• Jan 21st 2011 at 7:56PM
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Driving Tesla Model S – Click above to watch the video

What's the biggest problems with the Tesla Model S? According to some, it's the huge battery pack.

Let's start with some facts. Tesla says the Model S will be offered with three different battery ranges: 160, 230 and 300 miles. The smallest battery pack will be 42 kWh, the middle one will be around 70 kWh and, as we heard last year, the biggest Model S battery will be between 80 and 95 kWh. That's enormous, to be sure, and skeptics can criticize it for being too big, too expensive or too slow to recharge, but Tesla has long claimed that it has enough time to figure out how to make it work, even though it's the first company to try something like this.

In fact, during the recent Detroit Auto Show, we talked with Tesla spokesman Ricardo Reyes, who said that having three pack sizes for the Model S will make sense for electric vehicles in 2012, when the Model S is scheduled to arrive:

Where were we when the Roadster was introduced and where are we now? We're not begging battery manufacturers to allow us to put their batteries in our car. We're not begging people to please supply us with these batteries so that we can make this car that is unproven up to this point. It's a completely different world.

But not everyone understands this, which brings us to Paul Eisenstein's article on the Model S over on The Detroit Bureau. Paul is a friend of the site, but after the jump we'll address some of the things he said about the Model S and its battery packs.

Eisenstein's main criticism of the Model S' battery packs, especially the largest one, is the "problematic numbers" of recharging the pack. He writes:

The larger Model S, with its huge 300-mile battery, would, at best require about 14 hours to get back on the road – at best. ... That is, unless an owner were ready to head out on only a partial charge. But, at that point, what would justify paying the huge price premium for the extra kilowatt-hours?

By the time the Model S is available in 2012, Model S drivers will have four choices to fill up an empty battery pack when they're out and about: standard 110V outlets, public Level 2 240V chargers, DC Fast Chargers and battery swaps. No matter which battery pack you choose, you will not need to recharge during most normal commuting days. In day-to-day driving, the miles you burn getting to and from work and out for dinner will be easily, painlessly refilled while you sleep when using the common 240V home charging set up. The only time you'll need to fill up the entire pack is when you head out on a long road trip (and, as plug-in advocates have long argued, electric vehicles aren't for everyone, all the time. If you need to go cross-country, then rent a gas-powered car or plan for a relaxing trip).

Eisenstein is right that DC Fast Chargers, which can fill a pack to 80 percent in a comparatively short time, are currently quite rare, but they're more common than any mention Eisenstein makes of the fact that the battery pack in a Model S will be swapabble. It's odd he doesn't mention this important feature of the car in an article focused on the battery packs themselves.

What a swappable battery pack means is that all the worry about the high cost of the 300-mile pack is nothing more than crocodile tears. Don't want a 300-mile battery pack? No problem. That's why it's an option, and if you change your mind, you can have a big pack installed at any time. Granted, both 440V DC chargers and swap-out stations (or Tesla dealerships) require infrastructure, but if there's one thing that anyone following the green car scene quickly learns is that this industry moves ridiculously fast. There are plenty of problems and potential pitfalls to getting plugged in, but we're not comfortable betting against the possibility that there will be at least some places where DC charges are common come 2012.

[Source: The Detroit Bureau]

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    • 1 Second Ago
      • 4 Years Ago
      Paul: You're the one who's having the problems with math. The Roadster has a 53 kWh pack and can charge in 3.5 hours on a 240V 70A. On a regular dryer outlet (NEMA 14-50R) which is a 50A circuit (every household can handle this since almost all dryers in the US are electric), it can recharge the Roadster from empty in about 6.5 hours.

      You keep stating "Telsa can claim" about their charging times but there are over 1500 Roadsters worldwide so people have real data and experiences. Something I guess you don't with the Roadster. Why is the mass necessarily that much bigger for the 300 mile pack? Aren't they likely using a different chemistry for that pack meaning it may not be much heavier than the 230 mile pack? You're making many assumptions and refuse to believe the charging times that actual Roadster owners experience on a daily basis. Please try doing some actual journalism, possible interviewing real Roadster owners, maybe visiting Tesla HQ to see one get recharged in real time before claiming they're making their numbers up. Thanks.
        • 8 Months Ago
        Dryer circuits are 30A, not 50A.
        • 8 Months Ago
        Ok. The outlet is a dryer style plug (NEMA 14-50R) but the circuit may be 30A. Either way, it is trivial to have an electrician install a 50A circuit.
        • 8 Months Ago

        Yes, you are correct. A dryer normally uses a 30A circuit but it still uses the NEMA 14 outlet. An electrician can easily install a NEMA 14-50R outlet in your garage as they did in mine with minimal effort.
      • 4 Years Ago
      One more think I don't see how the big pack will take 14 hours to fill from empty. Tesla already recommends 50A service (the Teslas I see daily uses NEMA 14-50 outlets to charge), and that's 11kW charging. Even a 95kWh pack should charge in about 10 hours off 50A service.

      Maybe he's assuming level 2 chargers on the road will only be 30A? He could be right actually.
        • 4 Years Ago
        The "Level II" charging outlet actually covers a range from 30 amps up to 70 amps. The level II charging for the Leaf is just 6 Kw, but the Tesla charging outlet on a 70 amp circuit can charge at 16 Kw. That would allow charging a 100 Kwh pack in less than 6.5 hours.

        Eisensteins estimate of 100 Kwh for the 300 mile Model S pack may be on the high side, as he has to make some assumptions to make that estimate.
      • 4 Years Ago
      The 300 mile battery is less than twice the size of the Roadster's battery, so it's going to take the same multiple of time to fill on an equivalent charging source.

      I make that less than 6 hours for a full refill on a relatively cheap Tesla HPC.

      If reporters are going to write on tech subjects, they should at least know how to use a calculator.
      • 4 Years Ago
      The nearer you get to a full charge, the slower the charge. Not some straight-line relationship by a long shot.

      Lots of sources say the Model S will be around 3800 pounds.
      Will that be with the smallest battery pack ?

      If so, the larger packs will add considerable weight (and cost) to the car.
      Law of diminishing returns.
      Range will not be a linear relationship either because of the added weight.

      - - -

      Swappable ?
      Pretty involved process. Not something you'll be doing at your local Pep Boys.
      Special equipment for each car. Are you going to lower the batteries and slide them out on a special dolly? or Pick the car up-over the batteries (while the batteries are on a special fixture).
      Then there's the connections ~600 volts? and many other connectors.
      Fast swap? I'd guess a 3 hour flat-rate at an official Tesla dealer, hopefully under warranty.
        • 8 Months Ago
        Timo: I was about to disagree with your statements about battery chemistry and fast swap, but I have a high regard for your usually excellent posts. Then I realized that your statements about different battery chemistry and fast swap are both reasonable and likely true. Do you have links for this or is this just your best guess? I hadn't thought of the economics of a larger number of cheaper batteries vs. fewer expensive batteries for the lower range versions. I know Tesla states that the battery pack can be "rapidly interchanged", but compared to what, a Chevy Volt or Renault Fluence? I believe this battery swap must be done by Tesla and is not intended to be used as a quick range extension like Better Place. This does, however leave the intriguing possibility of renting the large battery pack from Tesla if one is planning a more extensive road trip than normal, then go back to the cheaper and smaller pack afterwards.
        • 8 Months Ago
        Range will not be affected much by added weight. A little, but not much. Also either changing from 160 to 230 miles or 230 to 300 miles will be made changing battery chemistry, not amount of batteries. That means no weight difference or very negligible one.

        Swapping, if it is going to be made, will be completely automatic in the same style than Project Better Place does battery swapping. Their record is a bit under one minute starting from car driving in swap station and ending at it driving off the ramp. That is completely possible. Just not for home tinkerers.
        • 8 Months Ago
        I don't remember where I have read that battery pack chemistry change, it was probably from some Tesla blog or interview, press release or similar.

        For swap, while I know that Tesla has said that it will be possible, I'm not at all convinced that it will be reality. For me it just doesn't make any sense in any large scale because of costly infrastructure and just because those will be used so little. I don't think anybody will be making such swap stations, before infrastructure is ready batteries themselves already give us over 600 mile ranges cheaply enough that nobody even considers swapping them. Only possibility I see is to have those in Tesla store/repair shop, where removing battery would be necessity anyway.

        Battery tech is advancing *fast*. What is lacking is industry which can't keep up with new innovations and can't change product lines fast enough to manufacture them. I think industry waits a bit and then makes leap forward when things settle down a bit.
        • 8 Months Ago
        Please go back to the first comments page and read Sam's post.

        Tesla's battery swap will not be a "quick-swap" like for instance Better Place.
        The Model S battery is a structural part of the chassis and has cables and coolant hoses hooked up to it, it will require some time at a workshop to replace.

        It's only meant to be used infrequently, for instance a one-off road trip where your current battery won't cut it.
        • 8 Months Ago
        Wether the weight will vary between battery pack sizes isn't known at this point.
        They've discussed that they have the option to use either fewer or less energy-dense cells in the small pack. The 300 mile pack will be built on currently experimental high-density cells.

        From an engineering and business standpoint though it makes more sense to use the same number of cells (i.e. same weight) for all packs. It lowers production cost because mechanical assembly is similar for all pack sizes, as is the suspension setup (a lighter car would have to have its suspension re-tuned).
      • 4 Years Ago
      The capacity is fine. If you want to go 200+ miles on batteries, you're going to need a lot of capacity.

      The physical size is not good. Furthermore, the battery chemistry is not great.

      Tesla is doing as well as they can do with off-the-shelf batteries. But there are no real advantages to off-the-shelf batteries except they allow a company of Tesla's scale to make a car at a better price point.

      If you can generate enough volume to buy enough batteries to go to suppliers and order large-format batteries in the right size and chemistry, then you reap huge benefits that Tesla simply cannot reach.

      Is the Model S level 3 capable? Level 3 is not easy, requiring monitoring of the individual cells in the pack and with so many cells in the Tesla packs, this will not be easy for them.

      I am very down on pack swapping. Unless you lease the packs, it doesn't make any sense. And I don't want to lease packs.
      • 4 Years Ago
      "The price won't be too different either."

      If that were the case, why buy (or even consider) 2200mah cells ?

      Fuzzy Logic ?

        • 8 Months Ago
        They're available now. The higher performance cells have only recently come onto the market, it takes time to test them before they can be offered to customers. Just wait, it will happen.
      • 4 Years Ago
      btw, the Tesla S is a perfect candidate for EV-Taxi operation:

      Thanks, Olmo
      • 4 Years Ago
      I'm surprised more dealers aren't trying to engineer up some larger batteries. To my understanding (and I could be totally wrong), EVs have a shorter running time than gas powered cars before a re-fuel/recharge is needed. If I had to choose between charging my car battery every night or two, vs once per week, I would choose once per week. I'm basically comparing it to a cell phone, because I hate needing to charge mine every night or two so that I don't have to worry about it dying and my alarm not going off in the a.m...

      I realize that there could also be some downsides to having a larger battery too... All I'm saying is that if more engineering is gone into a larger, longer-lasting battery, that may be a preferable choice. I also like the idea of different batteries to choose from (that all fit into the same car), but this might take away from the ease-of-use. I would probably leave one battery in the car 99% of the time, and it would be the largest one so that I didn't have to charge as often -- so now we're back to the first issue.

      My two bits..
      Paul Eisenstein
      • 4 Years Ago
      The fact that I'm doing some math -- and my math stands -- does not mean I am "criticizing" the Tesla S battery or its technology. If electrification is to work it can only do so if we understand and address the issues, challenges and potential problems of the technology.

      (And, to the other Paul, above, simply accusing those you label as critics "f&@% idiots" is only proof that you have no intelligent argument, just a rant! Anyone who reads my own publication, TheDetroitBureau.com, or my work on NPR, MSNBC and elsewhere happens to know I cover battery tech more than almost anyone other than dedicated e-bloggers and am probably best described as a cautious proponent, meaning I hope the tech works but believe we need discuss and address its issues as much as its pluses.)

      That includes the ability to charge vehicles, and to do that in a timely matter. I experienced that several times recently when testing BEVs at my home, popping circuit breakers shared with the circuit I have available for charging. A local NPR station polled a number of other journos, many of whom have had the same problem. Personally, I will be installing a Level II charger, soon, though to do so may require me to ...again...upgrade my electric service which, adding the new breaker box and the line from the pole, will add several thousand dollars on top of the charger itself. (I've already made preliminary calls to my electrician, so this isn't a guess.)
      BTW, Tesla can claim faster charge times but charging data are math-derived. And if you look at any other maker and compare the figures (using, critically, apples-to-apples comparisons) you will find there is not a way you can make the numbers pull off a 6-hour recharge of a roughly 100 kWH battery using its 220 volt charger. Ford will get 3.5 hours using that size charger for the roughly 24 kWH in Focus Electric. Leaf, with a charger half the size takes roughly twice as long. And that math is valid for everyone else. Perhaps I am missing something about the Tesla charger?

      Oh, and a last rant from me, but to anyone who believes going from 53 kWH to 100 or so is nothing special, remember that you have just added the equivalent of TWO MORE Nissan Leaf battery packs to the planned extended-range version of the Tesla Model S. Do you think adding that significant amount of mass, never mind cost, charging times, etc. is really insignificant? And you accuse me of not knowing what I am talking about??? Really?
      Paul A. Eisenstein
      Publisher, TheDetroitBureau.com
        • 8 Months Ago
        @Paul Eisenstein
        It's not the equivalent of two LEAF battery packs as Tesla uses cells with greater density. Additionally when the Model S comes out it's cells will probably be even better than what is available today.
        • 8 Months Ago
        @Paul Eisenstein
        Paul, perhaps you could also approve my final post to your blog which states:

        dpeilow says:
        Your comment is awaiting moderation.

        Well, JB Straubel has said that the pack will be 85-95kWh.


        Even if they used the very latest Panasonic 3.4Ah cells, then the pack will be at most 97.2kWh.

        You are adding padding on padding – there is no way the battery will be as big as you claim.

        I stand by my original assertion – “at best require about 14 hours to get back on the road – at best” is simply not true. Not with the math and not in my experience fast charging a Roadster.
        • 8 Months Ago
        @Paul Eisenstein
        Yes, Eisenstein, charging times are math derived, but it's a case of using the right figures - which you didn't do. You assumed that the Tesla charging system had the same power rating as used on the Leaf and the Ford Focus electric, when in fact it has a much higher power rating, resulting in charging times much shorter than what you had calculated.

        If you're a serious journalist, you should be willing to admit your mistakes and publish a correction.
        • 8 Months Ago
        @Paul Eisenstein
        Do you really believe that people that can afford a $60k to $90k car would balk at installing a 75A charger? I paid $1000 to have my house upgraded from 100A service to 200A service. Admittedly there would be some extra installation expenses but I am sure these customers would be willing and able to pay. 7 to 8 hours for a full re-charge is quite reasonable.
        • 8 Months Ago
        @Paul Eisenstein
        I have to disagree with you on the charging times. If Tesla uses the same 16.8 kW on-board charger in the Model S as is in the Roadster, the math shows 5.95 hrs. Factor in inefficiencies, cell balancing and its probably closer to 7-8 hrs. Of course this requires a dedicated 90 amp circuit to handle the 70 amp draw.
        • 8 Months Ago
        @Paul Eisenstein

        "85kWh to 95kWh" estimated by Tesla

        as stated in the linked NYT article
        • 8 Months Ago
        @Paul Eisenstein
        You haven't done the math properly. As I showed on your site, it's perfectly possible to charge Model S in 6 hours using an HPC at 75 A. See Clipper Creek for the product.

        I've charged a Roadster on the HPC in a garage in half the time.

        The Ford charger is 30 A, as I said, which is why they will take proportionately more than double the time.

        If someone is buying a loaded Model S and HPC, then adding another thousand for the install isn't a big deal. For commercial sites it's in the noise. This really is a non-story.
        • 8 Months Ago
        @Paul Eisenstein
        The Tesla HPC is rated for 16.8kW. Assuming a 100kWh battery and 95% efficiency, we arrive at a charging time of

        100kWh / (16.8kW * 0,95) = 6,27h

        using the 9.6kW mobile connector yields a time of

        100kWh / (9.6 * 0,95) = 10.96h, or roughly 11 hours.

        But you know what? That's not even the real issue here.

        Your size assumption for the as-of yet-unknown capacity of the big pack has crept up from "85kWh to 90kWh" estimated by Tesla to 100kWh. A nontrivial increase. Not only does your math not stand, but it's based on fuzzy estimates and unproven assumptions. Comparisons to other electric cars with vastly different battery pack construction and chemistry are also less than helpful in that regard.
        Your anecdotes about popping circuit breakers likewise do not constitute a valid basis for general statements, although they do highlight the common-sense fact that prospective electric car owners should check if their electrical system is adequate and factor in potential upgrade costs before making a decision to buy. Duh.

        Do you honestly not see why people would take issue with these things?

        I know that journalistic success demands a constant stream of publishing, but I and many others are rather tired of the large amount of speculation and opinionating in lieu of factual information. Until Tesla releases specifications for the battery packs, that's what all of this is. I don't have a problem with that. "We don't know and until we do that's that" is the only responsible position for a skeptic there is.
      • 4 Years Ago
      Apparently Paul Eisenstein hates EVs. Even after readers pointed out his unrealistic assumptions about people buying a Model S for up to $100k, would skimp on the home charger and try to live with a 220 25A charger instead of Tesla's recommended 75A charger, he defended his 14 hour charge time by saying high amperage chargers were not widely available for travelers.

      There are already some hotels that have the Tesla 70A charger for the Roadster, and if hotels want to attract Model S customers they will install the $2k 75A chargers for them. This is a very easy to solve problem for minimal cost.
      • 4 Years Ago
      I agree with others here that mostly you only need a small pack for a small sum total of miles per day. Think, if you could recharge at work, then the max battery capacity could be downsized roughly enough to get there. Several readers have mentioned a generator or the like which could be brought along when needed. Perhaps a small modular one could be made powerful enough to slowly charge the battery to get you adequate miles into your journey before stopping. Adding a high-speed recharge ability in combo seems like it would cover a large percentage of scenarios.

      It brings us to the following conclusion, if the readers here can think of plausible solutions, how come it's so hard for the manufacturers?
      • 4 Years Ago
      Why respond to questions nobody is asking?
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