Go home ChargePoint, you are drunk! - New home charging station

[eprosenx]

So ChargePoint has released a new J1772 home charging unit:

ChargePoint Home Flex | ChargePoint

Overall, it looks pretty nice. Comes with 14-50 or 6-50 pigtails, or it can be hardwired. It is software settable during setup to its max charge rate (I am not sure how I feel about this, I like the physical rotary dial of the Tesla Wall Connector for such a critical setting). This unit is WiFi connected which probably provides some interesting data possibilities and perhaps better time of use charge control than the Tesla currently provides (though I know at least with the Juice Box there have been issues due to perhaps a Tesla bug on starting charging later).

Note that I am not advocating for this over the Tesla Wall Connector for most Tesla users. The Wall Connector can do up to 80 amps of charging, it can be linked to other units to share a circuit, and most importantly, it has a Tesla connector end which is way more convenient than a J1772 connector (for Tesla owners).

But here is the kind of crazy / weird bit:

The logical rating would have been a max of a 48 amp charge rate (using a 60 amp circuit). But for whatever reason, this unit is rated at 50 amps.

I would argue that this has nearly no practical use as I don't even know of any current production cars that have greater than a 48 amp charger. (all current Tesla's max at 48 amps) Above a 60 amp circuit and you need to have a locking disconnect (though that can be a simple breaker lock-off device).

The unit also has a max wire gauge coming in of 6 AWG, so the only way I see you could actually use the full 50 amps would be to use 6 AWG copper MC cable or THHN in conduit (which is rated to 65 amps assuming 86 degrees Fahrenheit ambient and no other deration), and then you would need to use the "next size up" breaker rule to install a 70a breaker (on 65a wire) which is legit since the load to be served is only 50a * 1.25 = 62.5 which is less than 65 but greater than the next lower breaker of 60a.

It seems unlikely that many folks will try to get the extra two amps out of this. My prediction is a lot of these are installed with 6 AWG Romex and are set to a 40a charge rate, or installed with 6 awg copper rated to 75c on a 60a breaker so set to a 48 amp rate. I somehow doubt a lot will get installed at the full 50a rate, but who knows, maybe!

I am curious how this came to be. Perhaps during testing they realized they could seek a rating just a tad bit higher than 48 amps and the marketing folks jumped all over it so they could be a nice round "50 amps" and they could "beat" the competition that only had 48 amp units?

Weird. Thoughts?

 

[MIT_S60]

It would have been awesome if you could daisy chain these together and split power like the Tesla wall connector.

 

[eprosenx]

It would have been awesome if you could daisy chain these together and split power like the Tesla wall connector.

Yeah, to be honest, I wonder if that might be able to be added later as a software feature. Have them communicate over the network (I have some ideas as to how you could make that fail safe for when communication is lost).

(basically if two share a 60 amp circuit, have them share 48 amps of charge capacity, but if comms between them are lost, have them fall back to just 24 amps each in an isolated mode)

 

[Rocky_H]

The unit also has a max wire gauge coming in of 6 AWG, so the only way I see you could actually use the full 50 amps would be to use 6 AWG copper MC cable or THHN in conduit (which is rated to 65 amps assuming 86 degrees Fahrenheit ambient and no other deration), and then you would need to use the "next size up" breaker rule to install a 70a breaker (on 65a wire) which is legit since the load to be served is only 50a * 1.25 = 62.5 which is less than 65 but greater than the next lower breaker of 60a.

Well sure. I found the installation FAQ page for it, and it does specifically show in the table that to use the 50A delivered current setting, you need to use a 70 or 80 amp breaker.
ChargePoint Home Flex Installation FAQ | ChargePoint

 

[yuhong]

I think this is much like the labeling of the UMC as 30A even though 32A is actually used.

 

[eprosenx]

Well sure. I found the installation FAQ page for it, and it does specifically show in the table that to use the 50A delivered current setting, you need to use a 70 or 80 amp breaker.
ChargePoint Home Flex Installation FAQ | ChargePoint

Yeah, I read the install guide here:

https://www.chargepoint.com/sites/d...ePoint Home Flex Installation Guide CPH50.pdf

I get the 70 amp breaker since that is the "next size up" from the 62.5 amps of required rated current to charge at 50 amps and 6 awg copper can be rated to 65 amps if the wire is allowed to be used at the 75c rating (i.e. not NM cable). I do not understand how using an 80 amp breaker could be allowed since you can only use 6 AWG wire maximum. Weird that they mention it in the manual. Perhaps it could be allowed since the ChargePoint home says its terminal is rated to 105c and so if you used THHN it can be rated at 90c which allows 75 amps, so the next size up would be 80?

Just odd.

 

[doghousePVD]

Quote: I would argue that this has nearly no practical use as I don't even know of any current production cars that have greater than a 48 amp charger. (all current Tesla's max at 48 amps) Above a 60 amp circuit and you need to have a locking disconnect (though that can be a simple breaker lock-off device).

Models S and X pre-2019 can charge at 72A, and some can charge at 80A. I am sure the pickup truck and the new roadster will charge at least at 72A. (They will have 200 kWh batteries). I wouldn't be surprised if the "plaid" new S also has a fast charger.

 

[eprosenx]

Quote: I would argue that this has nearly no practical use as I don't even know of any current production cars that have greater than a 48 amp charger. (all current Tesla's max at 48 amps) Above a 60 amp circuit and you need to have a locking disconnect (though that can be a simple breaker lock-off device).

Models S and X pre-2019 can charge at 72A, and some can charge at 80A. I am sure the pickup truck and the new roadster will charge at least at 72A. (They will have 200 kWh batteries). I wouldn't be surprised if the "plaid" new S also has a fast charger.

Yes, totally agreed on all points you make. ;-) But my original statement holds true as well! No current production vehicle (Tesla's at least) charge at over 48 amps as currently being sold.

But indeed, the Tesla truck is going to have to charge faster I am sure!

 

[eprosenx]

Quote: I would argue that this has nearly no practical use as I don't even know of any current production cars that have greater than a 48 amp charger. (all current Tesla's max at 48 amps) Above a 60 amp circuit and you need to have a locking disconnect (though that can be a simple breaker lock-off device).

Models S and X pre-2019 can charge at 72A, and some can charge at 80A. I am sure the pickup truck and the new roadster will charge at least at 72A. (They will have 200 kWh batteries). I wouldn't be surprised if the "plaid" new S also has a fast charger.

Also, I was thinking about this in the context of needing to go up to wire larger than 6 awg (say 4 awg) just to get the extra two amps which does not seem like it would make financial sense, but clearly since the unit won't support 4 awg on its terminals then they intend you to do this with 6 awg at the 75c insulation rating, so I guess that makes more sense. You kind of get those extra two amps "for free" if you ran THHN wire or MC or something (other than the delta cost between a 60a breaker and a 70a breaker and the fact that you need a lockoff method).

 

[Eno Deb]

Better two amps too much than two too few.

I think the main attraction is that it is a connected unit that integrates with the Chargepoint app.

 

[yuhong]

Better two amps too much than two too few.

I don't think anyone cares either way, for many reasons.

 

[eladts]

Well, their commercial charge stations are limited to 30A instead of 32A you would expect with a 40A breaker. Go figure.

 

[Rocky_H]

Well, their commercial charge stations are limited to 30A instead of 32A you would expect with a 40A breaker. Go figure.

Yeah--it's almost like Chargepoint was leaving a bit more margin for...better reliability.
I'm sorry! I couldn't keep a straight face!

 

[eprosenx]

Well, their commercial charge stations are limited to 30A instead of 32A you would expect with a 40A breaker. Go figure.

Hah, excellent point. It is just weird on both fronts. (a lot of stations are only 30 amps for some weird reason - I wonder if it has to do with the rating on common J1772 handles, perhaps from other countries)

Also, another note: Their published charge rates are under selling this unit. They are quoting charge speeds at say 48 amps that are lower than what a M3 can charge at.

Their FAQ also insinuates that a GFCI breaker is only required by NEC if your EV charging receptacle is outdoors which is just totally false. (I mean, it sounds good and I think that is a more reasonably policy, but it is certainly not what is written in the 2017 NEC)

 

[davewill]

Hah, excellent point. It is just weird on both fronts. (a lot of stations are only 30 amps for some weird reason - I wonder if it has to do with the rating on common J1772 handles, perhaps from other countries) ...

I always figured that getting the extra two amps was going to require a bump up in wire size that wasn't worth it when planning thousands of stations. Tesla does things differently, using two smaller wires in place of one for each of the hot wires, resulting in a smaller more flexible cable.

The 30a J1772 cable I bought back then is a thick, stiff beast compared to either the Gen1 or Gen2 UMC cables.

 

[JeremyWhaling]

I wonder if it has to do with the rating on common J1772 handles, perhaps from other countries

Yep, that's it. Yazaki, ITT, and others including the one ChargePoint uses are commonly 30 amps. There are 32 A J1772 cables of course, but for some reason, not as common.

Ether 30 A or 32 A use the same circuit (40A), so it's not an upstream wiring issue. Likely to increase margin maybe but what's two amps between friends, eh?

 

[eprosenx]

Yep, that's it. Yazaki, ITT, and others including the one ChargePoint uses are commonly 30 amps. There are 32 A J1772 cables of course, but for some reason, not as common.

Ether 30 A or 32 A use the same circuit (40A), so it's not an upstream wiring issue. Likely to increase margin maybe but what's two amps between friends, eh?

You are probably on to something here. Maybe we are the only country with the complicated/ambiguous derating rules for continuous loads (plus all the countries that just follow the US NEC). I bet Europe has much simpler conductor sizing rules.

So yeah, perhaps ChargePoint builds their EVSE's around the max rating of the J1772 handles or the handle cords they use, which in this case may be 50a?

Who knows!!!

 

[CarbonFree]

It would have been awesome if you could daisy chain these together and split power like the Tesla wall connector.

National code does not allow this.

 

[miimura]

National code does not allow this.

As long as the connected devices ensure the loads are non-concurrent or the aggregate load is within the code requirements of a single device, it is allowed. Tesla, JuiceBox Pro, and Clipper Creek all sell EVSE that do this. ChargePoint certainly could if they wanted to.

 

[JeremyWhaling]

ChargePoint does as well, their CT4000 line can be put on one 40A circuit. If only one car is connected, it gets 30A. If two cars are connected and charging, each gets 16A. There's a beefy jumper to connect the two circuits together in the unit, and a configuring step during commissioning.