• Jan 25th 2010 at 7:48PM
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Although many have expressed a strong preference for having the cost of the battery pack included in the price of their electric auto, might a separate leasing arrangement be a more prudent approach? Darryl Siry certainly seems took think so, at least when it comes to the Nissan Leaf. In his latest writings for Wired, the former Tesla Motors mouthpiece has expressed some doubts that the Japanese manufacturer's power supply will be up to the task for the long term. And he may well have a point.

It all comes down to the Leaf's power pack lacking an active thermal management system, relying instead on a passive cooling set-up which, essentially, relies on a single fan to distribute heat evenly throughout the interior of the pack. If heat is not effectively dispersed, it may lead to early degradation of overall energy capacity and a premature shortening of the vehicle's range. Nissan's director of product planning for the U.S. Mark Perry responded by saying:
We don't need thermal management for the U.S., but we are looking at the technology for Dubai and other locations like that.... We've gone on the record saying that the pack has a 70 to 80 percent capacity after 10 years.
While that sounds somewhat reassuring, an earlier conversation with a product planner lower down the totem pole left Siry with the impression that the company had gone with the passive design because of packaging concerns rather than sound engineering determination. He contrasts the approach taken in the Leaf to the active liquid temperature control design in the Chevrolet Volt and suggests that Leaf buyers opt for battery leasing to avoid potential longer-term short comings. Read the complete article for yourselves and let us know whether this issue affects your attitude about battery leasing.

[Source: Wired]

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    • 1 Second Ago
      Sasparilla Fizz
      • 2 Years Ago
      And it appears the concerns for the Leaf pack were justified. Here's a Nissan Exec (from above): "We've gone on the record saying that the pack has a 70 to 80 percent capacity after 10 years." Here's a happy Leaf Owner @ 22 months of ownership, has ~20,000 miles (mostly 80% charges) and has lost a little over 17% of his range already. He's on the pacific coast in southern CA (not out in the Desert). Makes you wonder how much more range the vehicle will loose - Nissan saying 70% to 80% capacity after 10 years, that doesn't look likely at all.
      • 2 Years Ago
      70 to 80% after 10 years for the Leaf? The data from Tesla's Roadster shows about 80-85% capacity after 10 years for their vehicles with liquid battery cooling.
      • 5 Years Ago
      The Nissan Leaf uses a different battery chemistry, so the thermal needs are different. In particular, the battery of the Nissan Leaf is less prone to thermal runaway compared to the Tesla Roadster.
        • 5 Years Ago
        Uh . . . you said they had the same chemistry and then went on to explain how they have different chemistries. The latter part is what I was getting at . . . as you point out LiFePO4s are less dense and thus have less thermal issues.
        • 5 Years Ago
        Yeap + Nissan is already working on their next generation battery:


        Sirylicious article though. Keep em' coming.
        • 5 Years Ago
        All Li-ion batteries have the same basic chemistry with the exception of Li-ion poly. The actual difference among Li-ion batteries is given through the application of different electrode materials. Li-ion that use FePo4 electrodes as compared against conventional lithium cobalt electrodes have higher power density capability. Lithium cobalt have an inherent tendency to develop high temperatures by accordingly high power density. This is far less a problem for FePo4 electrodes. The structural integrity allows a higher power density and the possibilty of extreme temperatures is eliminated. The Chinese have switched their production of Li-ion cells for EV applications almost entirely to FePo4 to avoid the otherwise existing safety hazards. These batteries are safer, can be charged in less time and do not present the typical temperature safety hazard inherent of standard Li-ion cells / batteries. Their disadvantage is the somewhat nominal lower cell voltage but their price is far lower than that of conventional cells (250 - 300 USD / kWh). e. g.:

      • 5 Years Ago
      Here's an idea: If you live in the Arizona Desert, don't buy a Leaf. Problem solved.
      • 5 Years Ago
      Wow, they need to hire some battery engineers. This pack will have some nasty thermal imbalances leading to different ageing zones, leading to cells going out of balance. I've seen start-ups doing better battery designs then this.
        • 5 Years Ago
        Nissan has been working with lithium battery designs for 17 years. I'm willing to give them the benefit of the doubt. The battery lease concept (which they will be announcing pricing on this summer) removes the risk from my part.
      • 5 Years Ago
      Or perhaps the Volt pack is very over-engineered, but you are paying for that with the Volt's est. $40k price tag. Time will tell with the Leaf, but passive technologies work just fine for a lot of things.

      Moreover, saying *relies on a single fan* is wording which makes the reader envision a weak little fan that moves little if any air. We don't know the size or CFM rating of the fan, I image it's thermostatically controlled like many PC fans, and the metal enclosure for the cells will surely work as a heat sink.

      Sounds like they are working very hard to bring an affordable BEV to the masses.
      • 5 Years Ago
      "We don't need thermal management for the U.S., but we are looking at the technology for Dubai and other locations like that...."

      Guess he's never visited SW Texas, NM, AZ....and other locations like that. I'm thinking I-10 where it's legal to go 80 mph across the Texas desert to El Paso when the air hits 112° and the pavement makes fajitas of roadkill might need more than a passive system. But then, I can't imagine anyone in El Paso being willing to risk driving an EV past the city limit sign. Range anxiety would be an understatement.
        • 5 Years Ago
        We see temps here in the high 90s F with 80% or greater humidity on a regular basis during the summer. Our Winter average is in the 60s F.

        • 5 Years Ago
        I live in El Paso. I'd buy an electric car if it would go 100 miles between charging and manage crossing our Trans-Mountain Road (across the Franklin mountains that separate northeast and northwest El Paso - a rise of about 2000 feet ending at a mile high). Hot? Yeah, you bet.

        El Paso is about 26 miles from end to end. I typically drive 25 miles per day but, when I need to call on clients at the other end of the city, that's a good 55 miles round-trip (in addition to the other trips I make during the day so let's call it 75-80 miles and I'm covered with 20 miles of range to spare. If I bring an extension cord with me I can probably plug in to an outside outlet at a client's home or business.

        Battery leasing sounds like the only way to get this technology into the hands of consumers at a reasonable buy-in price. Combine it with a long-term extended warranty and we'll pay a flat fee for the privilege of driving a gas-free vehicle (and then the electricity cost).

        Until then, I'm driving my Scion xA. Maybe I can find a conversion for it? *grin*
      • 5 Years Ago
      Considering the number o competetors peaking ill of Nissan Leaf - I can only guess they are doing quite well.

      Personally I'd like to lease the battery - who wants to own a fast depreciating asset that is version 1 ? Thats like buying the first generation CRT HDTV for $15K.

      • 5 Years Ago
      Could it be that their prismatic cells are very stable?

        • 5 Years Ago
        I agree with you both.
        One big difference between the LEAF and the Volt is how much the cells are stressed;

        (I'm guessing that the battery pack voltage's and the motor voltage's are in the same ball park)

        The LEAF has a motor power of 80kW and a battery pack of 24kWh, meaning that the cells work, at most, at 3.3C (eg. if the cells are 10Ah they will each give 33A of current.)

        The Volt on the other hand has a 111kW motor but 'only' a 16kWh battery pack meaning that their cells will have to work at up to 7C (eg, if they have the same size of cells as the LEAF, 10Ah will have to give 70A)

        - this puts much harder demands on the Volt battery pack than what the LEAF experiences.
        If old school lead acid batteries would be used, the usable capacity due to the Peukert effect would be far less at the high discharge of the Volt.
        • 5 Years Ago
        Another factor is the Leaf may weigh as much as 1,100 pounds *less* than the Volt?

        • 5 Years Ago
        I would tend to agree Neil, I do think that since we don't know the chemistry or much other then the form factor that they need a liquid cooled pack just like the volt is a little silly, each company has a battery management that is different from the others.

        From what Nissan has said and the dedication their current CEO has I would reckon they are doing it right.
        • 5 Years Ago
        The big factor is that the LEAF uses a Mn based chemistry, while the Volt uses an Fe based chemistry. According to Nissan, the batteries run much cooler. The LEAF's batteries are also lighter than what's been listed for the Volt, despite having larger capacity.

        The more advanced battery chemistry makes the additional cooling un-necessary. They are overengineered on the battery chemistry side (after 2 decades on in-house development), making the system lighter and less mechanically complicated. Keeping it simple means there are fewer things to go wrong.
      • 5 Years Ago
      The Nissan battery design is inherently more temperature robust than Tesla due to the Li-Mag chemistry in combination with the laminated form factor.

      Note from the picture above that the Leaf battery is a shallow plate, packaged inside a structure with heat fins. The flat plate is an advantage of the laminated design. Compare this with the Tesla that is a solid brick with thousands of small lithium ion laptop cells, and you can see why Tesla needs liquid cooling. The Leaf battery has much more surface area and is simply more efficient at dissipating heat.

      The battery pack is sealed. The purpose of the fan is to distribute heat evenly, not to cool the battery per se.

      Given the Leaf battery will be a $10k lease, I think it's a fine solution for a v1.0 product.
        • 5 Years Ago
        "The Nissan battery design is inherently more temperature robust than Tesla due to the Li-Mag chemistry in combination with the laminated form factor."

        WTF is Li-Mag? Li Magnesium or Li Manganese? You probably mean Li-Mn. Mn chemistry is not inherently more robust, the active material in the cathode has a nasty tendency of dissolving in the electrolyte at high temperature storage (ie. sitting outside in the sun).

        What you see in that picture is a shitty cooling solution, the cells in the middle of the pack will run hotter and get out of balance in no time. Did you ever see cycle life and calendar life graphs at 55 or 65 degrees C? It tanks. FAST.
        I can't believe they are putting this POS in a production car.
      • 5 Years Ago
      The hottest large City in the world world is not in Arabia, it is Phoenix, Arizona.

      I think this underlines that Nissan /Renault are whistling past the graveyard. They have little technology in hybrids, and the emphasis they are placing on a tiny BEV when battery technology and pricing just is not there yet reveals desperation to me. The Leaf seems more and more an attempt to buy time, and add a patina of technological savvy that in't there. They can't even decide how to sell it; with or without a battery.
        • 5 Years Ago
        Seems a stretch to say that because the climate in Phoenix is extreme that if the Leaf is less than ideally suited there the car will fail!
        There are rather a lot of cars sold in places with less extreme climates.
        So they wait for gen II in Phoenix.
      • 5 Years Ago
      Much of the Southwestern US has Summer temps reaching well above 100*F, and occasionally over 110*F. The temps a car sitting in the sun all day can achieve are much higher. It is far from a homgeneous climate. They must know this if they did any research. Battery leasing sounds like a good idea. I expect that very quickly battery packs would be available that are more powerful and cheaper as development continues.
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