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Electric vehicle battery
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An electric vehicle battery (EVB) is a rechargeable battery used in electric vehicles, making them battery electric vehicles (BEVs).
Batteries are usually the most expensive component of BEVs, although batteries from old or wrecked electric cars can be bought for battery-to-grid mini-power plants. The cost of battery manufacture is substantial, but increasing returns to scale may serve to lower their cost when BEVs are manufactured on the scale of modern internal combustion vehicles.
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Encyclopedia
An electric vehicle battery (EVB) is a rechargeable battery used in electric vehicles, making them battery electric vehicles (BEVs).
Batteries are usually the most expensive component of BEVs, although batteries from old or wrecked electric cars can be bought for battery-to-grid mini-power plants. The cost of battery manufacture is substantial, but increasing returns to scale may serve to lower their cost when BEVs are manufactured on the scale of modern internal combustion vehicles. Since the late 1990s, advances in battery technologies have been driven by skyrocketing demand for laptop computers and mobile phones, with consumer demand for more features, larger, brighter displays, and longer battery time driving research and development in the field. The BEV marketplace has reaped the benefits of these advances.
Some batteries can be leased or rented instead of bought (see Think Nordic).
One article indicates that 10 kW·h of battery energy provides a range of about in a Toyota Prius, but this is not a primary source, and does not fit with estimates elsewhere of about /(kW·h). The Chevrolet Volt is expected to achieve 50 MPG when running on the auxiliary power unit (a small onboard generator) - at 33% thermodynamic efficiency that would mean 12 kW·h for , or about 240 watt hours per mile. For prices of 1 kW·h of charge with various different battery technologies, see the "Energy/Consumer Price" column in the "Comparison of battery types" section in the rechargeable battery article.
Rechargeable batteries used in electric vehicles include lead-acid ("flooded", Deep cycle, and VRLA), NiCd, nickel metal hydride, lithium ion, Li-ion polymer, and, less commonly, zinc-air and molten salt batteries. The amount of electricity (i.e. electric charge) stored in batteries is measured in ampere hours or in coulombs, with the total energy often measured in watt hours.
Charging
Batteries in BEVs must be periodically recharged (see also Replacing, below).
BEVs most commonly charge from the power grid (at home or using a street or shop recharging point), which is in turn generated from a variety of domestic resources; such as coal, hydroelectricity, nuclear and others. Home power such as roof top photovoltaic solar cell panels, microhydro or wind may also be used and are promoted because of concerns regarding global warming.
Charging time is limited primarily by the capacity of the grid connection. A normal household outlet is between 1.5 kilowatts (in the US, Canada, Japan, and other countries with 110 volt supply) to 3 kilowatts (in countries with 240 V supply). Many european countries feed domestic consumers with a 3 phase system fused at 16-25 amp allowing for a theoretical capacity around 20-30kw. however, this capacity is also required to feed the rest of the location and can hence not be used Practically and will also not be supported "en mass" by the DNO network. At this higher power level charging even a small, 7 kilowatt-hour (14–28 mi) pack, would probably require one hour. This is small compared to the effective power delivery rate of an average petrol pump, about 5,000 kilowatts. Even if the supply power can be increased, most batteries do not accept charge at greater than their charge rate ("1C"), because high charge rate has adverse effect on the discharge capacities of batteries.
In 1995, some charging stations charged BEVs in one hour. In November 1997, Ford purchased a fast-charge system produced by AeroVironment called "PosiCharge" for testing its fleets of Ranger EVs, which charged their lead-acid batteries in between six and fifteen minutes. In February 1998, General Motors announced a version of its "Magne Charge" system which could recharge NiMH batteries in about ten minutes, providing a range of sixty to one hundred miles.
In 2005, handheld device battery designs by Toshiba were claimed to be able to accept an 80% charge in as little as 60 seconds. Scaling this specific power characteristic up to the same 7 kilowatt-hour EV pack would result in the need for a peak of 340 kilowatts of power from some source for those 60 seconds. It is not clear that such batteries will work directly in BEVs as heat build-up may make them unsafe.
In 2007, Altairnano's NanoSafe batteries are rechargeable in several minutes, versus hours required for other rechargeable batteries. A NanoSafe cell can be charged to around 95% charge capacity in approximately 10 minutes.
Most people do not always require fast recharging because they have enough time, six to eight hours, during the work day or overnight to recharge. As the charging does not require attention it takes a few seconds for an owner to plug in and unplug their vehicle. Many BEV drivers prefer refueling at home, avoiding the inconvenience of visiting a fuel station. Some workplaces provide special parking bays for electric vehicles with charging equipment provided. In colder areas such as Minnesota and Canada there exists some infrastructure for public power outlets, in parking garages and at parking meters, provided primarily for engine pre-heating.
Connectors
The charging power can be connected to the car in two ways (electric coupling). The first is a direct electrical connection known as conductive coupling. This might be as simple as a mains lead into a weatherproof socket through special high capacity cables with connectors to protect the user from high voltages. The second approach is known as inductive charging. A special 'paddle' is inserted into a slot on the car. The paddle is one winding of a transformer, while the other is built into the car. When the paddle is inserted it completes a magnetic circuit which provides power to the battery pack.
In one inductive charging system, one winding is attached to the underside of the car, and the other stays on the floor of the garage.
The major advantage of the inductive approach is that there is no possibility of electrocution as there are no exposed conductors, although interlocks, special connectors and ground fault detectors can make conductive coupling nearly as safe. Inductive charging can also reduce vehicle weight, by moving more charging componentry offboard. Conductive coupling equipment is lower in cost and much more efficient due to a vastly lower component count. An inductive charging proponent from Toyota contended in 1998 that overall cost differences were minimal, while a conductive charging proponent from Ford contended that conductive charging was more cost efficient.
Recharging spots
In France, Électricité de France (EDF) and Toyota are installing recharging points for PHEVs on roads, streets and parking lots.. EDF is also partnering with Elektromotive, Ltd. to install 250 new charging points over six months from October 2007 in London and elsewhere in the UK. Recharging points also can be installed for specific uses, as in taxi stands. Project Better Place has begun in October 2007 and is working with Renault on development of exchangeable batteries (battery swapping).
Travel range before recharging and trailers
The range of a BEV depends on the number and type of batteries used, and the performance demands of the driver. The weight and type of vehicle also have an impact just as they do on the mileage of traditional vehicles. Electric vehicle conversions depends on the battery type:
- Lead-acid batteries are the most available and inexpensive. Such conversions generally have a range of 30 to 80 km (20 to 50 mi). Production EVs with lead-acid batteries are capable of up to 130 km (80 mi) per charge.
- NiMH batteries have higher energy density and may deliver up to 200 km (120 mi) of range.
- New lithium-ion battery-equipped EVs provide 400–500 km (250–300 mi) of range per charge. Lithium is also less expensive than nickel.
Finding the economic balance of range versus performance, battery capacity versus weight, and battery type versus cost challenges every EV manufacturer.
With an AC system regenerative braking can extend range by up to 50% under extreme traffic conditions without complete stopping. Otherwise, the range is extended by about 10 to 15% in city driving, and only negligibly in highway driving, depending upon terrain.
BEVs (including buses and trucks) can also use genset trailers and pusher trailers in order to extended their range when desired without the additional weight during normal short range use. Discharged baset trailers can be replaced by recharged ones in a route point. If rented then maintenance costs can be deferred to the agency.
Such BEVs can become Hybrid vehicles depending on the trailer and car types of energy and powertrain.
Swapping And Removing
An alternative to recharging is to exchange drained or nearly drained batteries (or battery range extender modules) with fully charged batteries. This is called battery swapping and is done in exchange stations .
On the other hand, MIRA has announced a retrofit hybrid conversion kit that provides removable battery packs that plug into a wall outlet for charging . Also XP Vehicles uses extension-cord-free charging hot-swap battery ( removable power pack to recharge at home without extension cord ).
Re-filling
Zinc-bromine flow batteries can be re-filled, instead of recharged, saving time.
Leasing
Three companies are working on battery lease plans. Greenstop has completed trials of their ENVI Grid Network which allows consumers to easily monitor and recharge electric vehicle batteries. Think Car USA plans to lease the batteries for its City electric car to go on sale next year. Better Place is trying to create a system for consumers to "subscribe" to a service that offers recharging stations and battery exchange.
In any case, electric utilities are already considering concepts which would include providing electric vehicles to users (at a low price) and get their profits from selling the energy .
V2G and afteruse
Smart grid allows BEVs to provide power to the grid at any time, especially:
- During peak load periods, when the selling price of electricity can be very high. These vehicles can then be recharged during off-peak hours at cheaper rates while helping to absorb excess night time generation. Here the vehicles serve as a distributed battery storage system to buffer power.
- During blackouts, as backup.
Pacific Gas and Electric Company (PG&E) has suggested that utilities could purchase used batteries for backup and load levelling purposes. They state that while these used batteries may be no longer usable in vehicles, their residual capacity still has significant value.
Lifespan
Individual batteries are usually arranged into large battery packs of various voltage and ampere-hour capacity products to give the required energy capacity. Battery service life should be considered when calculating the extended cost of ownership, as all batteries eventually wear out and must be replaced. The rate at which they expire depends on a number of factors.
The depth of discharge (DOD) is the recommended proportion of the total available energy storage for which that battery will achieve its rated cycles. Deep cycle lead-acid batteries generally should not be discharged to below 20% of total capacity. More modern formulations can survive deeper cycles.
In real world use, some fleet Toyota RAV4 EVs, using NiMH batteries, have exceeded 100,000 miles (160,000 km) with little degradation in their daily range. Quoting that report's concluding assessment:
- "The five-vehicle test is demonstrating the long-term durability of Nickel Metal Hydride batteries and electric drive trains. Only slight performance degradation has been observed to-date on four out of five vehicles.... EVTC test data provide strong evidence that all five vehicles will exceed the mark. SCE’s positive experience points to the very strong likelihood of a 130,000 to Nickel Metal Hydride battery and drive-train operational life. EVs can therefore match or exceed the lifecycle miles of comparable internal combustion engine vehicles.
- "In June 2003 the 320 RAV4 EVs of the SCE fleet were used primarily by meter readers, service managers, field representatives, service planners and mail handlers, and for security patrols and carpools. In five years of operation, the RAV4 EV fleet had logged more than 6.9 million miles, eliminating about 830 tons of air pollutants, and preventing more than 3,700 tons of tailpipe carbon dioxide emissions. Given the successful operation of its EVs to-date, SCE plans to continue using them well after they all log 100,000-miles."
Jay Leno's 1909 Baker Electric (see Baker Motor Vehicle) still operates on its original Edison cells. Battery replacement costs of BEVs may be partially or fully offset by the lack of regular maintenance such as oil and filter changes required for ICEVs, and by the greater reliability of BEVs due to their fewer moving parts. They also do away with many other parts that normally require servicing and maintenance in a regular car, such as on the gearbox, cooling system, and engine tuning. And by the time batteries do finally need definitive replacement, they can be replaced with later generation ones which may offer better performance characteristics, in the same way as you might replace old batteries from a digital camera with improved ones.
Safety
The safety issues of battery electric vehicles are largely dealt with by the international standard ISO 6469. This document is divided in three parts dealing with specific issues:
- On-board electrical energy storage, i.e. the battery
- Functional safety means and protection against failures
- Protection of persons against electrical hazards.
Firefighters and rescue personnel receive special training to deal with the higher voltages and chemicals encountered in electric and hybrid electric vehicle accidents. While BEV accidents may present unusual problems, such as fires and fumes resulting from rapid battery discharge, there is apparently no available information regarding whether they are inherently more or less dangerous than gasoline or diesel internal combustion vehicles which carry flammable fuels.
Research, Development and Innovation
R&D Magazine's prestigious R&D 100 Awards — also called the “Oscars of Invention”— for 2008:
Future
The future of battery electric vehicles depends primarily upon the cost and availability of batteries with high energy densities, power density, and long life, as all other aspects such as motors, motor controllers, and chargers are fairly mature and cost-competitive with internal combustion engine components. Li-ion, Li-poly and zinc-air batteries have demonstrated energy densities high enough to deliver range and recharge times comparable to conventional vehicles.
Bolloré a French automotive parts group developed a concept car the "Bluecar" using Lithium metal polymer batteries developed by a subsidiary Batscap. It had a range of 250 km and top speed of 125 km/h.
Firefly Energy has developed a carbon foam-based lead acid battery with a reported capacity from 90-160 Watt-hours/kg
The cathodes of early 2007 lithium-ion batteries are made from lithium-cobalt metal oxide. This material is expensive, and can release oxygen if its cell is overcharged. If the cobalt is replaced with iron phosphates, the cells will not burn or release oxygen under any charge. The price premium for early 2007 hybrids is about US $5000, some $3000 of which is for their NiMH battery packs. At early 2007 gasoline and electricity prices, that would break even after six to ten years of operation. The hybrid premium could fall to $2000 in five years, with $1200 or more of that being cost of lithium-ion batteries, providing a three-year payback.
UltraBatteries
Ultracapacitors (or "supercapacitors") are used in some electric vehicles, such as AFS Trinity's concept prototype, to store rapidly available energy with their high power density, in order to keep batteries within safe resistive heating limits and extend battery life . The Ultrabattery combines a supercapacitor and a battery in a single unit, creating a hybrid car battery that lasts longer, costs less and is more powerful than current technologies used in plug-in hybrid electric vehicles (PHEVs).
See also
External links
- , charging stations (EERE).
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