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Charging two Teslas

Subhuman

Member
Aug 1, 2013
538
1,018
United States
I have a question about charging two Teslas at once.

I currently have a Model 3 and the wife will be getting a Model Y tomorrow. My current electrical setup is a 200 amp service to the house with a 100 amp sub-panel in the garage. I currently have a Tesla HPWC on a 60 amp circuit charging the Model 3. I also have a 14-50 outlet on a separate 50 amp circuit ready to go for the Model Y. I plan on using a corded mobile connector for the Model Y.

Since the HPWC uses a max of 48 amps and the mobile connector uses a max of 32 amps, is there any issue charging both vehicles at the same time?
 

Subhuman

Member
Aug 1, 2013
538
1,018
United States
Is there anything else on the garage subpanel? Or just the EVSEs? Because charging both at the same time will be 80 amps out of the 100.

Just the garage door opener, a few fluorescent tube lights and number of standard 110 outlets throughout the garage. There is nothing else constantly running.
 

tezzla

Supporting Member
Jul 14, 2013
650
282
SoCal
I have my model 3 starting to charge at 10pm (lower rates from 10pm-8am) and set my wife’s model Y charge to finish at 8am. We don’t really drive that much and have never come close to overlapping.
 
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Subhuman

Member
Aug 1, 2013
538
1,018
United States
You can always dial down the amps if you’re concerned. Do you NEED to charge at max rates to cover your daily driving needs?

I have a long commute and typically arrive back at home with about 20% charge in the summer and commonly end up at 5% remaining in the winter. I charge to 90% every day. It takes about 6 hours to charge. I do get home as late as 8:00 pm often enough which puts charging complete at about 2 in the morning. I leave around 6:30 in the morning so I could get away with slower charging. However sometime I do need to charge as fast as possible if I have something going on at night that I might have to leave the house for ( I.e. dinner, kids practice, etc) This is were I wouldn’t want to slow charging down.

I thought about scheduling my wife’s car to start charging after 2 am but she is also usually home before me and could be charging while I’m not home.
 

HelixSpiral

Member
Oct 19, 2018
89
100
Cincinnati
If each car has its own appropriately sized circuit and the subpanel is a full 100 amps I don't see a problem from the garage end of things. But we don't know the load calcs for your whole house.
 
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Wshowell

Member
Jan 1, 2015
507
353
Arroyo Grande Ca
Thanks for the info Wshowell but I already have the two charging plugs installed so no need to split one outlet. My question is more in regards to capacity of the sub panel and overloading my breakers.
I reread your post after I posted and saw that you had already prepped for the two. I jumped the gun. I do concur that dialing down at the car level would be a good solution. Just because it’s a Nema 14-50 doesn’t mean the car needs to pull 40 amps. It remembers what rate to charge at via GPS. Remember with the HPWC you can also dial it down there too if you were worried about the car trying to pull full power. We have 2 HPWCs and since we aren’t ever really in a rush to charge I have both cars limited to pulling 30 Amps at our home and connected even though they are on 50 amp breakers. Our house is a 1972 construction and if we are heating our spa, drying clothes AND charging two Tesla’s, that might be more than our 50 year old breaker box needs to endure.
 

Subhuman

Member
Aug 1, 2013
538
1,018
United States
If each car has its own appropriately sized circuit and the subpanel is a full 100 amps I don't see a problem from the garage end of things. But we don't know the load calcs for your whole house.

My house originally only had a 100 amp service. I upgraded it to a 200 amp services a few years ago and added the 100 amp subpanel in the garage at the same time (it was 60 amp). Other than adding the Teslas, no loads have changed to the house. Since I never had an issue with the 100 amp services it should be safe to say that the remaining amperage should be good for the house.
 

Needsdecaf

Active Member
Dec 16, 2018
1,034
1,189
The Woodlands, TX
Switch the 14-50 and get another HPWC and connect them so they talk. Set maximum amps you want each one to run and they will load balance as needed.

But having said that, if you have the two breakers, you theoretically should be fine. That's why you only run 80% load of what the breaker is rated for. Personally I wouldn't want to high powered continuous draws pulling on the panel for that many hours. But I'm conservative.

One other thing to consider is that running the UMC on a 14-50 outlet, that device will max at 32 amps out of a potential 50 anyway, so you're already quite a bit below capacity. If you turn down the HPWC a bit off it's max, you'll be running both breakers with plenty of headroom.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
6,106
7,087
Boise, ID
Switch the 14-50 and get another HPWC and connect them so they talk. Set maximum amps you want each one to run and they will load balance as needed.
Probably not possible. @Subhuman didn't exactly say, but I would think this is a version 3 wall connector, not the version 2. The version 3 STILL doesn't have circuit sharing implemented!!
One other thing to consider is that running the UMC on a 14-50 outlet, that device will max at 32 amps out of a potential 50 anyway, so you're already quite a bit below capacity.
No--he already mentioned this:
I plan on using a corded mobile connector for the Model Y.
This is the "Corded Mobile Connector". It is based on the older Generation 1 mobile connector, so it does pull 40A, not 32A.
 

Subhuman

Member
Aug 1, 2013
538
1,018
United States
This is the "Corded Mobile Connector". It is based on the older Generation 1 mobile connector, so it does pull 40A, not 32A.

This is good to know. I was looking for information on the corded connector but could not find anything which is why I was assuming that it would pull 32 amps same as the current mobile connector.

Is this information listed anywhere on Teslas site? Knowing that it pulls 40 amps does change the calculus a little.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,106
7,087
Boise, ID
This is good to know. I was looking for information on the corded connector but could not find anything which is why I was assuming that it would pull 32 amps same as the current mobile connector.
Well, it costs twice as much, so it would have to have SOMETHING going for it with not having the flexibility of changing the plug type.

Is this information listed anywhere on Teslas site? Knowing that it pulls 40 amps does change the calculus a little.
No, it's not, which is very frustrating. They used to list the 40A on the old UMC, and they list 32A on the new UMC, but the never listed the current capability on this Corded one, which is stupid. And that's why that question gets asked repeatedly on this forum, because Tesla doesn't say.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,106
7,087
Boise, ID
Use the Model 3s umc On the Y and you should be fine
@Subhuman Yeah, I hadn't brought this up because it wasn't a question you had asked, but I don't see why there would be the need to go buy a Corded Mobile Connector. Both cars will come with a charging cable. Just buy the 14-50 adapter plug ($35) for one of them and use that.
 

TJKR

Member
Aug 11, 2018
103
75
California
I know someone who've had 2 Teslas for years.. they got a Gen 1 HPWC for their first Tesla. On 2nd Tesla they just use the UMC on 120V with intention of getting another HPWC. 2 years later they are still using 120V outlet on the 2nd car.

If you are not driving 100+ miles on each car daily, you can live with just one HPWC. If you have a supercharger near by, not even an issue.
 
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elptxjc

Member
Dec 15, 2019
752
143
El Paso, TX
I assume the garage is part of the 200 amps, right? Otherwise, you'd need a sub-station. That being the case, you could charge both cars as long as the other big current users are not working, which are the A/C units, and the drier (if using 220). Unless super hot like here in TX, where my A/C can run at any time, you could charge at night, and enjoy the cheapest rates, plus basically no other high electrical load, so no issues :). Good luck.
 

davewill

Active Member
Feb 5, 2014
1,823
1,966
San Diego, CA, US
It all sounds fine to me. It would be worthwhile to be sure it's all in good repair. If you just had them put in professionally, then that should be the case. I charge two EVs at the same time in my garage. In my case, both EVSEs are limited to 30a, with one on a 40a circuit and one on at 50a circuit.
 

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