Nickel metal hydride battery (Commonly abbreviated to “Nimh battery”) has dominated the market today. This is because the battery chemistry is advanced in performance, safety, the cycle of life, and other parameters. In addition to that, manufacturers are working to improve the cell. The cell is designed to be used on electronic products that consider run time. As a result of this, it is used in a wide range of applications. Before you buy a cell, it is essential to not some of the useful factors. Let us see safety, usage, and differences of nickel-metal hydride.
Are NiMh Batteries Safe?
Generally, batteries are safe to buy you need to take precautions. Nimh is a nontoxic cell to human beings but harmful to other living things such as plants. However, the main problem is electrolytes. When exposing to extreme temperatures, electrolytes react with materials to create gas.
Proper charging means fully charging a cell according to the manufacturer’s rule. You can determine the completely charged battery by examining charge currents as well as recording charge time. Moreover, you must charge a battery at a moderate temperature. Extreme temperatures can cause an internal circuit. This produces heat thus makes the cell to be unsafe. You can buy a battery charger that measures temperatures. It will alert you when the temperatures rise.
Proper Storage
Cells are not stored inside a device. Remove the battery from the equipment and put it in the original package. In addition to that, store it in a cool dry place to avoid heat. Also, cells should not be put in contact, ensure they are separated.
Ventilation
It is recommended to ventilate the room for charging cells. Electrolytes are produced during charging and they emit hydrogen. The gas colorless and odorless hence you cannot recognize. The downside of hydrogen is that it is highly explosive. It mixes with oxygen in the air when produced. Since hydrogen is lighter than oxygen, it accumulates above oxygen. For this reason, it can result in a massive explosion in the room. On top of that, hydrogen can cause eye and skin problems.
Easy Safety Tips To Follow
Cells should always keep devices away from children. This includes wrist watches, remote controls, thermometers, cards, and other products that have batteries.
Do not expose lose batteries to pets and small children. Keep them away from access.
Create awareness by teaching friends and parents on keeping cells away.
If your child has swallowed a cell, run to the hospital, and do not give the child anything to drink.
What are NiMhBatteries Used For?
Mobile Phones
Nickel metal hydride has a greater density. The cell is designed to be a slim geometry. This gives an energy density of about 60Wh/kg. The cell takes up to 300 life cycles. Ways to increase cycles include draining and recharging the device for about four times.
Laptops
Laptops use several types of cells including nickel-metal hydride. The batteries work well in portable computers and last longer, unlike nickel-cadmium. If you want to increase the life cycle of nickel-metal hydride on a laptop, you should discharge more often.
Computers
Computers that use NiMH last longer. Also, they deliver great performance.
Digital Cameras
A good digital camera should work for long before it drains. Before the introduction of lithium-ion, most digital cameras used Nimh and still use.
The charge cycle is referred to as the charging and discharging process of a rechargeable battery. The lithium-ion battery has a powerful ability to perform longer charge cycles compared to nickel-metal hydride. This parameter contributes to the high cost of lithium-ion batteries. There are ways you can do to increase life cycles. For example, reducing the battery temperature, choose the right termination charge, prevent high charge, and discharge.
Voltages
Voltage is the characteristic of a cell. It is examined through chemical reactions, polarization, and components of a battery. The nominal voltage of a lithium-ion is about 3.70V. On the contrary, nickel-metal hydride operates at a nominal voltage of 1.2V in each cell. A high nominal voltage is great because it increases watt-hours.
High Power
Lithium-ion battery operates at higher voltage hence it delivers more power compared to nickel-metal hydride. NiMH produces has lower voltages that can support high power.
Chargers
Nickel metal hydride and lithium-ion need specific chargers. These chargers have different types of electronics. You cannot use a different charger on li-ion because it can result in accidents. Manufacturers have designed chargers that show currents, voltages as well as charge time. Also, it examines the rate of charging and cuts the process in case of issues. Conversely, nickel-metal hydride chargers do not come with safety parameters.
Size
Lithium-ion is a more advanced cell with less weight than most battery technology. Nickel metal hydride is among the heavy cells. Weight is a crucial factor to consider when it comes to transportation. Lithium-ion can be moved from one place to another without using much energy.
Dangerous
Nickel metal hydride is not as dangerous as lithium-ion. Nickel metal hydride does not cause a fire when exposed to oxygen. Lithium-ion explodes when exposed to oxygen. Therefore, it requires a protection circuit to guarantee safety.
Price
The most important thing when you buy a cell is checking the price of a product. The cost of lithium-ion is almost three times s more of other batteries. Nickel metal hydride is affordable. The rise of demand for cells in consumer electronics will make the price of lithium to go down.
Top Nimh Battery Manufacturers Recommend
Himax was founded in 2002 and started to produce nickel-metal hydride batteries, and successfully developed high power and Low-self discharge NiMH batteries. Now Himax Nimh batteries are widely used in applications that require higher power, such as radio control cars, toys, power tools (e.g. electric drill, saws, angle grinders, etc.), and some medical devices in the global market.
https://himaxelectronics.com/wp-content/uploads/2020/09/NI-MH-Battery-Pack-1.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-09-08 02:54:312024-04-26 03:50:18Nimh Battery: Safety, Usage And Difference
Nickel metal hydride (NiMH) batteries are an improvement from nickel-cadmium (NiCd) batteries, especially as they replace cadmium (Cd) with a metal that can absorb hydrogen.
NiMH can provide higher capacity than NiCd batteries, have less obvious memory effect, and be more environmentally friendly without the toxic cadmium.
What is a memory effect?
The memory effect is a phenomenon that occurs when the battery contents crystallize over time and use. This generally occurs in NiCd batteries, less in NiMH batteries, and not at all with lithium batteries. It is generally believed that low-voltage NiMH batteries have no memory effect while both high-voltage NiMH and NiCd batteries have this memory effect.
The memory effect is caused by the repeated partial charging and discharging of the battery. If a Ni-MH battery is used for 40% and then charged to 80%, the battery will “remember” this and will temporarily reduce its capacity, resulting in a shortened use time.
How do I avoid the memory effect on NiMH batteries?
To prevent this memory effect, it is recommended to recharge the batteries after use or discharge them on a charger with a discharge function. Recharging a battery that is still charged will produce a memory effect.
To fully discharge the battery, the battery must be placed in standby mode for about 24 hours. After it is fully discharged, it can be fully charged. After so many cycles, the battery capacity can be restored unless the battery is damaged.
In general, to avoid the memory effect, it is recommended that consumers choose nickel-metal hydride batteries or lithium batteries.
If you want to know more about NiMH batteries, or other related information. HiMax is mainly engaged at NiMH batteries and lithium batteries, please feel free to contact us via email: sales6@himaxelectronics.com
https://himaxelectronics.com/wp-content/uploads/2020/09/NI-MH-Battery-Pack.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-09-01 03:19:532024-04-29 01:37:00Ni-MH Batteries And Their Memory Effect
Compared to a lithium ion polymer (LiPo) battery, the nickel-metal hydride (NiMH) battery is a relatively safe battery as it is well designed in terms of safety performance due to its material and structure.
Generally, the NiMH rechargeable batteries rarely leak, unlike alkaline batteries. However, both alkaline and rechargeable batteries contain electrolytes, which could induce leakage when the batteries are used incorrectly.
By this logic, nickel-metal hydride batteries may explode. The principle of explosion is that the air pressure inside an object becomes too large, so the container cannot be contained. When the container breaks, it results in an explosion as the air pressure is released in an instant.
If a battery is used improperly, there can be an overcharge/discharge, short circuit, and even increase in internal voltage. To prevent the battery from exploding, a recoverable safety valve will open and reduce the internal pressure, thereby preventing an explosion.
What are NiMh batteries?
The nickel-metal hydride battery is mostly used in mobile-communication equipment, power tools, and medical equipment.
NiMH batteries are divided into high-voltage and low-voltage batteries. The high-voltage NiMH battery was first developed by M.Klein and J.F. Stockel in the United States in the early 1970s. Since then, there has been a tendency to replace nickel-cadmium with nickel-metal hydride batteries.
The positive electrode active material of Ni-MH battery is Ni (OH) 2 (called NiO electrode), the negative electrode active material is metal hydride, also called hydrogen storage alloy (the electrode is called hydrogen storage electrode), and the electrolyte is 6 mol/L potassium hydroxide solution.
The batteries are produced by different methods according to how they will be used. Different methods include the sintering, pulping, foam-nickel, fiber-nickel, and infiltration process.
Many batteries use the slurry-pulled negative electrode and the foamed nickel positive electrode to form the battery. The charge-discharge chemical reactions are as follows:
Hab: hydrogen adsorption; the process from left to right is the charging process; the process from right to left is the discharging process.
Features of NiMh batteries
Low-voltage nickel-metal hydride batteries have the following characteristics:
The voltage is 1.2 to 1.3V, which is equivalent to that of cadmium nickel batteries. The energy density is high, which is also more than 1.5 times that of cadmium nickel batteries.
They can be charged and discharged quickly, and they have good low-temperature performance. They are sealable and have strong resistance to overcharge and discharge. There is no dendrite formation, which prevents short circuiting. Overall, low-voltage NIMH batteries are safe and reliable.
High-voltage nickel-metal hydride batteries have the following characteristics:
The batteries have better over-discharge and overcharge protection, can withstand higher charge-discharge rate and also does not have dendrite formation. The mass specific capacity is 60Ah/kg, which is 5 times that of nickel-cadmium batteries.
They also have a long cycle life (up to a 1000 cycles) and excellent low-temperature performance. They are fully sealed and require less maintenance, and the capacity does not change significantly even at -10℃.
Below are just a couple of preventative measures to prevent NiMH batteries from exploding.
Avoid overcharging during use
Users should avoid overcharging because it is easy to cause the positive and negative electrodes in the battery to swell. This will cause the active material to fall off, the separator and the conductive network to be damaged, and the battery ohmic (Ω) polarization to become larger.
Storage of NiMH batteries
The nickel-metal hydride battery should be fully charged. If the battery is stored for a long period of time, the function of the hydrogen storage alloy of the battery negative electrode weakens, which affects the battery life.
Learn more about Himax NiMH batteries
Himax’s nickel-metal hydride batteries are the world ’s leading level, offers up to 2 times the C-rate of same size standard Nickel Cadmium Batteries. Due to their higher discharge rate and energy density features, users can use on more powerful equipments and applications.
Himax offers are variety of NiMH Battery Cells with wide temperature ranges. These Cells provide new electrode development which allows for a wide temperature range and long life. The cells have good availability with a wide cell selection that includes stable and compatible sizes.
There are three types of medical batteries commonly seen in hospitals and clinical settings, and it is important to be able to distinguish them in order to know which custom battery adapter is the right fit when analyzing battery life:
Removable batteries: Nurses charge these packs on charging stations and get periodic analysis in the service center. Typical uses are defibrillators, infusion pumps, diabetic monitors, and surgical tools.
Built-in batteries:Increasingly, batteries are internal to the devices and are charged while the device is connected to the grid. Battery maintenance is done by the bio-med technician by opening the instrument. Typical uses are modern defibrillators, patient monitors, ventilators, surgical tools.
Standby batteries: These batteries are built into instruments on wheels and service as backup during transit and at bed-side. Many of these batteries are still lead acid. The depth of discharge is small if the nurse remembers to connect the AC cord. Typical uses are COW (Computer-on-wheels) blood transfusion units, as well as portable x-ray.
Dave Marlow, a certified biomedical equipment technician at the University of Michigan Health System, categorizes the battery as a “mixed bag of challenges”, with different medical facilities having different assortments of capabilities, battery technologies, manufacturing approaches, user training and experience differences. This is due to the fact that medical batteries must be designed, manufactured and labelled specifically for their use with specific medical devices (source) making the list of batteries designed for each machine essentially endless.
https://himaxelectronics.com/wp-content/uploads/2020/06/Medical-battery.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-06-09 06:03:482024-04-26 03:48:11Identifying Different Types of Medical Batteries
Toyota is all set to enter the growing all-electric car market having technology edge of lithium-ion battery that could equip it with more power without significant extra cost.
Toyota City, Japan: Engineers at Toyota Motor Corp say they have tamed volatile lithium-ion battery technology, and can now safely pack more power at no significant extra cost, giving the Japanese automaker the option to enter the growing all-electric car market.
While rivals including Tesla Motors and Nissan Motor Co began adopting lithium-ion battery technology nearly a decade ago, Toyota has largely held back due to concerns over cost, size and safety.
Lithium-ion batteries can be unstable and have been blamed for incendiary Samsung smartphones and smoking Dreamliner airplanes.
Having Toyota endorse lithium-ion will be a fillip for the developing technology, and gives the automaker the option to produce for an all-electric passenger car market which it has avoided, preferring to put its heft behind hydrogen fuel-cell vehicles (FCVs).
Toyota says its Prius Prime, a soon-to-be-launched plug-in electric version of the world’s top-selling gasoline hybrid, will use lithium-ion batteries, with enough energy to make the car go around 60 kms (37.3 miles) when fully charged before the gasoline engine kicks in. Because of different methodology in measuring a car’s electric mode range, the Prime’s 60 km range will be listed in the United States as around 25 miles (40.2 kms).
‘Safety, safety, safety’
Many lithium-ion car batteries use a chemical combination of nickel, cobalt and manganese. These store more energy, take a shorter time to charge, and are considered safer than other Li-ion technologies. But they can still overheat and catch fire if not properly designed, manufactured and controlled.
“It’s a tall order to develop a lithium-ion car battery which can perform reliably and safely for 10 years, or over hundreds of thousands of kilometers,” said Koji Toyoshima, the chief engineer for the Prius.
“We have double braced and triple braced our battery pack to make sure they’re fail-safe … It’s all about safety, safety, safety,” he told Reuters.
Toyota has mainly used the more mature nickel-metal hydride batteries to power the motor in the conventional Prius, widely regarded as the forefather of the ‘green’ car, though it did use some lithium-ion batteries from 2009 in its first plug-in hybrid Prius, around the time the first all-electric cars powered by lithium-ion batteries – such as the Tesla Roadster and Nissan Leaf – came on to the mass market.
Toyota’s confidence in its battery’s safety and stability comes from improved control technology that precisely monitors the temperature and condition of each of the 95 cells in its new battery pack.
“Our control system can identify even slight signs of a potential short-circuit in individual cells, and will either prevent it from spreading or shut down the entire battery,” said Hiroaki Takeuchi, a senior Toyota engineer involved in the development.
Working with battery supplier Panasonic Corp – which also produces Li-ion batteries for Tesla – Toyota has also improved the precision in battery cell assembly, ensuring battery chemistry is free of impurities.
The introduction of even microscopic metal particles or other impurities can trigger a short-circuit, overheating and potential explosion.
“The environment where our lithium-ion batteries are produced is not quite like the clean rooms where semiconductors are made, but very close,” Takeuchi said.
Battery experts say increasingly sophisticated systems that can track individual cell conditions are becoming closely-held trade secrets.
“State of charge management, safety management and algorithm development is becoming one of the higher tiers of proprietary internal development,” said Eric Rask, principal research engineer at Argonne National Laboratory, a US department of energy facility outside Chicago.
“It’s very internal, very strategic, and companies are seeing management algorithms as a competitive advantage.”
Falling prices
Toyota has also been able to shrink the size of each cell, for example, closing the distance between the anode and cathode, where active ions travel when charging and discharging.
This has doubled battery capacity to around 8.8 kilowatt hours, while only increasing the battery pack size by around two-thirds and its weight by a half.
Battery experts say lithium-ion battery cell prices have fallen by about 60% in five years to around $145 per kilowatt hour as larger-scale production has made them cheaper to make.
Falling battery prices have enabled Toyota to develop its more compact, efficient battery, while also adding more sophisticated controls into its battery pack, Toyoshima said. Toyota declined to say more on its costs.
While Toyota sees FCVs as the ultimate ‘green’ car, the United States and China are encouraging automakers to make more all-electric battery cars as they push alternative energy strategies.
“Developing lithium-ion batteries for both hybrids and plug-ins will enable us to also produce all-electric cars in the future,” said Toyoshima said. “It makes sense to have a range of batteries to suit different powertrains.” Reuters.
Several NiMH replacement hybrid car batteries we recommend.
https://himaxelectronics.com/wp-content/uploads/2020/04/Hybrid-battery.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-04-28 06:42:492024-04-29 01:26:23Warming To Lithium-ion, Toyota Charges Up Its Battery Options
Battery pole piece spot welding machine work principle:
Battery pole piece spot welder use of ultrasonic metal welding principle, ultrasonic metal welding should be classified as don’t need preheating welding. Oxidation surface is the great friction welding which division, and at the same time two parts are pressed together. This program let two materials to produce the atom so close to the action. Far below melting point relatively slight increase of temperature in the welding process is not important factors. At the same time, because the basic material not liquefied, so there is no microstructure changes, also will not damage to internal structure. Ultrasonic cell metal special welding machine is suitable for: aluminum + nickel, nickel and copper foil, aluminum + aluminum foil, multilayer copper foil, multi-layer aluminum foil, multilayer copper nets, multilayer aluminum mesh, aluminum plate + aluminum strip, aluminum nickel composite belt + aluminium plate, aluminum shell bottom + ni-clad-al strip double point welding; And with nickel and copper foil, nickel band and aluminum belt, aluminium strip and aluminum foil, aluminum band and aluminum cover, aluminum shell and ni-clad-al strip of the material such as the single point, multipoint, single, multi-layer, square, form and process of welding. Features suitable for battery, hardware, electrical appliances and motor industry.
Battery pole piece spot welder features:
due to the bench ultrasonic cell metal welding machine machine 80% use import parts and components, to ensure low failure rate and machine section structure design is reasonable;
ultrasonic lithium ion battery metal welding machine of welding mould can according to different application fast and convenient to change;
ultrasonic cell copper foil nickel sheet welding machine with German import piezoelectric ceramic transducer, stable and durable;
miniature ultrasonic power battery cover sheet welding machine operation easy, built-in electronic protection circuit, the use of safe,
independent research and development, and the ultrasonic cell metal welding mould and welding head, reached the advanced world level, reduce the enterprise cost;
ultrasonic nimh battery pole piece very ear welding machine used for the same kind of metal welding, to foreign non-ferrous metal implement single point or multipoint welding, especially copper aluminum nickel sheet, line, take welding.
Battery pole piece spot welder advantages:
The machine use desktop integration design, reasonable structure, beautiful appearance, Vertical motion, positioning accuracy is high, the welding effect is good; Welding head and the integral design of the mould can ensure the consistency of the welding effect, and extend the welding head life; New mould manufacture and maintenance cost is low, the welding of high efficiency; Advance to set the energy, time of welding parameters, constant welding parameter to ensure the welding quality. The operation is simple, convenient assembly, easy maintenance, can according to the customer the production needs of customized; Combined with quality control system for automatic process monitoring, without professional technician, on-site staff need to accept a day of training that will operate. Features suitable for wire and guide piece of the connections between, lithium nimh battery electric etc with nickel sheet alloy plate ni-clad-al strip connection, household electric parts and wire welding, all kinds of high or low conductivity metal and alloy, etc.
https://himaxelectronics.com/wp-content/uploads/2020/03/01.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-03-30 07:15:422024-04-26 07:08:43Battery pole piece spot welding
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.
https://himaxelectronics.com/wp-content/uploads/2020/01/Hybrid-car-battery.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2020-01-13 09:18:512024-04-26 08:38:38Do hybrid cars cause pollution？
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.
https://himaxelectronics.com/wp-content/uploads/2019/12/Hybrid-battery.jpg400800administrator/wp-content/uploads/2019/05/Himax-home-page-design-logo-z.pngadministrator2019-12-23 06:14:222024-04-26 08:25:51Are Hybrid Cars Here to Stay?
