Charging Model S and Model X at the same time

[robaross]

What changes will I have to make in my electrical service to charge my twin charger S and twin charger X (both needing full charges) at the same time? Or do I just stagger the charge times, since each will require about 5 hours.

[dsm363]

What changes will I have to make in my electrical service to charge my twin charger S and twin charger X (both needing full charges) at the same time? Or do I just stagger the charge times, since each will require about 5 hours.

You'll need to make the your house has the proper service. Do you know if it is 100, 200A...etc? There are a lot of people on here with more technical knowledge than me but an electrician visiting your house could see what you have and recommend what service you'd need. Staggering charge times would help. Also, dropping your charging to 32A maybe a well.

Most people don't need to charge at 80A at home but if you see the need to do that for your Model S and X at the same time, you may have to upgrade the service to your house depending on how new it is and what service you already have going to your house. Most people would do fine with two separate 50A outlets for those cars. That's what I have for my Roadster and Model S although sometimes charging at 70A would be handy.

[ElSupreme]

What changes will I have to make in my electrical service to charge my twin charger S and twin charger X (both needing full charges) at the same time? Or do I just stagger the charge times, since each will require about 5 hours.

Unless you have 240VAC 200A you need to stagger the start times. The High Speed Charger, and the Car should both be able to do this.

To fully use the twin chargers you need 20kW service or roughly 240VAC at 100A service or better per car. So you can charge the car at 240VAC at 83A or 20kW.

EDIT: These are dedicated or unloaded circuits when you are charging the car. Having your house AC running at night on the same 100A as your car will trip your breaker.

[Todd Burch]

Let's talk reality here:

How often will you need to fully recharge both cars, at the same time, within just a few hours from start of charge to finish? My guess is that such as situation is extraordinarily unlikely...and is probably the only situation that would come close to overloading 200A service (attempts at 2x70A charges)

99.9% of the time, I suspect you can just drop charging rate to 240V@32A each, as dsm suggests. Install 2 NEMA 14-50s (one per car), and perhaps one HPC if you feel you might need higher charging rates.

Personally, my commute is 80mi round trip each day and I can't see needing anything beyond a NEMA 14-50.

[dadaleus]

Agree. I have a HPC 70amp for my Roadster. I'll be putting in high amp charge stations for the S and the X as well. I know I can't run all three at the same time at full amp, but I can't possibly imagine a circumstance where I'd want to do that.

For example, with the Roadster I usually keep it dialed down to 32amp. But I'm glad I have it for those times when I have needed it:
- Guest Roadsters dropping by (always fun). I do have 200amp service and so I've had 1 Roadster charging at 70amp and another at 40amp off the NEMA 14-15 at the same time with no problems. Of course I didn't also have the AC running or I could have been getting close.
- I've had a couple times I forgot to plug it in at night and charged it up in the morning before work
- There have also been times when I was getting sorta low on a standard (non-range) charge from driving long distance for work, got home and charged it at 70amps while I cleaned up for a date with my wife

None of those would require charging two cars at maximum charge rate (except maybe the guest situation) at the same time. But I like having the option to charge one car at the maximum rate for when I do want it. It's all about flexibility.

[doug]

Of course this issue could be easily handled with software. You just say how much range you need and by what time for each vehicle and a computer figures out when to start/stop charging whichever car and at what rate considering a variety of conditions (such as TOU metering, priorities, etc.).

[Eberhard]

i have a 32A 3-phase socket. I can charge on different phases with no problems and can still charge my Roadster on the third phase, doing real 3-phase charging

[dadaleus]

Of course this issue could be easily handled with software. You just say how much range you need and by what time for each vehicle and a computer figures out when to start/stop charging whichever car and at what rate considering a variety of conditions (such as TOU metering, priorities, etc.).

I've always wanted such a feature built into the car software even with just one EV because I have a (possibly superstitious) belief that it's better to charge the car as slowly as possible (to a point at least). I will often plug in with the (non-range reserve) battery nearly depleted knowing that the lowest power rates start at midnight, and I have to calculate in my head what amperage will get it charged by morning. It already knows the start time so it would seem trivial for me to input a target finish time and have it figure out what amperage to use to get there. It could auto adjust the amperage as needed to stay on track as well.

[doug]

It already knows the start time so it would seem trivial for me to input a target finish time and have it figure out what amperage to use to get there. It could auto adjust the amperage as needed to stay on track as well.

Of course. The Model S/X should have all the hardware and communication capability to do it. The Roadster 2.X should have it as well, though it's unclear if Tesla will make that available. It's also unclear whether or not Tesla will get around to implementing such a feature. Though it should be possible with Mark's OVMS project. (Open Vehicle Monitor System (OVMS) - Technical Discussion) managed by your home PC or even a smart phone. There are enough smart people here to make it happen.