Original URL: http://www.theregister.co.uk/2007/03/08/tesla_car_examined/

Electric cars may not be solution to all world problems

Flame storm fails to alter reality

By Lewis Page

Posted in Science, 8th March 2007 19:42 GMT

Recent Reg coverage of the green motoring field has been sternly criticised by some for too brusquely dismissing the fully-electric car, so we're back today with a look at battery-powered wheels.

Yesterday's piece said: "Unfortunately, the limits of current battery technology mean fully-electric vehicles with petrol-car performance aren't on the cards for now. And a plug-in hybrid is distressingly expensive, as it requires a big, capable battery pack to be of any use."

The various sizzling flames this drew were usually based around the Tesla Roadster, an all-electric sports car currently under development. In essence, it's a Lotus Elise with a massive lithium-ion battery pack instead of an engine and fuel tank. The Tesla's best stat is its neck-snapping acceleration, 0-60 mph in "about four seconds" which would certainly leave most petrol cars in the dust.

promo shot of red Tesla Roadster They might not stay there for long, however, as the Roadster tops out not far north of 130mph, about the same as a £17,500 five-door Vauxhall Astra hatchback. That wouldn't normally be a reasonable beef to raise against the Tesla – not many people ever drive so fast – but the Tesla is squarely in the supercar market with its sexy Lotus body, two seats, tiny boot and $100,000 price tag – almost distressingly expensive, in fact. A petrol car in this bracket, such as the Porsche 911 Carrera S ($92,000-$96,000) can reasonably be expected to show top speeds around 180mph on the test track. So the Tesla offering doesn't, actually, deliver petrol performance – even in pure zoom-zoom, and that's the Roadster's best thing.

It also has practical issues, much more serious than a fairly irrelevant inability to go at wildly illegal speeds. The Roadster is predicted by its makers to achieve between 200 and 300 miles per battery charge. One must bear in mind that this is a manufacturer stat on a lithium-ion battery pack, much like standby/talktime for a mobile phone. However, let's assume that in this case the figures are completely correct. A competitor like the Porsche 911 does considerably better, going anywhere from 290 to 425 miles on a tank of petrol, but this isn't a massive thing compared to saving the planet.

The big snag is what happens next. The Porsche driver fills up in minutes and is on his way again. So does the putative hydrogen or ethanol-fuelled driver of the future, when hydrogen or ethanol might actually be available. Even a mobile-phone user can make calls while plugged in, or put in a fresh battery. But the Tesla Roadster isn't going anywhere or doing anything for a minimum of three-and-a-half hours while it charges up again. You aren't going to swap a 900lb battery easily.

At least electric connections are already widely distributed, unlike hydrogen or ethanol stations. Garages and motorway service areas wouldn't need a huge infrastructure investment to offer electric charging, though they'd need an awful lot more forecourt space if electric cars or trucks ever began making long journeys en masse.

But not many longhaul motorists are going to want to spend as much time sitting on forecourts charging up as they do on the road, so in real life most electric vehicles are going to be charged overnight. Realistically then, based on the Tesla specs, electric cars are mainly useful for out-and-back trips of 100 miles, or journeys of 200-odd miles followed by an overnight stay.

Then we come to the awkward question of service life. Again, experience with mobiles and laptops suggests that performance is going to worsen significantly as the charge cycles mount up. Presumably the 200 to 300 mile, four seconds 0-60 figures are for a new battery. Does that mean that after a few years a $100,000 Roadster is going to be badly degraded?

Tesla claims that the Roadster's powerpack has a "useful" life of a hundred thousand miles. A petrol car isn't going to be in spanking shape after that sort of distance, but it'll potentially still have a lot of use left in it, and its performance won't have dropped off in any noticeable way. The Roadster is going to need the main component of its power train replaced, every time.

Tesla assures us that its lithium-ion batteries are fully recyclable, which is just as well with 900lb of them going in the green bin after every 100,000 miles of motoring. One does note that reprocessing of li-ion batteries is done by fairly energy-intensive heat treatment, but that should be OK in a future where electric power is reasonably priced, green and plentiful (in any other future, Tesla-type cars make no sense at all).

Normally it would be time to say at this point "but this is first-generation kit – soon things will be much better". Not this time. Electric cars are primarily battery packs. Batteries have had decades of work and billions of dollars poured into them by the laptop and phone makers. They are fairly mature technology.

Barring a sudden leap forward in high-temperature superconductors or something else out of left field, the Tesla Roadster should be fairly representative of what can actually be done. Or, to put it another way, what's on the cards for now. The Roadster looks like a pretty cool ride, and Tesla motors is a laudable endeavour, but they aren't going to bring in green motoring all on their own.

Neither the Roadster nor its successors are going to replace cars or trucks for long journeys nor multiple medium-distance journeys per day. This leaves electric wheels stuck with the commuter, school run, milk float and shopping jobs, and a certain kind of high-end supercar customer. Anyone who wants to do more than 250 miles in a day at all often – to visit friends or family, do deliveries, make meetings, carry freight, go touring – is quite likely to buy something else.

Electric vehicles have always had their place, and most likely always will. The electric milk float came in decades ago. Li-ion or other near-future automotive battery tech may very well give all-electrics a bigger, even a significant market share in time. But all-electric vehicles can't yet replace huge segments of the existing carbon-powered motor industry.

If we're worried about global warming or Western dependence on foreign resources, we need a big majority of road vehicles to move away from fossil fuel, not just some classes of them for some jobs. This means that hydrogen, biofuels, or some other sort of kit will have its place, probably alongside or hybridised with electric vehicles or – just perhaps – largely bypassing them. ®