Tesla owner drives 452 miles on single charge | Hacker News Reader

Tesla owner drives 452 miles on single charge

techcrunch.com

76 pointsSQL221962 comments

The (imo, more interesting) stats in the video are missing from the article text body:

   Total Distance:        728.7km,     452.8mi
   Total Energy:          77.5kWh
   Average Energy:        106Wh/km,    171Wh/mi
   Driving Time:          18:40 hours
   Average Driving Speed: 39.0km/h,    24.2mph
   Total Stops:           1 hour
   Total Time:            19:40 hours
   Max Elevation:         94m,         310ft

24mph is an excruciatingly slow average speed for a 450 mile journey. No wonder they were able to be so efficient.

so, basically slower than a pro on a bicycle

nice one

Also a lot less energy efficient. They claim 171Wh per mile, that's 147 kcal per mile. On a recent 17 mile ride, I applied 591kJ (141 kcal) of work to the bicycle. So a bicycle ridden by a non-pro is almost 18x more energy-efficient than the car. (Of course more than 141 kcal of energy is required to get your muscles to do 141 kcal of work on the pedals. But not 2500 kcal worth, like the car would require. I wish a 1 hour bike ride burned 2500 calories.)

A pro, or at least someone comfortable with averaging 25mph over a long distance; given a relatively flat course, would probably require an average power output in the region of 300 watts. So even if we take the higher speed into account this works out around 12Wh/mile. ..but if we take weight into the equation; assuming the rider and his bike are on the chubby side and work out a combined 100kg - we get 0.12Wh/kilo/mile. Most of the tesla range are over 2000kg excluding passengers, so taken as a Wh/kilo/mile calculation it actually works out around slightly more than 1/3 greater efficiency at 0.086Wh/kilo/mile. Not too bad..

Of course a bicycle that is what... 1.2x human weight... is more efficient than a car that is probably ~10x human weight, when you measure it by vehicle rather than kcal per mass.

The weight of a car is not optional. If I want to move some mass between point a and point b, and I do it by car, I have no choice but to haul along that extra ~10x my weight. Measuring by kcal/mass ignores this practical reality in favour of a more precise definition of "efficiency".

Also if you're riding a bike that weights 1.2x your body weight, you have the wrong bike! Good god!

Neither 4 passengers, pile of groceries, comfortable dry seats, infotainment & air conditioning are optional on bicycle.

In other words apple to oranges comparison.

Don't know if you were kidding but I think the implication was the combined mass was 1.2x your weight. Of course even then, that's still a pretty heavy bike (I think my commuter clocks in at about 10% of my weight)

What would the pro's average speed be over the total distance? And what would an ordinary human being manage?

It is obviously the speed that makes the difference. This guy only got about 110 miles (180 km) out of a fully charged 85 kWh Tesla, driving on the German Autobahn at 160 km/h:

http://www.teslamotorsclub.com/showthread.php/32873-Discharg...

The Tesla is poorly suited for Autobahn driving because it will actually overheat and slow down if you keep driving at 120mph(200km/h) for longer periods of time, and that's not really difficult on the autobahn, especially at night.

Given those stats, his average power usage was 4.1kW, or about 5.5HP. Not bad considering that's input power including all peripherals and losses, not just power to the wheels.

This is about 20% less than the rule of thumb number for the power needed to keep a modern mid size car moving at about 100km per hour. I forget where I read it.

So yes pretty good.

And this is the principal reason why internal combustion engines are so inefficient in practice, they are used at a tiny fraction of their rated output for most of their working lives.

Of course the comparison is not quite as favourable as it at first appears because we should really measure the input power not at the output of the battery but at the input of the battery charger (equivalent to measuring the fuel pumped into a petrol engine's tank). Still impressive even if the conversion efficiency of the charger and battery combined is only 50%.

Cool, do you have a source for that rule of thumb? That's a new one for me. That's about 8HP to the wheels to keep it rolling at 100km/h right? So obviously more than that from the engine.

Re: measuring at battery input rather than output, that's a good point. Would definitely be higher that 50% charging efficiency though. I would guess at least 80% - probably > 90% if you charge it slowly enough. (Haven't done any research on Tesla chargers or batteries specifically, but I did used to be a power electronics engineer. High charging efficiency is important both for cost and, perhaps as importantly, because a slight reduction in efficiency can mean a lot of extra heat that you have to deal with.)

Alas i can't remember and a quick web search doesn't find anything I recognize. But I did find this that mentions 10hp at 50mph: http://energy.typepad.com/the-energy-blog/2010/02/energy-nee... And a few hotrodders discussing the question here: http://www.hotrodders.com/forum/how-much-hp-required-60mph-1... This on PhysicsForums: https://www.physicsforums.com/threads/power-and-tq-needed-to...

And finally a paper with real formulas and better explanations: http://wps.aw.com/wps/media/objects/877/898586/topics/topic0...

Looks like my 5kW wasn't too far off.

It required approximately 5.5 horsepower to propel the vehicle.

I commented in another similar post but it seems to be lost...

My friend did 438 miles with his P85 by drafting behind a semi the entire trip. With the extra range (efficiency!) of the P85D I'm certain he could have hit 500, easy. I don't recall how many Wh/mile he was doing but it was crazy low.

I'm not sure why he hasn't been contacted about his drive, but Tesla does have the data and he's asked a couple engineers to look up his car and confirm. :-)

Truck drivers really don't like people driving close enough behind them to be in their slipstream. If you're that close, they can't see you.

Should I be concerned they can't see me when I'm behind them? I can brake quicker than they can and they can't really do anything negative toward me aside from braking hard. Really, you're assuming all the risk. If something happens up ahead you're going to be totally unaware (the main danger of following closely).

They do this themselves, at least in Europe. It's scary like hell that they follow each other, neck by neck, hour by hour with the shortest possible tracking distance.

Less than one second spacing is illegal in Norway and Germany. Three seconds is recommended.

At 90km an hour (maximum speed for lorries) that is 25m, about four times the length of my car. Is that close enough to get any useful effect?

But can't they also talk to each other over CB radio? Seems like that would make it safer. And of course it's a lot easier to see a truck right behind you than it is to see a car.

Still they block the exits for cars that need to merge. Happened once to me, a train of ten trucks slipstreaming right when I needed to take an exit. Couldn't slow down and merge at the end and the head was already after the exit.

Had to match carefully speed and merge the car in a space I wouldn't have used for parking. And the asshole even blew the horn at me!

Seriously, fuck those idiots doing it. Driven for years on highways and all scary things ever only came from truck drivers needing to save those 10 bucks/five minutes.

> Had to match carefully speed and merge the car in a space I wouldn't have used for parking.

> needing to save those ...five minutes

So you wouldn't have parked there but you have no problem squeezing between two moving objects 10x your weight/inertia at highway speed? All so you can take an exit (that you were inexplicably in the left lane when you realized you needed it) rather than just take an extra five minutes and turn around at the next exit?

Hard to imagine why he blew his horn.

The lorry driver was in the wrong he was driving with an illegally small space between him and the vehicle in front.

I'm not disputing that. I'm disputing the intelligence of looking at a spot barely big enough for your car that is moving at highway speeds and sandwiching yourself between two vehicles, either one of which could kill you with inertia alone, and then wondering why you might get honked at for it.

not every state has 5 minutes between exit luxury highways

So? Distance between exits doesn't change the fact that what he did was reckless and dangerous.

My uncle did that in his car behind a truck when he realised he had little gas and maybe 50+ miles to the next gas station.

He used his CB to contact the truck in front of him, who welcomed him to draft him along.

During the trip, both my uncle and the driver heard many other trucks call his truck on the CB To warn there was a car tailgating in the draft.

Think he bought the driver lunch when they got to the next town with a gas station.

obvious tip: this works for gas cars too. if you're extremely low on gas and in the middle of nowhere, draft a semi ... very carefully. luckily they don't brake very fast.

i did this more than a couple of times during college road trips when i was broke as a joke.

Can confirm, had to do this once only and I hated it. Got in to the next town and put 65.4L into my 65L tank. Never again.

It didn't help that the service station I had hoped to reach when I started getting low was shut because they had run out of petrol.

Sometimes on long motorcycle rides you can take a few minute break behind a semi. Especially on a bike with no windscreen, your arms get really tired of pulling you against 60~ mph wind for hours. Pull up close behind a semi and the wind will disappear. Keep alert, like you said though.

It might be better to just take a break at a rest stop. A friend of mine was on a long distance ride across the U.S. and was killed doing this.

Sorry about your friend. While will get you more mpg, it's not worth it. When the truck hits their brakes you want enough time to stop. Other dangers are them kicking up rocks that can easily crack your windshield, and blown out tires (one hit my sisters car and took out a chuck of her bumper).

As I posted on the other thread (that didn't seem to get a lot of attention), the range is actually worse on the P85D (270 miles on the P85 and 253 miles on the P85D),

The P85D is rated at 295 miles. I don't know where you're getting 253 at.

The P85 is 275.

edit: ugh, this is weird. Even their site lists different ranges per car and they've added a calculator to estimate range based on speed, temperature, and whether or not you're running AC.

I guess the "rated range" is full of holes.

Isn't that just asking for rocks in your hood?

I read an article on hypermilers the other day. They indeed can push the MPG in high double digits (e.g. 70MPG in accord) but... the approach is not very practical:

- Switch to neutral and roll as much as you can,

- Drive only in optimal range,

- Close the windows,

- Do not run A/C or radio,

- Do not run lights,

- etc.

Needless to say they annoy pretty much everybody on the street who is around them.

So yes, good result, but not very practical.

There's a middle ground: Avoiding unnecessary acceleration & deceleration.

I don't hyper mile, but I do get far better gas consumption than rated. I let people merge, leave safe follow distances, and don't aggressively close traffic gaps which actually improves traffic flow by reducing waves of jams.

http://www.smartmotorist.com/traffic-and-safety-guideline/tr...

Mind you, I've been in cities where this type of behavior may get you murdered, but where I live this creates a more relaxing drive. If I feel like speeding I'll go to a race track :)

Wouldn't switching to neutral increase fuel usage?

When you're in gear, the engine is kept moving by the momentum of the car. When you switch into neutral and break the connection between the movement of the car and the engine, the vehicle has to use fuel to keep the engine moving and not stall. Yes, resistance will cause you to slow down quicker in gear than in neutral, but during that time you should be using basically no fuel compared to using the same amount of fuel that your vehicle would be using while idling if you're in neutral.

Basically, while you're coasting in gear, you're using the car's momentum to run the engine rather than fuel. When you switch to neutral, the car's momentum keeps the car moving forward, but the engine needs fuel to keep going.

EDIT: Popular Mechanics has an article on it http://www.popularmechanics.com/cars/hybrid-electric/a5977/c...

No. The Model S will break the car for regen purposes if you are in gear. So you will lose speed but get a tiny bit more energy added to the battery. It's better to just go into neutral because that whole process is inefficient.

I haven't had the privilege of driving a Tesla, but I have driven a Volvo prototype electric car[0] and it had two modes. One "emulate a petrol car" mode where letting off the accelerator would simulate engine braking (via regen). Then it had a "highway mode" where letting off the accelerator would just coast as if it was in neutral. The highway mode meant you could avoid wasting your momentum on a highway due to slight foot movements in speed regulation.

Do Tesla cars have something like this?

[0] http://www.plugincars.com/volvo-c30-electric

Depends how new it is and the car. Older cars still fueled the engine either way. Newer ones cut the fuel themselves, as you intimated.

I think the rule of thumb is that carburetor engines have simplified idle mechanism.

So realistically anything younger than 30 years is more fuel efficient. Also safer.

Right, big deal. "Nyland and the charitable friend who drove with him had to cruise an excruciatingly slow 25 miles-per-hour at near zero elevation to pull off the feat." This is like those solar car events where people find some long, straight road and drive bicycle-like things with solar panels very slowly. With a good road and hard tires, it takes very little energy to go a long way, slowly.

Those solar cars aren't slow.

> By 2005, several teams were handicapped by the South Australian speed limit of 110 km/h (68 mph), as well as the difficulties of support crews keeping up with 130 km/h (81 mph) race vehicles. It was generally agreed that the challenge of building a solar vehicle capable of crossing Australia at vehicular speeds had been met and exceeded.

https://en.wikipedia.org/wiki/World_Solar_Challenge

When I first saw the headline on techcrunch I thought they modified the car somehow to get that range. That would have been a lot more interesting than just some guy cruising at 25mph.

Having persuaded my LEAF to a predicted 120 miles on a charge https://scontent-atl1-1.xx.fbcdn.net/hphotos-xfa1/v/t1.0-9/1... I can very much appreciate the accumulation of tricks, nuances, and talent needed to actually achieve such range. Kudos to them for actually driving that 450.

I'm afraid the EV market is going to collapse shortly before it can really take hold and eventually dominate. (Georgia just ended its massive tax credit for EVs, and the dealers are bailing out of the EV market with plans to ship all the used lease-returned vehicles overseas.) Great vehicles on the cusp of seriously viable battery range.

what the heck, 19 hours for what a 7-8 hour trip max? If it's not real world, then why give it a headline? A scooter can get 95 miles to a gallon of gas. To me that's amazing.

Because those poor saps that wrote the article pay their bills by the click.

The hypermiler thing always seemed kind of dangerous. https://en.wikipedia.org/wiki/Energy-efficient_driving

59 mpg in a plain old accord is impressive though.

If you're hypermiling to save money, good on ya. If you're hypermiling to save the environment, I suspect you're fooling yourself. The extra gas burned by people rage-driving around you has got to easily outweigh your gains.

> his two-year-old Tesla

Video is of a P85D, which was announced less than a year ago.

AFAIK lithium-ion batteries wear out quickly with deep discharges, so I wonder how much range he'll get on his next charge (or alternatively, how much capacity he lost.)

I don't think this is the case. Lithium batteries are generally much better with deep discharge than lead acid. Trying to power a heavy load below a certain threshold voltage will quickly and permanently damage them, but generally there is a low discharge disconnect that kicks in before this point. I don't presume he'll notice any particular ill effect.

Like nkurz said, the battery management circuitry will usually disconnect the battery before it discharges enough to damage the electrolyte. Granted, this depends on the circuitry in question (i.e. your $0.05 battery controller chip from Shenzen may not do this), but I would hope that Tesla is actually investing in proper battery management circuitry.

Given that the car won't let you discharge below 20% margin, it probably isn't affected at all.

Is there something special he's done to get this much milage out of the car? It's only rated for about 300mi on a full charge, so I'm curious if it's just luck, or more?

I'm guessing you didn't watch the video or read the article, they didn't do anything special, just drove super slow on a very straight road.

> Average Driving Speed: 39.0km/h, 24.2mph

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