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Old 06-03-2019, 06:28 PM   #1 (permalink)
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Chargers that share available power

Which, if any, of the available quick chargers talk between themselves to share the available power?

Let me back up a bit. Much to my surprise, my workplace is looking to Green up their image by (among other things) installing some EV charging in our parking lot.

The general idea appears to be one lighting transformer to be shared by several chargers along one line of the parking lot. There are .. maybe 30? .. parking stalls in this line. I don't expect that the budget will allow for 30 quick chargers. But the stalls that don't have quick chargers should at least get a dedicated 20A 208V weather-resistant receptacle ... which is better than the existing 15A not-weather-resistant receptacles we use for our block heaters in the winter

The largest reasonable size transformer (fits into a parking stall, so we lose just one of them) appears to be about 250 KVA, if we are stepping down to 208V three phase ... but are we? Our input is 575VAC (Canada) three phase. Since some of the quick chargers are up to 800V (last I read) I'm not sure if we can actually step down the voltage. Perhaps I need to drop to 460V instead, or perhaps the chargers boost from 208V three phase? If the charger can be fed directly from 575 VAC three phase, we can use more power (the feeder is 600A) ... then the limiting factor would likely be the size of the cable we are willing to bury.

Having the feeder breaker trip or the transformer overheat is not reasonable. I expect that vendors have figured out a way to share the available power ... but I don't remember reading about that. I think I remember reading that the Tesla chargers measure voltage drop and reduce output based on that.

I'm confident that many people have investigated this and come up with good solutions. I'm not looking for a cutting-edge solution. But it would be nice if it was as future-proof as I can manage.

Thanks in advance!

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Old 06-04-2019, 10:38 AM   #2 (permalink)
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200 ish volt for charging seems universal, not fast but not week long slow so whatever you use up there for dryers should work for stock chargers. The quick charge people go exotic voltages. You might want to look at the appropriate specs because you dont need to go full blown tesla.

Block heater taps would even work. So what if you only half charge dring the work sift, it's free. Charging on 120 for 8 hours would still get me home and back.
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Old 06-04-2019, 12:56 PM   #3 (permalink)
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J1772 don't talk to each other or share the circuit as a as I'm aware.
Only tesla does that and I think they work in pairs.
Then you have 3 or 4 different DC fast chargers at the moment.

They are not going to pay to install DC fast chargers unless it's to do for profit charging. I occasionally see them used and they still run $8,000 to $10,000 each.
I don't know how much they are new.

Just put in some J1772 like everyone else.
Our nation electric code has guidelines for installing evse circuits.
In the US large numbers of public charging stations grouped together normally use 208v.
Then the chargers can be limited to anything from 6 amps all the way to 24 amps for a normal affordable j1772 charge setup.
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Old 06-04-2019, 01:53 PM   #4 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
Our nation electric code has guidelines for installing evse circuits.
In the US large numbers of public charging stations grouped together normally use 208v.
Then the chargers can be limited to anything from 6 amps all the way to 24 amps for a normal affordable j1772 charge setup.
I'm interesting in the 'Then the chargers can be limited to anything ...' part. Is that a manual setting on each charger, or can I install a supervisory controller that talks to these units ... or perhaps there is some other way?

There is presently one model X, a couple of chevy Volts, one Mitsubishi outlander ... I think that about does it for the parking lot survey.

I'd like to think that things will be getting better in the near future. One or two stalls that can give you enough juice to get home if you are only at work for a couple of hours (over-time call-out) would be nice. For the rest of them, I agree for now.

If 'this is important, for some reason, right now' and I have the budget to 'do it better', or have a plan to make it better later but I need to bury a bigger cable ... or whatever boundary condition will limit options ... Well, I'll go as far as I can with the budget I'm given.

Sounds like fast chargers are kinda non-standard. I'll contact the vendors directly and see what they say. I like to have SOME info before I go there
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Old 06-04-2019, 02:13 PM   #5 (permalink)
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J1772 is a simple, cheap, dumb charging protocol it doesn't have instrumentation and controls.
The J1772 sends a signal to the car telling the car how big it is, say a 24 amp capacity, then a car like my old leaf will accept up to 16 amps because that's all it can handle.
Newer cars will take all 24 amps.
The J1772 units don't talk to each other. If they did it would be some proprietary control and evse system. To me that's a waste of money.

The cheapest thing would be to run 4 wire wye 240/480v on 4 gauge wire. That way it can handle 70 or 80 amps.
Let's say 70.
So if you ran 30 charging spots and ran 1 line to 10 spots that would allow for 6 or 7 amp charging on each spot.
What I would do is run 9 spots, 1 line to 3 spots and limit the charging current to 20 to 22 amps or less.

Unless this is for profit charging?
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Old 07-16-2019, 11:08 PM   #6 (permalink)
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The EV charging industry is way less inviting than I was hoping

- J1772 chargers appear to be 230V input
- ChaDemo .. or some variant ... also appear to be 230V but can be 208V 3 phase

Anything higher than 'Level II' is apparently a secret ... and you need to be a dealer ... or have an NDA ... or some other strange silliness ... in order to get information.

No one appears to be taking 'green-washing of dirty industrial sites' as an opportunity to sell/install some product.

If anyone has info on a set of chargers that will co-operate between themselves to 'share' a 600 amp feed at 575VAC 3 phase ... please get me some contact information.

I have 30 parking spots. Not all need to charge all of the time ... for example, 1 charger with an appropriately long charge cable could service 2 or 3 parking spots. But each parking spot not covered by a 'quick charger' would at least get a dedicated 20A 208V weather-resistant receptacle.

Are there any vendors out there that will share some information?

This is an industrial site, that is not selling charging services, but that would like to provide charging for employees and contractors in exchange for looking like a progressive, eco-friendly company. I'm sure that the project will get pasted onto some corporate literature ... so there may be additional sales as other sites seek to implement a solution that has already had the details worked out.
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Old 07-16-2019, 11:20 PM   #7 (permalink)
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Quote:
They are not going to pay to introduce DC quick chargers except if it's to accomplish for benefit charging. I periodically observe them utilized regardless they run $8,000 to $10,000 each.
I got an email saying that the thread had been updated, but could not find this post

If you have vendor info, please pass it along!

I have $30K to gather specs, costs, etc this year in preparation for an install in July 2020.

If it costs $500K, it likely won't get approved. But if I can get something reasonable for $200K it might. Or it might get trimmed to $150K. The $500K install ... which eventually will get done .. since electric vehicles are where we are headed .. may need 2 runs of 350 mcm 3 phase cable buried. The install of the buried cable costs way more than the copper cable. So I'll find the money somewhere to get the right cable buried instead of the minimum cable size for the cheaper option.

I'm *NOT* ripping up the parking lot twice!
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Old 07-17-2019, 05:40 AM   #8 (permalink)
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Most if not all of the public chademo units are 480v 3 phase powered in the US. 3 phase 240 and 208 are probably available for convenience. If you have 480 or whatever is common in Canada maybe 380v? Use that for rapid chargers.

What's providing the power?
Probably start there. Mainly what's the voltage?
Then if it's not a big enough transformer, service feeder, or enough remaining capacity to tie into there may be no point in running an mcm size wire.

I have learned more about the j1772 protocol. It appears that it can change on the fly in 1 or 2 amp steps from 6 to 70 amps. The pilot signal can chang and direct the car to draw less power. But I do not know of any j1772 setups that talk to each other like that to limit the amps on the feeder, but it appears possible and as if that were the intent of the design.
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Old 07-17-2019, 12:59 PM   #9 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
Most if not all of the public chademo units are 480v 3 phase powered in the US. 3 phase 240 and 208 are probably available for convenience. If you have 480 or whatever is common in Canada maybe 380v? Use that for rapid chargers.
575 VAC is the 'normal' industrial voltage in Canada

Quote:
What's providing the power?
The feed is coming from a 1250 KVa transformer, through a load center. The load center breaker is rated for 600A continuous.

Quote:
Probably start there. Mainly what's the voltage?
Then if it's not a big enough transformer, service feeder, or enough remaining capacity to tie into there may be no point in running an mcm size wire.
The cable is over-sized for voltage drop, nominally 3%. 2 runs of 350 MCM is easier to bend around the corners and route into the electrical equipment than a single run of ... 500 MCM maybe?

Depending on which area of the parking lot is dug up and whether they put the cable along a fence or some other area that does not see vehicles parked on top ... 600 - 800 feet from the load center to the common point of the chargers. Sorry for the wishy-washy numbers ... I'm on vacation ... I don't have my design notes handy.

Quote:
I have learned more about the j1772 protocol. It appears that it can change on the fly in 1 or 2 amp steps from 6 to 70 amps. The pilot signal can chang and direct the car to draw less power. But I do not know of any j1772 setups that talk to each other like that to limit the amps on the feeder, but it appears possible and as if that were the intent of the design.
In a best-case future, where electric cars are purchased as quickly as people replace cars ... it is STILL *VERY* unlikely that we would ever see 600A used for charging electric cars and trip the load center breaker, at least for a long time to come. But due diligence dictates that it be looked into. If there are some vendors investigating how to do it ... that's one more column on my technical evaluation spreadsheet.
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Old 07-17-2019, 05:45 PM   #10 (permalink)
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That's such a long run it may be better to have the power company run a service lateral and use a standard residential 37kw pad transformer. But they may have a maximum limit to the length of the underground wire.
If you have 575 volt then you already need a transformer. A residential over head high voltage to single phase is probably cheaper than an industrial 575 to 240v transformer.
To run 37kw on 4,160v they would only need to run about a 12 gauge feeder wire. So the trench, conduit ect would be small, so less parking lot to fix.

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