AC Charging between 10 and 19.2 kW ?

[jlsoaz]

As best I can tell on a quick look the present L2 J1772 standard allows for AC Charging up to 19.2 kW, but the highest AC Charging I can see evidence of in the American markets is 10 kW (Toyota RAV4 EV).

http://www.toyota.com/rav4ev/features.html#!/mechanical_performance/4480" onclick="window.open(this.href);return false;

I realize there may be things here I'm not getting right, but I am wondering if anyone can help me understand:

Is there such a thing as AC charging out there in this sparse area between 10 and 19.2 kW? Perhaps in Europe (Renault?). If not, why not? Is it a matter of the weight and cost of the onboard charger? Are there regulations in the US or elsewhere pertaining to going above 10 kW AC charging?

What about DC Charging below the 20 or 30 kW range, does this exist for EVs?

The lack of extended discussion (at least, from what little I can find) as to this mathematical middle ground seems a bit odd to me. In theory, that speed of charging would be something I'd be interested in, in some situations. Maybe it's just a matter of the fact that DC fast charge is faster and requires less onboard cost and weight.

 

[TomT]

Tesla has 20Kw available on the S.

As best I can tell on a quick look the present L2 J1772 standard allows for AC Charging up to 19.2 kW, but the highest AC Charging I can see evidence of in the American markets is 10 kW (Toyota RAV4 EV).

 

[GRA]

As best I can tell on a quick look the present L2 J1772 standard allows for AC Charging up to 19.2 kW, but the highest AC Charging I can see evidence of in the American markets is 10 kW (Toyota RAV4 EV).

Tesla has 20Kw available on the S.

And the HPWC for the Roadster was in that range too. I think all the public chargers that Tesla installed for the Roadster (many of which have since been converted to J1772 plugs) were rated for 70A @ 208/240 V.

 

[KJD]

As best I can tell on a quick look the present L2 J1772 standard allows for AC Charging up to 19.2 kW, but the highest AC Charging I can see evidence of in the American markets is 10 kW (Toyota RAV4 EV).
http://www.toyota.com/rav4ev/features.html#!/mechanical_performance/4480" onclick="window.open(this.href);return false;
I realize there may be things here I'm not getting right, but I am wondering if anyone can help me understand:

When you look at how much the CHAdeMO equipment costs and then compare that to the high powered AC equipment it makes you wonder why not use more of the AC units. This clipper creek unit is a fraction of the cost of any DC charge station.

http://stores.intuitwebsites.com/ClipperCreekInc/-strse-9/CS-dsh-100/Detail.bok" onclick="window.open(this.href);return false;

If the LEAF could make use of that power it could do a full charge in just over an hour right ?

 

[LTLFTcomposite]

6.6 seemed like it was a long time coming but I too have wondered why not 10kw or more. Does the fatness of the cable become an issue?

 

[planet4ever]

When you look at how much the CHAdeMO equipment costs and then compare that to the high powered AC equipment it makes you wonder why not use more of the AC units. This clipper creek unit is a fraction of the cost of any DC charge station

You're trying to compare light switches with computers. That high power Clipper Creek station you pointed to is still just a fancy switch, like all EVSEs. It doesn't modify voltage; it doesn't change AC to DC; it doesn't have to match the voltage and current the battery controller asks for. It just passes house current straight through to the car.

To do high power AC charging you need a large, heavy, expensive charger built into the car. To do DC charging, you don't use any charger built in to the car. All the weight, size, and cost is outboard (except for the cost of the battery controller computer). The car just passes the QC current straight through to the battery.

Ray

 

[cwerdna]

Tesla has 20Kw available on the S.

From http://www.teslamotors.com/models/design" onclick="window.open(this.href);return false;, they seem to want $2700 for that. I doubt that includes installation for a High Power Wall Connector and any required electrical work. 240 volts @ 20 kw = 83.3 amps.

 

[KJD]

When you look at how much the CHAdeMO equipment costs and then compare that to the high powered AC equipment it makes you wonder why not use more of the AC units. This clipper creek unit is a fraction of the cost of any DC charge station

You're trying to compare light switches with computers. That high power Clipper Creek station you pointed to is still just a fancy switch, like all EVSEs. It doesn't modify voltage; it doesn't change AC to DC; it doesn't have to match the voltage and current the battery controller asks for. It just passes house current straight through to the car.

Yes I know that. Simple is good. More reliable that way.

To do high power AC charging you need a large, heavy, expensive charger built into the car. To do DC charging, you don't use any charger built in to the car. All the weight, size, and cost is outboard (except for the cost of the battery controller computer). The car just passes the QC current straight through to the battery.

In the home built world the price difference between a 30 amp charger and a 75 amp charger is about $1600. When you look at how much faster the LEAF would charge this seems like a reasonable amount. No need to put it on every car, but offer the option to those that want it.

The difference in weight of the these 2 chargers is 18 pounds. I think the LEAF could handle that.

http://www.manzanitamicro.com/products?page=shop.browse&category_id=14" onclick="window.open(this.href);return false;

 

[Woosie]

I figure when Nissan gets around to offering a true 150-200 mile range Leaf, total charge time still needs to fit within a 4 - 6 hour timeframe, to accommodate charging overnight. A6.6kWh AC charger won't cut it, so something between 10-12 kWh AC charger is needed. So, the J1772 plug interface will still support t his need...one less thing to think about.

 

[Randy]

My experience is that many people reach a threshold of difficulty with their home electrical panel/service when attempting to install a 100 amp branch circuit that would be needed to charge their Tesla at 20 kW. In many cases, it will involve expensive upgrades.

If your panel is 400 amps, adding 20 kW seems to work most of the time.
If your panel is 200 amps, adding 20 kW may work some of the time with no mods (depends on what else you have).
If your panel is 100 or 125 amps, you will probably not be able to add 20 kW of charging load legally (with a permit). You probably don't have enough panel or main feeder capacity...
If your panel is less than 100 amps, the best you can probably hope for is a 20 amp circuit or maybe a 40 amp circuit if you're very lucky and even then it may be a problem....

And here's an infrastructure nugget that you may find interesting. At the utility where I work, about half of all transformers feeding customers are nameplate rated for about 25 kW. And they are shared between an average of 6 homes...That alone is one reason why utilities are extremely interested in knowing about the location of high powered EV charging. Transformers will have to be changed out to accommodate high powered charging in many cases....

High powered EV charging isn't as simple as it appears...

 

[Woosie]

Good point about the panel. Luckily, I have a newer 200A panel so I should be fine.

 

[siai]

I know it was engineered for it but it just looks to me like the J1772 connector isn't going to be reliable at high power. I noticed that the area around the end of the connector gets a little warm when charging my LEAF with it's 6.6 KW charger vs. my older LEAF with the 3.3 KW. With the 6.6 KW charger the EVSE is delivering a little under 30 amps. I can't imagine running over twice that current though the pins on the connector. If there was any mositure, dirt or minor damage in the connector (which will find it's way in at public stations) it seems like a failure waiting to happen. I have read that the pins on the higher current EVSE's are silver plated and there are different recepticles to handle higher current. Although I have never done it to the LEAF (because it is leased) I do own a I-MiEV that I charge at just under 12 KW with a DC charger that draws a little over 50 amps off the A/C line. At 360 volts (which the I-MiEV operates at) the DC current is only 33 amps which is much easier to handle through the connector then the lower voltage/higher current AC. Non of the connectors or cables get warm at all during the charge which lasts just about one hour from low battery warning to 80%. The reason I go only to 80% is that the charger is only a constant current then a constant voltage charger that has no way of comunicating with the vehicle. For safety reasons (although the balancers are operating and I can monitor the cell voltages) I don't want to risk a cell overvoltage. All that being said, I feel that if you need to charge above the levels of the 6.6 KW charger on a normal basis, there should be some way of doing it without going up to the levels (and charge rate) of the Chademo. There should be some style of home "charger" not EVSE that could be used through the Chademo port (or should I even mention the SAE combo plug) that would work in the 10 to 20 KW range. There is no need for most people to carry around a larger, heavier built in charger in the car and then deal with a J1772 public EVSE infrasture that is usually limited to 30 amps.

 

[arnolddeleon]

I know it was engineered for it but it just looks to me like the J1772 connector isn't going to be reliable at high power. I noticed that the area around the end of the connector gets a little warm when charging my LEAF with it's 6.6 KW charger vs. my older LEAF with the 3.3 KW. With the 6.6 KW charger the EVSE is delivering a little under 30 amps. I can't imagine running over twice that current though the pins on the connector.

Check with your EVSE vendor to make sure that you don't have a defective nozzle. There are known cases where nozzles are defective and cause excessive heating at higher current draws which should not have been a problem.

http://www.mynissanleaf.com/viewtopic.php?f=26&t=10749" onclick="window.open(this.href);return false;

arnold

 

[jlsoaz]

Thanks for the various points and responses, thought-provoking and helpful.

One side-point is that a reason for my puzzling over this is not over-focus on speed of charging (personally I am fine with L1 charging under some circumstances), but I have just found it a bit of conspicuous puzzler not to see more discussion of this kW middle ground.

Since cost and weight and volume trade-offs seem to be a big part of the issue, along with several other things such as questions about real-world higher-kW capability of J1772, it might be useful for us to set up a credible table of these trade-offs and expected changes particularly on upcoming cost changes, to get a better idea of what we're talking about. So, for residential, something like:

Residential charging:

AC 3.3 kW
AC 7.2 kW
AC 15 kW
AC 20 kW
DC 10 kW (possible?)
DC 15 kW
DC 20 kW (+)
Wireless (not sure of the power ranges or other parameters here):
Wireless (not sure of the power ranges or other parameters here):
Wireless (not sure of the power ranges or other parameters here):

For each of these columns something like:

estimated Cost of off-board equipment, now and 5 years from now.
estimated Cost (or range of cost) of installation of off-board equipment, now and 5 years from now.
estimated Cost of onboard equipment now & 5 years from now.
estimated Volume and weight penalties of onboard equipment now & 5 years from now.
efficiency
durability
safety & health
other notes/comments on pros/cons.


One additional question that comes to mind is whether, in theory, the AC charging, with its onboard weight and cost penalties, is really necessary at all. I guess a DC Fast-charger generally is at present something like $20k just for the equipment, but could it be $0.5k-$2k for a lower DC charger? Just asking the question, probably there are some good answers.

Keeping an open mind, am conscious also of needing to learn more about how wireless shapes up in this table, including as to the onboard volume, weight and cost penalty side of things.

 

[Nubo]

There's a great book from physicist Richard Feynman ("Surely You're Joking, Mr. Feynman!")

This passage illustrates, I think, a principle that may apply to this charging question.

I went over to one of the other guys and said, "You're a mechanical engineer; I don't know how to do any mechanical engineering, and I just got this job.

"There's nothin' to it," he said. "Look, I'll show you.

There's two rules you need to know to design these machines. First, the friction in every bearing is so-and-so much, and in every gear junction, so-and-so much. From that, you can figure out how much force you need to drive the thing.

Second, when you have a gear ratio, say 2 to 1, and you are wondering whether you should make it 10 to 5 or 24 to 12 or 48 to 24, here's how to decide: You look in the Boston Gear Catalogue, and select those gears that are in the middle of the list.

The ones at the high end have so many teeth they're hard to make. If they could make gears with even finer teeth, they'd have made the list go even higher. The gears at the low end of the list have so few teeth they break easy. So the best design uses gears from the middle of the list."


I had a lot of fun designing that machine. By simply selecting the gears from the middle of the list and adding up the little torques with the two numbers he gave me, I could be a mechanical engineer!

 

[TonyWilliams]

Tesla has 20Kw available on the S.

From http://www.teslamotors.com/models/design" onclick="window.open(this.href);return false;, they seem to want $2700 for that. I doubt that includes installation for a High Power Wall Connector and any required electrical work. 240 volts @ 20 kw = 83.3 amps.

80 amps at 250 volts = 20kW

 

[planet4ever]

240 volts @ 20 kw = 83.3 amps.

80 amps at 250 volts = 20kW

So does 100 amps at 200 volts. Not sure what your point is, Tony.

Ray

 

[wwhitney]

80 amps at 250 volts = 20kW

So does 100 amps at 200 volts. Not sure what your point is, Tony.

I believe his point is that the Tesla charger draws up to 80 amps, and Tesla calls the charger 20kW on the basis of a 250V nominal supply.

Wayne

 

[TonyWilliams]

240 volts @ 20 kw = 83.3 amps.

80 amps at 250 volts = 20kW

So does 100 amps at 200 volts. Not sure what your point is, Tony.

Ray

The point is that it doesn't pull 83.3 amps... the Tesla HPWC is rated at 80 amps and 250 volts to get 10kW. Above 250 volts (like it experiences when installed at a Supercharger station on one leg of 480 volts, or 277 volts), it ramps down the amperage to 36. It does not exceed 10kW.

It won't pull 83.3 or 100 amps. The J1772 limit (at Tesla's insistence) is 80 amps, up from 30 amps originally.