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Tesla Only Wall Charger or Tesla Universal Wall Charger (House Power Share Feature)?
- Thread starter davenlei
- Start date
Or put in a critical loads panel and a generator transfer switch and connect to the outlet in the bed. Extra points if you show the electrician the generator specs from an off the shelf generator and hide the Tesla.
Don’t forget there isn’t a neutral in the Tesla plug or the WC. So that will need to be addressed if islanding during a power outage.
Don’t forget there isn’t a neutral in the Tesla plug or the WC. So that will need to be addressed if islanding during a power outage.
So I ended up ordering the universal charger with powershare capability. I know I will need a gateway but have been planning for those expenses anyway down the line. I would rather just get the wall charger with powershare for futureproofing when I do get to that point. Tesla site says will ship in a few weeks.
Eric33432
Member
I am wondering how the car can send 120/240 volt split phase power into a house during a power failure since there is not a neutral pin on the NACS connector?
In the case of my Tesla solar inverters, they too only have the 240 volt connection (and a ground) to my electrical service. There is no neutral. But they only work when connected to the grid, and use the secondary of the poco transformer as an autoformer to power 120 volt loads that need neutral current. That is one of many reasons they will not work when there is a power failure.
Certainly to power a home will require additional equipment to convert the 240 only Universal Wall Connector output voltage to 120/240 volt split phase power?
In the case of my Tesla solar inverters, they too only have the 240 volt connection (and a ground) to my electrical service. There is no neutral. But they only work when connected to the grid, and use the secondary of the poco transformer as an autoformer to power 120 volt loads that need neutral current. That is one of many reasons they will not work when there is a power failure.
Certainly to power a home will require additional equipment to convert the 240 only Universal Wall Connector output voltage to 120/240 volt split phase power?
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Eric33432
Member
Yeah, but the Tesla Gateway does not have an autotransformer in it. That would be a pretty large piece of steel and copper, and to me not very Tesla-like! And I did not see an autotransformer listed in the Universal Wall Connector requirements for V2H, nor did I see that a Powerwall was required. The gateway is designed to work with the Powerwall, which IS a 120/240 volt split-phase device, so it does not need an autotransformer. They use solid state power-electronics, not steel and copper to develop split phases power. The inverters, since they are grid tie only when operating without Powerwall, can rely on the poco transformer for that purpose. When operating with Powerwall, the Powerwall provides the neutral (split-phase) current.
I think the most desirable way for all this to be set up would be to have everything work like a Powerwall does.
There is, or will be, a new Powershare version of the Tesla Gateway that does have an auto-transformer. (Or you can have at least one Powerwall to provide that functionality.)
Watts_Up
Well-Known Member
Just to be curious, do you know the internal voltage of a Powerwall battery cells?
I wonder it is like the 400V of a Tesla propusion battery or like the 48 V used for home Solar Energy.
Eric33432
Member
I am probably missing something because I don't get why so many people are seeing this as such a huge problem, when it sounds like the answer is totally dead simple.
The backfeed from the wall connector has Hot1 and Hot2. The panel in the house is grounded and has that ground tied to the neutral bus.
So it has Hot1, Hot2, and the center Neutral. All three wires are provided for the full split phase. Why do people think it doesn't and needs extra equipment to create neutral?
The backfeed from the wall connector has Hot1 and Hot2. The panel in the house is grounded and has that ground tied to the neutral bus.
So it has Hot1, Hot2, and the center Neutral. All three wires are provided for the full split phase. Why do people think it doesn't and needs extra equipment to create neutral?
Actually neutral and ground can only be connected together at the first means of disconnect. Everywhere beyond that they have to be kept separate by code. The Gateway is normally your first means of disconnect, unless you have a main breaker before that, likely in the meter panel. So ground and neutral would be bonded in the gateway, but then in your "main" circuit breaker panel, and all sub-panels they have to be kept separate.
You really think that Drew, and Tesla, don't know what they are talking about? (When he says that you have to have a Powershare Gateway, with an auto-transformer, or Powerwall to create the neutral.)
Because you have to be able to flow current on neutral back to the power source. (A 120v outlet won't work without neutral.) But you don't ever want current flowing on ground.
They could likely hack things and make it work by not having a ground, and using the ground pin on the NACS/J1772 port as neutral, but that wouldn't be code compliant. (And would require special wiring in the EVSEs.)
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Eric33432
Member
And because the ground on the car is not connected so that you get 120 volts from each hot line on the NACS connector. It is a strictly 240 volt device. In other words, the 240 volt output is not referenced to the neutral.
Imagine a transformer with a 240 volt output, no center tap like on a normal transformer for split phase. Even if the electrical panel you hooked it to had a neutral bonded to the ground, how could you possibly get 120 volts out of that?
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Watts_Up
Well-Known Member
The battery voltage isn't exposed outside of the Powerwall, so it makes no difference. (They only input/output AC.)
Watts_Up
Well-Known Member
You are right, but what I was wondering was if the Tesla Powerwall was based on similar technology used for solar power components with MOSFET.
or like the Tesla Powerpack who I imagine might be based on high voltage DC with high frequency transfer such as IGBT or Carbide Silicon.
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Dang, so the Tesla Wall Connector that I bought but haven't installed yet won't be able to do this, but if I already have a Powerwall/Gateway, I can buy and install a UWC and potentially be ready for endless off-grid once we have a compatible car (assuming that you can get by with ~5x the daily house usage in battery storage, to account for cloudy days of reduced production) and if you needed more power in an extended outage, there's the possibility of driving the car to a supercharger that does have power and bringing more power home... I wonder/hope that the bidirectional charger can be retrofit the same way some Teslas gained CCS compatibility?
If you already have a Gateway and Powerwall the Tesla Wall Connector will work fine. You only need the Universal version if you don't have a Powerwall.
It is probably possible, but highly unlikely that Tesla will offer a retrofit. (It would likely require replacing a minimum of the PCS inside the battery, which costs around $2k.) I really think they will only offer it on new models, and the warranty will likely have related provisions. (Like the battery warranty being limited to 8 years, 125k miles, or <n>MWhs of energy via Powershare.)
Thanks for the clarification on the Wall Connector for Powerwall owners. That would be great!
I don't want to give Tesla any ideas to increase the price, but even $2-6k would be a bargain for existing Powerwall owners who also have Tesla cars purchased say, a year ago, before 20k price drops. If I sell and upgrade that locks in a 30k or more loss for additional battery functionality with similar car functionality (or in some cases worse since they keep deleting features) so it doesn't look like as much of a deal. But for those who can retrofit for even 6k, a 75kwh home battery for $6k works out to $80/kWh which is unheard of when purchasing just home batteries (that same $6k gets you one 13.5kwh Powerwall after 30% fed tax credit). For those who were going to spend $50k on a new car and have that additional home battery ability essentially for free if they have a Powerwall, that creates a lot of incentive to stick with a Tesla and not a competitor (unless/until there is standardization on protocols).
Instead of Tesla offering an upgrade to a bi-directional on-board charger, I would prefer that Tesla provide a firmware update that's compliant with other bi-directional DC chargers that use CCS like dcBel or Wallbox Quasar. That is a much better solution for Tesla cars that are already on the road. With a CCS adapter and CCS compliant charge port controller, it's just firmware to allow DC to flow out of the vehicle and telling the charger how much it's allowed to take. Heck, they can even charge a fee to enable this feature.
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