There's been a lot of talk recently about the coming wave of electric cars, and a lot of promising advances in battery technology. There are more hurdles than just that - as you can read below the fold.
As it stands today, we're on the verge of a revolution in how we drive around. Electric cars, while not nearly cheap enough to be practical, are no longer inching closer to being competitive, they're stampeding. And I can't wait. However, in order to compete with their gas counterparts, there are several ways that electric cars have to either match or surpass them.
Pound for pound, electric motors are more powerful than gas motors, sometimes FAR more powerful. Another big difference is the torque curve. Without getting too technical, the torque curve is a big part of the equation of how fast the car accelerates. Electric motors generate maximum torque at 0 RPM. Another advantage is that an electric motor responds at the speed of electricity - roughly 5/9ths light speed. A gas car responds at the speed of the gas being pushed into the cylinder, so there is always a delay between foot mashing and throttle response. In short, this means that an electric car will have explosive acceleration from a dead stop. The reason a tesla does 0-60 in 4 seconds is not because the motor is so powerful, it's that all the twist the motor can produce is being placed on the ground the moment you stomp on the 'gas'. Most ICE and Diesel motors have to wind up to at least 1800-2000 rpm before you get to the grunt. In short, for acceleration, Electric wins hands down. This is what has gearheads like me rejoicing. The downside of all this low end grunt is that it peters out near the top of the RPM band. All that neck snapping thrust drops steadily as you wind up the motor, and as tesla discovered, getting a transmission that can handle all that torque is not easy. You can do a direct-drive powertrain without gears on an electric motor if you're willing to deal with less-than-stellar acceleration on the highway.
As far as efficiency goes, most electric motors run at about 90%, including heat losses from the battery when trasferring power to and from the electric motor. Couple that with regenerative braking, which converts momentum back into electricity (albiet not nearly as efficiently as electricity is converted into momentum) and you make further gains. A typical ICE is not only about 20-25% efficient, but when you slow down all you're doing is converting your momentum into waste heat. For efficiency, ICEs aren't even on the same planet as electrics.
Maintenance is another area where electrics score over gas cars, for a number of reasons. Regenerative breaking means less wear and tear on your braking system. Electric motors are known to last for years of continuous use without any maintenance. If an electric car stops, it's either the battery, the motor, or the control unit, so it's much easier to fix. No fluids to change, as electric motors are sealed units. The downside is, if the motor breaks, its a replacement, not a fix, which would be expensive.
One area where electric and gas cars are equal is content. It's just as easy to equip an electric car with a stereo, power windows and doors, and any other modern convenience as it is a gas car.
Where electrics currently fall flat on their faces is range and refueling time. It's been called the 'NY to LA' problem - if you want to drive from NY to LA in a reasonable amount of time, you must have a gas powered car. Between the relatively short range of an electric and the long recharge times, electrics simply can't compete. Another issue is that you can't carry any fuel with you - while you can throw a half dozen 5 gal jugs in the back of your pickup and effectively double your range, you can't throw a second set of batteries into your EV. Due to this, you would have to have some alternate method of taking long trips, either by renting a second car when necessary, having a zipcar account, or simply owning a second car. This may be impossible for people who can only afford a single car.
Another issue is charging. A lot of people talk about 'putting in a charger' at home. If you have a garage, great, no problem. What if you have to park on the street, as many do? The other issue is time. Almost any car can be refueled in 5 minutes. Any electric with any kind of range is going to take hours, even with a dryer-sized socket. The only realistic way to recharge a car-sized battery quickly would be to have a second set of batteries trickle-charging from your home circuit that would dump it's charge into your car when you plug it in. This would be very, VERY expensive, as the batteries are by far the most expensive component of the car (Tesla claims a replacement pack will cost $36,000 - or the cost of a brand new base BMW 3 series). For refueling, gas cars have a huge advantage at this time.
Why is recharging such a bear? Let's look at the math. The Tesla uses a 53kWh battery to get about 240 miles. Let's say (and for the sake of easy math) a competitive electric car needs 100kWh of energy to go 400 miles, a range that is competitive with any gas powered car. What would it take to charge that car in the same time it takes to refuel your gas burner? Well, 100kWh means 100kW of power for one hour. Assuming perfect efficiency (which is impossible) that means you need to push 100kWh into the car in 5 minutes, or 1/12th of an hour. 12*100 is 1200kW, or 1.2Megawatts. For comparison, your dryer sized outlet at home can push about 6000W, or 6kW. You'd need two hundred of them flying in formation to get that kind of power. The other big issues are, how on earth do you get a cable thick enough to handle that kind of juice, and how do you insulate it in such a way that it doesn't accidentally kill you? The electric chair used 1850V at 7.5A, or about 14 kW of current. If 14 kW can kill you pretty efficiently, imagine what 1.2MW would do. On the other end of the safety spectrum, how do you make sure that the batteries are safe during a collision? You can't 'turn off' a battery, and they would be a threat to any emergency crew trying to 'jaws of life' you out of your car.
The last great hurdle of electric cars is cost. Dollar for dollar, electric cars are far more expensive than gas burners, even at $4 gas. From a pure cost basis, ignoring the other limitations of electric cars, they can be no more than 10% more expensive than a similar gas counterpart to be considered 'on par' as far as fuel goes. Other maintenance costs might further offset that, but there's no real data for that that I could find.
So, where are we today?
Power/acceleration? Pound for pound, electric is better.
Speed? Gas is still king for top speed.
Content? Tie, though Tesla's sedan is gorgeous.
Fuel Efficiency? Electric, no doubt about it.
Refueling time? Gas still has a huge advantage.
Maintenance? Electric is probably cheaper. Time will tell.
Range? The gap is closing, but gas still has a big lead.
Cost? Gas cars will be cheaper for the next decade.
There are still some major technical hurdles to overcome, but I have every confidence that I will see a 'practical electric car' in my lifetime. I look forward to the demise of the ICE, and hopefully I'll be under my shade tree with my kids showing them how to squeeze another 50 lb/ft of torque out of their clean, shiny electric sports car.