Study Says V2G Discharge Seriously Detrimental To EV Batteries

3 months ago by Mark Kane 70

Nissan LEAFs and e-NV200 at V2G station in the UK

A research team at the University of Hawaii at Manoa examined the impact of bi-directional charging between electric vehicles and the grid (V2G), and pretty much came up with the result one would expect – that it hurts the EV’s battery; finding that constant use brings the expected lifespan of a battery pack to under 5 years.

V2G

Laboratory tests were performed using Panasonic’s 18650 NCA cells.

According to the study, additional cycling (charging and discharge) of the EV’s battery, decreases its capacity and increases resistance, which in general would make V2G uneconomical.

This has been, in the past – and in conjunction with smaller capacity batteries especially, one of the largest hurdles to V2G tech being more widely adopted.

The difference of capacity drop seems big according the University’s research:

“The team concluded that a V2G step twice a day increased battery capacity loss by 75% and the resistance by 10%. This step once a day accelerated the capacity loss by 33% and the resistance increase by 5%. Forecasts based on the measurement results indicated that that V2G implementation would decrease the lifetime of the battery packs to under 5 years.

The team also found that calendar aging influenced the cells little enough that it was beneficial to charge the cells twice a day instead of once. Charging twice per day resulted in 5% less capacity loss and similar resistance increase compared to once per day.”

source: Durability and reliability of electric vehicle batteries under electric utility grid operations: Bidirectional charging impact analysis via Green Car Congress

Tags: , , ,

70 responses to "Study Says V2G Discharge Seriously Detrimental To EV Batteries"

  1. unlucky says:

    DARPA-e had a program to study this like 5 years ago. At that time the pack wear cost of V2G was far, far too large for V2G to make any financial sense. It may be a bit better now.

    Using your car as a power source really only makes sense when there isn’t another power source handy. That means on job sites or for emergency power cuts at home.

    But it is good to do studies on this periodically since as we make better and better packs the story may change.

  2. Pushmi-Pullyu says:

    Well, duh.

    Electric companies should pay to install their own battery packs for grid backup, not rent the use of battery packs in EVs. In fact, it only makes sense for them to do the latter if they’re not paying a fair market value for the rental. If they were paying a fair price, then they’d be better off buying their own.

    So any EV owner who would agree to rent his battery pack to the electric company would not only wear out his battery pack faster than it was designed to, as compared to the expected lifespan of the car, he would also get ripped off by the electric company!

    There is just no way this makes sense for the EV owner, period. Any EV owner who is even tempted to sign a V2G deal with an electric company, should investigate the cost of buying a replacement battery pack for his car.

    1. Brian Rose says:

      Right, a better idea (which I believe has been tried in Europe) is for customers to receive payment from the utility if they allow the charging of their car to limited based on grid usage & peak load times.

      Times where the EV owner would opt in to this would be when plugged into home or work for many hours so allowing no charge during some of that time isn’t a big deal (especially for those with 200+ mile range who don’t have to charge every day).

      The only downside is potential crowding of charging stations as a result

      1. Pushmi-Pullyu says:

        Certainly, that should be part of the future “smart grid”, where time of use for intermittent demands can be deferred to a later time if the grid is overloaded.

        That won’t put any extra wear-and-tear on an EV’s battery pack.

    2. Bojan says:

      One possible application for V2G would be for it to cover only exceptional circumstances. That way, utilities would have their own batteries for regular daily cycling, but for exceptional peaks, for which it would be uneconomical to maintain additional battery capacity, they could use V2G with an appropriate compensation for the vehicle owners. So, V2G would not play a part in daily solar storage, for which the utilities would have their own specialised batteries, but V2G could play a part in replacing low-utilised reserve capacity.

  3. ClarksonCote says:

    The conclusions seem meaningless without discussing the rate of discharge. If you’re discharging a pack at 1kW I can’t imagine it hurts the battery much, since it takes over 20kW to drive a constant 65mph.

    In other words, I would expect V2G to be a non-issue when implemented on a larger scale. Each EV’s contribution would be minimal.

    1. DJ says:

      So you think what, that charging and discharging a battery slowly doesn’t hurt it? Even if you do it slowly it will result in more battery degradation than if you didn’t do it at all. It’s the nature of the battery tech we currently have.

      1. Bojan says:

        However, batteries also degrade with time, even if they are not used at all. Thus, a battery of a car that isn’t driven much may provide its owner more value during its lifetime if it is used in V2G, even if the lifetime itself is shortened by being used this way.

        That being said, utilities should definitely have their own batteries specialised for daily cycling, V2G only makes sense to cover exceptional circumstances, in which case the owners of the cars could also get a higher compensation per kWh delivered.

        1. DJ says:

          Do a lot of people really buy an EV that don’t plan to drive it? Personally if you’re only gonna put 1,000 miles on your car a year I would suggest someone get a used ICE 😀

      2. ClarksonCote says:

        No, there is some degradation, but it is minimal.

        There is no way at all that a 1kW discharge for a couple hours a day could cause the stated 75% additional degradation. It’s simply impossible.

        To achieve that kind of degradation, they must be pulling some significant power for some significant time.

        Again, the details are important here. These findings – as presently stated –
        will likely discourage the general V2G concept and label it a bad idea, which is very likely the wrong conclusion to come to.

        1. Pushmi-Pullyu says:

          While you certainly have a point that rare use, or use limited to rather low power, would cause less additional aging of the battery pack, at the same time you are making a surprising number of assumptions based on pure guesswork… or worse, on the assumption that the electric utility has the EV owner’s best interests at heart.

          For example, I can easily see that if the economics were favorable, the electric utility would happily drain your battery pack at 10 or even 20 kW for several hours every night.

          It’s hard for me to understand why you would just assume the power drain would be limited to only 1 kw or less, or that the electric utility wouldn’t engage in heavy use of this resource under certain circumstances. If heavy use of all the EVs which were plugged in, in a certain neighborhood every night, would allow them to delay installing a needed new substation for that neighborhood, they why wouldn’t they do it?

          I agree it’s unlikely that we’d see widespread heavy use of this over a long period of time, but you’re ignoring several facts, such as the fact that electrical distribution on the grid isn’t uniform everywhere.

          1. ClarksonCote says:

            I could say the same thing about your assumptions. 🙂

            My assumption is based on every description I’ve ever heard about how V2G would work.

            In part because it ensures that the vehicle owner isn’t stranded with an empty battery. They need to be minimally affected to be willing to participate.

            1. Bill Howland says:

              I’ve always said V2G is dumb and a dead-end.

              Now an asynchronous V2H is ok – I use it myself for emergency purposes, same as you do.

              Utilities and wind farms and solar farms will come up with their own battery solutions where longevity of the batteries is paramount, and the weight of them is not a consideration.

              This is only one test – but probably an honest one.

              The only time I ever see someone wanting to seriously try V2G is when the costs of batteries become trivial. We’re getting there but still probably decades away unless there is a stair-step technology advance in the near future.

              But when battery costs DO become trivial, no sensible utility would bother with something as dinky as an individual car. They’d buy all the batteries they need, themselves, and not having to deal with every single dinky car.

              The other question is, who will voluntarily pay for the 2 quadrant synchronous inverter when they would normally be satisfied with just the plain old battery charger in the car?

              Other than this university-styled testing, utlities in general just plain aren’t interested in it (unless through Smart Metering schemes they’ve figured out yet another way to bilk the public).

              For many decades, utilities have dealt with load smoothing problems with Load-Shedding arrangements.

              Now, large windfarms or large solar farms may have sufficiently erratic output that colocated batteries or flywheel systems are really the only answer to prevent excess wear and tear on their existing central stations, and the colocated part eliminates distribuiton headaches/heating/expenses that you’d have with the individual cars.

        2. Martin Winlow says:

          Call me old fashioned if you want but *****SURELY***** it is relevant what amount of energy is taken out (and replaced) in the V2G process? Yet, the article makes no mention of it!

          Hardly a very scientific study if this issue has not been dealt with. It seems inconceivable that anyone would sign up to a V2G agreement under these circs and I would think the battery owner would be able to dictate how often, how much and when energy would be drained (and, obviously, what the utility would pay the battery owner for the facility) and if not I, for one, wouldn’t touch it with a barge pole!

      3. BenG says:

        Yeah, but a trickle discharge of 1 kw and maybe 2% pack capacity, followed by trickle charge, is not going to be a problem for a battery that can put out more than 100 kw. As the study linked in a post below explains you can even design a V2G charge/discharge algorithm that improves battery health and longevity.

        I know that I’ve erred at times by leaving my laptop plugged in constantly: it’s better to cycle the battery through a good bit of its capacity on a regular basis (i.e. at least once a month let it drop to 20% charged) than it is to leave it plugged in all the time.

        Obviously the owner would get paid a big premium over off-peak rates in exchange for putting use on his/her battery. Dynamic market pricing is essential, and if the price for a kwh of electricity is high enough during a grid event, then some people may want to cash in on it.

        1. Pushmi-Pullyu says:

          “Obviously the owner would get paid a big premium over off-peak rates in exchange for putting use on his/her battery.”

          No, obviously the electric company is going to offer the EV owner the same fixed rate they offer everyone, on a take it or leave it basis. They’re not going to negotiate a separate price with every individual EV owner.

          And since they’re running a business, they’ll offer a rate which favors them — not the EV owner.

          1. BenG says:

            As I said before: “Dynamic market pricing is essential, and if the price for a kwh of electricity is high enough during a grid event, then some people may want to cash in on it.”

            There is already dynamic market pricing at the wholesale level. It’s not too much of a stretch to imagine utilities offering customers the option of switching to such pricing to go along with V2G.

            Of course the utility wouldn’t offer anything that’s unfavorable to the utility, but if there were a price spike on the wholesale market to $1/kwh during a grid event of some sort, the utility would still do very well to pay $.80/kwh to a V2G supplier, which might be enough for people to sell them a few kilowatts if it’s convenient.

    2. MikeM says:

      I suspect that if the SOC (state of charge) during V2G operations were to be limited to within a range – say 50±10%, it would have little effect on the battery.

      I checked the report but it’s paywalled and the available charts are super low resolution and (to me) illegible.

      1. Pushmi-Pullyu says:

        If you suspect that, then you would be wrong.

        A 50% DoD (Depth of Discharge) cycling performed on a regular basis would certainly age the pack noticeably. In fact, if you have an EV with a good sized battery pack, odds are that would put more use on the pack than using it for a daily driver.

        If you had, say, a Bolt EV, and the electric company cycled your battery pack 50% every night, that would be the equivalent of putting an additional ~118 miles on it every day! They say the average car is driven only about 40 miles per day, so a 50% DoD every night would be pretty heavy use.

  4. (⌐■_■) Trollnonymous says:

    No thanks on V2G.

    I am perfectly fine with just power to my home for emergency purposes.
    An 8KW Puresine will work fine.

  5. Barn Burner says:

    “Charging twice per day resulted in 5% less capacity loss and similar resistance increase compared to once per day.”. So in fact the study shows that we should all charge at work under a solar canopy using free solar electricity (9am-3pm wholesale rates have gone negative in some areas already and it will be better in the future), then drive home, plug in and power the evening peak, then recharging with cheap baseload from 12am to 5 am, drive to work, rinse and repeat. Of course this only works when using less than 1/2 of battery capacity. Modern LiON batteries can take 1000s-10,000s of cycles if only charged and discharged from 25-75%. Assuming a 60 KWh, 200 mi, thermally protected battery and a normal 50 mi commute, the will be insignificant impact. However, a 24 KWh Leaf without thermal protection and a 50 mi commute will lead to even more degradation unless V2G-half is used (charging on/off only, no discharging)

    1. unlucky says:

      Why would I charge twice a day if I have a 50 mile commute and a 60kWh pack?

      I don’t even need to charge once a day in that case.

    2. Pushmi-Pullyu says:

      Yeah, I puzzled over that bit in the article. I think what they mean is that using shallower cycles will wear the pack out slower, even if it means more cycles.

      For example, if you could cycle the pack at only 20% DoD, but do it twice a day, that would result in less aging of the pack over time than cycling it 40% once per day, even though it’s the same number of kWh.

      But that’s assuming optimal conditions. Not very many people are going to be able to precisely break up their charging to 1/2 at home and 1/2 at work on a regular basis, and still be sure they’ll have sufficient charge for unplanned side trips.

    3. bro1999 says:

      That’s always been a question of mine….is it better to do 3 partial charges or 1 full charge. I guess partial charges are better? Maybe?

  6. David Murray says:

    This is no surprised to me. In fact, that’s why I was against the idea the moment I heard of it and I’ve never been excited by it. Why would I want to sacrifice my vehicle’s battery pack to benefit the electric company whom I’m already paying for my electricity?

    1. DJ says:

      Hey, if you’re leasing then who cares right 😀

      1. ClarksonCote says:

        It sounds like they are fully discharging the battery and at a significant rate. Everything that crowd-sourced V2G has professed will NOT be done.

    2. Doggydogworld says:

      By the time V2G is a real thing EV batteries will easily handle the extra cycling.

      The SW US could get to 80% renewables with EV-V2G (or even V2H) and Ice-AC in commercial buildings. Monthly costs for electricity + transport would be at least 50% lower. It’s a no brainer. Doesn’t mean it’ll happen – utilities can be pretty obtuse.

  7. Counterintuitively, done correctly, V2G could actually be good for EV batteries:

    “This new research into the potentials of V2G shows that it could actually improve vehicle battery life by around ten percent over a year.

    For two years, Dr Uddin’s team analysed some of the world’s most advanced lithium ion batteries used in commercially available EVs – and created one of the most accurate battery degradation models existing in the public domain – to predict battery capacity and power fade over time, under various ageing acceleration factors – including temperature, state of charge, current and depth of discharge.

    Using this validated degradation model, Dr Uddin developed a ‘smart grid’ algorithm, which intelligently calculates how much energy a vehicle requires to carry out daily journeys, and – crucially – how much energy can be taken from its battery without negatively affecting it, or even improving its longevity.”

    https://m.phys.org/news/2017-06-energy-electric-vehicles-power.html

    1. BenG says:

      Very cool, and believable, IMO.

      Batteries do better with use than sitting unused on a shelf or being plugged in all the time.

      Trickle discharge and charge cycles added into normal use will not significantly hurt battery life.

  8. Hauer says:

    There will be some fine print. Like the “sorry for your warranty being voided due to racing with your car.”

    1. Murrysville EV says:

      Excellent point.

      As noted above, if your battery is running the equivalent of 118 miles in place in your garage overnight, then your car’s mfr might not cover a warranty claim.

  9. theflew says:

    I think V2H (home) makes sense for emergency power outages that might last a couple of days. On the other hand V2G makes no sense.

    1. ClarksonCote says:

      V2G makes a lot of sense.

      Unfortunately this report fully discharges the battery at least once a day using high rates of discharge, and that is not at all what V2G is.

      V2G is intended to be crowd-sourced reliability where very small amounts of energy and power are drawn from each vehicle. This proper technique has minimal/negligible effect on the battery.

      I’m very shocked that the authors of this study put out these kind of findings without caveats. Makes me feel like they were paid off by special interest groups against this sort of technology.

      1. Pushmi-Pullyu says:

        I agree that heavy used every day by the electric company, so heavy that it results in 75% greater capacity loss than average daily driving*, is not a very likely scenario.

        But then, your scenario of never more than minimal use, and never draining the pack at more than 1 kw, strikes me as a naively optimistic scenario for the EV owner.

        In reality, if you give the electric company the right to use your battery pack as a backup, then they’re going to use it in the way that their engineers think best benefits them. If you want their use to be limited to only 1 kW or less, then you had durn well make sure that is specified clearly in the contract. Personally, I doubt that’s going to happen. They’re not going to negotiate separate deals with different EV owners. They’re going to have a standard contract written by their lawyers, and you can either sign it or not.

        *…if that’s what is being claimed in the article; it’s not entirely clear to me.

        1. ClarksonCote says:

          My scenario is not naive and it shouldn’t surprise you.

          You’re not thinking large scale. I’m not sure where your assumptions are coming from but if V2G appreciably affects an EV owners range, they won’t participate.

          This is why everything I’ve ever read talks about taking out a little bit of energy across a large swath of available vehicles, rather than any meaningful percentage of a single EV’s battery.

          1. Bill Howland says:

            Please name the utilities that want to pay a bonanza for that precious 1000 watts out of the car. Also, what is the round trip 24 hour cost to get say, 5 kwh out of the car every 24 hours? What are the standby losses of the V2G inverter that must be constantly working?

            If this is so compelling to Utilities, why hasn’t mine offered it yet?

            1. ClarksonCote says:

              Where is there a requirement for them to pay a bonanza. At large EV adoption scales, they only need to pay what supply/demand dictates, and if that’s cheaper than their own deployment of energy storage.

              So I may get some minor discounts on my bill when they pull a small amount from my battery. If financially attractive to the utility and transparent to my own battery usage and ta health.

              I agree with you that those who believe that EV owners will be making tons of money off V2G – should V2G come to fruition – are way off base.

              1. Bill Howland says:

                The only way I see this being somewhat efficient is to have the car being discharged being collocated with the source of erratic energy – for instance the solar panels on my roof.

                Or, since during the daytime the cars aren’t in the garage, a charge at work car farm along with solar panels at the same work location. But then that sounds like a heck of a lot of cars would be required to buffer the solar panel output.

                I discount any other type of scheme because of the circulating current losses between the intermittent generation and the nearest load.

                When ev’s are rated, the efficiency of charging the battery is counted, but the discharge inefficiency is NOT. It is accounted for by saying the car takes 400 wh/mile or whatever when the car really only takes 300-350 and the other 50-100 is heating the battery, and/or running ancillary loads.

                But if you are planning on using the car to buffer erratic output, then you have charging AND discharging losses – plus battery degredation. I just don’t see this happening, and apparently Tesla doesn’t either.

                If you walk around a Tesla supercharger for instance, you’ll see all kinds of heat coming from the supercharger bay itself (the big fan on top), the transformer(S) changing voltages, and then plumes of heat coming from the car itself.
                If this “S” was used to buffer, then you’d have around DOUBLE this heat loss on the discharge side, and that is probably why you never see a Tesla used in one of these schemes.

                Wholesale electricity for me on average last year was 2 1/2 cents / kwh. No way can I move electricity in and out of my car battery to compete with that pricing.

                Now POWERWALLS can work since the huge markup some utilities are allowed to charge may be arbitraged by them and the customer can beat the utility at its own scam.

                Otherwise, the big solar, or wind generator can collocate their own batteries or flywheels themselves.

                1. Phr≡d says:

                  Not sure that this adds anything, by my -personal- imagination is a case where a parking garage has 50 slots-with-power, reserved for EVs. This known source could then be used to smooth a brownout for a Very limited time.

                  I am sure that it is very complex, but with X parking garages times X EVs in a downtown location, V2G -seems- like a nice emergency fill for the utility if surprising power draws occur. Guessing that those draws for a brownout shouldn’t last an extreme amount of time?

                  I’m only here to learn, thanks for a reply Bill (or others), if you see this.

                  it again, -seems- like a logical extension of the program that our half-million population burg put in place to control air conditioners – when a peak alert was issued, your AC wouldn’t run for up to an hour. My imagination says first, stop charging the EVs connected at the parking garages. Next, -if Necessary- draw from them

                  1. Bill Howland says:

                    Yeah your scenario sounds all right, but there are easier ways to handle the problem that Utilities have used for decades, namely load shedding agreements.

                    If it looks like customer load is going to exceed the available supply, utilities notify their large customers to shed load for the next 24 hours, or whenever they specify. Customers do this voluntarily since they get a discount by not stubbornly continuing to use the same amount as they did the day before, mainly by running their emergency generators – machines that require routine exercise anyway, and they might as well run when it is needed by the utility – so that they can get a discount on their Bill.

                    Whenever I bring up problems with ‘frequency stabilization’ the V2G guys say it is for ‘brownout protection’.

                    Whenever I bring up problems with “Brownout Protection”, the V2G guys say it is for “frequency stabilization”.

                    Therefore, seems the big benefit of V2G is that is provides money for plenty of engineering consultants, and lets them have fun with proposed smart-metering schemes, but I have yet to see anything that amounts to much.

                    In the states, the big thing is summer air conditioning loading on a hot day. Some utilities are experimenting with turning up the temperature on your NeST thermostat when they are desperate, but this is just another version of a load shedding scheme that has proven its value for many decades.

                    Personally, I don’t feel V2G schemes are ever going to work because:

                    1). Car owners will be a bit nervous over increased wear and tear on their batteries.

                    2). Most electric cars have loses when charging, and these will essentially double when sending power back to the grid (roughly the same amount of losses as when charging), but then you have to recharge the car again.

                    3). If done IN AN EMERGENCY as the scenario you stated, its much easier what with the more and more internet connected NeST thermostats to simply allow the utility to fiddle with it.

                    4). Circulating current and charge/discharge losses make it relatively expensive to get juice in and out of the car in the first place.

                    5). If needed to buffer erratic solar panel/wind farm output – the ‘generators’ can buy their own batteries, or flywheels, and colocate them to eliminate ‘circulating current’ losses.

      2. arne-nl says:

        Just what I expected. I couldn’t read the report because it is paywalled, but wide charge/discharge cycles are much more damaging for Li-Ion batteries than shallow cycles. IoW, 1 full cycle from 100% down to 0% is more damaging than two half cycles (from eg 80% down to 30%). The latter is of course what you would logically do for V2G operation.

    2. M3 - Reserved -- Niro TBD says:

      V2H stabilizes the home demand that subsequently puts less strain on the Grid. Just like home PV systems have made tremendous strides on daytime demand, the alerts for reduction requests on the grid come on the duckbill shoulder times 6p-9p when the sun goes down, everyone arrives home and fire up the TVs, computers, and AC.

      That’s where a V2H setup would work tremendously (as the concept of Powerwall) and industrial sized batteries in lieu of peeker plants.

      Imagine if all our inverters are able to connect a EV to it for the temporary support (V2H) for those short few hours. No added cost on capital — and would very much stabilize the grid on demand quite easily

  10. William says:

    ” Beings”, should read “brings”.

    1. Jay Cole says:

      Thanks for the heads-up William, fixed!

  11. foolcell says:

    What a load of nonsense check this out vtg works

    Phys.org: Clean energy stored in electric vehicles to power buildings. http://google.com/newsstand/s/CBIwjcaukzU

  12. vdiv says:

    Agree, this doesn’t pass the smell test. When properly used V2G has the same effect as preconditioning your EV or driving to the local 7-11 and back.

    Regardless, some think that the cost and complexity of V2G-capable stations at the scale at which it is useful are not worth it. Just deploy purpose-built, stationary and dedicated storage (i.e. get more batteries) to balance the grid as it is already done.

  13. M3 - Reserved -- Niro TBD says:

    So what to tell all these Powerwall people with this? The premise on Powerwall is FULL discharge cycles daily during the household demand times.

    These are the same cells coming off the line that supply their vehicles, so what’s the dealeo then?

    Whether it’s strapped to the wall or on 2-4 wheels, a battery is just that. Either there is degradation and/or resistance wear and tear or not significant enough to balance the savings.

    I didn’t read the paper, but need to balance the capacity/performance loss over time vs the savings garnered over that same time to see if balanced.

    Last time I checked; Powerwall took 7 YEARS for ROI for us in SDGE country and that’s with full on arbitrage and TOU.

    That’s VERY different from a V2H setup where you’ve already paid for the battery sitting idle on the concrete pad/garage where you can leverage it for 10kwH and recharge at night (not so unlike driving an addition 40miles and recharge nightly).

    1. Pushmi-Pullyu says:

      “These are the same cells coming off the line that supply their vehicles…”

      Hmmm, are you sure? I think you’re making an apples-to-oranges comparison. The cells inside those PowerWalls may look like the same cells as the ones that get put into Tesla cars, but they may have different chemistry inside.

      As I understand it, the original PowerWall offering was for two types; one to be used only occasionally, the other designed to be cycled daily. So right there, that should tell you that not all battery packs are created equal, even if they are both from Tesla Energy.

      If you get the PowerWall that’s intended to be cycled for daily use — and if memory serves, Tesla quit offering the other type — then it had darn well better be engineered for that. Contrariwise, passenger cars are typically used only 5-10% of the hours in a day, which goes along with the 40 miles a day average use.

      Again if memory serves, the PowerWall is guaranteed for X number of years, and if it drops below a certain capacity during that time, then Tesla will replace it. (Correct me if that’s not right, please!) So, again, Tesla had darn well better engineer that to be cycled every day, because that’s the use that they’re guaranteeing. If they don’t, then it’s Tesla who will have to pay for a lot of replacements.

      1. Ambulator says:

        In particular, Tesla cars use NCA batteries but the powerwalls use NCM batteries for greater cycling capacity.

        1. M3 - Reserved Niro - TBD says:

          I believe Tesla is making the 2170 batteries now for both Powerall, and Tesla car products.

  14. Cameron says:

    Different cells can be optimized for different performance specifications. Vehicle batteries might be optimized for peak current and weight where home backup batteries would be designed for max cycles.
    I agree that V2G is a great feature in an occasional emergency. But for every-day use, you achieve most of the benefits of V2G by just allowing utility control of vehicle charge scheduling, without the battery cycle degradation.

    1. Pushmi-Pullyu says:

      Exactly right, and thanks.

      As you say, home energy storage systems don’t need high power output, the way EV battery packs do; and home energy storage systems need to withstand a fairly high DoD on a daily basis, which EV battery packs generally don’t.

      In fact, if what I remember is correct: Tesla guarantees its PowerWall can be cycled every day and not lose more than a given percentage of capacity over several years of use. Right there, that should tell us that they’re not using EV batteries inside the PowerWall. As you say, they’re using batteries optimized for maximum cycles.

    2. M3 - reserved Niro -TBD says:

      Powerwall is not designed for backup battery like old lead battery backups. It’s meant for daily DEEP cycling. Take a look at their website videos and PV system videos on what the purpose of these systems are for.

      It would essentially be the same as what a car demand on driving would be draining, so the force in demand on acceleration/discharge and driving three hours on the road in no different than a household draw current would be.

      One could argue that a Tesla car battery has higher demands on draw than a household battery (especially one in Ludicrous mode). So the argument that a Tesla Powerwall battery not lasting as well as a Tesla EV battery is kind of baffling.

      Tesla Poweralls are 7-15kwh batteries while the EV packs are 60-100kwH packs. the cycling on the average EV pack would be minimal on a V2H setup.

      I have a small 20-25 kWH pack in our Fiat and Spark EVs and minimal degradation on cycling down to 10% on regular basis over the past three years. Tesla batteries have been reported to stand up well too.

      Point is, V2H can do much better and we’d be much better off with V2H programs — but that would kill the Powerwall demand— hence NO push from Tesla to move on that revenue source.

  15. Brave Lil' Toaster says:

    In other news, contrary to what some environmentalists believe, magic pixie dust is not the solution to all of our problems.

    This is hardly surprising. News, yes, but still.

  16. jamcl3 says:

    The use case is flawed. You can sell power at a price you choose. There are many markets where peak pricing can be 100 times higher than average, and you can profit far above the cost of battery wear. Texas had a spike closer to 1000 times higher than average for a few days last winter if I recall. (Texas has no “capacity” market.) And the U of D begs to differ also: https://www1.udel.edu/V2G/resources/V2G-Cost-Benefit-Analysis-Noel-McCormack-Applied-Energy-As-Accepted.pdf

    1. ModernMarvelFan says:

      “you can profit far above the cost of battery wear”

      If it does, then why doesn’t utility just add their own battery to offset that peak “pay out”?

      Their own battery will sure cost less than your vehicle V2G battery for sure on a wholesale level.

  17. ModernMarvelFan says:

    Duh! V2G only works if you lease the car… LOL.

    Battery “wears out” with time, number of cycles. Temperature, SOC, amount of cycling..etc are just accelerating that wear/tear.

    Unless the owner is paid properly for those wear and tear, why would anyone do it? If they are paid Properly, then why would utilities pay for it since they can just buy the battery and do it themselves?

    It is silly idea to start with.

    It is almost no different than renting your car out (Turo) vs. Hertz/Avis rental fleet. Would someone get a Malibu rental from an owner or Hertz/Avis?

    1. M3 - Reserved Niro - TBD says:

      http://www.businessinsider.com/15-tesla-powerpack-battery-projects-2017-3/#tesla-is-also-powering-another-luxury-resort-on-malolo-island-a-volcanic-island-in-fiji-2

      –Batteries for as needed demand actually do make sense. It’s just how it’s deployed and timing/cost is the issue.

      Traditional peaker plants are getting replaced by these PP systems for the exact same reason for a V2G/V2H concept in a dispersed model.

  18. Bill Howland says:

    Now a battery scheme like a Tesla POWER WALL does make sense to me, especially if you want to arbitrage confiscatory Time-of-use rates.

    If Consolidated Edison customers are ever FORCED onto TOU, the Tesla powerwalls will be selling like hotcakes in NYC.

    Net Metered residential customers are not allowed to have batteries, but the vast majority of customers are NOT net metered and therefore there is no restriction to saving money.

  19. Bill Howland says:

    Apparently Tesla doesn’t look foundly on V2G, it seems only NISSAN LEAFs are the ones that are ever tested.

    Their powerwall solution seems both to them (and me) the way to go.

    Net metered residential customers (in NY State) are not allowed to have batteries, but every one else has no restriction.

  20. jim stack says:

    FACTS PLEASE, The Univ of Delaware has been doing V2G with BMW MINI-E vehicles made by AC Propulsion. They only discharge a small amount and it pays $1,200 a year.
    With a good cooled battery there will be no capacity loss over time. Just a few kWh off a Tesla 100 kWh pack will tickle the battery and make it stay healthy. READ http://www.V2G-webs.com

    1. Bill Howland says:

      Can’t read your link Jim, or at least my IE can’t find it.

      $1200 from one car? What are the characteristics of the draw/replenishment of the battery?

      The thing that has never been explained to me, is, why doesn’t the utility do the buffering themselves, or if it is the homeowner or business owner, why dont they take powerwalls and arbitrage the juice they buy themselves?

      I suppose using cars to buffer intermittent solar and wind production is theoretically conceivable, but I’d think it would be much cheaper for the utility/or solar/wind provider to do it themselves.

      The only real issue here is to prevent wear and tear on central stations. The utility has an incentive to avoid this damage – but many utilities are solving this problem by putting heating pads on their turbines – usually electrically powered so that there is SOME load on the turbine so that the blades don’t overheat.

      Due to the unique Joule-Thompson coefficient of Steam, it gets HOTTER as it expands, and must DO WORK to self-lower its temperature. Therefore it is important to always provide a decent mechanical load on the steam turbine to prevent it overheating.

      Dump batteries colocated with the solar/wind installations can either quickly suck in power during sunshine bursts or else wind gusts, and likewise can provide juice during clouding or low wind conditions to get rid of the extreme erraticness of the powergeneration. Flywheels also work.

      But distribution power losses are minimal since the ‘circulating current’ is just going trivial distances. It would be much more involved an affair to have huge circulating currents between distant wind mills and the EV’s supposedly that would buffer them.

      I suppose the same thing could be said for a home mounted solar panel – ev car installation – except for a few slight problems. The cars are mostly out of the garage during the daytime.

      Fortunately, this problem is already mostly solved. Hot days with plenty of sunshine are already increasing the air conditioning load. SO many times ALOT of solar energy from the roof is being used to aircondition the self-same house.

      Demand charges usually are not charged on residential services, but it is conceivable that IF every single house has solar panels, then Demand charges will be needed to convince the owner to throttle his solar output, (or, to charge his car, do his dishes, etc) – limiting the excess production during the early morning when the airconditioning is not needed.

      This would be one case where prematurely turning the air conditioning ON would lower the electric bill, since you wouldn’t be charged an excess demand charge by sending gobs of juice back to the grid at any one time.

      1. Bill Howland says:

        The heating pads I mentioned obviously are for often-cycled turbines so that there is no thermal shock on restart (as the blades can get damaged if they get too hot, it is also important to keep the blades hot enough if shut down so they can restart with little wear). No Cold Starts.

      2. Doggydogworld says:

        Bill – utilities would use V2G instead of their own batteries for two reasons:

        1. Sporadic use. Annual cost for batteries is around $25/kWh (mostly financing the $250/kWh capital cost). If they only need the capacity 25 times per year, that’s $1/kWh. A v2g car owner who agrees to provide 10 kWh those 25 days would get $250, offseting roughly half hist annual charging cost (4000 kWh at 12 cents/kWh).

        2. Grid stabilization, e.g. handling fluctuations when a power plant or transmission line trips offline. They’d have to massively oversize a battery bank for such quick response, but a million EVs which can instantly switch from 7.2 kW charging to 7.2 kW discharging provides 14 GW of capacity at near-zero cost.

        1. Bill Howland says:

          No I don’t see this at all. If the utility is desperate, they implement load-shedding agreements with their large customers that have large emergency gensets. They need occasional exercising anyway.

        2. Bill Howland says:

          Show me one place where this is seriously implemented as a failsafe for a desperate utility.

  21. M3 - Reserved; Niro - TBD says:

    @Jim – unfortunately many don’t understand V2G/V2H concepts. Several ongoing miniprojects for grid stabilization in U of California systems.

    UCSD has its own minigrid complete with PV, Fuel Cell, V2G system.

    The current battery/Car companies don’t have an interest in V2G/V2H because they want to sell their own powerwall/stationary systems to get more money. Why sell on battery pack, when you can sell two?

    That’s the problem and the solution is somewhere between government mandate (like forced readiness for PV+EV power on new homes), energy company incentive (unlikely), or 3rd party inverter company that will do the heavy lift for this.

    The problem is there is no financial incentive for any company to promote V2H/V2G. The only one potential is a car company WITHOUT an energy plan — Looking at you GM and Kia.

  22. Bill Howland says:

    One million evs charging going to discharging.

    No problem in a town of 50,000.

    Didn’t know Californians had 30 car garages and the 2/3 of them were always charging and at home. Or that they were 100% evs when it is more like a few percent.

  23. Brian says:

    They used 30% of the battery capacity instead of the 5% every V2G paper I have ever read suggests.

Leave a Reply