• Oct 9th 2009 at 9:58AM
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The battery pack powering the Tesla Model S down the road will reportedly be supplied by Panasonic. Greentech Media broke the news after talking to "sources close to the Japanese electronics maker." Tesla had no comment.

Earlier this week, Panasonic said it had developed a cheaper way to string small laptop batteries together to provide enough power for an automobile. Currently, the Tesla Roadster uses 6,831 small cells (like those used in portable computers) in its battery pack. The Model S is expected to use three different packs, with either 5,500 cells (in the version that gives the car a range of 160 miles) or 8,000 cells (for ranges of 220 or 300 miles; better chemistry in the longer pack makes the difference).

The Model S is expected to go into production in late 2011. Panasonic said its cheaper packs could enter commercial production in 2013.

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    • 1 Second Ago
      • 5 Years Ago
      Take a look at this article in GCC.


      It's been stated these Panasonic packs will be distributed at significantly lower prices than current. I think I read 1/2 price somewhere.

      Don't forget Panasonic is one of the biggest (if not the biggest) player in the Li battery game. They have maturing manufacturing capacity with associated lower costs.

      Panasonic are not altruists. There's no reason to over discount with so little competition in the market. They also want to hook bigger fish than Tesla. If large format is the best way to do that, they would head in that direction.

      Folks may be shocked in a few years time when they learn how little it actually costs to produce Li batteries in high volume. I have been an analyst in a similar manufacturing industry for over 20 years. I believe I have a reasonable handle on the precursor costs, raw material costs, production and distribution costs.

      Free Tip: We use external supply chain subject experts to estimate our supplier and competitors manufacturing costs. They are generally accurate with the smaller suppliers, but almost always underestimate the leverage advantages and negotiating power that larger companies have.
      • 5 Years Ago
      5,000 cells sounds like 5,000 more things that can go wrong.

      No moving parts you say? We have RAM modules at work that unexplainedly go wrong.
        • 5 Years Ago
        The software and safety features allow for multiple individual cells to go bad in various ways and not affect the rest of the batteries. At least in the Roadster, the battery pack is also split up into multiple blades (I think ~11) so a segment of the pack can be replaced without having to replace the whole unit. It should be even easier in the Model S because of the ability to do those quick battery swaps... in the Roadster, it's basically an itegral part of the chassis and requires significantly more work to remove and reinstall.

        One of Tesla's real core technologies is the battery maintenance and safety and so far the results have been very good. There is a warranty on the battery when you buy a car, too...
        • 5 Years Ago
        Ok... Keep your car repair bills. I'll take an EV thanks...
      • 5 Years Ago
      If the BMS is designed correctly, that would require 5000 balancers to equalize the charge for every cell of the battery pack. One of the most sophisticated and complex tasks of an EV is the BMS. If it's not designed correctly, the total life of the battery pack is jeopardized.
      The less cells, the less balancers and the less the possibility of lurking faults and lower complexity level. The large number of cells implemented by Tesla have never been to my taste. I would accept this principle for a prototype only but never for a series model.
      Additionally, the large number of cells add superfluous weight to the pack resulting from the numerous cell cases. That is counter-productive for the aim of a lightweight EV.
        • 5 Years Ago
        Hi Chris,
        I know that a battery pack is comprised of series and parallel circuits. All series switched cells in one string must be monitored / balanced individually; the number of cells in a string give the total voltage for a string. Multiple strings switched parallel account for the total capacity of the battery pack.
        The internal resistance of a cell can never be duplicated for another cell or others; it's physically impossible. The charging current for a string of cells is the same for every cell in that string. Due to the varying internal resistance of the individual cells, some cells are charged faster and some slower. When the dangerous phase of charge is approached (4.25 V by Li-Ion) some cells have achieved this level whereas others are still below (maybe 4.0 or 4.1 V) depending on their internal resistance. If charging of a string is cut-off when a single cell in a string first reaches max. permissible voltage, then the rest of the cells in that string are not fully loaded. A balancer simulates an electronic load parallel to a cell and virtually matches the internal resistance to the other cells within that string and detours a partial current to prevent overcharging and destruction of a cell. Both, overcharge beyond a permissible level and discharge below a permissible level lead to the inevitable destruction of a cell. As long as it is not possible to produce cells with exactly the same physical properties (internal resistance) and assuring that they remain exactly the same during charging and discharging, you'll either have to accept that you will never have all your cells charged to max. level or you'll have to spend a balancer for every cell to assure full capacity.
        • 5 Years Ago
        Battery balancing isn't done on a "cell by cell" basis, as would be the case if they were all strung in one series string, they are using a "series-parallel" arrangement instead. For a series-parallel arrangement, voltage balancing would only be required at each voltage level in the string, so for 3 volt cells strung up for a total voltage of 300 volts, it would only require 100 voltage balancers, no matter how many cells were used.

        BTW, if there were 5,000 cells in series, each at 3 volts, total voltage would be 15,000 volts!
      • 5 Years Ago
      Interesting how NOBODY else can match Tesla's performance and range, yet EVERYBODY seems to know how to do it better!
      • 5 Years Ago
      Panasonic is full of bull. So in 4 years we will be able to buy batteries that are exactly as good as what we have now? Wow talk about advances in technology. What are they doing in their research department, playing Wii?
        • 5 Years Ago
        You missed the part about them being significantly cheaper.
      • 5 Years Ago
      Frankly, I'm astonished that Tesla is still going with laptop batteries for the Model S. While a necessary compromise for the Roadster for expediency, they could have gone with something much more advanced (designed for auto use requirements) and in much larger cells (auto sized) - which should be cheaper and have a longer life. Their choice might be a good strategy if you could get one of these packs for $2k or something, but they will still be monstrously expensive and the cells designed for laptops and their uses (and expected lifetimes which are much shorter than cars).

      This is seriously disappointing and if I were in the market for a Model S, it would temper my enthusiasm - you're back to Roadster technology for the battery - the significantly cheaper Volt will have better battery tech....unbelievable choice on Tesla's part, maybe it was expediency again.

      Seriously disappointing.
        • 5 Years Ago
        Serge got it right. Tesla surveyed what was available, and chose those small cells as they had the highest energy density and the lowest price per Kwh available at that time. Currently, that is still the case, but Tesla isn't wedded to it, if larger format batteries with higher energy density and lower price per Kwh comes on the market, they'll switch fairly quickly.
      • 5 Years Ago
      Geronimo and Sasparilla make good points. Keep in mind, however, that the Model S is still 2 years out. Tesla is using lithium ion laptop cells now because it is the best, most sensible option available. If something better comes around before the Model S is ready, there is no reason why Tesla would not change to that technology. They have not married themselves by any means to laptop style cells for any of their cars, including the Roadster, into the future.

      The choice to go with them now stems from laptop cells being available from multiple manufacturers, which means price competition is possible and supply chain needs are secured. Clearly, going with a battery that might be simpler and work better is something that Tesla would love to do. But purchasing what is essentially a prototype battery that is only available from a single supplier would put Tesla into a corner and may not be a smart business decision. There is a lot to be said to choose an existing, proven technology that is widely available. As more advanced technologies, including batteries made specifically for EV use (which don't exist commercially yet), become available and become proven to be reliable, etc, you can absolutely, positively expect Tesla to make the switch.

      I'm not sure how you guys can fault Tesla for "still using" these types of cells when the alternatives are either not available for mutliple years or are in pre-production prototype phase. Sure, there are batteries made by single companies that have higher energy density but they are more expensive and have no history to prove long term viability. It's good to be on the forefront of technology but choosing to go with a bleeding edge technology that might not work would be a horrible, horrible decision for a consumer product that centers on the battery working and being reliable long-term.

      This entire blog posting, btw, is basically hearsay/rumor. It could be completely and totally false.
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