Power Sharing HPWC

[MXWing]

But it's generally a hotel--therefore overnight--therefore lots of time. It may be a little tight, but do the math. Let's say four cars that all need a pretty big fill up. Maybe 70 kwh each. That would be 280kwh total for the four cars. At a 20kW total feed, that would be 14 hours needed, but that is the absolute worst case with all four being used and almost empty. If any of them gets full, it dynamically allocates the power level among the others, speeding them up. So yeah, most of the time, a 100A breaker will be totally fine for 2 or 3 wall connectors, while 4 may be pushing it.

Makes sense. So the correct answer than is 2 - 100 amp runs and 8 Wall connectors.

Where it gets interesting though is if companies come out with adapters to allow non Teslas to use wall connectors. Imagine people would not be pleased if I plugged in my 16AMP Volt into a destination charger as an example.

 

[MP3Mike]

Where it gets interesting though is if companies come out with adapters to allow non Teslas to use wall connectors. Imagine people would not be pleased if I plugged in my 16AMP Volt into a destination charger as an example.

Why? As long as it does the proper signaling the other 64 amps should be available from the other shared HPWCs.

 

[brkaus]

But it's generally a hotel--therefore overnight--therefore lots of time. It may be a little tight, but do the math. Let's say four cars that all need a pretty big fill up. Maybe 70 kwh each. That would be 280kwh total for the four cars. At a 20kW total feed, that would be 14 hours needed, but that is the absolute worst case with all four being used and almost empty. If any of them gets full, it dynamically allocates the power level among the others, speeding them up. So yeah, most of the time, a 100A breaker will be totally fine for 2 or 3 wall connectors, while 4 may be pushing it.

I was doing the same math. I also think 4 per 100a breaker would work. Everyone isn't going to show up empty. Everyone isn't going to arrive at the same time. 3 should be ideal.

 

[MXWing]

The best way is for each wall connector to have its own breaker. You could put a 100A breaker in the main panel and run wire to a sub-panel close to where the wall connectors will be. Then, put a 100A breaker for each wall connector in that sub-panel. You will also have to run the low voltage communication wire between the two wall connectors. This does not have to follow the same path as the power wiring. Absent a higher or lower spec, I would assume that the low voltage wire should not be longer than 100m (330 ft). I don't think the power has a distance limitation as long as you compensate the wire gauge to avoid excessive voltage drop.

Sub-panels aren't that expensive and breakers run $50 each. I would think it would be easier/more standard to use a sub-panel than a junction box with splices.

Having a breaker for each would also allow maintenance on one HPWC without killing the other.

The cost of the box would be similar, and I don't think the breakers cost a whole lot more than the splicers that are necessary for that size of cable. (You can't just use wire nuts.) So it is really best to go with a small sub-panel and breakers. That way if one fails you can easily de-energize it to work on it leaving the other one still operational. (Though if the master fails you would have to change the setting on the slave to get it working again.)

One 100A breaker in the main panel. This single circuit is shared by all 'connected' HPWCs. From here this circuit feeds either a junction box with splices going to multiple HPWCs or instead a sub-pannel with multiple 100A breakers feeding multiple HPWCs. A sub-panel is used instead of the junction box and the additional breakers provide a disconnect for each HPWC. Many jurisdictions require a disconnect switch, the breakers in the sub panel serve as disconnect switches. The communications wire between the HPWCs assures that total power drawn does not overload the main 100A circuit. Hope this helps.

Would you be be able to please recommend some specific models for good sub panels / circuit breakers to do this setup with?

Thanks

 

[brkaus]

Would you be be able to please recommend some specific models for good sub panels / circuit breakers to do this setup with?

Thanks

My house has GE panels. Big box home improvement stores have several 125A GE panels for sale - surface, flush, indoor, outdoor. 8-16 space panels were ~$30 and 100a breakers are $40.

I'm not sure if any brand is better than the other, sorry.

 

[Rocky_H]

Would you be be able to please recommend some specific models for good sub panels / circuit breakers to do this setup with?

Thanks

Square D and Siemens are also pretty good brands.

 

[gutowskia]

Would you be be able to please recommend some specific models for good sub panels / circuit breakers to do this setup with?

Thanks

Matching your main panel brand is a good idea in case you have to relocate some of the circuits. Your electrician can advise in your particular situation.

 

[TonyWilliams]

I would assume that the low voltage wire should not be longer than 100m (330 ft). I don't think the power has a distance limitation as long as you compensate the wire gauge to avoid excessive voltage drop.

The published limitation is 49 feet / 15 meters, with shielding around the two twisted pairs.

 

[tga]

Matching your main panel brand is a good idea in case you have to relocate some of the circuits. Your electrician can advise in your particular situation.

This. The prior recommendations (GE/Square D/Siemens) are all good, but matching your main panel is probably the right way to go (assuming it isn't something dangerous, like FPE/Zinsco).

Would you be be able to please recommend some specific models for good sub panels / circuit breakers to do this setup with?

Thanks

Not to sound like an ass, but you are planning to hire an electrician for this job, right? If you're asking this question, you probably don't have the experience to safely do the work yourself.

 

[Bryantclan]

Interesting conversation, one question though how many people add the extra charger to bring there charge rate up to 80amps?

We have an X (90) and S (75) on order that show up in Dec. When we bought our current two plugin cars (a volt and a fusion) 3 years ago I installed a 100 amp sub in the garage with the plan of needing more power for charging down the line.

I could not come up without a use case that required adding more then 200 miles over night (and almost always far less) back to each car each night which is really close to there effective range.

How many people really turn there batteries over more then once a day?

My other logic as others have stated was beyond just the service limitaion of 200 amps (which is really 180 continues) the street transformer would very quickly saturate its core in the summer with two cars pulling 80kva.

As it stands with two 40kva chargers we are really close to my main and are eating 80% of the transformer when you add in the house loads.

 

[MXWing]

This. The prior recommendations (GE/Square D/Siemens) are all good, but matching your main panel is probably the right way to go (assuming it isn't something dangerous, like FPE/Zinsco).


Not to sound like an ass, but you are planning to hire an electrician for this job, right? If you're asking this question, you probably don't have the experience to safely do the work yourself.

Correct. A man's go to know his limitations.

Just had some electricians do the work today.

I went with the recommended advice. 100Amps to a Subpanel. And then 100 Amps to each Wall Connector on a separate 100 Amp Breaker.

 

[agloutney]

I have purchased two 2nd generation wall connectors to replace my original one and set them up for load sharing. Still gathering all the parts I'll need but so far haven't been able to source the required communications wire. Anyone know where you can get 18 AWG 2 conductor shielded wire rated to 600V?

 

[araxara]

I have purchased two 2nd generation wall connectors to replace my original one and set them up for load sharing. Still gathering all the parts I'll need but so far haven't been able to source the required communications wire. Anyone know where you can get 18 AWG 2 conductor shielded wire rated to 600V?

All you need is RS485 cable. RS485 is the interface that's used on the Wall Connector. I picked mine up from eBay. Here is a link to the one I bought: 60ft feet RS485 Signal Transmission Cable for Control CCTV PTZ Security camera | eBay

Previous to using this cable, I used some shielded twisted pair wire. I also had problems with my HPWCs at the time and after replacing the wall connectors, I switched to RS485 cable. Have not had any issues since then.

As a side note, the problems I had with my wall connectors were probably due to lighting strike (both wall connectors were dead). I also installed a surge suppressor in my dedicated breaker panel after installing the new wall connectors.

 

[jelloslug]

I have purchased two 2nd generation wall connectors to replace my original one and set them up for load sharing. Still gathering all the parts I'll need but so far haven't been able to source the required communications wire. Anyone know where you can get 18 AWG 2 conductor shielded wire rated to 600V?

Beldon 3088A has the 600V rating that is speced out.

 

[smorgasbord]

Installing two 2nd gen wall connectors. Using one 100amp breaker and #3 AWG wire (#8 for ground), running in 1" conduit for a total run of about 25 feet. Charging a Roadster and a Model 3 (I believe the Roadster can utilize the full 80 output!) regularly, but friends with Teslas may charge at times.

I'd like to run the communication wire in the same 1" conduit for appearance reasons. To do this I need a suitable cable with the proper insulation rating. Does anyone have pointers a cable with the necessary insulation rating (and what is that insulation rating)?

 

[araxara]

I'd like to run the communication wire in the same 1" conduit for appearance reasons. To do this I need a suitable cable with the proper insulation rating. Does anyone have pointers a cable with the necessary insulation rating (and what is that insulation rating)?

Since the wire is used for RS-485 communication, I don't think you need to worry about insulation rating. See above for suitable wire that I used. The wire above that I got does not have any markings on it, so I can't tell you the rating. The wire is for low voltage and does not need to be in conduit. But if it were in the conduit, the worst that can happen is that the #3 wire melts or something, but that would really not do much as far as safety is concerned, because you would have bigger problems than the insulation rating of the RS-485 wire.

 

[smorgasbord]

Since the wire is used for RS-485 communication, I don't think you need to worry about insulation rating.

I do need to worry since that won't meet code in the US.
Besides, RS-485 cable is typically at best 22ga and Tesla specs 18ga.

 

[brkaus]

I believe the manual says the comm cable must be run in conduit.

Sorry, can’t help on where to find the cable. Someone here posted, but I can’t fibd the thread now.

 

[brkaus]

Actually, a part number is right above your post.

https://catalog.belden.com/techdata/EN/3088A_techdata.pdf

 

[smorgasbord]

Actually, a part number is right above your post.

https://catalog.belden.com/techdata/EN/3088A_techdata.pdf

Thanks, but I can't interpret what is required to match the "insulation rating" of the 3 AWG I'll be using. Here's what the Belden tech sheet says: