When you think of high-performance sports cars, the last thing that comes to mind is a battery powered vehicle. Yet, surprisingly, the present record for the fastest battery-powered vehicle belongs to American Eric Luebbin who reached an astonishing 215mph at Bonneville in 1997.
The benefit of electric vehicles on the environment is significant, even when UK power stations’ emissions are taken into account. If all UK cars and vans were converted to electric by 2010, then it would reduce emissions of CO2 by 10% of 1994 levels, since electric vehicles give >25% net reductions in CO2 emissions compared to petrol engine vehicles. But although government initiatives can boost the use of electric vehicles, major work on the battery front will be needed in order that battery-powered electric vehicles will be able to effectively compete with those powered by the internal combustion engine. That was the thinking, at least, when the Big Three American automakers, the US Department of Energy, the Electric Power Research Institute and several key battery manufacturers formed the Advanced Battery Consortium back in 1991. The $262 million partnership allowed the companies to pool their technical knowledge and funding to focus on the most promising battery technologies to advance the potential of electric vehicles.
One of the goals of USABC was to help develop electrical energy systems capable of providing electric vehicles with the range and performance that would be competitive with gasoline-powered vehicles, and to fund high-risk, high-cost advanced battery research and development. To help out, several major contracts for advanced battery research and development were awarded in order that battery companies could examine the potential of both mid-term technologies such as nickel-metal hydride (NiMH) and sodium sulphur as well as carry out longer term research into technologies such as lithium-ion and lithium polymer.
According to the USABC, battery technologies such as NiMH and lithium-ion have the potential to effectively double the range and performance of electric vehicles compared to advanced lead-acid batteries. And longer-term battery technologies, such as lithium polymer and lithium-ion disulphide, have even more energy and power – enough to make the range and performance of electric vehicles comparable to petrol-powered vehicles.
With any battery technology, however, there are a few key criteria that must be met. First, the batteries must deliver as many kilowatt hours of power as possible as inexpensively as possible. Secondly, they must have as high an energy-to-weight ratio as possible. Thirdly, the battery life measured in cycles must be as high as possible. And finally, the recharging time of the battery set used in the car must be as short as possible, ideally comparable to the time that it takes a motorist to fill a conventional petrol tank.
Except for cost targets, the USABC is close to meeting its mid-term performance goals for NiMH technologies. Energy and power performance targets, which determine range and acceleration, appear to be within reach. Those mid-term goals set by the consortium specified that batteries should be capable of delivering 150-200W/kg, at a specific energy of 80Wh/kg-100Wh/kg. Battery life was set at five years and the cost was to be £100 or less per kilowatt hour.
In a typical electric vehicle, such a battery system would be able to produce an acceleration of 0 to 50mph in 12sec, a driving range of 100-125mile in normal usage and a battery cost of between £3000 and £4000.
In the longer term, the USABC set itself the goal of delivering a battery with a specific power of 400W/kg, a specific energy of 200Wh/kg and a 10 year battery lifetime at a cost of £60 or less per kilowatt hour. In effect, the result of such an effort would allow a vehicle based on the battery to accelerate from 0-60mph in nine seconds with a 200mile driving range. The cost of the battery would be less than £3000 and would amortised over 10 years.
Despite the technical challenges, the effectiveness of vehicles based on NiMH batteries has already been demonstrated. Last October, for example, a 32kWh NiMH battery pack developed by Ovonic Batteries powered a Solectria Sunrise EV from Boston to New York on a single charge at normal highway speeds over a US interstate and in city traffic.
The Solectria Sunrise, a prototype four-passenger sedan, was powered by a 42kW nominal/50kW peak Solectria AC induction direct-drive engine with regenerative braking. The vehicle’s range between charges was well in excess of 200mile, while its top speed was 75mph, due to the fact that it was regulated by a motor controller. The Ovonic NiMH EV battery packs used in the design provided a cycle life of over 800 full charge/discharge cycles, a recharge capability up to 60% of capacity in 15min, and an energy density of >80Wh/kg.
However, the USABC admits that challenges remain in battery cost and manufacturing. To cut costs, USABC is focusing on three key areas: raw materials, battery design and volume manufacturing. USABC partners and their suppliers are investigating ways to lower material costs or use materials more effectively. Battery developers are working to design batteries that are smaller and lighter which automatically leads to an increase in vehicle performance. By far the most difficult challenge is addressing the issue of volume manufacturing. If the volume goes up, the cost will come down. However, increasing volume on a product that most consumers can not afford is a real challenge.
So it might seem that the lead acid battery, at least, is under threat from the NiMH battery types. But in 1992, members of yet another alliance, this time the Advanced Lead Acid Battery Consortium, embarked on a programme to improve the life and the recharge time of lead acid batteries. The result was that the cost of the lead acid design was reduced to £94.50/kWh down from £126/kWh, the energy to weight ratio was improved from 25Wh/kg to 50Wh/kg and battery life was improved from 75 cycles to over 500 cycles. Recharging time was improved from 100% in 8h to 80% in 15min.
According to Dave Rice of Hawker Batteries, while NiMH or lithium-ion batteries might today offer the best range, they still come at a price premium. By comparison, he adds, lead acid batteries are considerably less expensive. Rice also believes that the purely electric passenger vehicle may be commercially some way off yet, with most developers building electric vehicles such as buses and vans for inner city use where travel is limited to less than 80miles/day.
So, until batteries drop in price and charging outlets become more commonplace, there’s little hope that the private motorist will go electric. Or is there? One German company, City Com thinks differently. They are betting that the larger automotive vendors have it all wrong.
Since 75% of automobiles are occupied by one person and travel fewer than 25km daily, City Com reasoned that present battery technology is better suited to the development of an entirely different sort of vehicle – the City El, an automobile that runs off three 12V 90Ah batteries, and can travel a distance of 50km. It might not break any of Eric Luebbin’s records, sporting a top speed of just 50km/hr, but for just under 12,000DM (£4,000), maybe they are onto something.
The Aalco sponsored `Bluebird Electric’, driven by Donald Wales, grandson of Sir Malcolm Campbell, set a new UK speed record for electric vehicles at a little over 116mph, beating the old mark by 10mph. Later the project will make an attempt on the US-held world record.
Developer Technology Timing Start Date Budget
Ovonic Nickel-metal hydride Mid-term May 1992 $25.4Saft Nickel-metal hydride Mid-term Dec. 1992 $20.7Silent Power Sodium-sulphur Mid-term Aug. 1993 $12.1Yardney Nickel components Mid-term Jan. 1994 $3.45Varta-Duracell Lithium-ion Mid-term Jan. 1995 $18.0Saft Lithium-ion disulphide Long-term Dec. 1992 $17.3WR Grace Lithium-polymer Long-term Jan. 1993 $29.23M – Hydro Quebec Lithium-polymer Long-term Dec. 1993 $32.9
Mid-term battery technologies, such as NiMH and lithium-ion, havethe potential to effectively double the range and performance ofelectric vehicles compared to advanced lead-acid batteries, thecurrent state of battery technology. Long-term battery technologieswould have even more energy and power, enough to make the range andperformance of electric vehicles comparable to today’s gasoline-powered vehicles.}}
INFORMATION: HAWKER BATTERIES Tel: Leatherhead (01372) 821500