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Recently Tesla is in the news with their sexy electric cars.

There was some discussion here a while back and I thought I’d do a little follow up since some of “The Faithful” showed an interest.

Tesla claims 300 miles highway range on a single charge. Is this possible? How do they do it?

Well I was skeptical so I did about ten minutes of research on the ‘net. Highly unscientific, but enough to do some “back of the napkin” calculations.

“Watts” and “horsepower” are equivalent measures of power, just different units… like knots and mph…

746 Watts = 1 hp.

A kilowatt = 1000 watts

1 hp = 0.746 kw

So lets figure “it takes what it takes” in power to move a particular vehicle down the road at 60 mph. You have to overcome aerodynamic drag, rolling resistance, and the losses of the mechanical systems like bearings and so on. From a practical standpoint you also have to do stuff like run headlights and heat or air conditioning and probably a GPS and a radio.

For a “talking point” let’s say that Tesla has done their homework and produced a car that can be pushed along at a steady 60 mph using a constant 30 hp. This is not easy to accomplish. Even harder since you have to figure they need to carry the weight of their batteries along with everything else. I start with this as an assumption. I have no hard data that it is true, but as you will see the math pretty much works out, so I think I'm close. But 60 mph on 30 horses is pretty darn good engineering.

At 60 mph it takes 300 minutes to go 300 miles.

300 minutes is 5 hours.

So you are pulling 30 hp out of the batteries for 5 hours to go your 300 miles. (assuming no electro-mechanical losses, and no accessories, which is really not any more reasonable than assuming it is a perpetual motion machine, but for now it simplifies things.)

What is this in terms of electrical consumption? How much energy do we have to put in the batteries to get this much energy out?

The answer is 30 hp X 746 W X 5 hours = 111900 Watt-hours or 111.9 kwhr

So lets back this out and see how much that is in volts and amps on an overnight charge of 12 hours:

111900 Whr / 12 hours = 9325 Watts

Watts = Volts X amps

Most of us only have 240 volts available as our highest household voltage so 9325 / 240 = 38.9 amps.

So we are charging for 12 ours at roughly 40 amps and 240 volts to get our range…. Assuming no losses in the entire process.

It turns out the Tesla markets a “twin charger” for the home at 80 kW. This is essentially twin 20 amp 240 Volt circuits in your garage hooked up simultaneously to the car get the required charge in a period of about 12 hours to be able to travel about 300 miles. (They don’t say it takes 12 hours, that is from the above calculation)

That is pretty extreme, but it isn’t totally crazy.

Many houses have a main breaker of 100 amps at 240 volts, so at least in theory it is getting close to do-able in your garage. You probably can’t run your dryer, your hot tub, your central air conditioner, and twin-charge your Tesla all at once, but hey, it is getting close provided you don’t mind charging batteries at maximum rate for 12 hours to be able to drive 5 hours…. Charging batteries at a maximum rate is tricky in itself… but lets ignore that for now.

But suppose your destination has only has ONE typical dryer outlet, you had better plan on charging for 24 hours before you drive home. 48 hours if you are going to plug into a 110 volt outlet, and longer if it is the typical 110V outlet with a 15 amp breaker.

As a sort of easy rule of thumb the typical 15 amp 115Volt USA outlet is maxed out at 2 hp. So you can do rough calculations backward if you please:

2 hp X 15 hours = 30 hp-hrs or 1 hour of driving at 60, or 60 miles range.

2 hp X 12 hours = 24 hp hours…. so you would get at best 24/30 = .8 hours traveling at 60 mph, so something like 48 miles range.

A 240 volt outlet at 15 amps is roughly twice the voltage, so twice the power in, so 12 hours charge on a single 240 V 15 amp circuit gets you up to 96 miles.

And so on. These are very rough estimates, but good enough to talk about over beers.

The only part of any calculation that is harder than those above is the hp used to travel is related in part to the speed squared…. Because of air resistance…. So going a little faster draws a LOT more out of the batteries, but going a little slower saves a lot too.

Most reviews I saw talk about range in the 200+ category, which is more believable than 300 miles but still very impressive.

However if you figure a single 240V 20A charger for 12 hours your best range (by Tesla claims) would be half, or 150 miles. And if you could only charge for 8 hours it would be about 100 miles.

Now don’t forget that all of this hen scratch math assumes magical batteries and motors with no losses. Losses are impossible to avoid. Losses in charging, in battery storage, in running the batteries and in the motors and drive train will occur. It is why we can’t put a windmill on our electric car to charge our batteries as we drive. Mother Nature just doesn’t allow us to build perpetual motion machines. Yeah, she’s a bitch. Losses happen. And headlights have to be run, computers need to check our airbags, ventilation systems need to be operated, and so on.


BUT WAIT! There’s more!

Tesla is also adding another element that is very exciting:

along the highways on both the East and West coast they are installing a network of charging stations called “Super Chargers.” You still have to cool your heels for a while as the batteries charge but at least in concept there is a place you can go to draw big amps to charge your batteries. However this still isn’t the best part;

Tesla says it is hoping to roll out on the West Coast by year end (2013) an automated battery hot swap system!

You drive into a charging station, park over a special bay, and in 90 seconds your old battery pack is gone and a new one is installed. Just like your DeWalt Driver Drill, you don’t wait around for a charge, you just swap out the battery pack. 90 seconds and you are gone with a full charge, and if it takes 15 hours for them to recharge your old batteries, that isn’t your problem…. Tomorrow someone else will get that pack, fully charged!

Now they haven’t solved the method of payment for this yet, but that is simple and will come. People have been swapping out empty welding gas cylinders and propane tanks as a way of life for generations. You never really “own” your tank, you just buy the gas in it.

Hot swap a battery pack with a 200 mile range in 90 seconds? Now we are talking about a viable system… though it is a lot of infrastructure to build.

The question is will people like it and buy it?

But a better question might be will the Tesla battery Swap System become some sort of de-facto standard?

Can Tesla license their battery pack design, conceived to be hot-swapped by automated equipment, to other potential electric car manufacturers and charging stations?

I’m still a skeptic about the ultimate popularity of PEV (Plug in electric vehicles) for highway driving. However if this system were to be widely accepted in urban centers it could be pretty darn successful.

Why urban centers? Because you spend a lot, if not most of the time stopped and drawing very little form the battery in city driving. And when you do move it isn’t at highway speed.

In an urban driving environment you are not so interested in range as duration. Add regenerative breaking to recapture some battery charge as you stop after every start and you are getting to look pretty good for a city taxi or mini-van or small service vehicle. An 8 hour + driving shift with a 90 second battery swap at the end is pretty darn good and it looks to be within reach.

Tesla has piqued people’s interest by making a sexy car, and focusing on removing objections when the public compares them to gasoline powered vehicles. But they are just selling the sizzle…. the real value here is in licenses for their hot-swap battery design with a network of urban swap-stations serving far more mundane vehicles.

IMHO If Tesla is going to make it big, that is where you will find the steak.

Peter

Interesting read. The hot swap would definitely make it more palatable in the urban areas, but not so much here in the country.

I priced them yesterday (S model).

60K for a bare bones, small battery model. 92K decked out the way I would want it.

That's a lot of coin for a car. Any car.

Peter,
If you had the right charging system in your garage, what would it cost to fully charge that battery pulling off the grid? I know depending on where you live the price of electricity varies but it has got to add up to more than running air conditioning for a month.
It seems like half of the projects I do end up delayed because the batteries in my Ryobi tool set go dead halfway through the project.
Car batteries are not there yet either.

Wouldn't it be nice to be able to spend 90K on a novelty item!

Forgive me for being a crotchety old bastard, but at this point electric cars are still just a load costly crap... Like Kevin eluded, think of your monthly electric bill. I'll bet that the addition of charging batteries to your normal electrical usage would be greater than what you would feed a gas guzzling SUV.

Again, horse pucky!

Estimates on the Tesla Web site say $10.19 for a full recharge... which is more or less same that I would pay where I live in the northeast (if I had a Tesla). Remember A/C runs around the clock day after day, while the Tesla recharges for 10 hours then is done. But there are other considerations, including it's like running a canyon trip. You can't refill until you get home, so you had better darn well plan for how far you are going, and hope you don't hit unexpected headwinds or delays on the way back home, or you're coming home on rope.

When you start running the calculations for return on investment, it just does not add up to the kind of numbers you would hope for it to. Last time I did that was before buying a Prius, and the return on fuel savings (at 45-50 MPGs), compared to another inexpensive economy car that got, say, 30 MPGs (at $3.50/gallon), took well over 100K miles before the Prius became the more cost effective solution. In the case of the Prius, it will easily last that long (and a whole lot longer) and be inexpensive to maintain, so it can be financially justified... but just barely.

Ultimately, it shifts from a financial decision over to a lifestyle decision, since it is almost impossible to justify spending $90-$100K for a car just to save on gas money compared to less expensive alternatives.

A hot swap sounds great...but its not like a tank of gas were each fill is as good as the last for years and years.
Batteries degrade and your new battery may be swapped for one with several dead cells or on the verge of going.
I'd hate to get the battery that is deemed an unacceptable core exchange.

One of my customers rebuilds the battery packs...strange things... each cell looks like one of those big long flashlight tubes with a bunch of "D" batteries stacked end to end...so old school its scary simple. Of course they are not "d" batteries...but they look darn close.

Sorry but until battery technology improves quite a bit, electric cars are nothing but a tree huggers wet dream or an extra for someone with plenty of extra cash. Cbs this morning show had a piece on the Tesla this am on how it rates as a safe care. Nothing more than a left wing propaganda piece. No one mentioned the truth about cost per mile.

When the Prius first came out the local Toyo dealer had one of their mechanics drive it from wpb to n.c. using only electric power pulling over everytime batteries went down, charge and the local paper followed them. Took 3 and a half weeks round trip and only burned 8 gallons of fuel.

IN the comments section someone replied, I could ride my horse round trip faster than that and use no fuel.

Every time I ask a hybrid owner about battery replacement costs, charging costs and disposal or partial recycling of old batteries not one has a clue.

Playmates are sexy too, but I wouldn't buy one of them either cause like an electric car, the short ride ain't worth the cost.

Bruce, I have no idea what they were trying to prove by driving the Prius on battery only... the vehicle is not designed to work that way (other than the current Prius plug-in). I have two of 'em in my car fleet, and the first one had a battery failure at 70K miles. Was covered by the 100K warranty, and the dealer took 3 weeks to replace because he had to order replacement batteries from California. It was the first one they had ever had to change. The dealer said it was probably a $3K+ repair at that time. These days, $3K is not all that much for a major car repair. Priuses are widely used as cabs these days. Every cabbie I talk to driving a Prius says the batteries last 300K miles - as long as the vehicle does. What is more surprising to me is that the vehicle itself lasts that long in hard service.

I'm afraid that I, too, have no clue about eventual recycling costs, but at this point the recyclers are offering to buy dead lead acid batteries... so who knows. There will be a lot of them being recycled in the next decade so hopefully Toyota has a clue of how to recover some of the materials, or rebuild the battery packs for reuse in other Priuses. Where I live, there are multiple independent recyclers that buy anything electronic for recycling the gold, copper, etc. that is inside.

Alas, I am hijacking this thread, so I'll let it go at that.

The only good "eco-play" on an all electric car is to redistribute pollution.

It isn't less polluting overall because you have to make the electricity somewhere, and in this country that generally means coal or oil or nat gas plants. You can talk about wind and hydro and solar, but they aren't there yet either.... so the tree huggers loose their argument as far as I am concerned about there being less pollution total.

If you burn the oil in a power plant it isn't 100% efficient. Then you transmit the electricity over the grid, with losses. Then you charge the car... with losses, then you discharge the batteries, with losses, all to drive the electric motors... with losses....

So who are you kidding? Just put the oil in the car's tank and save all those extra steps and losses.

However I can see how in a concentrated environment like LA or maybe other major cities it could reduce noise and air pollution locally. This could be a nice benefit.

As for purchase cost and amortized costs, well the present Tesla as it is now is still the sizzle, not the steak. The people they are selling to right now either don't care about amortized costs because they have tons o' bucks... or they are too stupid to consider them. Don't kid yourself. A lot of stupid people have a lot of money.

Anyway the present iteration of Tesla is still pretty sketchy in tems of being a good investment... but if it turns into the standard battery pack and that standard makes all sorts of electric vehicles viable in cities, well... then they might have something.

As for swapping good packs for bad.... if it gets big it won't be the car owners problem anymore than getting a bad tank of gas is today. The charging stations and their business plans would have to have a system of identifying the bad packs and cycling them out of use for reconditoning or recycling.... the way welding gas and propane outfits cycle bad cylinders out of circulation.

An aside here because it is pertenent to people , cars and dumb ideas;

When I was in LA circa '91 there was a big press afoot to limit local air pollutants by forcing everyone to buy a brand new car. There are lots of old cars in LA, many pre dating modern smog devices and the logic was to get them al off the road and make everyone drive newer cleaner cars... But what the eco-heads didn't consider is that with all the old cars going to junk yards, and all the resources, energy and pollution to smelt the steel and make the plastic and rubber to build all the new cars, it would create more pollutants than it would ever save.

People are dumber than anybody!

I still prefer the sound of a spooling turbo on a V8. Now before that V8 had a turbo and stand alone programming I was able to knock down 26 MPG. Keep in mind the aerodynamics of my ride are horrible for the most part. If I was able to get 26 MPG on old technology factory computer (1988) on a car with aerodynamics equal to a porta potti I would think almost any new car should be able to get well over 40-50 MPG these days. Trucks/SUVs excluded of course.
The exorbitant purchase price of even some of the Hybrids seems to be ridiculous. If you can recover the cost at 100K miles that is great. But to drive 100K miles and break even while never having the "fun factor" while driving, I will pass on that! What ever happened to that guy Brown and his gas? He might have been on to something!

The 1975 diesel Rabbit got 45 mpg.......in the city. 55 on the highway.

Nothing is enviornmentally friendly if you stop and think about it. So they need to stop hugging trees.

In the mall by me they have Tesla all over the place on display. They are really putting the push on. It is not worth the money Drop a good diesel in and like Mike said, you get 50 miles to the gallon day in and day out. Really engineer the thing and I bet they can get 75 if they wanted.

The existing Tesla models have not been intended for mass market. The owners I have encountered (in California) seem to fit the typical demographic I have seen analysts describe, where the Tesla S is a 3rd or 4th vehicle, so the range anxiety is not an issue as the electric car is used where the range is not an issue. A large part of their base seems to have made "feel good" purchases.

We will see how Tesla does when they finally come out with a mass market car. Their larger market may continue to be pollution and fleet MPG offsets.

They are beautiful cars, need to be seen in person to be appreciated. Too bad they don't carry a twin turbo v12!

On a good note...getting these cars out there in any shape and form is a learning experience for both manufacturer and buyers. More they learn the faster improvements can be made and implemented on the next model. I'll sit back and wait til they get it down pat and pricing comes down...or if I come into money and can buy a 90,000 car that I can play with and feel good as I am helping the environment while saving money to boot( snicker). But on a sad note it would be sitting next to a Lamborgini in the garage which I'd have to start and rev daily...oh the sound of those cars.

For me, I prefer to fill at the pump. I went the route of having to plug in a diesel block heater on real cold nights at work...kinda fun the first few nights...but got tiresome quickly after that. Not to mention the couple times a new manager came in and didn't know I had permission from owner pulling the plug on me. Between that and trying to find a station that carried diesel was a real pain.

I rode in one--the guy who installed my solar panels drives it. Remind me to find a cheaper vendor next time! The thing is unbelievably beautiful--silent--and gave me chills when he put the hammer down. It's the fastest pickup I've ever experienced in an automobile. The thing's a rocket. He claims he gets 300 miles per charge. And I thought I was being virtuous with my 45 mpg Jetta TDI...

Wow, I just noticed this thread about Tesla and electric vehicles- I aint even goin there! Too many variables as to the intended use of them to say yay or nay.
You don't want to know how many batteries I replace on the first, AND second gen Prius. They deplete like any battery. They have internal shorts, like any battery. They have the inability to hold a charge, like any battery, over time. (This is the most common). Now, the plug in for example is intended for the driver who has a short commute I was told, and he/she only has 30 miles or less of driving distances one way. That will keep your engine off for the duration if you egg shell your accel pedal. So long story short, the plug-in's rating would be considered for commuter style driving short distances for miles/gallon. Of course the DIRTY source of electricity it takes to charge the batteries when you get to work and home far outweigh global conservation, but do you really think the average consumer knows this? Nope.
Tesla- O.K, I'll go there. Got a lot of cash? Want a fun car to drive in a different way nobody else has? Want to try to fool yourself your helping global or personal "carbon footprint"? It's fun to drive and very fast due to TORQUE you wouldn't believe until you drive one. Only problem here- as soon as you leave your million dollar house your performance depletes! I myself will stick with gas for performance and diesel for towing/boating. Try to make an electric car light enough to equate to over 7 thousand horsepower out of a top fuel and run 3.7 secs in 1/4. Try to climb 3 thousand feet of Tehachapi mountains with a 15k lb load behind you, on electric only. Try it in a boat- no way. Batteries would sink it to try to compete with oil burning.

I just looked up the S model and apparently it will run in the low 12's @ about 110. That is impressive, but for that kind of money and a lot less you can buy a good variety of 12 second cars. Novelty sums it up though. I don't buy into this green happy horse s*%t for one minute. Most people are not smart enough to realize the electricity coming from the wall outlet comes from petroleum/fossil products unless you are getting it from a reactor. They have been blinded by the machine.

Tesla may not be practical, but they look fun to drive. That is a pretty good leap for an electric vehicle, no?

Alabama Power has a Tesla that is used for promotions. I happen to be friends with one of the guys that have the privilege of driving the car home from time to time.

Acceleration is wild...........really wild.........cornering and handling is unbelievable..............

The quietness and lack of noises is nearly deafening

I give it 2 thumbs DOWN........."AIN'T GOT NO THUMP".......'AIN'T GOT NO ROAR"...........just don't get yer blood pumping! ! ! !


hb

The real tricky part for Californians in PG&E territory is that pricing for electricity runs in tiers...you get so many kilowatt hours at a certain price. Then the price goes up. There are three or four tiers in total. If you live in an area where you have to run your AC during the summer and have a family of four as I do, you regularly hit the penalty tier which is 300% of the baseline tier. In real terms, my typical $250 PG&E bill will regularly jump to $650 during the summer. That's in an 1800 square foot house since my divorce. My PG&E bill in my 3380 square foot house prior to my divorce averaged $500 a month and hit a personal record $1680 in one month during a heat wave in which we had something like 20 days over 100 degrees and low temps in the high 70's. PG&E was feeling generous that month and gave me a $200 discount due to the extreme weather, so it was only a net $1480. LOL!

Bottom line: There is NO WAY the average Californian is going to be able to afford adding charging an electric car daily to their PG&E bill without some kind of MAJOR subsidy.

JohnV8r wrote:The real tricky part for Californians in PG&E territory is that pricing for electricity runs in tiers...you get so many kilowatt hours at a certain price. Then the price goes up. There are three or four tiers in total. If you live in an area where you have to run your AC during the summer and have a family of four as I do, you regularly hit the penalty tier which is 300% of the baseline tier. In real terms, my typical $250 PG&E bill will regularly jump to $650 during the summer. That's in an 1800 square foot house since my divorce. My PG&E bill in my 3380 square foot house prior to my divorce averaged $500 a month and hit a personal record $1680 in one month during a heat wave in which we had something like 20 days over 100 degrees and low temps in the high 70's. PG&E was feeling generous that month and gave me a $200 discount due to the extreme weather, so it was only a net $1480. LOL!

Bottom line: There is NO WAY the average Californian is going to be able to afford adding charging an electric car daily to their PG&E bill without some kind of MAJOR subsidy.

You just have to get creative like the dirtbag that lives two doors down from mom. He lives in a semi, so a common wall is shared...he cut thru his wall and spliced into his neighbors electrical junction boxes in a couple spots. It was noticed after the walls were opened up in a demo after Sandy.


....and as long as your getting discounts, rebates, incentives and subsidies from the government and power company its much cheaper...even if it cost you more.

OR... you could install a generator and buy gasoline or Diesel fuel for that, and use the gen set to charge your electric car at night.....

Oh wait.... here's the answer: maybe you could skip the gen set and put the gasoline or Diesel straight into the car and just burn it there when you need it.

10 gallons of fuel can go 300 miles these days. How much does it take to run the gen set for 12-15 hours at 80kW ?

The way politics and science goes pretty soon you will get gov't subsidies for charging your electric car, but then you can use the batteries in the car to drive the air conditioners in your house.

We've already had that discussion here where our town installed a couple of "free electric vehicle charging stations." Not only do you get "free" electricity for your car, you also get preferred and reserved parking spots.... all you need is a van full of batteries and you can run your lights and TV in your house all night on free elctricity from the town!

Of course that electricity was generated by 100% non-polutting FM... (that's "F..ing Magic." The same stuff that scientifically challenged people assume makes radios and airplanes work.)

Peter

Peter- Now your just getting silly. just plug the car into the cigarette lighter for a charge.

Carl wrote:Peter- Now your just getting silly. just plug the car into the cigarette lighter for a charge.

Best answer of the year.....


My 16kw generator would burn about 16 gallons of diesel to provide one full charge, plus about 6% of an oil change interval.

Okay, I have to wade in now. I own an electric car. It is not a Tesla, it is a lowly Chevy Volt. It can burn Gasoline, but the way we use, mostly for commuting to and from my business which happens to be a recycling company. We live in a region where over 95% of the electricity is supplied by hydroelectric, so it is renewable. The car charges overnight on a 110 plug in as well as at the 240 volt charger that are at both plants. I would love to have a Tesla, the sedan was not available when we bought the Volt, so it was not an option at that time. In Canada, the Volt is a $50,000 car, so no bargain either, the extra 20K for a Tesla would be cool. My other car is a Ford F350, so I guess I am just balancing things out. We also run 4 diesel/electric hybrid trucks where the electric battery runs the auxilary hydraulics and those trucks use 66% of the fuel that the identical truck uses on the identical route with the same driver.

I think for a given application in certain sets of circumstances that electric and hybrid vehicles are more effecient and effeciency is one of the main underpinnings of sound environmental and economic principals. If resources are scarce, use them wisely and effeciently and you will do the least amount of harm to the environment and create as little impact as possible, just like many of you have chosen to run diesels in your 31s instead of 454s. The capital cost is rarely justified by the fuel saving, but there are other elements that drive us to make that decision time and again.

Jamie MacKenzie wrote:It's the fastest pickup I've ever experienced in an automobile.

One advantage of an electrical motor is that you have the full 100% of torque available at any motor speed...

This has been an interesting read. The Tesla surely has a cool factor that you don't see in a Nissan Leaf or Prius. It wasn't long ago techno geeks spent $5000 on a flat screen TV, so I'm not suprised they are selling well.

Charging stations or battery swaps require a massive infrastructure to work on a big scale. The Chevy Volt in theory is a nice hybrid idea but at it's most efficient runs 35 miles on electric.

My 2013 Durango gets 23 MPG a big improvement from the 11MPG on my 1996 Bronco, I'm happy with that.