Thank you for the response Charles. Before I thought you were suggesting that Tesla Motors invented or exaggerated transmission issues to cover up battery problems.
On Mon, Mar 10, 2008 at 3:54 PM, Charles Whalen <[EMAIL PROTECTED]> wrote: > Joseph, > > I'm not sure where you heard about or came up with the idea about any > "conspiracies" between Tesla and its various suppliers, but I haven't heard > of any. > > It is true that Tesla has had continuing transmission problems and has been > quite open about discussing them. What they have not been entirely open and > forthcoming about, at least in public, are their battery problems. > > Please see some of my previous posts in the last day or two on this subject, > but in case you missed them, I will try to present some of the points here > again. > > Some Tesla customers, based on where they live and their climate, have been > told to expect up to 10% capacity loss per year on the battery pack, and > hence up to 10% loss in range per year. This is entirely consistent with > the well known, well established experience with LiCoO2 batteries going back > over 10 years now, as previously discussed. Yes, that is energy loss (and > hence range loss), not power loss, or at least not noticeable power loss > throughout most of the SOC range. But this phenomenon will actually > manifest itself in some degree of power loss at the lower end of the SOC > range. The reason for that is because the factor that drives this energy > capacity loss over time is an increase in impedance over time, so that will > be most visible in terms of power loss at the lower end of the SOC range. > > Another big problem with Tesla's battery pack, that is now fairly widely > known and discussed in industry circles, and as previously discussed here, > is the fact that Tesla is now underwater on the cost of vehicle, with their > cost now exceeding the $100,000 price that the first 100 buyers prepaid for > it, this being due to the doubling in price of cobalt over the last year > from $26/lb. to now over $52/lb. and the resulting large increase in the > cost of the battery pack. > > A related problem is that the market for 18650 LiCoO2 laptop cells is > extremely tight right now, and Tesla is reportedly having trouble sourcing > sufficient volume, as are all the laptop makers. Part of this is due to > further recalls of these cells due to continuing safety problems with them, > most recently from Panasonic with a big recall. > > The growing awareness of the safety problem and danger of these cells is > becoming an increasing publicity and marketing problem for Tesla and AC > Propulsion. As I mentioned previously, AC Propulsion has already had a > battery pack fire with their 18650 LiCoO2 packs. And as previously stated, > no major automaker is willing to use this chemistry or these cells, and the > US government's top battery scientists have said they're not safe for use in > electric vehicles. > > One of the biggest problems with Tesla's and ACP's battery packs has just > been discovered in the last year, and that is the realization that > cylindrical cells are the worst possible form factor for use in EVs and are > basically not very well suited for EV use. The reason this is just being > realized in the last year is because previously, most testing of these cells > was bench testing done in labs, under controlled conditions, but in the last > year, a lot more testing in the EV industry of these cylindrical 18650 and > 26650 cell-based packs has moved out of the labs and into vehicles, where > you have serious heat and vibration issues that don't exist in the lab, or > at least the simulation of those conditions in the lab does not always > represent very well the variability of what you find out in the real world > in actual vehicles. Testing that has been done in the last year by OEMs has > revealed that cylindrical 18650 and 26650 cells have an unacceptably high > failure rate with vibration and that the end caps tend to short out, > including with A123's 26650 cells, by the way. This presents serious safety > problems. GM's top battery and PHEV drivetrain engineers in their Chevy > Volt division are well aware of this, so much so that they are now quite > concerned about using A123's cylindrical 26650 cell-based packs in their > Volt and other planned PHEVs. This is a big problem and one reason why GM > is multisourcing battery pack development contracts to several different > manufacturers with different chemistries and different form factors. > > It has long been known that the spiral-wound design of the cylindrical form > factor has the worst thermal properties of all type of cell designs. Pouch > and prismatic form factors are much more efficient thermally. This is > readily apparent and just common sense if you think about it, because with a > spiral-wound cylindrical design, the heat generated in the center of the > cell has a long way to travel to get to the exterior. > > This is not a problem for the application for which cylindrical cells were > originally specifically designed, which was for consumer electronics, i.e. > cell phones and laptops, with their constant-current, very low power draws. > But it turns out that cylindrical cells are a very poor design and not very > well suited for the high-power, variable-current demands of an electric > vehicle. Again heat and vibration are the issues here with EVs, neither of > which exist in cell phones or laptops, ... for the most part (unless you > leave your cell phone or laptop sitting in the front seat of a car parked > out in the hot sun, in which case they have been known to catch fire and > explode ... sort of a case in point). > > In an EV, with its high power and variable current demands on the batteries, > heat is generated in those batteries. In addition to the need to dissipate > that heat, which cylindrical cells do very poorly, this constant heating and > cooling causes the cells and their casings to expand and contract. This > turns out to be a problem for spiral-wound cylindrical cells, as you can > imagine just by thinking about it, and is another failure point and weakness > of them. > > So battery and electrical engineers working in the EV industry are now > discovering all kinds of problems with cylindrical 18650 and 26650 cells in > EVs, which of course were never designed for that purpose and application, > so this shouldn't come as any surprise really. > > Finally, here is the problem that I referred to yesterday with the lack of > economies of scale of Tesla's and AC Propulsion's battery pack design of > hand-assembling and tab-welding many thousands of 18650 cells into a > vehicle-sized battery pack. This is an excerpt from a private discussion > thread between 6 battery and electrical engineers who work in the EV > and related industries: > > "The big problem with this is that small-format 18650 and 26650 cells are > only just barely *marginally* economically viable for small-scale serial > production of 20 vehicles per year (which is ACP's current production rate > with their eBox) to a few hundred vehicles per year (which is Tesla's > anticipated production rate, starting this spring) for the tiny niche of > well-heeled early-adopters who are willing to pay $75k (eBox) to $100k > (Tesla Roadster) for a showcase trophy BEV. But tab-welding and assembling > thousands of 18650 LiCoO2 (ACP and Tesla) or 26650 LiFePO4 (Continental for > GM with A123's cells) cells into a vehicle-sized pack for a BEV or PHEV will > *never* be economically viable for large-scale commercial production on the > scale of a large automaker like GM, which has announced that it intends to > produce tens of thousands of PHEV Volts per year right from the first year > (November 2010 production launch date announced but will probably end up > being more like 2012 in reality). Tab-welding and assembling thousands of > small-format cells into a vehicle-sized pack is an extremely labor-intensive > task that will never work for mass-production, not to mention the enormous > EE challenge of designing and integrating a complex, sophisticated BMS to > manage all of those thousands of cells in a massively parallel-serial > configuration." > > Best regards, > > Charles Whalen > Delray Beach, FL > > > > On Sun, 9 Mar 2008 23:35:15 -0400, Joseph T. wrote: > > > >> "This fact, as well as other problems with Tesla's battery pack, is the > >> real reason for Tesla's continuing delays (with the transmission > >> problem excuse being largely a smoke-screen)....Tesla's senior > >> executives have admitted to at least some of their customers > >> (from my communications with them) that they expect the battery pack's > >> calendar life to be about 4 years and definitely need replacing by 4 or 5 > >> years." > > > > A smoke-screen? So this means the multiple different transmission > > suppliers and different transmissions have been part of some > > conspiracy? Tesla for sure has had two different transmissions (the > > two-speed and the one-speed, both which can be verified because > > auto-magazines have tested both) and are now working on their final > > third one. Tesla Motors has actually, explicitly stated that batteries > > haven't been a problem for them at all. they made a whole blog post > > saying that the battery pack wasn't the reason for delays. On the FAQ > > section, they claim a loss of 30% performance after 5 years and 50k > > miles. According to ProEV, they said this 30% loss should only be in > > energy capacity, not power output. > > > > _______________________________________________ > Florida EAA mailing list > [email protected] > http://www.floridaeaa.org > _______________________________________________ Florida EAA mailing list [email protected] http://www.floridaeaa.org
