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Model S and Model X Sharing Same 100 amp service?

[email protected]

Supporting Member
Sep 30, 2014
79
180
United States
All: Model S charges on our antique 100 amp (50 amp breaker) service. Pretty soon, we hope, big brother Model X 12121 will be sharing the charging. Issue: if they both are charging at the same time, I think we will have overload and our old Zinsco breaker either will trip or it will be Ms. O'Leary's cow all over again....So, the cars have to charge serially. I do not want to get up at 4 a.m. and switch the plug, so I want to plug both cars in and go to bed. One car can charge, and then the other. If the timers are set correctly , no problem. If not, there could be one. Query: do the cars talk to one another to ensure there is no overload? If not, they should because I am certain we are not going to be the only ones with this issue, and it could be a problem....Tailwinds! John MS 41448
 

liuping

Active Member
Jul 23, 2013
2,242
896
San Diego
All: Model S charges on our antique 100 amp (50 amp breaker) service. Pretty soon, we hope, big brother Model X 12121 will be sharing the charging. Issue: if they both are charging at the same time, I think we will have overload and our old Zinsco breaker either will trip or it will be Ms. O'Leary's cow all over again....So, the cars have to charge serially. I do not want to get up at 4 a.m. and switch the plug, so I want to plug both cars in and go to bed. One car can charge, and then the other. If the timers are set correctly , no problem. If not, there could be one. Query: do the cars talk to one another to ensure there is no overload? If not, they should because I am certain we are not going to be the only ones with this issue, and it could be a problem....Tailwinds! John MS 41448

You can dial both cars down to 20 Amps and they could both charge at the same time with no more load on the Service panels than one charging at 40 Amps.
 

gjunky

Trifecta: Solar and both cars are EVs
Mar 26, 2012
1,251
407
Scottsdale, AZ
Why don't you set the charge rates on both cars to a lower rate? Not sure what you meant with 100a / 50a breaker. I assume that means you have a panel with a 100a capacity and charging the Model S on a 50a breaker. That would mean your Model S is now charging at 40a (220v). Can you set them both at 20a to avoid an overload? They will of course take twice as long to charge (each) but the total charging time will roughly be the same.
 

thimel

Member
Feb 27, 2015
605
471
We have a Nissan LEAF and a Tesla Model S. We have just one charging station and charge each one every other night. If you don't do too many miles a day, this might work for you.
 

omarsultan

Active Member
Jun 22, 2013
2,910
7,968
Northern California
We will have the same issue, albeit with a 100A breaker on 200A service. I will add a second HPWC when the MX arrives, but I am not sure what I will do:
1) Dial down each HPWC to only charge at 40A
2) Let each charge at 80A and use the charing timers to make sure each vehicle charges serially

I do wish Tesla has a two-headed charger with logic like the SC charger, so it intelligently shares the circuit.
 
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FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
All: Model S charges on our antique 100 amp (50 amp breaker) service. Pretty soon, we hope, big brother Model X 12121 will be sharing the charging. Issue: if they both are charging at the same time, I think we will have overload and our old Zinsco breaker either will trip or it will be Ms. O'Leary's cow all over again....So, the cars have to charge serially. I do not want to get up at 4 a.m. and switch the plug, so I want to plug both cars in and go to bed. One car can charge, and then the other. If the timers are set correctly , no problem. If not, there could be one. Query: do the cars talk to one another to ensure there is no overload? If not, they should because I am certain we are not going to be the only ones with this issue, and it could be a problem....Tailwinds! John MS 41448

I would never recommend anyone charge *any* EV on any considerable load with a Zinsco breaker panel - that's very, very dangerous considering how many faults and fires have been considered with Zinsco and Federal Pacific (US) panels. I double my recommendation for 2 EV's - even if you have timers set, if there's any chance whatsoever that both could charge at once, you'd have a pretty significant risk for a fire.

If you haven't read up on the dangers of Zinsco panels, I'd recommend that you do so.

The cars do not communicate with each other. I'd recommend working with an electrician - consider replacing your main panel and upgrading service at the same time; while it will cost a few thousand dollars, it will provide you with the right infrastructure to charge 2 EV's and most importantly, will be safe.
 

goneskiian

Active Member
Nov 16, 2012
2,621
810
Bellevue WA
All: Model S charges on our antique 100 amp (50 amp breaker) service. Pretty soon, we hope, big brother Model X 12121 will be sharing the charging. Issue: if they both are charging at the same time, I think we will have overload and our old Zinsco breaker either will trip or it will be Ms. O'Leary's cow all over again....So, the cars have to charge serially. I do not want to get up at 4 a.m. and switch the plug, so I want to plug both cars in and go to bed. One car can charge, and then the other. If the timers are set correctly , no problem. If not, there could be one. Query: do the cars talk to one another to ensure there is no overload? If not, they should because I am certain we are not going to be the only ones with this issue, and it could be a problem....Tailwinds! John MS 41448

I would never recommend anyone charge *any* EV on any considerable load with a Zinsco breaker panel - that's very, very dangerous considering how many faults and fires have been considered with Zinsco and Federal Pacific (US) panels. I double my recommendation for 2 EV's - even if you have timers set, if there's any chance whatsoever that both could charge at once, you'd have a pretty significant risk for a fire.

If you haven't read up on the dangers of Zinsco panels, I'd recommend that you do so.

The cars do not communicate with each other. I'd recommend working with an electrician - consider replacing your main panel and upgrading service at the same time; while it will cost a few thousand dollars, it will provide you with the right infrastructure to charge 2 EV's and most importantly, will be safe.

Thanks FlasherZ. I thought I'd read that name (Zinsco) somewhere recently...

In the Home Charging FAQ on the Tesla Motors website:

Will I need to upgrade the electrical panel of my home?

A licensed electrician will need to do a load calculation on your home to determine how much power is available for home charging.Homes which are more likely to need a utility upgrade are homes with only 100 amp services, many large electrical appliances, or older unsupported electrical panel brands such as Federal Pacific, Zinsco, or Sylvania. Note that most modern homes have a 200 amp electrical service and may need a utility upgrade to support a Wall Connector installed with a 100 amp circuit breaker.

Home charging installation | Tesla Motors
 

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