Wednesday, May 27, 2009

Electric Math



The major flaw of electric cars is their lack of range. Top Gear dramatically demonstrates this in the above video. (Some would say they not only over-hyped the problem but actually mis-lead viewers about it.) Even as I've thought about how fun a Tesla Roadster would be, I realize it would not be practical for a long trip. An electric Smart car with an 80 mile range would be even worse and don't even think about one of the lesser models (some with a range of only 40 miles).

A few days ago I thought about range again and was surprised.

First the good news. Well over 90% of my wife and my driving is in town. Occasionally I make the 70 mile drive to work. Sometimes we make the also 70 mile drive to my sister's house in Apple Valley. We also make an up to 100 mile drive to visit family in LA and Orange County. For all of this an electric car with over a 100 mile range is actually more convenient than a gasoline vehicle. No need to go to a gas station -- just plug it in at night, while I'm working or while we're visiting.

Long trips are another problem. Having to stop and charge for several hours ruins the chance of making any significant mileage. One idea is I can just rent a car. I've often rented cars for vacations. Years ago it was because I owned cheap vehicles that were not that much fun to travel in and that I was afraid would break down. More recently I've rented because my car was too small to carry all the luggage or people coming on the trip. For an occasional traveler like me, this makes good sense. Why pay a premium (and the extra fuel costs) for a large car that I'll only need once or twice a year?

The thing I realized a few days ago is that Telsa's promised S Class changes the range problem. The S Class will have a range of 300 miles and can be charged in 45 minutes. It also will have quick-swappable battery (five minutes). And, by the way, it will have plenty of passenger and luggage storage capacity for a long trip.

Obviously if battery swap stations are available, there is no problem. A five-minute battery swap is as quick as a gasoline fill-up. But working out the kinks of battery swap stations any time soon (if ever) seems highly unlikely.

How will a long trip work with charging? From our house to Arcata, where our daughter Ruth lives, is 660 miles. It's about 12 hours counting our relatively quick stops. We get gas, take bathroom breaks and get our food to go. With a 300 mile range S Class, we would have to stop at one of the scattered places south of Stockton. They're sparse, but exist. We have stopped in the area many times because we have about the same range in our current car, a Scion xB. Instead of a 20 minute food-to-go break, we'd have to stop for about 50 minutes. I assume we could leave the car charging while we get something to eat nearby.

Since Arcta is 660 miles we need another stop to refuel. Humans usually need another stop too. Willits is a good place. The way we go it's about 230 miles more. That means we'd have about 70 miles left in the "tank". From Willits to Arcata is another 145 miles, so we'd only need a small charge, say another 80 miles. 80 miles of charge should take less than 15 minutes. (A full, 300mi, charge takes 45 min. 45min * 80/300 = 12min. I rounded up). By leaving the car charging while we pick up snacks and visit the restroom we can probably get away with our normal 20 min stop.

That means the only slow-down is our first longer stop, which adds 30 minutes to our travel time. The trip becomes 12 1/2 hours instead of a 12. The extra half-hour is spent sitting down to eat rather than juggling food in the car, not a bad trade, especially for the driver. Is losing a half-hour good? Of course not. But it's not that terrible.

But what about longer trips? There's no way you can go across the country, right? Yes, I'll admit that if you want to drive non-stop, pound out 900 or 1000 mile (or more) days the S Class will slow you down. But for me, that's a bit insane. 600 to 700 miles a day is more than enough driving for me. I prefer to rest and start again the next day.

Conclusion? Range is still a problem, but for me it becomes a small problem not a large one. I realize I can live with the S Class as my primary car. In fact, most of the time it would make my life easier than a gasoline powered car.

2 comments:

Don the Baptist said...

Pros 1, Cons 0.

Anonymous said...
This comment has been removed by a blog administrator.