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V2G article send to me via Nissan Leaf's facebook page

Discussion in 'EV (Electric Vehicle) Discussion' started by mitch672, Mar 15, 2010.

  1. mitch672

    mitch672 Technology Geek

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  2. daniel

    daniel Cat Lovers Against the Bomb

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    This idea was being promoted by CalCars a long time ago, in connection with their Prius-Plus concept. Note that, due to losses when charging and discharging a battery, for this to be economical, the power company would have to pay you considerably more than they charge you. They might be willing to do this as part of a peak shaving strategy. Of course, they'd also have to promise to restore the charge to your battery before you need to drive your car.

    In regions where the peak demand is in the afternoon for air-conditioning, your car is probably depleted from your day's driving, and further depleting it to sell a few kWh back to the grid may shorten the life of your battery pack.

    In regions (such as North Dakota) where the peak demand is on cold winter nights, giving juice back to the grid will leave your car with less than a full charge for your morning commute.

    I think the whole idea of V2G needs to carefully consider vehicle usage patterns in conjunction with peak demand patterns and battery life as it relates to the added charge-discharge cycles and depth of discharge. Do you really want to put your $10,000 battery through the additional wear and tear of added cycles, in order to get $2 from the power company any time there's a demand peak?
     
  3. rpatterman

    rpatterman Thinking Progressive

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    The whole V2G concept sounds wonderful and is a great reply to the phantom EV problem of "what happens to the grid when everyone has an EV?"

    IF everyone had an EV, there would be a tremendous battery capacity to deal with peak loads and in THEORY it is a win/win concept.

    BUT until battery management becomes foolproof, few will risk an expensive battery for a few dollars.
     
  4. ljbad4life

    ljbad4life New Member

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    It's not a win/win situation for pure ev's as it stands today. Battery strain/ added charge cycles is not a good thing. Add to the fact that EVs sole means of propulsion is electricity, diminishing the range between 9am-7pm is not going to sit well with the public, people will have to run errands unexpectedly and having a limited range become more limited is not a good thing.

    I agree that once evs break the 200+ mile barrier then it won't hurt to loose a couple of miles, but as it stands 100 miles is the bare minimum that people feel safe with.

    This would mostly benefit Hybrid and PHEV hybrids owners the most(at this moment). Cheaper battery, there would be such a thing as "extra energy" and if someone depleted their battery by 50% and wanted to drive 200 miles they still could, they would take a mpg hit, but it wont physically stop them.
     
  5. rpatterman

    rpatterman Thinking Progressive

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    Agree that not a win/win TODAY with EXISTING and power management. But the CONCEPT is worth keeping alive because when EVs reach 50% of vehicles on the road there will be a termendous amount of potential battery capacity available to smooth out the grid supply/demand curve.

    Anyone good enough at math that could venture a guess at total available capacity? or when we reach 50% EVs?

    If we do get to 50% EVs the biggest problem will be peak grid demand, so anything that can be done to reduce peak demand or store peak production will be needed. The sooner our grid moves to time of day metering the better.
     
  6. adric22

    adric22 Ev and Hybrid Enthusiast

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    I certainly wouldn't want to run extra cycles on my expensive battery just for some pocket change.

    If maybe we were using ultra-capacitors or something that doesn't really have a limited number of charge cycles, then I guess that would be fine.

    Also, I wouldn't want to risk needing the car in an emergency only to find the battery was depleted because of something like this.
     
  7. ljbad4life

    ljbad4life New Member

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    I've always thought it would be a good idea to use ultra capacitors to speed up charging. Where the UC's soak up the charge quickly then have each UC fire separately over time to charge the battery slowly (essentially a charge with UCs could take 5 minute and spread out the charge to the battery to 1/2hr).

    I also think once batteries become carbon nanotube based, the batteries will be far more durable. So they can indure more cycles
     
  8. daniel

    daniel Cat Lovers Against the Bomb

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    The problem with using UCs for charging is that if the UCs have enough capacity to grab enough charge to fully charge the battery pack, you would not need the battery pack!!! You could just use the UCs. Problem is, right now, the biggest capacitors made cannot do the job. (Yoo-hoo, EEStor! Where are you???!!!)

    Where UCs could be useful is as a buffer between the motor and the batteries, allowing more charge to be captured during brief hard regen braking and delivered during brief periods of acceleration.

    According to Nissan, the lithium-manganese battery in the Leaf will have a calendar life of ten years, regardless of the number of charge-discharge cycles.

    The bigger issue with V2G is that your car would not be charged when you need it. The whole idea of V2G assumes that the car is a static storage device. In fact, the car is principally transportation, and the two uses (transportation, and peak-shaving storage) conflict with each other.
     
  9. ljbad4life

    ljbad4life New Member

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    I was thinking more of a 50/50 split between UCs and the battery. If you take the leaf for instance. A quick charge takes 26 for about 100 miles. you could half the charge time and increase the distance (UCs are lighter that li-ion batteries)

    If a manufacturer says it will last 10 years no matter what, it makes me feel a little uneasy about their product. It leads me to two conclusions:

    1)they are lying. all other manufacturers state that battery life is dependent on several factors and can shorten and one manufacturer states otherwise is usually stretching the truth (from experience). I will admit the manganese could be the defining factor, but I have never heard of any battery that is LI-ion based not deteriorate after many charge cycles

    2)The car will be so aggressive at protecting the battery it will compromise convenience and could jeopardize safety.

    edit*-I've always read and heard that Using Ultra capacitors for car use is impossible because UCs cant hold a charge for an extended amount of time.
     
  10. daniel

    daniel Cat Lovers Against the Bomb

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    The problem is still that capacitors of the size required do not exist. As for leakage, we'll have to see how much leakage there is when and if someone actually builds a big enough capacitor. (Anybody heard anything from EEStor since they missed their last self-imposed deadline to deliver working EESUs to Zenn? Are they making excuses? Have they announced a new deadline? Or have they just closed up shop and fled to Argentina with whatever remains of their investors' capital?)

    All lithium batteries have a calendar life. They deteriorate even if not used. Nissan is merely saying that their battery is so robust that calendar life is dominant over charge-cycle life.

    The car will indeed protect the battery, just as the Prius does. I was told categorically and emphatically that the 100-mile range was with that protection, and was at slow-to-moderate freeway speed. (I think he said closer to 60 than 80 mph.) How would aggressive battery protection jeopardize safety? The car will tell you approximately how many miles you can drive on the remaining charge. The Prius certainly does not do that. Of course that will be more accurate near the end than near the beginning.

    If they are lying about range, their reputation will take an enormous hit right at the start.

    There will be expanded battery packs available at some undetermined time in the future, and the car will be upgradable to the bigger batteries. This may be the first car ever that the manufacturer will upgrade after purchase. If you want a different engine or added safety features in a conventional car, you have to buy a new car, or go to an aftermarket mod shop.