Tesla Model S unveiling live streaming at 3:30ET

Rather than praying for opportunity charging places, I'd be arranging for them in advance. Of course, you've got three years to make arrangements.

The stock Xebra went 15 miles its first year or two. Now I think new ones come with a 20-mile battery pack. Aftermarket 40-mile battery packs are common, but those lead batteries really don't like to drop below 50% or sit partially-discharged for half a day. So Xebra owners typically plan their trips, taking into account known charging places. Some employers allow charging at work, and some businesses allow customers to charge. I've taken the route of having enough range for my whole trip. If I need to drive father than my (extended, aftermarket) battery would allow, I take the Prius.

As you know, driving style affects range, just as it affects FE on a gas car. If you are going to come close to your range, you need to drive accordingly, and you need to know where the charging locations are. And don't forget to allow for the possibility of detours lengthening your drive.

What you've got going for you is that the Tesla (like the stock Xebra) can plug into any regular 110-v. plug. It's a slow charge, but at least it's a charge. My Xebra has an aftermarket pack and proprietary charger that draws 25 amps, so does not plug into a regular plug, and the Porsche probably won't either, assuming it ever comes.

I'm just saying, on those long road trips, plan your opportunity charges ahead of time.

 

I was referring to the Tesla Roadster battery being projected to last 7 years or 100,000 miles. At that point they estimate it will be at 80% of original capacity.

But the replacement options will actually improve the performance of the Roadster. For example, the batteries they are expecting to use in the Model S have 50% more energy density per volumetric unit.

At some point when it comes time to replace the Roadster batteries in 7 years, you might see a Roadster get 400 miles of range instead of the current 244. Or there is possibility of having a battery chemistry that stresses performance over range.

 

By all means, use those limits! Just not on a trip that's going to push your range limit.

Once you've been driving for a while you'll know your real-world range on your roads and your driving style. And the same feather-foot techniques that give you your best FE in the Prius will give you the best range in the EV.

My gut feeling is that it should be safe to plan a 250-mile trip on a 300-mile battery. I would not plan a 275-mile trip, though, because a headwind or a detour could strand you.

When I first got my Xebra, and again when I put the LiFePO4 battery in it, I made a test drive: First I drove all the way downtown and back, with a detour up north. When I was near home I looked at my voltmeter (the Xebra does not have an SOC meter) and made a pretty long loop around my neighborhood, followed by successively smaller loops, until I was as near empty as I wanted to risk. I then knew my range.

The Tesla S will have better metering. Maybe an SOC meter. Maybe a miles-remaining indicator. And probably the owner's manual will warn against going below a certain level. Keeping above that level, you can do this sort of test, though it will take longer in a 300-mile car than in a 40-mile car.

Once you know your real-world range you'll know what you can plan, and where you need to plan charging stops.

Okay. That's what I've read. The laptop batteries have a long history of use, and those figures are probably reliable. And with a 200-mile-plus range, an 80% reduction is not significant. My guess is 15 to 20 years before the average Roadster driver needs to replace the batteries. But he'll be wanting to trade in the car before then, because there'll be something even better.

I wonder about this. LiFePO4 is thermally stable, which is a good feature in an EV battery, but they have a lower energy density than the laptop batteries. As far as I know, no battery in existence today and suitable for an EV has a greater energy density than the batteries in the Roadster. With production set to begin in a little over 2 years, and delivery in 3, I think it's overly optimistic to expect to have batteries in production with 50% more energy density.

I am optimistic that in seven to ten years there will be significant improvements in battery technology. But optimism is not certainty, and I would not base a vehicle purchase on the assumption that by the time the car is a decade old there'll be a better battery for it. That better battery (if it exists) will go into my next car, because when my second EV is ten years old, I'll either be too old to drive, or looking for better car technology. (I'm already driving my first EV, and I know I'm not going to keep it for ten years. I will be replacing it with the first available EV that's better.) The Tesla Roadster and S sedan look perfect now, but in a decade they'll look pretty outdated, and the early buyers will be trading them in. It's the folks buying them used in 8 to 10 years who might want to replace the batteries. But if the 160-mile car still can go 100 miles, a used-car buyer might not want to fork over the money to double that range.