The Electric Vehicle Thread

[Koolau]

Obviously, it was planned that when more charging stalls get occupied, the power will be shared, and each will get less than 250 kW.

I also remember the chart you shared, showing the max power is only applied when the battery is empty, then tapered off when the battery starts to fill up.

So, yes, you do not need the full 250 kW per stall. I stand corrected.

PS. The 250 kW number is somewhat misleading, because no EV can take it continuously. But it is common among all EV makers to advertise this peak charging rate, not just Tesla.

I don't understand the grid well enough to imagine the answer to this question: What if a dozen Teslas roll in, virtually at the same time and plug in with 20% batteries. Do all 12 get 250 kW. IF they do, what if the "grid" can't supply that much? What happens? Thanks

 

[ERD50]

I don't understand the grid well enough to imagine the answer to this question: What if a dozen Teslas roll in, virtually at the same time and plug in with 20% batteries. Do all 12 get 250 kW. IF they do, what if the "grid" can't supply that much? What happens? Thanks

It would depend what service Tesla paid the utility to install. If they really intended to support 12 250kW chargers at the same time, they'd need to pay for a 3 MW service panel (just like a homeowner pays for a 100A or 200A service).

To put 3 MW into perspective, a typical coal plant is ~ 800 MW, so ~0.4% of an entire plant. Or about 2000 homes at average draw.

They might be using Tesla Power Packs to smooth this (I've seen no evidence of this though), or they just cut the max current to the cars (more likely).

If the utility is needing to cut back to avoid a blackout, I imagine they have some sort of agreement in place with the large draw users.

-ERD50

 

[audreyh1]

I don't understand the grid well enough to imagine the answer to this question: What if a dozen Teslas roll in, virtually at the same time and plug in with 20% batteries. Do all 12 get 250 kW. IF they do, what if the "grid" can't supply that much? What happens? Thanks

It depends on the utility transformer. If for example it’s rated to supply 1500KVA then it could supply full 250kW to 6 cars simultaneously if they were all at a low state of charge. If there are more than 6 cars concurrently (and chargers) power is going to be shared.

Practically speaking cars don’t show up simultaneously nor at the same state of charge. As the battery fills each car draws less and less power, so there is more power available to other cars. So more chargers are installed than the utility transformer max.

As to whether the grid can support these large utility transformers - well the power company itself installs them and connects the power feed.

 

[NW-Bound]

I would think that any management of the load would be implemented on the charger, and not on the transformer. The charger has all the smarts. In some installations, a charger stand has 2 cables, one on each side, not unlike gas pumps with two hoses on the opposite faces. These "dual cable" chargers know to split the power between the two cables as is appropriate.

A while back, I shared the info on my residential utility set up. Three of my neighbors and myself share this pad-mounted 50kVA transformer. So, on the average that's only 12.5 kW per home.

I had mistakenly believed that I had access to 200A x 240V = 48 kW. Yes, I do but only if the 3 neighbors don't draw any power. In the summer, my highest daily usage got to 100 kWh/day, and that's less than 5 kW on the average.

Even in the summer when the central AC runs max out and the home owner happens to be doing a laundry load and cooking at the same time, I don't think he exceeds the 12.5 kW per household. And even if he does, it is not likely that his 3 neighbors do that at the same time.

Hence, there are no circuit breakers, no fuses inside the pad-mounted transformer that I could see, that recent time when they swapped out the transformer because the old one leaked oil. Yes, I was curious and went out to watch. I also saw how the 7 kV line and the 4 house circuits were hooked up to the transformer.

Anyway, back to the EV charger I think the charger with all the smarts would have a programmable built-in limit function, as part of the load management. How high this limit should be set would be negotiable with the utility company.

What will be interesting in the future is when 4 of the houses on a 50 kVA transformer all have EVs, and they all want to draw 50 kW to charge their EVs. Even at 25 kW, that's 100 kW total on a 50 kW transformer.

We will get there at some point, and the utility will require some retrofit smart hardware to prevent blowing out the poor transformer.

 

[Koolau]

It would depend what service Tesla paid the utility to install. If they really intended to support 12 250kW chargers at the same time, they'd need to pay for a 3 MW service panel (just like a homeowner pays for a 100A or 200A service).

To put 3 MW into perspective, a typical coal plant is ~ 800 MW, so ~0.4% of an entire plant. Or about 2000 homes at average draw.

They might be using Tesla Power Packs to smooth this (I've seen no evidence of this though), or they just cut the max current to the cars (more likely).

If the utility is needing to cut back to avoid a blackout, I imagine they have some sort of agreement in place with the large draw users.

-ERD50

Wow. 12 cars = 2000 homes. I can see issues ahead. I know everyone is talking about charging at home at off-peak, but there are a LOT of cars out on the Interstate and when they're mostly EVs, that's gonna be a lot of electricity NOT at off-peak times. That's a lot of solar panels and windmills if we outlaw coal, oil and gas. YMMV

 

[Koolau]

It depends on the utility transformer. If for example it’s rated to supply 1500KVA then it could supply full 250kW to 6 cars simultaneously if they were all at a low state of charge. If there are more than 6 cars concurrently (and chargers) power is going to be shared.

Practically speaking cars don’t show up simultaneously nor at the same state of charge. As the battery fills each car draws less and less power, so there is more power available to other cars. So more chargers are installed than the utility transformer max.

As to whether the grid can support these large utility transformers - well the power company itself installs them and connects the power feed.

I guess as long as the utilities add more capacity, it might work. Unfortunately, we've already seen that some places can't keep up with the load and yet they are requiring EVs. I hope that doesn't spread to other areas. I would think we should build the infrastructure before requiring EVs. Such an approach is likely to induce folks to ditch their ICE in favor of an EV rather than hold on to their ICE "just in case." YMMV

 

[ERD50]

Wow. 12 cars = 2000 homes. I can see issues ahead. I know everyone is talking about charging at home at off-peak, but there are a LOT of cars out on the Interstate and when they're mostly EVs, that's gonna be a lot of electricity NOT at off-peak times. That's a lot of solar panels and windmills if we outlaw coal, oil and gas. YMMV

A lot of this will average out, so those peaks aren't an everyday concern.

But I wonder, as EVs become more common, what about holidays? I think we've already seen (as would be expected), backups at charging stations when there are a lot of people doing a holiday drive to relatives. With a lot more EVs, that will be a lot more peak power.

Maybe the charge stations will need a LOT of power packs. But that's needs more than a 1:1 (for losses) for each car charged above the utility limit, and those peaks may last for hours, and there won't be an opportunity to recharge those power packs until the surge is down. Then that would be many, many batteries to charge. Could take days, weeks?

Maybe pull up a semi-load of pre-charged power-packs?

I suppose a back up Nat Gas generator wouldn't be considered? Might be just what is needed though?

-ERD50

 

[audreyh1]

I would think that any management of the load would be implemented on the charger, and not on the transformer. The charger has all the smarts. In some installations, a charger stand has 2 cables, one on each side, not unlike gas pumps with two hoses on the opposite faces. These "dual cable" chargers know to split the power between the two cables as is appropriate.

Plenty of smarts in the charger, but there are separate cabinets that do the load management. Here is a fairly common 250kWh Tesla supercharger installation. A V3 cabinet is attached to every 4 superchargers and handles load management to those chargers. In addition the V3 cabinets talk between each other to handle power sharing.

This is a fairly new V3 supercharger in Clyde Texas on I-20 near Abilene. These happen to be pre-fab units - the V3 cabinet and 4 chargers come already mounted on their concrete base, so they are very quick to install. Other sites may mount chargers and cabinets individually.

 

[Koolau]

A lot of this will average out, so those peaks aren't an everyday concern.

But I wonder, as EVs become more common, what about holidays? I think we've already seen (as would be expected), backups at charging stations when there are a lot of people doing a holiday drive to relatives. With a lot more EVs, that will be a lot more peak power.

Maybe the charge stations will need a LOT of power packs. But that's needs more than a 1:1 (for losses) for each car charged above the utility limit, and those peaks may last for hours, and there won't be an opportunity to recharge those power packs until the surge is down. Then that would be many, many batteries to charge. Could take days, weeks?

Maybe pull up a semi-load of pre-charged power-packs?

I suppose a back up Nat Gas generator wouldn't be considered? Might be just what is needed though?

-ERD50

I couldn't find a good figure for how many EVs are actually on the road. I read that 5% of sales are EVs. In any case, as a first approximation, I think we could say EVs might be 2% now. That's just a blip and some places are short of electricity.

When states make ICE sales illegal, that will change rapidly. Call me glass-half-empty but I just don't see us keeping up with the electrical demand - especially since every new power plant must go through years of environmental studies and legal challenges (even Windmill farms.) Hope I'm wrong and YMMV.

 

[NW-Bound]

I guess as long as the utilities add more capacity, it might work. Unfortunately, we've already seen that some places can't keep up with the load and yet they are requiring EVs. I hope that doesn't spread to other areas. I would think we should build the infrastructure before requiring EVs...

I have not seen utilities voicing much concern. I think they don't want to be seen as "anti-green". If I were them, would wait until there's a problem then say, "gimme money to fix the problem you created". Else, you get accused of crying wolf.

Oil and gas companies are doing the above. Way better to wait for the customers to come crying to you.

A lot of this will average out, so those peaks aren't an everyday concern.

But I wonder, as EVs become more common, what about holidays? I think we've already seen (as would be expected), backups at charging stations when there are a lot of people doing a holiday drive to relatives. With a lot more EVs, that will be a lot more peak power.

Maybe the charge stations will need a LOT of power packs. But that's needs more than a 1:1 (for losses) for each car charged above the utility limit, and those peaks may last for hours, and there won't be an opportunity to recharge those power packs until the surge is down. Then that would be many, many batteries to charge. Could take days, weeks?

Maybe pull up a semi-load of pre-charged power-packs?

I suppose a back up Nat Gas generator wouldn't be considered? Might be just what is needed though?

-ERD50

Power packs or bulk batteries for transferring to EVs can easily be done. The problem is that they aren't cheap. And to install them for the "once-in-a-while" need is not going to be economical.

I am sure Tesla and Electrify America have thought about this and try some modeling with queuing theory (see: https://en.wikipedia.org/wiki/Queueing_theory). If they are not currently installing backup batteries, it's because it costs too much. No business can be sustained running at a loss. Tesla stopped "free lifetime charging" long ago. It even cuts back on referral bonuses as I read.

In the end, it's not the availability of technology but financial considerations that drive these things. As always.

Plenty of smarts in the charger, but there are separate cabinets that do the load management...

Yes. I don't know how they arrange it, and what I meant was that the load management would be done on the energy user side (the charger) and not the utility side.

 

[ken830]

Do you have some links for that? All I could find is a mention of Tesla Power-packs at the Electrify America sites:

https://electrek.co/2021/12/02/elec...-tesla-powerpacks-over-140-charging-stations/

And I keep reading about the "sharing" of max current between Superchargers - wouldn't batteries alleviate that?

-ERD50

I don't believe anyone has collected that information centrally. But if you are able to physically visit many of the larger Tesla Supercharger sites, you can see with your own eyes the battery storage cabinets. They are labeled. There are many threads on teslamotorsclub.com where people find new Supercharger sites and continually update them with photos during construction. You will see photos of the battery cabinets occasionally.

the "sharing" of max power between Supercharger stalls is a power thing mostly limited by the chargers power capacity. The duration for any car to be able to utilize the full power of the charger is very short, so it makes sense to put in multiple (generally 2) stalls to share a single stack of chargers.

 

[Popeye]

In addition to improving service reliability in targeted areas, the system improvements will also pave the way for additional clean energy resources, like solar, and support vehicle electrification throughout the service territory. Retiring aging substations and upgrading portions of the electric system with new equipment and increasing the voltage of nearby circuits also increases the ability to support more customer-owned solar generation facilities. Ensuring reliable power also becomes more critical as the use of electric vehicles expands and customers increasingly rely on charging capabilities at their homes for vehicles.

https://www.peco.com/News/Pages/Pre...mentstoEnhanceElectricServiceReliability.aspx

Check to see what your local utilities are doing now. PECO is in the middle of a five year plan for reliability that is also looking towards vehicle charging among other things. I can’t imagine that utilities are ignoring this future state. If they are then the govt regulators must be asleep at the wheel. Pun intended!

 

[ERD50]

https://www.peco.com/News/Pages/Pre...mentstoEnhanceElectricServiceReliability.aspx

Check to see what your local utilities are doing now. PECO is in the middle of a five year plan for reliability that is also looking towards vehicle charging among other things. I can’t imagine that utilities are ignoring this future state. If they are then the govt regulators must be asleep at the wheel. Pun intended!

I question how far that goes toward supporting some large shift to EVs, as some predict (or mandate!). More from that link:

The plan will focus on three priority areas of infrastructure improvement for accelerated investment, all which are aimed at preventing outages for customers. Those areas include preventing outages related to more extreme storms, proactively replacing electric cable, and replacing or retiring aging substation equipment and small substations.

Working to prevent storm-related outages
To combat the effects of a changing climate and more frequent and severe storms, like the storms of this summer, PECO will invest approximately $441 million on targeted investments in areas that have experienced repeated storm-related outages. Improvements include replacing poles, wires, and other equipment to better withstand wind and ice and retiring older substations and upgrading portions of the electric system these facilities serve.

Replacing electric cable
Approximately $605 million will be invested to accelerate the targeted replacement of approximately 1,000 miles of distribution cable, typically installed underground, to prevent frequent and extended outages.

Replacing or retiring aging substation equipment and small substations
Approximately $21 million will be allocated to proactively replace aging substation equipment, including switchgear and associated equipment like transformers, within substations to prevent issues before they occur. Nearly $300 million will also be dedicated to retiring additional small, obsolete substations. ...

None of that addresses generating *more* electricity that EVs will consume. OK, there's this:

... In addition to improving service reliability in targeted areas, the system improvements will also pave the way for additional clean energy resources, like solar, and support vehicle electrification throughout the service territory. Retiring aging substations and upgrading portions of the electric system with new equipment and increasing the voltage of nearby circuits also increases the ability to support more customer-owned solar generation facilities. Ensuring reliable power also becomes more critical as the use of electric vehicles expands and customers increasingly rely on charging capabilities at their homes for vehicles.

So it "paves the way" for more solar. But we can't rely on intermittent renewables for things like a peak EV charge demand on holidays. What are they going to do, announce " Hey, EV owners, cancel your Thanksgiving trip to Grandma's, we are getting a week of cloudy conditions, with low wind. There's always 'Zoom' and a frozen turkey TV dinner!"? Or maybe we should be pushing hybrids/plug-in hybrids (which can bypass the charger for gas when needed)?

-ERD50

 

[NW-Bound]

^^^ I would think that if PG&E and Southern Edison spend money on the infrastructure, their main focus will be on minimizing the PSPS (Public Safety Power Shutoff) due to potential wildfire in the presence of strong winds.

The home owners deserve higher priority than EV drivers.

 

[Popeye]

I question how far that goes toward supporting some large shift to EVs, as some predict (or mandate!). More from that link:



None of that addresses generating *more* electricity that EVs will consume. OK, there's this:



So it "paves the way" for more solar. But we can't rely on intermittent renewables for things like a peak EV charge demand on holidays. What are they going to do, announce " Hey, EV owners, cancel your Thanksgiving trip to Grandma's, we are getting a week of cloudy conditions, with low wind. There's always 'Zoom' and a frozen turkey TV dinner!"? Or maybe we should be pushing hybrids/plug-in hybrids (which can bypass the charger for gas when needed)?

-ERD50

This is their distribution side of the business. So they focus on that aspect. Personally I worry more about the local grid than generation. We have lots of nuclear generation in their service area. I remember them claiming it was about 60% of the generation. At some point generation will be the constraint but overloading the local grid in a neighborhood inside a city like Philadelphia has the potential to be a problem much sooner.

PECO is a subsidiary of Exelon. Exelon is in the middle of separating the two halves into separate companies. One for the utility business and one for the generation business. The generation company is looking to be majority nuclear. They plan to grow by acquiring nuclear plants as other do similar splits. They did just play chicken with Illinois. They started the process to retire two plants but then the state came up with some money for them. They reversed course and will keep the plants open.

I think there’s a lot going on in this industry with mergers and spin-offs. It will surely be interesting times ahead.

 

[Montecfo]

I pass by a Tesla charging station about once a week. (It's about 70 miles away and it's the closest one around here) I think it has about 7 or 8 stalls and usually they are all vacant... Sometimes I'll see one car there and "once" I saw two.

Still not mainstream here.

It will be a long time before they are. Range and charging time a non-starter (grin) for most folks. Plus cost is prohibitive even with heavy subsidies.

 

[Popeye]

Indeed, the United States is undergoing a shortage of a range of transformers — spanning smaller, pole-top units on city streets to Virginia Transformer’s massive units — for reasons that vary depending on the equipment. That means utilities could struggle to add enough new wind and solar generation to meet the country’s net-zero goals and to keep the lights on when storms damage their depleted transformer stockpiles.

https://www.eenews.net/articles/how-a-transformer-shortage-threatens-the-grid/


Apparently there’s a transformer shortage! I haven’t heard this before. This is why changes to complex systems need a comprehensive plan. It seems everyone else makes them more cheaply than the US and they are struggling to hire folks to increase production. I’m sure some of this is hungry piggies squealing for some govt money. They want a wage subsidy program. But I can imagine the factories making these can’t ramp up overnight.

 

[NW-Bound]

https://www.eenews.net/articles/how-a-transformer-shortage-threatens-the-grid/

Apparently there’s a transformer shortage! I haven’t heard this before. This is why changes to complex systems need a comprehensive plan. It seems everyone else makes them more cheaply than the US and they are struggling to hire folks to increase production. I’m sure some of this is hungry piggies squealing for some govt money. They want a wage subsidy program. But I can imagine the factories making these can’t ramp up overnight.

I have not heard about transformer shortage either. There have to be other things that we also need.

From the above article:

To reach the Biden administration’s goal of a zero-carbon grid by 2035, U.S. generation capacity would have to triple compared to its 2020 level, according to a recent report from the National Renewable Energy Laboratory. Power line capacity nationally would have to double or triple.

Tripling generation capacity is one thing, but if the new generation is by renewable energy, has anyone figured out how much energy storage will be needed to match supply to the demand? And how much it will cost?

 

[Car-Guy]

has anyone figured out how much energy storage will be needed to match supply to the demand? And how much it will cost?

They can't be bothered with such minor details.

 

[acronymous]

For grid storage and other fixed applications, redox flow batteries look very promising. Various chemistries are being evaluated.

 

[Koolau]

I have not seen utilities voicing much concern. I think they don't want to be seen as "anti-green". If I were them, would wait until there's a problem then say, "gimme money to fix the problem you created". Else, you get accused of crying wolf.

Oil and gas companies are doing the above. Way better to wait for the customers to come crying to you.

I agree that the utilities are sitting pretty right now. Once they are strained for production, they'll look like hatchlings in a nest waiting for the gummint to bring them food. So as they raise their prices (hey, new electricity is expensive) "we" will actually be paying for their expansion. May be time to buy their stock but YMMV.

 

[Koolau]

^^^ I would think that if PG&E and Southern Edison spend money on the infrastructure, their main focus will be on minimizing the PSPS (Public Safety Power Shutoff) due to potential wildfire in the presence of strong winds.

The home owners deserve higher priority than EV drivers.

Unfortunately, it is becoming clear that the "actual" needs of consumers is taking a back seat to gummint policy demands. Does anyone think a "few" consumers who routinely have their power cut to prevent forest fires will trump adding more SuperChargers? YMMV

 

[Koolau]

They can't be bothered with such minor details.

I just wonder if there is anyone in "power" actually educated in the subject sufficiently to understand how important the details are. For want of a nail, and like that... YMMV

 

[Koolau]

For grid storage and other fixed applications, redox flow batteries look very promising. Various chemistries are being evaluated.

Heh, heh, let us know when those are available. Seriously, the technology is advancing rapidly - so rapidly that it may be difficult to commit to a given technology for fear that the "next big breakthrough" will render the "current standard" obsolete in a few months. YMMV

 

[Car-Guy]

I just wonder if there is anyone in "power" actually educated in the subject sufficiently to understand how important the details are. For want of a nail, and like that... YMMV

IMO, that's easy to answer... NO!