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Interesting.

However, my key issue with V2G is not really battery life, but that if batteries end up being cheap, then a combination of smart charging and dedicated batteries would be easier and probably cheaper to implement, so why bother with V2G?
 

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Discussion Starter #3
Interesting.

However, my key issue with V2G is not really battery life, but that if batteries end up being cheap, then a combination of smart charging and dedicated batteries would be easier and probably cheaper to implement, so why bother with V2G?
Part of the issue is battery costs and production constraints. The world would need 100 Gigafactories just to convert the current fleet of vehicles to EV. There might not be enough production capacity to support both EV production and grid-tied battery systems for some time. Regardless, redundancy seems like a good idea.
 

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I'm wondering if they're just counting cycles faster and beating the clock. What happens when I need to use the car and I don't have a full charge because the utility has been borrowing it?
 

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Discussion Starter #5
I'm wondering if they're just counting cycles faster and beating the clock. What happens when I need to use the car and I don't have a full charge because the utility has been borrowing it?
I'll have to see if I can find the study, but if I remember correctly, PG&E reached out to a group of i3 owners to run a V2G test. Also, I believe it was Google had a small fleet of plug-in Prius that were set up for this. In those cases, they only used a small amount of the vehicle's battery capacity. Apparently, even 1 kWh can have a huge impact on leveling out demand.

Regardless, there would need to be some kind of controls placed on it, and the owner would need to opt in and be able to specify limits. I could see an Uber-like program. Also, though hard to implement, I could see charging companies accepting "deposits" of electricity that could later be used as credits. Here's the scenario I envisioned:

Each day, I pull into work with a large amount of capacity. During the peak hours each day, they draw X units (say, 1 kW equals 1 credit). The amount they take is saved as a credit in my account. When I decide to go on a trip, I can use participating chargers to cash in on the credits I've accumulated. It could make long distance trips cheaper (essentially paying home, base rates), and it could be a good hedge against a potential volatility in DC fast charging rates.
 

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Colour me doubtful.

A university whose existence depends on attracting Government grants just happens to discover that the politically favoured idea of V2G works well in a computer model devised by said university.....

.... so if another university came up with a computer model which said the opposite, which one do you think would get the next round of grant funding?

And they say scientific research is not biased..... ho ho.....
 

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Draining my battery to fuel a building is GOOD for my battery? Good for the building owner, more like!
 

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Colour me doubtful.

A university whose existence depends on attracting Government grants just happens to discover that the politically favoured idea of V2G works well in a computer model devised by said university.....

.... so if another university came up with a computer model which said the opposite, which one do you think would get the next round of grant funding?

And they say scientific research is not biased..... ho ho.....
“The results are also appealing to policy makers interested in grid decarbonisation.”
Ho ho indeed. "Here, use my algorithm to prove my algorithm's findings!". I'm curious how using anything lengthens its useful life. Of course, and as usual we EV people live in a magical world.

However, the new study suggests that this process is more complex than thought and that in fact, it can be exploited to improve a battery’s lifetime.
I love these lines. We suggest "in fact".

"Research of this type is playing a valuable role in generating further business interest in V2G by overcoming opposition centred around battery degradation,” he told Clean Energy News.
Science starts with a conclusion it likes and works backward from there. Oh wait.....

By what magic of chemistry and physics does this happen? I was looking for this information. Did I miss it?
 

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It says they "developed a ‘smart grid’ algorithm to calculate how much energy a vehicle requires to carry out daily journeys, and how much energy can be taken from its battery without negatively affecting it, or even improving its longevity."

To me, that means they probably figured out that the vehicles did not need to be kept fully charged all the time, which is hard on the batteries. They probably kept the cars somewhere around half charged, which is very good for longevity, and then transacted a small enough amount of power in and out of them so that the extra cycling was the smaller effect. This is great when your driving habits are regular, but not great when you suddenly need to take a longer trip and the car is not ready.
 

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Discussion Starter #14
Leaf charges to 95% from what I can gather online.

How many Leafs will I need to run one MIG welder for a day?

Don't forget, I need that power back at 5 PM so I can go home.
How many hours of use are you actually getting out of your MIG? It should be easy to calculate just using your power bill. A Leaf can charge back to 80% in under 30 minutes.
 

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<snip> I'm curious how using anything lengthens its useful life. Of course, and as usual we EV people live in a magical world.
Well, I can't speak for batteries, but I know for a fact that many aircraft work better when they have regular, moderate use (as opposed to occasional use). Like, if you fly one 10 hours a month, it will require (on average) more maintenance and part replacements than one flown 40 hours per month. I work with that data every day...

I agree with you that a battery may be different and this sounds odd, but it's true that sitting at a high SoC for long periods is not as good as a lower SoC, or varying SoC. So perhaps V2G "keeps things moving" at lower SoC throughout the day, and I'm guessing you can set how much they're allowed to take so you can still get home. So it might be the equivalent of doing some partial charges at medium SoC during the day, which is plausibly gentler on the battery than sitting at its highest SoC all day (if you charged at work). I'd like to see more studies, but I wouldn't immediately dismiss these findings...
 

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I agree with you that a battery may be different and this sounds odd, but it's true that sitting at a high SoC for long periods is not as good as a lower SoC,.......
There's a lot of good information on Battery University (you could spend weeks reading all of it).

Most chargers for mobile phones, laptops, tablets and digital cameras charge Li-ion to 4.20V/cell. This allows maximum capacity, because the consumer wants nothing less than optimal runtime. Industry, on the other hand, is more concerned about longevity and may choose lower voltage thresholds. Satellites and electric vehicles are such examples.
.......or varying SoC. So perhaps V2G "keeps things moving" at lower SoC throughout the day, and I'm guessing you can set how much they're allowed to take so you can still get home. So it might be the equivalent of doing some partial charges at medium SoC during the day, which is plausibly gentler on the battery than sitting at its highest SoC all day (if you charged at work). I'd like to see more studies, but I wouldn't immediately dismiss these findings...
The main thing is that topping (fully charging) a lithium ion battery is what does the most damage. Nissan is not as conservative as GM with this as they charge theirs to 95%.

The Nissan Leaf Case

An interesting tidbit I just picked up:

Similar to an EV, Li-ion in satellites must also endure a lifespan of 8 years and more. To achieve this, the cells are charged to only 3.90V/cell and lower. An interesting discovery was made by NASA in that Li-ion dwelling above 4.10V/cell tend to decompose due to electrolyte oxidation on the cathode, while those charged to lower voltages lose capacity due to the SEI buildup on the anode.
As far as someone knowing how much battery I need to get home I call BS. I may need to stop somewhere for food, or maybe I have a date or something. A couple of extra miles outside of my usual travel and I'm stranded unless I have a REX.
 

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Correct! In their wisdom, the GM engineers decreed that the Volt's traction battery should use only 65% of its capacity, never getting depleted below 25% or charging above 80% of total capacity, in order to insure a long battery lifetime. As I understand it, some of the EVs out there are not so conservative and push the traction battery much harder.

Therefore, it seems unlikely that the Warwick modelers incorporated the Volt's specific battery characteristics in their modeling or had the Volt in mind when they made the claim that "V2G Improves EV Battery Life".

Also, I wonder if the Volt charging system would even allow "withdrawals" as well as "deposits" without rewiring the car.
 

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Correct! In their wisdom, the GM engineers decreed that the Volt's traction battery should use only 65% of its capacity, never getting depleted below 25% or charging above 80% of total capacity, in order to insure a long battery lifetime. As I understand it, some of the EVs out there are not so conservative and push the traction battery much harder.

Therefore, it seems unlikely that the Warwick modelers incorporated the Volt's specific battery characteristics in their modeling or had the Volt in mind when they made the claim that "V2G Improves EV Battery Life".

Also, I wonder if the Volt charging system would even allow "withdrawals" as well as "deposits" without rewiring the car.
Well, it's a balance between range and battery longevity. Gen1 Volt could afford to be super conservative because long range wasn't needed due to the engine (not that you could get long range from the small pack anyway). Note that gen2 does about 75% SoC window, likely because analysis of gen1 performance led them to conclude that they were overly conservative originally. All BEVs do higher (usually 90-ish) out of range necessity, I'm sure Bolt is no exception. I'd think BEVs would be the focus for an analysis like this (rather than PHEV/EREV) due to larger batteries... something like the Volt might be considered too small for V2G. Though wikipedia says many of the current trials are being done with modified PHEV, so who knows? Wish the article provided any specifics... we're all just speculating.

I know of no current EV that allows 2-way power delivery via J1772 (is that even in the spec?). Any V2G car would have to have equipment specifically designed for that purpose.
 
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