Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?

Comment Re:He forgot to charge the car....... (Score 1) 700

Extension cord is not recommended for Volt. Other EVs may or may not work, depending on what they need and how their built-in chargers are constructed.

Since this Tesla has a pretty long range, and a large battery, I suspect that the voltage drop on a cord would be too much. Some power supplies may become unstable because of that. I had a device that failed in any extension cord, and worked right only when plugged directly into the wall. (But that was, of course, a bad design.)

A pair of #10 wires will give you 2V drop at 100' under 10A, and 3V drop at the same length under 15A. You can be sure that an EV charger will suck all it legally can out of the outlet; the breakers there are typically 15A, so I'm afraid 10A is all that one can draw.

Outside of the voltage drop, another problem may be in the impedance of the cable. 60 Hz is a pretty low frequency, but still the long cable will be a transmission line with distributed inductance and capacitance. If the TL is not matched to the source and destination then it can present random impedances to the source and to the sink, all the way from infinity to a dead short. This also can cause instability of the charger. But the cable must be pretty long for those effects to become measurable at this frequency; a quarter wave piece will have to be about 930 miles, ignoring the velocity factor. Power distribution grids have to take this into account all the time, but most homeowners only have cables that are somewhat shorter.

Comment Re:Fault Irrelevant: Shows Flaw (Score 1) 700

How long would you have to wait to get a full charge off, say, a 110v outlet (the most commonly found)?

Per discussion elsewhere in this thread, a common 110/120V outlet will not even be enough to keep the charge topped off. A 240V outlet will charge the car at a glacial rate (that's what was done at Norwich, as I understand.) Perhaps that would work for an overnight recharge at home. Only the 100 kW, 480V supercharger gives you a chance to charge the car reasonably fully and reasonably quickly.

Comment Re:Fault Irrelevant: Shows Flaw (Score 1) 700

If you're in a position the get tax credit/deductions for your transportation expenses, can you isolate that portion of your electric bill used to charge your car?

As matter of fact, yes. I have two electric meters on my property, and the utility company would be happy to install more if I need to. Each has a separate power drop from the transformer, and they are used for different purposes. They are even on different rate plans because one has a 6 KW solar panel attached to the grid.

Comment Re:CEO Switchout (Score 1) 700

You know the same things affect endurance in standard cars as well, right?

Of course. Heater might be not a problem, but A/C would be, and headlights, and some power-hungry accessories. But, as you imply, most gasoline cars have twice the range of the Tesla. Any gasoline car could easily make a 160 miles trip without refueling, and none of the fuel would be lost ovenight (except in a ghetto :-)

but the estimation of range is actually easier (electricity doesn't vary in octane, for instance.)

I disagree. You buy the same fuel and you get about the same performance. Admittedly, the modern diluted gasoline is not as good as the pure one, but that is politically driven, and it is common to the large area; it's not something that varies from station to station. A tankful of gasoline is a known quantity.

On the other hand, an electric charge is hard to measure, especially when it is stored not in a single capacitor but in billions of molecules. There is no mechanism by which you can reliably tell how much juice the battery has left. You only have indirect measurements, such as the electromotive force and the internal resistance of the cell. And you also have the records, how many coulombs went in and were taken out. You cannot shove a dipstick into the battery and look at the level; a gas tank allows you that, if you need to. (You are required to do that on airplanes.)

On top of that, the battery has unpredictable charging and discharging patterns. When you fuel a gas car you know that once you are done the tank is physically full (the level reached the cutoff tube in the handle.) When you fuel an EV you cannot be even sure if the battery is fully charged; even the definition of "fully charged" is debatable. Look at the reporter's numbers - he got "remaining miles to empty" all over the place, from 240 to 185, after a charge at the supercharger, all under computer control. This variability is not good.

Then there is yet another factor. The battery has self-discharge. It may be a huge current; combined with thermal issues, the reporter's car lost 65 miles of range just after being parked for 8 hours. This is not easy to take into account because people are not used to care for their cars that much. A gasoline car will not lose energy - not overnight, and not even after being parked at the airport for two weeks. (An EV would be scrap after two weeks without charge, as other Tesla owners found out after their Roadsters got bricked.)

There is yet another small factor. Battery's capacity is a function of the discharge current. If you drive faster you get far fewer miles than if you drive slower, or with the wind, or downslope. This is an issue that is independent from losses of efficiency due to drag or due to suboptimal mode of the engine. A gas tank will deliver power regardless of how much of it you want, whether it is a drop per minute or a gallon per minute. A battery doesn't work like that, and those losses are harder to calculate.

Experience of this reporter proves it. I am sure the guy is perfectly capable of driving a gas car. But he failed with this one, because the car has too many quirks. You have to make caring for this car into your second, if not the first, goal in life. Only then it will be usable. You cannot run an EV with the same lack of care that we practice with gas cars. An EV is a very fragile toy, and for that reason it is not very well suited for majority of drivers. If I may use a computer analogy in a discussion about cars, an IBM/370 mainframe is not a good alternative to a smartphone, even if it is faster. A mainframe requires trained operators to run it. So is this Tesla car.

Comment Re:He forgot to charge the car....... (Score 1) 700

The whole car isn't supposed to be used in winter.

We've taken great pains to ensure our car works very well in cold," Musk said. "In fact, our No. 1 Tesla Roadster owner owns four cars in northern Norway, where it's permanent midnight during the winter. Incredibly cold obviously, and he uses it as his daily driver, so the car is actually designed to work very well in cold. We have an intelligent thermal control system that's actually able to shunt heat from the motor into the battery pack and in cold weather will actually close shutters in the front of the car to keep the car insulated. We've taken great pains to ensure that the car works very well in the cold, which is why we're so incensed by this ridiculous article."

Comment Re:Streisand effect (Score 1) 700

How many watt-hours do you think are in a Tesla with a 300-mile-range battery pack?

About 86 kWh per the article.

If we stick to 15A, 120V RMS then a standard outlet is providing us with 1.8 kW. A charge of 1 hour would deliver exactly that, 1.8 kWh - even assuming that there are no losses anywhere (which can't be.) To fully charge the car you'd need 47 hours, or two days. If the battery keeps losing charge as it did overnight then you cannot even keep it topped off at low voltage.

This makes your comment true, of course - and it makes any prospects of low voltage recharge (at those Wal-marts, and at unlocked outlets elsewhere) pretty much useless. You have to have a high power charger for the car, or else it does not go anywhere. The conclusion of this reporter's road test, and of this simple calculation, is simple: EVs cannot be sold (for road trips, at least) unless a network of charging stations is in place. But there are many rural locations where there is simply not enough power to feed a charger with. A 86 kW charge over one hour requires, for example, 480V and 180A. A single supercharger station is said to provide 100 kW of power.

Comment Re:Streisand effect (Score 1) 700

I read all articles. How do I "maintain a certain temperature" of a car that is parked outside? Do I have to warm it with my body, for example? Do I need to park this car in a heated garage? If so, this was never mentioned to the reporter. On the other hand, a "software glitch" *was* mentioned by the Tesla rep. Did you even read the article?

Comment Re:CEO Switchout (Score 1) 700

Let's be practical. You departed from Milford (4) for Groton (5). The distance to there is 79 miles. The computer in the car said "Charge completed" and shows you 185 miles to empty. You need 79*2 = 158 miles. The margin is 27 miles. The reporter didn't even use heater on this leg. Note that the car itself failed to correctly forecast the trip, and after traveling only 79 miles he had 90 miles remaining from the original 185. He already "travelled" (virtually) for (185 - 90) = 95 "car miles" (as the car saw them.) Now the remaining charge is not enough to return! What can he do if there is no recharge arrangements? Should he turned around on the freeway and went back to Milford, where he has no hotel and no need to be?

How can he EVER get to Groton in this car? Are you saying it's not possible? The car was charged as full as the computer considered "full" and the shown range was sufficient. How much should have the reporter added? He had 27 miles of reserve; should he have added 30 instead? 50? No, none of that would be adequate. First, the car saw the trip to Groton as 95 miles, so if he turns around in Groton and heads back he would need 2*95 = 190 miles of range. Then he lost (90-25)=65 miles overnight, so those need to be added as well: 190+65 = 255 miles. This is outside of the range of the car!!! It didn't have that much charge ever, even when brand new! Conclusion: this car cannot make it from Milford to Groton and back, not without an overnight charge... which was not available. Epic fail.

I can understand that an owner of a $100K luxury car can, of course, knock on a few doors and ask for a place in someone's garage. Try that at 9pm or later in a place where nobody knows you. Chances are you will have to park your car at the local jail, while the police is sorting out your very suspicious story.

Chargers for this car are far between. As the attempt of charging at Norwich shows, the low voltage charging is barely enough to compensate the self-discharge. You'd need to leave the car plugged in for a long, long time (like the whole night) to charge it, and even that might not be enough - you'd need a high voltage home charger.

What are your options now? You are on a dark freeway, and you are miles away from any village or a town. You do not expect to find an outlet anywhere in those places, especially at night and in winter. Your only arranged accomodation - the hotel - has no outlets in the parking lot, and you cannot drag enough 120V power to the car even if you had a long extension cord. (What hotel will permit you to just drop it onto the roadway in any case?)

I'm just explaining here that you will be flat out of options. Your car depends on superchargers to be in some way fit for the road - and you are already too far away from those. You went too far not because you couldn't do math, and not because you used a heater - but because your car first overestimated its abilities, and then it lost most of the remaining charge that, in theory, could carry you most of the way back to the supercharger.

Apparently the same kind of idiot that starts under charged, adds a detour, and insist on running out of power to prove a point.

There is no need to repeat Tesla's allegations. The detour occurred BEFORE the supercharging at Milford. What effect could it possibly have on car's performance after it was fully recharged (per car's computer) at the supercharger?

Comment Re:CEO Switchout (Score 2) 700

But they can expect the user to understand that the range would be reduced accordingly.

No, they cannot. Please tell me, how many miles should I deduct from the "remaining miles" indicator if I want to have +60F in the cabin, and it is +10F outside, and the speed will be 55 mph to the northwest, and the wind is 20 mph from the east, and there are three of us in the car (one is a dog of medium size.)

Myself, I cannot imagine how to calculate that in my head. Those are all important variables, you cannot do without them. The analytical solution is probably impossible; CFD methods have to be used to build up lookup tables, and interpolate from there.

Comment Re:"Real World" conditions (Score 1) 700

Do you record your exact fuel economy, maintain full GPS tracking logs, and keep track of exactly how quickly you accelerate and how fast or slow you drive every mile in your car? No, you don't, and neither does the rest of the world.

I own a Prius, and I watch the mileage. Owners of high efficiency cars tend to do that. There are forums where they compare notes and discuss their numbers. Tesla would have no problem whatsoever in collecting the data if they pay the owner a $1 (or something) for 100 miles of submitted tracks. The software can remove portions of tracks that the owner considers private; submissions will be cryptographically signed all the way from the car to the PC and to the Interweb. Trivial to implement, and creates more interest in the car's doings.

When was the last time you got the MPG that your car's manufacturer promised?

I'm still getting it, though the gasoline is diluted with ethanol these days.

Comment Re:Heater (Score 1) 700

Please tell me more about this car that warms the passenger compartment by just blowing heat off of the radiator.

All cars made in 20th century use this method. The heater core is connected to the liquid cooling system; technically it is a second radiator, smaller and closer to the firewall. It is bypassed with an automatic valve to help with the warm-up of the engine block.

Hybrids like Prius also use this method; but Prius has additional electric heaters that can provide heat instantly, primarily for defrosting the windshield as soon as you start the car. Traditional cars deny you the heat for about 5 minutes, and if the windshield fogs over it's just sad (Rain-X time.)

Comment Re:Heater (Score 1) 700

I've yet to see a car with an electric driven A/C... but I'm always interested to hear about it.

Prius has an electric A/C, as well as power steering and braking. The ICE operation is entirely optional, as it has to be because the car can remain in EV mode up to 42 mph.

Comment Re:He forgot to charge the car....... (Score 1) 700

He wasn't supposed to plug it in overnight. There are no charging facilities in Groton. Does the car come with a 1,000 feet extension cord? Oh, by the way, you cannot use an extension cord to charge an EV. You have to park right next to the external outlet. Can you find one on a wall of a hotel, in darkness, especially if the outlet isn't there to begin with? Snow banks may prevent you from parking anywhere close to the building; you may be unable to even walk to the wall (there might be bushes under the snow, or flower beds, or whatever.)

The reporter should have carried a gasoline generator in the car. That is the truly essential component of a modern EV, as it appears.

Comment Re:Musk to NYT (Score 1) 700

which amounted to a total of 2 miles.

It could also be an involuntary detour - say, an accident that blocked all but one lane. Will Musk blame the reporter for that too? "If you drive our $101K car make sure that you never slow down; if that happens, stop and call us so that we can recalculate your options. On the other hand, forget it - we will screw it up even more."

at some point he hit 75.

There are plenty of stretches of freeways with negative incline. On 680, for example, near Livermore. You take your foot off the pedal and the car still accelerates past the speed limit. Other cars around you do the same, of course. It's a pretty long descent, and it recovers a lot of energy that you spent climbing the hill.

if you are going 55 in CA, even in the slow lane, you'll get your ass ran into the ditch.

The typical speed on 280 is 70-75 mph, with 65 posted. Drive slower at your own risk. I-5 has 70 mph posted limit.

If Tesla dares to publish the logs we will find out where the reporter exceeded the speed and what was the slope of the road there. But in any case he did that way before the last charge at Milford, so I don't understand why would that matter at all? Did that mile or two at 75 mph permanently damage the luxury car? This looks to me like Musk is throwing everything he has at the reporter, hoping that the people will not realize when and where the alleged events took place.

Slashdot Top Deals

The universe is an island, surrounded by whatever it is that surrounds universes.