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Old 06-03-2019, 06:28 PM   #1 (permalink)
thingstodo
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Join Date: Sep 2010
Location: Saskatoon, canada
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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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