(Comments from Blogger)
2017-01-14 by Ned Funnell
Nice analysis, thanks. I wonder if the old J1772 external ventilation protocol might see a descendant? A robotic coupling could attach cooling hoses nearly as easily as a 1000A DC connection, and a large off-vehicle chiller (or a small one with a sizable reservoir and attendant recovery time) could take the paradigm of off-board charging further.
2017-01-17 by Unknown
Nice man! Good job with this analysis
2017-01-18 by Unknown
Had the same thought about a connection for cooling hoses with the robotic snake charger. The predecessor’s excess heat could be partly reused for pre-heating the battery for a lower internal resistance as mentioned in the article. Moreover the overall efficiency of the Supercharger would be better.
As Elon called a mere 350 kW a children’s toy on twitter (2016-12-24) my guess is that Tesla will go with Supercharger V3 for 100 kW times 2*Pi = 628 kW. They seem to be crazy enough for that. Unfortunately that would really require a new connection and maybe also the new 2170 cell form factor. Hopefully Model3 will be ready for it…
2017-01-18 by Fred
Very interesting stuff. Go look up Chargepoints new 400Kw charging system. All about upping the voltage. I’’ wondering if Tesla could just rewire the whole pack, and up the voltage, not the amperage. I know the drive train is designed around 400V, so it would require a lot of change. I personally think 350Kw charging is for Model S V2.0. Let’s see…
2017-01-19 by Russell Graves
I don’t think trying to manage external coolant connections is worth the likely leaks and problems - quick coolant disconnects like that are just a perpetual pain.
The pack will heat up in a hurry if you keep the coolant flow down, so getting it warm if you have a 350kW source isn’t hard.
2017-01-19 by Russell Graves
Upping the voltage is certainly the easier way to make it happen. However, I was interested in how feasible it looked at the current 400V systems - it’s an awful lot of amps, but not entirely unreasonable.
2017-01-21 by Michael
I’ve found on road trips I can’t even take a bathroom break and grab refreshments in under 10 minutes. Given that, an electric car that I can plug in and get hundreds of miles of capacity from before I can pee and grab a coffee, is just fine by me.
2017-01-23 by jf
guessing that since the initial S’ work did not need hardware changes for v2 superchargers that they designed the original system with a theoretical capacity that was quite large… does the existing design imply anything about the maximum capacity of the existing fleet? Does 600kw get you <5min refuels?
If car-feedback-software, utility load costs and cooling are mostly outside-the-car issues so I’m wondering how far the current system could go at 80-90% capacity.
Also if the powerpacks are the answer to supercharger 3 demand spikes, does this mean a big increase in relative capex for tesla? Somewhere they said v2s cost about about 200-300k per location. I’m asking cause if I go to tesla powerpack page and quote a 50kw pack at 2hr duration, at 600Ah they list you could presumably around a half a modelS100D charge entirely from one pack… but then it’d take 2hrs to recharge that supercharger’s pack… is this correct? And you’d spend $60k retail per pack (maybe 50-55k per pack at cost, if musk’s 10% tesla energy gross margin target is right). If that timing is correct it seems a little slow for many locations, esp w/model3 coming.
I’m just wondering, based on your analysis and taking their pack costs into account… how many packs on average per charger would be required? I don’t have a sense of either (the total capacity of the entire system or the extent of the system to powerpack charging needs) but I’m curious because if- as seems likely- getting <5min charges is key to m3 demand, this seems like a potentially larger than expected capex charge. Wikipedia claims there are 5000 superchargers across 800 locations worldwide at moment.
If it’s one-pack per every two superchargers- even if they upgrade them in 2 years- that’s probably not that big of a deal (just considering the packs as biggest new cost driver, no idea on arms/cooling/etc). If it’s a pack per supercharger that seems like it would be significant though. Also if they are constantly discharging and recharging packs isn’t that going to work out to the same demand load as if there were no packs? Curious what your thoughts would be.
I’d love to see another article regarding your thoughts on v3 possible configurations and costs. Here’s the pack quoting page I used to generate guesstimates: https://www.tesla.com/powerpack/design#/ If nothing else it’s another reason why they have to charge for supercharger use…
2017-01-23 by Russell Graves
I think you hit the law of diminishing returns pretty quickly - 350kW is feasible if the cell internal resistance is low, but much higher and the heat becomes a problem even with low IR cells, and the voltage rise gets you out of the constant current phase and into constant voltage (with dropping current) at lower and lower percentages of charge. And it’s harder on the cells. It might be doable with some of the newer packs, but it’s going to depend heavily on the particulars of the cells, and I simply don’t have good enough information to play with. I did get my hands on a 2013 era Model S cell to play with, though…
As far as the actual stations go and the battery packs, I don’t have nearly enough information to do any analysis there - but I will say, they have that information, demand charges are insane for high power installations, and it’s a great place to retire old packs to. The capacity of a pack just doesn’t matter as much when it’s in a stationary installation designed to mix and match packs. If you were charging cars at the supercharger 24/7, at 100% utilization, there would be no real benefit to having stationary packs, but that’s not the use case - even the highly utilized chargers have lulls.
But, all that said, I simply don’t think <5 minute charging matters that much. The Model 3 demand (please, M3 is already taken) is quite strong without any information at all about the car.
2017-01-23 by jf
thanks for quick response russell.
obviously your analysis above is somewhat speculative. just know that if your mind ever wanders to particulars of charger v3 configurations, you will have at least one reader. (or you can write these articles on seeking alpha, get paid and get large #s of readers)
I agree 400k is strong demand and will keep them busy for a year or two at least. I’m very interested in balancing physics of the cars vs the company statements, because the former is harder and more expensive to change than latter. As tesla is growing fast there is always a gap between the two which means money to be made. Lovely when a fun past-time intersects this way.
Anyways thanks again for your interesting analysis.
2017-01-23 by Russell Graves
I have no idea how Seeking Alpha works. It seems to be a platform for splitting a reasonable amount of content into a teaser page and nag screens for you to subscribe. I can’t say I’m terribly interested in it.
Mostly, with regards to the charging stations, I don’t have enough information to make informed analysis, and I have no idea how to find it. I don’t actually own one of these cars, partly because there’s not a single service center in my state, and partly because I bought a house for not that much more than a loaded Model S.
2017-01-23 by jf
Re: SA… that’s certainly true for some stocks that are not followed by many people yet want analysis. (incidentally these articles are often better than free articles, which leads me into why i mentioned it in a few paragraphs)
I think for high-publicity stocks like tesla, they drive enough traffic for SA most articles are free. You can see here for yourself: http://seekingalpha.com/symbol/TSLA
I do think some SA contributors write tesla articles just to generate interest in their paid ideas. A lot of the SA articles are bearish and crappy. there’s some good bearish articles and a much smaller number of good bullish articles, which I know is out of balance from the price.
I understand your concern but I think you did a pretty good job here of taking publicly available information and making some objectively valuable analysis of it. I think if you look at what you wrote here and compared it to most of what is written there… yours would have a unique readership because there are only one or two other people with engineering or physics understanding writing on SA.
anyways… do what you want i just think your article is good and i’d love to see more fwiw.
2017-01-24 by Russell Graves
One of my New Years Resolutions was more research posts like this - so I expect you’ll see more, though not always about Tesla.
The next few weeks are back into small Arduino projects and libraries, though.
2017-03-22 by Unknown
Interesting post! I enjoyed reading about your battery speculations and some of the related real world observations (40M ohms vs 20M ohws)
2017-04-18 by Unknown
Something else to consider is by the time we see 350kW charging it probably will not be for a 100kWh pack. Elon announced a semi recently so there is no reason to think the pack won’t be 200 or 300kWh meaning the amount of power to each cell at a 350kW charge would be significantly lower than it would be for a P100D. Even the Model S will probably be 110 or 120 kWh by then which impacts the math some. Good writeup btw.