteries in satellites use a similar system in which the battery discharges less than 10% during a satellite night. NASA achieves this by over-sizing the battery.
One of the limitations of NiMH is moderate energy conversion efficiency. This translates to the battery getting hot on charge and discharge. The charge efficiency is best at 50-70% state-of-charge. Above 70% the battery cannot absorb the charge well and much of the charging energy is lost in heat. Operating a battery with a partial charge requires a larger mass that lowers the energy-to-weight ratio and efficiency.
The Japanese car manufacturers have tried several battery chemistries, including going back to lead acid. Today, the focus is on lithium-ion. The cobalt-based lithium-ion is one of the first chemistries in the lithium family and offers a very high energy density. Unfortunately, this battery system cannot deliver high currents and is restricted to portable applications.
HEV manufacturers are experimenting with manganese (spinel) and phosphate versions. These lithium-ion systems offer an extremely low internal resistance, deliver high load currents and accept rapid charge. Unlike the cobalt version, the resistance stays low throughout the life of the battery. To verify the characteristic of manganese-based lithium-ion, a research lab applied 30,000 discharge/charge cycles over a period of seven years. Although the capacity dropped from 100% to 20%, the cell retained its low internal resistance. The drawback of manganese and phosphate is lower energy density but these systems provide 20% more capacity per weight than NiMH and three times more than lead acid. Figure 2 illustrates the energy densities of the lead, nickel and lithium-ion systems. It should be noted that lithium-ion systems have the potential of higher energy densities but at the cost of lower safety and reduced cycle life.
Figure 2: Energy densities of common battery chemistries.
Lithium-cobalt enjoys the highest energy density. Manganese and phosphate systems are thermally more stable and deliver higher load currents than cobalt.
The Lithium-ion systems are promising candidates for both the HEV and plug-in HEV but require more research. Here are some of the roadblocks that need to be removed:
Durability: The buyer requests a warranty of ten years and more. Currently, the battery manufacturer for hybrid electric vehicles can only give eight years on NiMH. The longevity of lithium-ion has not yet been proven and honoring eight years will be a challenge.
Cost: If the $2,000 to $3,000 replacement cost of a nickel-metal-hydride pack is prohibitive, lithium-ion will be higher. These systems are more expensive to produce than most other chemistries but have the potential for price reductions through improved manufacturing methods. NiMH has reached the low cost plateau and cannot be reduced further because of high nickel prices.
Safety: Manganese and phosphate-based lithium-ion batteries are inherently safer than cobalt. Cobalt gets thermally unstable at a moderate temperature of 150°C (300°F). Manganese and phosphate cells can reach 250°C (480°F) before becoming unsafe. In spite of the increased thermal stability, the battery requires expensive protection circuits to supervise the cell voltages and limit the current in fail conditions. The safety circuit will also need to compensate for cell mismatch that occurs naturally with age. The recent reliability problems with lithium-ion batteries in portable devices may delay entry into the HEV market.
Availability: Manufacturers of manganese and phosphate cells can hardly keep up with the demand. A rapid increase of lithium for HEV batteries would put a squeeze on battery production. With 7 kg (15 lb) of lithium per battery, there is talk of raw material shortages. Most of the known supplies of lithium are in South America, Argentina, Chile and Bolivia.
The plug-in hybrid electric vehicle (PHEV)
Imagine a plug-in electric vehicle that can go 20 miles (32 km) with a single charge from the electrical outlet at home. There is no pollution and the neighbors won’t hear you coming and going because the vehicle is totally silent. With the absence of gas tax, the road system is yours to use for free. Or is it?
As good as this may sound, the savings will be small or non-existent because of the battery. Dr. Menahem Anderman, a leading expert on advanced automobile batteries, says that we still have no suitable battery for the plug-in HEV and that the reliability of lithium-ion technology for automotive applications has not yet been proven. Unlike the ordinary HEV that operates on shallow charges and discharges, the plug-in HEV is in charge depletion mode that requires deep discharges. To obtain an acceptable driving range, the PHEV battery will need to be five times larger than the HEV battery. With an estimated life span of 1000 full charge and discharge cycles, the battery would need to be replaced every three years. At an estimated $10,000 per battery replacement, the anticipated cost savings would be quickly exhausted.
Modern cars do more than provide transportation; they also include auxiliary devices for safety, comfort and pleasure. The most basic of these auxiliaries are the headlights and windshield wipers. Most buyers would also want heating and air-conditioning systems. These amenities are taken for granted in gasoline-powered vehicles and will need to be used sparingly in a PHEV.
Analysts give another 10 years before a viable plug-in HEV will be available. The promise of a clean-burning fuel cell car is still vivid in our memory. Analysts now estimate 20 years before the fuel cell is ready for mass-produced cars. There are rumors that the fuel cell may never make it into an ordinary car. If this is true, a dream will go down in history with the steam-powered airplane of the mid 1800s that was simply too cumbersome to fly.
The paradox of the hybrid vehicle
At the Advanced Automotive Battery Conference in Hawaii, a delegate member challenged a maker of HEVs with the claim that a German diesel car can get better fuel economy than the hybrid. The presiding speaker, being a trained salesman, flatly denied this notion. There is some truth to his claim, however. On the highway, the diesel car is indeed more fuel-efficient but the HEV has the advantage in city driving. Power boost for fast acceleration and regenerative breaking are advantages that the German diesel does not offer.
Someone then asked, “What would happen if the HEV depletes its batteries while driving up a long mountain pass? Will the car have enough power?” The answer was that the car would make it with the IC engine alone but the maneuverability would be restraint. To compensate for this eventuality, some HEV manufacturers offer SUVs featuring a full-sized IC motor of 250 hp and an electrical motor at 150 hp; 400 hp in total. Such a vehicle would surly find buyers, especially if the government provides grant money for being ‘green.’ It’s unfortunate that the buyers of a small car or the commuters taking public transport won’t qualify for such a handout.
Conclusion
We anticipate that lithium-ion will eventually replace nickel-metal-hydride in hybrid electric vehicles but short service life, high manufacturing costs and safety issues will stand in its way today. We need to remind ourselves that the automotive market can only tolerate a marginal cost increase for a new battery technology. In terms of added capacity, lithium-ion offers only a 20% increase in energy density per weight over nickel-based systems. The nickel-metal-hydride has proven to work well in current HEVs and a new chemistry would need to offer definite advantages over present systems to find buyers.
Toyota, Honda and Ford are leading in HEV technology. Other major automakers are expected to offer competitive models by 2010. Currently, Panasonic EV Energy and Sanyo supply over 90% of the HEV batteries. Both companies are also developing lithium-ion batteries.
While Japan and Korea are focusing on manganese systems, the USA is experimenting with phosphate, the chemistry that made the A123 Systems famous. Europe is relying on clean-burning diesel. These engines are so clean that they won’t even stain a tissue that is placed on the exhaust pipe. BMW is working on a zero emission hydrogen car.
Time will tell who will be the winner in the race for cleaner, more fuel-savvy vehicles and longer-living cars. In terms of longevity, the diesel would be the winner today. We hope that future batteries will one-day have the endurance to match or exceed the robust diesel engine.
