• Oct 5, 2009
Tesla Roadster – Click above for high-res image gallery

While the lithium ion battery technology that everyone expects to be at the heart of the upcoming generation of electric vehicles was initially used in consumer electronics devices, only one company so far has committed to using laptop-style cells. Tesla Motors builds a battery pack for the Roadster that consists of 6,831 cells of the type used in portable computers. Virtually every battery maker developing lithium ion for automotive applications is creating larger format cells that have what is referred to as a prismatic (flat rectangular) shape.

Interestingly, one company seems to be taking a different approach. Panasonic – which has a joint venture with Toyota to produce nickel metal hydride and lithium ion batteries for hybrid and plug-in vehicles – reportedly intends to produce automotive battery packs using laptop cells. The company claims to have developed a new method for connecting the cells which will bring the cost down by half compared to the larger format cells. The savings are claimed to come from using existing production facilities and tooling to produce cells.

However, critics suggest that while it may be true that producing cells on existing equipment will be cheaper than building new lines for prismatic ones, the quantity of cells required if EV sales approach projections over the next decade could quickly outpace this approach. Using larger format cells means far fewer interconnects are required and the complexity of building packs from the cells is greatly reduced. Because of the size of packs needed for car applications, the prismatic cells also provide greater density and improved thermal management.

Photos copyright ©2009 Drew Phillips / Weblogs, Inc.
[Source: Reuters]

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    • 1 Second Ago
      • 5 Years Ago
      Larger issue: the rare earth metals used to make the batteries are being horded by China.


      Trillion dollar opportunity: Synthetic alternative to rare earth metal, or augmented by synthetic, batteries.
        • 5 Years Ago
        The rare earth metals discussed in that report are used in nickel metal hydride (NiMH) batteries like those found in the Prius and other hybrids while electric cars like the Tesla Roadster use lithium ion batteries which don't use lanthanum or the other "rare earth" metals.
        • 5 Years Ago
        @pjbuchan but you forget mining said material is EXTREMELY dirty and the EPA and other various three lettered agencies would put a strangle hold on anyone who tried to tap those resources
        • 5 Years Ago
        true but we have untapped REM here in the USA that china tried to buy from us a couple years ago. we could tap those to try to bring the costs down on these things...
      • 5 Years Ago
      LOL @ the last photo. "Oh. The salesman forgot to mention that my Tesla runs on batteries."
      • 5 Years Ago
      • 5 Years Ago
      I can't see how this truly makes sense. As batteries get bigger, the amount of materials (plastic casing) required for a given amount of electrolyte (insides) goes down, cutting the costs. Also, since there is less casing in a given volume, there is more electrolyte, upping the energy density.
        • 5 Years Ago
        Sorry, I was mistaken. 3.7 is the nominal charged voltage of the lithium polymer batteries that I was thinking of. Minimum voltage is slightly lower, 2.7-3.0 volts, and are usually depleted after less than ~200 charge cycles.

        Single Lithium Polymer cells, such as cell phones, and other rechargeable small electronics. Also small removeable cells that power my Blade CX2 and micro-CX helicopers. the CX2 uses two 3.7v cells in a common envelope (7.4v, ~800mAh), the micro-CX uses a tiny single cell, about the size of a tab of sugar-free gum, also 3.7 volts. Both fly for about 6-9 minutes on that charge, and that is just keeping a few ounces of weight aloft.

        Laptop batteries are usually somewhere between 3 and 12 cells, depending on size and demand. (netbooks have 3-6 cells, laptops usually 6-9 cells, up to 12 cells for extended-use batteries that extend out of the machine's perimeter.)

        I am concerned enough for the fact that the new apple machines have their batteries fully enclosed within the body of the laptop. Supposedly they have many more charge cycles, and a higher mAh rating... but apple batteries have tended to swell on occaision in the past, and if they do so in the newest machines, they could actually cause damage to both the battery and the machine's electronics, and maybe actually permanently bend the aluminum of the case.

        That is just a laptop... I don't want to have to deal with many dozens or hundreds of cells enclosed in a car, especially in a car accident.
        • 5 Years Ago
        Energy density is still nowhere NEAR liquid fuel, though.

        I work on laptops. I see depleted batteries and even some swollen batteries every week.

        Short cycling, and lots of use depletes them. They don't have charge memory like nickel based batteries sometimes do... but they DO deplete after so many charge cycles.

        What gets 250 miles now will probably get 60-75 miles later on, before cells start failing.

        Larger cells also probably have higher minimum voltage, below which the battery becomes damaged. Lithium polymer cells of small size, tend to have a minimum voltage of about 3.7 volts. Below that, it causes damage, and potential fire risk to the cells.

        Not to mention the cost of replacing those batteries...

        Not to mention the volatility of those batteries in a car accident. What happens if there is a high-current short circuit? What happens if rescue workers clip a high voltage cable in the car? They are supposed to be trained, but there is an adrenaline rush, and a push to get people out of a wrecked car.

        Especially if the lithium batteries are at risk of auto-igniting if they are exposed to oxygen. Oxygen and other non-metals, and Alkali Metals or hydrogen, (Periodic column 1A) combine readily in each other's presence, due to the ionic compatibility. In hydrogen's case, it makes water, so much so that hydrogen doesn't exist in the atmosphere, it is ALWAYS naturally bound to something else, like oxygen and carbon. In lithium's case, and most of the other metals, and most other combustibles, combining with oxygen makes FIRE.

        Liquid petrochemical fuel (made up of such compounds of carbon, hydrogen, and usually oxygen) is actually more stable in an oxygen atmosphere than lithium is. Organic petrochemicals release energy when their bonds are broken by an ignition source, and usually best under pressure. Lithium and oxygen put out energy when they combine, and they combine readily, without pressure, and sometimes without external ignition source.

        Working with lithium batteries all day, and even playing with little lithium battery-powered RC helicopters from time to time... I don't want lithium batteries in my car. I remain unconvinced that they are safe in emergency situations, or that they are a better electrical energy storage substrate than the chemical energy inherent in liquid fuel.
        • 5 Years Ago

        First of all, the thermal conditions and discharge cycles of a laptop and a car is quite different. From what I know ,Tesla has a fairly extensive thermal regulation (coolant) to keep li-ion batteries in top shape. In a laptop, the batteries are tend to be near a very hot location (it is near the heat from the processor). In cell phones, is pretty much right next to it. Tesla's pack also has 2 fuses for each cell. Physically there is an aluminum shell around the whole pack (and individual steel casings for each shell) to prevent rupture. Tesla has gone to great length to prevent thermal runaway. And in regards to discharge, the Tesla runs in "standard mode" by default, which limits max and min charge levels for longer battery life.

        Have you seen gasoline fires (many happen every year)? It is hard to imagine li-ion being much worst. In any case, most automakers are not using laptop cells for their batteries so this should be even less of an issue.

        As for high voltage wires, the battery pack will automatically disconnect when it detects an accident. And so far we already have plenty of hybrid vehicles running with high voltage wires and there hasn't been an epidemic of people being electrocuted.

        I think we'll do fine with lithium batteries as long as we design our safety systems well.
      • 5 Years Ago
      Why isn't autoblog banning these bots?
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