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Supercharger event September 24


Looking forward to concrete information...


It is very interesting that I've seen almost no solar installations here in Vancouver. Yet the summers are characterized by almost continuous sunshine.

However ... the other seasons are the problem. Spring and fall are wildly unpredicatable. A cold, cloudy, wet Spring persisted all the way to July this year; we took to asking, "How's Junuary been for you so far?" Fall's been great, but that looks like it will end next week, and there's likely to be very little sun from October to April, at least. So most of the year is diffuse lighting; that's great for the plants, because there's no shadows and they're very good at exploiting the indirect illumination. Solar cells, not so much.

And latitude makes a big difference. After spending decades at about 43°, moving to 49° here was a shock. The summer days are very long, but the winter's are very short. And the sun gets noticeably lower on the horizon than I'd ever seen it before. Even at noon. Result: winter days make for really lousy solar harvesting. Short, and dim.

So even the best solar charging station would be useless about 70% of the year here, or nearly so. On the other hand, BC has large historical hydropower resources, and grid power is plentiful, and about 7¢/kWh.

This is just one sample of an environment where the CA model doesn't apply, and in fact would be outrageously expensive and ineffective. WA state is almost identical. New England is different again, as is the North Central Midwest.

One size cannot fit all.

Brian H, wow! Thank you for a balanced and detailed argument free of ad hom arrogance. Now, when you accept that there is some room left for speculation, and that others may fill that in with different expectations or opinion than yours, we may actually be getting somewhere...

I must have missed the part where I said that my concept would work absolutely everywhere in the world without exception. Frankly I think its a little ironic to accuse me of being California centric (for the record I am Australian) whilst you practically dismiss solar completely out of hand because you don't feel it would work in your home city.

I have no issue with different solutions in different areas, for example in BC your power is 90+% Hydro so if your reason for considering solar originally was the long tailpipe argument then in your region using grid supply purely is absolutely fine. Some stations may benefit from a mid size wind turbine positioned nearby if the wind resource is superior to the solar resource.

I still suspect supercharging stations will incorporate storage of some kind because the enormous instantaneous power demand would be so taxing on the grid, particularly in regional areas. I see three areas of particular interest with regards to batteries at superchargers, first the potential to use batteries that may have failed QC testing in terms of suitability for use in a car but are fine for use in a fixed installation in a supercharger. Second is the potential to buy back used Roadster battery packs and in the future Model S battery packs and recycling them into new supercharger installations. Finally superchargers could be a very good test bed for battery R&D.

Here in Australia we have abundant solar insolation, solar PV is now below $2 per watt retail and grid power sells for 27 c/Kwh, in other words you'd have to be near bat s&^t crazy not to use solar on the roof here.

Finally I think it would be silly to ignore the reality that considering the Californian situation is important because California is significantly over represented in terms of Tesla sales, at least at this stage.

@Docrob, is that Australian dollar or US dollar for solar panels (not that is matters much, at current exchange rate those are almost identical), and how do you calculate that "per watt" (what does that actually mean)?

Its Australian Dollars but as you say we are pretty close to parity, a bit over actually so its a little cheaper in US dollars. Per watt means cost per installed watt of peak capacity. As in a 5kw solar array which would supply the power needs of a typical home costs less then $10,000. The power to supply all the power used for typical daily driving habits in an EV needs about 3kw, which means a lifetime worth of EV fuel can be bought for $6,000 or the equivalent of about 2 years worth of equivalent gas powered motoring.

Do your figures include any kind of tax rebates/subsidies/incentives? Also, what lifetimes would you expect from a solar array and an ev battery? And how much of the cost of grid power is due to taxes?

Oh yeah, and how much is the tax on gasoline?

That includes our REC rebates which vary according to the size of the system between 50c/Kwh to $1/KWh ie unsubsidised solar is about $2.75/watt.
Lifetimes, I expect about 25 years from solar panels, about 15 from the inverter, but many solar systems are still going strong after 30+ years with only a little output degradation. EV batteries are a bit of an unknown but I think 10 years is reasonable with a little capacity loss.

About 10-15% of our electricity costs are taxes and government programs, about 33% each for generation and distribution and the remainder retail margin.

Gasoline (we call it petrol in Australia) is currently selling for about $1.50 per litre. This is equivalent to about $5.94 US dollars per gallon, about 30% of that cost is federal fuel taxes and GST tax.

@Docorob, I'm also in Australia and I think your numbers are a fair way off. Solar panels are around 20% efficient. A Wiaico 285w panel is 1.6m2 in size. In Sydney you can expect about 4kWh per 1kW system installed, on average. On average the amount of energy hitting the earth is about 1kW per m2, so a 50m2 roof at 20% efficient panels is a 10kW system. That would deliver around 40kWh per day in Sydney, 50kWh in Alice springs.

I'm all for renewables, but let's keep the numbers real.

Hum? Mark E, that's what I got from Docrobs numbers. 5kW system = 20kWh/day = about 7300kWh / year. Sounds quite typical home to me. A bit large side home, but still typical, nothing fancy.


I generally see about 10% loss due to charging. While that is a hit, the combination of allowing hookups to single phase 240 rather than both costly and permit intensive three phase along with the ability to not get charged high use fees by back feeding the grid during charged/non use times would outweigh the loss. You also would only see that extra loss on a percentage of a charge. Take a single car charge of 100 KWH in full sun, the grid would supply 50KWH, the solar would supply 17KWH, and the batteries another 23KWH. The station would be fully recharged in another 20 min, and have "lost" about 2KWH due to battery charging inefficiency. In dark it would be 50/50 with a station recharge time of just over an hour and an inefficiency loss of about 5KWH.


Oh and I'll toss station material costs into the mix, solar - 30K, one super charger - 10K, 300KW battery pack - 100K, plus the "station" call that 10K, total station cost 150k. Then I would say that it can do 16 30 min charges durring the daytime and 16 at night.

Full Charge of 85K pack in 1 Hour---according to Tesla Rep....anybody else have that confirmation?

That's pretty good----wonder how many chargers will be at each station?

And---can you "reserve" a charger via Touch Screen---when you are lets say up to 1 hour away?

As to where the power comes from---yea it would be nice to have it come from renewable sources---but I wouldn't be sad if it was hooked right into a nuke or natural gas power plant 20 feet away.

Main thing for me in all this is to get off the gasoline/diesel heroin habit.

Full Charge of 85K pack in 1 Hour---according to Tesla Rep... anybody else have that confirmation?

As far as I know: WRONG. Half charge in half hour is not the same as full charge in one hour.


I don't think you can get a full range charge in an hour because the charge rate slows down at the end. On the other hand, I don't think many folks will have the stomach to run it right down to zero either, so a full range charge isn't normally going to be required--particularly if the distance between superchargers is the three hours Elon has indicated.

I'm pretty sure the rep is going by the website where it talks about 300 mph charging.

I'm pretty sure the rep is going by the website where it talks about 300 mph charging. (jerry3)

Yes it does. But don't skip the fine print. There it says: "A Supercharger can charge about half the battery in 30 minutes." Why wouldn't it state that it can recharge an empty battery in 60 minutes? That would be simpler and at least as spectacular a statement. The accurate wording should ring a bell. (And besides, as you note, we all know that charging is slower and more stressful on the battery the closer to full the charge level is already. To be entirely precise, the website should state: "... the first half ...".)


Right. I also suspect that 30 minutes of supercharging doesn't degrade the battery nearly as much as 60 minutes of supercharging would. My gut feeling is that that 60 minutes is 3x or 4x what 30 minutes is.

My 2cents...

If you are putting batteries in these chargers just skip the whole charging the car bit for 30 minutes and give me a battery swap/rental system, then you only need 2 or 3 batteries rather than 10. Why the heck would I want to wait 30 minutes on the side of the road when there is a perfectly good battery charged inside the machine.

I agree with Brian on many points here. It is very inefficient to charge a battery from a battery. As long as Tesla is guaranteeing the battery I'll take it ( Even in Saint Louis the solar panels will end up with snow on top of them for days unless you are paying someone to go out and scrap it off.... or are we now going to waist energy with heaters to melt it off.

Solar grid tied is all that is needed and a good idea. If you can get 240 or 208 volts there you can get 480 volts. Don't waste the time with added batteries. Tesla has already said they are 480 volt anyway. So solar panels pumping onto the grid. Charging from the grid.

swap/rent.... means I go by a Tesla service place and rent an 85kw battery and swap it along the way while traveling. When I return home I pick up my battery.

If you are putting batteries in these chargers just skip the whole charging the car bit for 30 minutes and give me a battery swap/rental system, then you only need 2 or 3 batteries rather than 10. Why the heck would I want to wait 30 minutes on the side of the road when there is a perfectly good battery charged inside the machine. (Sudre_)

This seems so obvious... yet it isn't. Firstly, the usual arguments against battery swapping apply: To make battery swapping work, the batteries must be owned by the provider and leased to the consumer. For whichever reasons, Tesla decided to sell the batteries. Also, battery swapping implies a commitment to a certain form factor and certain internal (electrical and electronic) specifications. This brings up a whole world of compatibility issues (think Microsoft Windows) that hinder development and deployment of new battery tech -- something we all have very strong hopes for. In the supercharger scenario, the charger provides the compatibility layer for whatever battery tech is inside, and that's it.

Secondly, batteries suitable for stationary use may not be suitable for use in cars. In particular, they may be cheaper for a variety of reasons (cheaper battery tech, used/worn batteries, lighter packaging to bring down cost for conditioning, you name it...), all of which boil down to a significantly lower energy density. Too low to store 85 kWh inside the floor of your car.

Another thought that may sound a little unconventional, particularly for the tree huggers among us... ;-) The solar panels and/or wind turbines of those supercharger installations will likely produce excess electricity for some time to come -- there just aren't enough Model Ss on the road to start queuing in front of those chargers, and even when there are more most of them will be charged in their home garage most of the time. With this said, it really doesn't matter if we lose a few percent charging battery-to-battery, or waste a few extra kWh on heating the panel to melt off snow and ice. The only thing that counts is that "it just works" and that they generate enough electricity to cover this "maintenance energy" plus the occasional supercharging customer. Don't be so greedy!


A few questions about you swap proposal?

Have you now created the need for an indoor enclosure, perhaps a sink and bathroom for the person working there, and some more machinery that wasn't already required?

Is this swap station going to be staffed 24/7/365 or can I only swap batteries from 9-5?

The person working there ( I take it I am not swapping them myself) is he trained? Qualified? How well is he paid? $7*24*365 = 61k yr...

When you say very inefficient, how much is very? Do you disagree with my 10% value?

I'm not sure that you realize how hard it can be to get three phase in some areas of the US. I am not allowed to have it run to my house where I live. Adding a three phase feed requirement is not a minor jump from single 240.

The key to the batteries and the solar is to allow fast charging, low grid load, and stay away from those terrible high use fees making the station cost very little to install and support.

My solar panels do a fine job of shedding feet of snow at my house, the angle on them seems to do the trick on its own. They are mostly black, they get hot on their own, no need for special heaters.

Swapping is a great idea, but it's going to be many years until the demand is anywhere near high enough to support the infrastructure to make is a reality.



Well, if they only built out enough to support the Model S cars currently on the road they'd have a serious problem in not too long a time. And perhaps they can sell the energy back to the electric utility. Even if they are solar/wind powered, they are still going to want to hook up to the grid in case they do have more cars charging than they have off-grid capacity.

No to to proof read this so I'll let Brain get the errors... gotta run.

Peter7, be reasonable.

The system can be automated??? I have no clue or care. There is a company called Better Place in other countries. Go look them up.

Gas stations work pretty good now with someone sitting at the counter all day and electricity is cheaper than gas.

The person working at a car wash that dries your car. How well is he trained? The guy at Jiffy Lube how well is he trained? Swapping a battery isn't rocket science. Tesla designed the pack to be easy and quick to swap..... altho Elon might be a rocket scientist so maybe it is a little tougher.

6%-10% loss to charge the batteries inside the machine. 6%-10% loss to charge the car. total 12-20% loss. That's not good in my opinion. Even if it is only 5% each for your total 10% that it twice as bad as just swapping the battery.

Getting three phase anywhere is EASY! I am an electrician. If you are putting poles out to get any voltage to location you can just put in larger wires or one more wire (single phase is 2 wires). You are not bringing 480 volts to a remote location (voltage drop every 100 feet). You are bringing a minimum of 4160 volt single phase to the location. A transformer will step it down to 480 volt three phase.

You forget that Brian H is right about solar. If you live South it is great and your system might work most of the time. If you live North you have 5 hours a day to charge with. Look up the charts on a solar sight. That 5 hours is an average over sun up to sun down and cloudy days throughout the year.

Most of the time they will shed that snow. I've had ice and snow sit on my 12/12 pitch roof for a week straight. Ice is the bigger problem. I guess no one will charge for those days.

It is going to be years before demand is enough for Tesla to really need superchargers anyway much less the expensive ones purposed. $80,000 to $100,000 in batteries to build one. Or use cheaper lead acid and replace them every 5 years?

oh and Volker.Berlin,

I totally agree with you. Just leave the whole batteries at the supercharger thing out of the equation.... swapping or not.

@Timo: Your numbers are correct, a 5kW system will produce around 20kWh per day on average (in Sydney).

The numbers I was disputing are these;
" Docrob | September 19, 2012

Comparing the image released to the car pictured under it the roof is about 12-13 metres long, assuming it is 2 car widths wide makes about 4 metres wide giving a total area of 50 square metres. Around the US solar insolation varies but on average solar output is about 5kwh/sq. metre/day, so a solar array on the supercharger pictured in Tesla marketing could produce 250 kwh/day, In California and Nevada this would be closer to 350 kwh per day."

I've yet to see solar panels that can *deliver* 1kW/m2 or 5kwH/m2/day. In order to do that and average of 4 hours usable sunlight throughout the year the panels need to be close to 100% efficient.

If I could generate 250kWh per day from my 50m2 garage roof I'd be doing it. That'd power 6 houses easily.

Swapping is also a "heavy lift" operation. It almost certainly requires robotic handling of the battery; not a job for Joe Lugnut standing under a car lift!

So it's very capital intensive. Inventory management of the batteries is also no joke; how many do you have to keep on hand fully charged at all times to accommodate spikes in demand?

But the biggest issue may be that it requires a whole different ownership setup. The company must own the batteries, and lease them. That's a huge change. I guess Renault & Better Place have a system worked out. Time will tell if that's successful.

In the US, it would require a huge number of swap stations, tho'.


So your the kind of guy who likes to toss out a stupid idea and walk out of the room without listening or thinking about any feedback hmm?

If not, comments like " I have no clue or care" sure make it seem that way.

Once again, you are not paying attention to the real costs associated with installs or on going operational costs. How much do you need to train someone or how much you need to pay someone to pull a 85KWH battery out of your S and put one back in is very real. I think that you are reasonably looking at paying out 100k a year minimum to someone for this, and keeping it up at the hours people would want will probably cost twice that. That seems like an awful lot of cost for something that you yourself are saying is going to be years before there is solid demand for them.

If you are electrician, then you should know what the penalty fees look like for exceeding power draw limits. Do you not think those should be factored into this? How much extra is it to permit 3 phase? Why can't I get 3 phase into my house when I ask if it's so easy?

The second battery loss you are talking about is always going to be there, so we are talking about a extra loss of 5-10%.

Yes, solar only produces when the sun is up. I would only expect it to generate about 100KWH a day (with the same 5 hours you mention that I always use for my calculations), but, generally again, this will be enough to stay away from those excess fees and reduce the install costs to the point that it makes it an easy decision to put it in.

I've never seen or heard of a transformer that will take single phase 4kV in and output three phase 480V. Could you point me at one?

Oh, and about Better Place, yes I've already been following them for a long time, thanks. There is a very good reason they chose where they are to install the system. Installing the same in the US at this point is silly. Just about everything is possible, that doesn't make it a good idea.


After reading all the comments, I will back off my "off-grid" prediction for the Superchargers. I agree there is not enough solar in all areas to guarantee capacity is waiting for you. We have already seen the teaser photo, so we know there is no wind turbine incorporated. It is nearly impossible to find a place that does not have wind or solar, but lets not get off topic. Elon is not a proponent of wind, so it just won't happen.

I still do not think the Supercharger will pull 90 kW off the grid to charge a car. I think it will use internal power conversion to deliver 90 kW per vehicle from an internal storage. It may have a 40A - 100A 240V connection to restore capacity to the Supercharger along with the solar array. This would avoid the need to have a 140+ amp 480V grid connection.


SInce you are an electrician, can you comment if 140+ amp 480V is a normally available electrical service at a gas station or small shopping plaza (think highway exit). 480V isn't hard, but having 140+ EXTRA amps available at any time is the difficulty. Or other QC service providers are justing giving me a run around?

Most all medium/large commercial has a minimum of 480 volt 200 amp service.
I would imagine that most small gas stations have a 240 typical service or a 208 three phase. There is a good chance that places like Quick Trips would have a 480/277 and 208/120 volt panels.
Shopping strip stores a lot of times have both. Anything in the last 10 years would be at least a 200 amp panel. Older place might only have a 100 amp panel.
It really depends on the builder/arch/EE and what they spent at the beginning.

Peter7 ,
I am not going into any more details about batteries at Superchargers, swapping or not, because I think both are a bad idea because of maintenance on the batteries and wasted efficiency. That's why I don't care. My original point was IF you put batteries at the chargers. That's most likely not going to happen. You have blown it up in to how the system would work. I don't care both are a bad idea... one is just a really bad idea.

There are no fees for exceeding your power draw limit on a commercial property -IF- you calculate it correctly and get the correct contract to start with. Please take note of the IF because you must have missed it in other comments. I have a 200 amp 240 volt service. If I draw 240 volts and 180 amps all day long I do not get an extra fee tacked on. From what I understand about de-regulated states (that are getting costs rammed up their a..) if the superchargers feed solar power back on the grid it spins the meter backwards. If the charging car pulls it off the grid it runs the meter forwards... that's simple. SO if the solar panels put 100kWh of power out for 5 hours that's 500kW for that day. If 10 cars charge half their battery that day they use 425kW of power. Tesla receives a payment (rams it up the utilities a..:-) from the electrical company for 75kW, $ at whatever the contract says... not a bill for over usage. Why waste money on batteries. One charger, one 480 volt 200 amp panel, $25-100 permit the price changes from place to place. (that's just for the service)

I will let Brian H discuss any solar panel issues because I actual like the idea of solar but it's not cost effective in MO.... unless Liz's deal works out with all the credits. In MO we pay 5 to 7 cents per kWh... very cheap. Brian H does have some very good points about it tho... altho with prices dropping like they are I am getting temped to buy some. We are regulated tho so I only get back literally penny's for each kWh.

If you stop off at a rest stop in Death Valley (any middle of nowhere) and discover the place has power from the grid. The utility company did NOT run a 120/240 volt single phase residential service 300 miles to that location. They would get 1 volt (ok exaggerating here) out of it. They ran a 4160 single wire (most likely) with a ground wire on top of the pole (for lightning strikes). If larger service is need they will run three phase.

If anyone else wants to explain transformer windings and how they work to Peter7 go right ahead. He can google for his own info in my opinion. Tesla (the man) wrote the book on that stuff already.

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