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Bad practice to make a rule out of single occasion. If Tesla removed some automation from M3 assembly line half a year back, it doesn't meant that all of them will be made by hand in couple years.
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Charging two Teslas at once?
- Thread starter Keith909man
- Start date
whitex
Well-Known Member
Not likely you'll be done in a hour like you claim. Out of curiosity, with all your worries about future proofing, why did you only run AWG4 instead of AWG2 or bigger (for future faster chargers you think are coming)? Your entire argument was how the wire gauge increase is a tiny cost and everyone should go max. Knowing that HPWC can handle up to 80A charging, why didn't you prewire with AWG2? Even if your car can't take 80A, if you have 2 cars, combined they will almost for sure.
We originally put two 14-50 outlets in the garage about 4 years ago. At the time, we had NO Teslas and the wall connectors didn't support load-balancing. Eventually we bought two Teslas but we really only charged one at home since I had free charging at work. Soon we got a third Tesla and I changed jobs and no longer had free workplace charging. We had to pay more attention to when we would charge since we had two outlets but three cars. We ended up replacing the two 14-50 outlets with three wall connectors. They are wired to allow 80 amps but we currently only have them on an 80 amp breaker providing 64 amps of continuous load. This allows us to charge three cars simultaneously without having to worry about when we plug in or when we schedule the cars to start charging. We actually have four Teslas in the garage currently but only three of them are daily drivers. The fourth car can be charged via 6-20 or 5-20 outlets or with a WC if one of the other cars isn't plugged in.
Anyhow, I would suggest planning for the future if the budget allows. We ended up having to rewire almost everything when we put in the wall connectors. The wiring for the 14-50 outlets is still there but they aren't currently hooked up. Had I known we were going to buy eight Teslas in three years (and if the WCs would've supported load-balancing at the time), we would've just installed WCs originally.
Anyhow, I would suggest planning for the future if the budget allows. We ended up having to rewire almost everything when we put in the wall connectors. The wiring for the 14-50 outlets is still there but they aren't currently hooked up. Had I known we were going to buy eight Teslas in three years (and if the WCs would've supported load-balancing at the time), we would've just installed WCs originally.
davewill
Active Member
Your point is valid enough, although there are plenty of J1772 EVSEs available that have 14-50 plugs on them. Clipper Creek, JuiceBox, and OpenEVSE for starters. Jesla deserves a mention as well. Your neighbor could have bought one of those and used it with your plug while waiting for his electrical work to be done, then either just plugged it in at his place, or had it hardwired in. However, expecting a random visitor non-Tesla owner to have one in his trunk (I do, but I'm weird) is a bit optimistic.
Something else to consider. Most of you are talking about NEMA 14-50 which requires 4 wires. 3 #6 Hot-Hot-Neutral and one #10 ground. A NEMA 6-50 does not require a neutral. Neither does the HPWC. Price the wire/conduit/install difference. It may be worth buying a 6-50 adapter which you can carry with you while on the road.
Sure, I know there are many companies that sell wall mounted EVSEs with 14-50 plugs. I was responding to that comment of a "visiting EV" just stopping by your house and being able to plug in with a cord they have with them, and that isn't likely. ...unless it's you.
Discontinuing the 80A and then further discontinuing the 72A is more than one occasion. My wife in supply chain planning has a saying: "Three points form a trend line." We're almost there.
No, you can't use the 90°C column on the table. Even if your wire were rated for it, the HPWC isn't, and you'll have that hot wire melting the plastic bits inside the HPWC. Assuming you ran THWN or similar wire, you're looking at 85A rated, 68A continuous, and the HPWC set at 64.
Unless the wire you ran was Romex or NM-B, which would put you down to 70A rated and 56A usable.
Ampacity Charts - CerroWire
davewill
Active Member
Actually, that IS three points. Max available was 80a, then 72a, now 48a. Personally, I think it's the end of the trend, and they are unlikely to make the max offered any lower, but I don't see any reason to assume it will rise in the foreseeable future and plan charging installs with that assumption. I would not be surprised, however, to see the max a new wall connector can handle drop at some point. Bigger wires are expensive and heavy. If the cars can't use it, why keep offering it?
Above that's about an answer I gave to somebody else who believes that his #6 is rated for 75A, and uses it for 80A-capable HPWC.
Anyway, would be interesting to see how the circuit with 80A max HPWC configured for 72A behind 90A breaker can come to 95A continuous.
And BTW, transition point for cheapest ABS is 108°C.
whitex
Well-Known Member
We all do what we think is best. Personally I build for what I need now, and worry later how to upgrade. I used to worry ahead of time and too many times my upgrade preparations ended up being "close but not quiet what I want" when the time to upgrade came. I will be installing the second HPWC probably this spring or summer (already have it in a box, just don't feel like working on it when it's cold and wet - had it not taken 9 months to arrive it would have been installed last summer). I could wait to see what charger the Taycan will need and pre-build for it, as it's likely going to replace my Tesla in 2020, but I figure I'll worry about it if and when it comes. I do have a NEMA 14-50 by each car for temporary setup if needed (even though it's half as capable as a direct hardwired line).
It was rather astounding how badly they fell behind on fulfilling those signature wall connector orders. I'm still at 8 months and counting waiting on one from June last year.
MacGreiner
5YJ
I received 4 of them in the past few days so they must be fulfilling the backlog.
Residential breakers terminals max out at 75C as well.
And both of them were talking about charging at 48A on a 60A circuit. #6 THHN in conduit is good for 65A.
Just to reiterate, I'm advocating for using #4 by default even at 48A. Don't think current rating may be a concern even after Tesla re-enables 70..80A charging rate.
Would be more interesting to see what everyone thinks about dual HPWC load sharing from single #6 wire, that has been promoted here as one of best solutions.
Would be more interesting to see what everyone thinks about dual HPWC load sharing from single #6 wire, that has been promoted here as one of best solutions.
whitex
Well-Known Member
I'm going to take an educated guess here. From wiring perspective it's the quickest to install - no safety disconnect required for 60A, easier to work with wires, gives you up to 48A shared between 2 cars. Many homes don't have more than 48A to spare anyways without a more advanced load balancing system (there are some which work with HPWC, throttling cars down when you turn on your oven or a hot-tub kicks in). Given then most Teslas max out at 48A today, it is the best bang for your buck - each car can max out if needed, but usually they share to get overnight refill. If you go with AWG4, you still can't use a bigger breaker without a safety disconnect - those are bulky and cost money. AWG4 wire is more expensive, harder to work with and requires a larger conduit too. Even if you leave a bunch of slack in boxes, you still have to open up existing conduits and pull wires (which after a while will not move easily) in order to upgrade. All that said, most people with 2 cars will be quiet happy with 48A shared system, and probably will never upgrade anyways.
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