Question about Adding solar and/or batteries to existing system

[ScubaSteve22]

I have a 9k PV array connected to a SMA inverter and then into a dedicated panel.... I also have 3 powerwall batteries connected to that same panel.

That panel connects in to a Tesla Gateway.

I'd like to add additional PV solar panels... I assume I can just take that new array into a new inverter and add another breaker in that panel and be good to go... no other changes really to be made (assuming the panel, wiring, etc. can handle the additional capacity).

Is that correct?

As far as additional additional batteries go, am I stuck with Tesla Powerwall batteries, or is there some way to integrate non Tesla batteries into the system?

Appreciate any help/guidance!

 

[Vines]

I have a 9k PV array connected to a SMA inverter and then into a dedicated panel.... I also have 3 powerwall batteries connected to that same panel.

That panel connects in to a Tesla Gateway.

I'd like to add additional PV solar panels... I assume I can just take that new array into a new inverter and add another breaker in that panel and be good to go... no other changes really to be made (assuming the panel, wiring, etc. can handle the additional capacity).

Is that correct?

Yes it is pretty much that easy, you will risk your warranty though.
Your new PV will need to be monitored, so it will need to run a wire through the existing CT's which measure your PV production.

You cannot have more than about 7 kW of PV for each Powerwall, so don't install too much solar.

As far as additional additional batteries go, am I stuck with Tesla Powerwall batteries, or is there some way to integrate non Tesla batteries into the system?

Appreciate any help/guidance!

I wouldn't mix and match different AC-coupled batteries within the same microgrid. You could have a cascade system where if one set of batteries runs out then another takes over but this seems overly complicated and with little value.

I would just add Powerwalls if you want to expand since you are already in the Tesla ecosystem.

Are finding that 3 Powerwalls isn't enough capacity? How often do you drain them?

You might consider some smart load management, or even setting up monitoring on a per-circuit basis so you can better understand where your power is going.

 

[tfan2018]

You cannot have more than about 7 kW of PV for each Powerwall, so don't install too much solar.

I wasn't aware there was such a limitation?

 

[getakey]

I wasn't aware there was such a limitation?

yeah confused by that too
what if I have existing solar of 12 kW and later add one PW

 

[jjrandorin]

I wasn't aware there was such a limitation?

yeah confused by that too
what if I have existing solar of 12 kW and later add one PW

Then, you run the risk of, during a power outage, there being too much PV for the powerwall to handle and it shutting everything down. That can be worked around by the installer only allowing "some" of the solar to operate during a power outage (so that it doesnt overload the powerwalls input capability) or, if your install is such that you have lots of roof planes or something where you have a large nameplate system but its not generating that much peak energy at any particular time.

I believe that no more than 7kW per powerwall is what tesla recommends. Like I said, a competent system designer can "design around it, by having part of your PV shut down during a power outage" or if your peak input never hits higher than what one powerwall can take in as peak energy input due to shading, roof planes, angle, etc.

 

[ucmndd]

yeah confused by that too
what if I have existing solar of 12 kW and later add one PW

@jjrandorin explained it pretty well. A powerwall can charge at a max of 5kw.

If you experience a grid outage during peak solar production with a 12kw array, you’re very likely producing more power than a single powerwall and your house loads can absorb, so the powerwall will have no choice but to raise the grid frequency and take your solar offline.

To endure long-term outages, you need solar and storage installed at a reasonable ratio (about 7kw max of PV per powerwall).

 

[tfan2018]

Wouldn't the powerwalls just revert to the behavior before PTO, where excess energy is just lost instead of flowing to the powerwall instead of it outright shutting down (assuming you mean you all power completely despite having a powerwall) because there is too much solar for the powerwall?

 

[ScubaSteve22]

Your new PV will need to be monitored, so it will need to run a wire through the existing CT's which measure your PV production.

The CT for my solar is in between the inverter and the solar/battery panel... so I assume I'd just grab another CT and add it to the same location with my new inverter? Are these Tesla parts purchasable online somewhere?

What about phasing between two different inverters? Do I need to worry about anything regarding sine wave sync between the two? I'm not an electrical engineer, but want to understand things so that when I hire someone I make sure it is all done correctly.

Are finding that 3 Powerwalls isn't enough capacity? How often do you drain them?

Yea, I could definitely use at least 1 more powerwall, but right now I need more solar production.. I'll worry about the battery situation later. Anyone in SoCal have a Powerwall for sale?

 

[jjrandorin]

Wouldn't the powerwalls just revert to the behavior before PTO, where excess energy is just lost instead of flowing to the powerwall instead of it outright shutting down (assuming you mean you all power completely despite having a powerwall) because there is too much solar for the powerwall?

In an off grid situation there is no where for the energy to go. The answer to your question is "no, it will shut down if it gets too much input in an off grid situation". We have had a few people here be subject to it actually. Not only does the powerwall shut down, but because there is too much power and no place for it to go "the system" meaning powerwall, gateway, solar" shuts down with the effect being that you have a big PV system, 1 powerwall and no power at all (in a grid outage).

 

[charlesj]

First thing to do is call your power company and see if they will allow you to add more solar panels.

 

[tfan2018]

In an off grid situation there is no where for the energy to go. The answer to your question is "no, it will shut down if it gets too much input in an off grid situation". We have had a few people here be subject to it actually. Not only does the powerwall shut down, but because there is too much power and no place for it to go "the system" meaning powerwall, gateway, solar" shuts down with the effect being that you have a big PV system, 1 powerwall and no power at all (in a grid outage).

Ok but that still sounds like the situation before PTO where excess solar is just wasted, so what if I toggled permission to operate from No to Yes? then I would expect the behavior to be like pre-PTO where all the excess solar is just "lost"

 

[power.saver]

Ok but that still sounds like the situation before PTO where excess solar is just wasted, so what if I toggled permission to operate from No to Yes? then I would expect the behavior to be like pre-PTO where all the excess solar is just "lost"

It's not the same. Pre-PTO means solar generation never exceeds house plus battery demand and no exports, so there is never any excess generation to contend with if the grid goes down. Pre-PTO you can open your grid breaker and run off-grid just fine, as production won't exceed demand.

In normal post-PTO operation, solar production can exceed house plus battery demand and the excess is exported. This works fine until you get into a very specific situation when solar generation exceeds house demand plus 7kW times the number of PWs. When this happens, and the grid goes down, the total production can exceed the ability of the battery to receive it, and so the PW will shut everything down to protect the equipment from this overload condition. Which is why you should not install more than 7kW of solar for each PW. You could put some of the extra solar on a non-baked up circuit, but it can't be used during a grid outage.

The difference between pre-PTO and post-PTO with overload is due to the instantaneous nature of a grid failure. With pre-PTO the PW will regulate the solar production to prevent overloading, but in post-PTO at the moment the grid fails, there isn't time to wait for the inverters to begin curtailment which takes a few seconds. The system must immediately shutdown when an overload is detected.

 

[tfan2018]

Now I get it, thanks for the thorough explanation

 

[ScubaSteve22]

Hello all!

I have an existing setup with a Tesla Gateway 2, (3) Powewalls, and a SMA inverter supporting a 9kw PV array... this is the 125AMP panel I have where the powerwalls are terminated via 30amp breakers and the PV array is terminated via the 40 amp breaker from the inverter:

I am planning on adding an additional PV array as well as an additional Powerwall.

First off, yes I am going to use a professional licensed electrician, but I just want to have a little data and some basic understanding before I get to that point... so I have a couple questions:

1) With two spaces available on this panel, can I add another 30amp breaker in the top left position to add the additional Powerwall battery?

2) I am planning on going with micro inverters on this new PV array... will I be able to add another breaker in the bottom right spot and move the existing breakers up, to support this new PV array? It'll be either a 40amp or 50amp breaker based on my amateur calculations.

3) Based on the above, that only being a 125amp panel, would that panel need to be replaced with something bigger? I wasn't sure based on adding the breakers up vs. actual maximum real life power moving through everything. I also assume the wires coming off this panel connecting up to the Gateway would need to be verified to ensure they support the total load and weren't undersized when originally installed.

4) Do I need to worry about any kind of phasing issue with having two different PV arrays coming in, one on a string inverter and the other micro inverters?

5) I have a CT on the wires from the existing inverter. Would I also clamp the wires coming from the new micro inverter PV array, or does the Tesla Gateway support multiple clamps for solar input?

Thanks everyone!

 

[TacoGuy]

1). I believe the combiner panel you are currently using is at its maximum capacity (1.25xRated AMPS). The good news is that you can source a new combiner rated at higher current capacity to offset this issue. My current combiner is rated 400A and is also at its limit.

2) I don’t think so per A -> #1

3) Depends on how many batteries you want to install, and how they are interconnected. Rated combination panel should be within 1.25 current spec or lower. If all connections add up to 1.25xRated Current or less you are within tolerance.

4) You will likely need a DC junction before you go through your inverters to add more PV. Assuming you are not past the rated capacity of the MPPTs in your existing inverters, otherwise an additional inverter will be needed.

5) Tesla uses NEMO CTs I believe, they are 3rd party devices that are then linked to the tesla app by tesla.

 

[Big Dunc]

I have just read the above with interest. I have a 10.5 kW PV system, although it is two arrays facing in different directions so never produces anything like that. Most I have seen is 8.5 kW being produced in two and a half years. I have one powerwall.
On a sunny day, I selected "off grid" when the powerwall was full to see how it would behave in a power outage situation. The powerwall increased the frequency to back off the PV system pretty sharpish. It did not shut the whole system down, it just really restricted inverter output to about the house load. I proved this by then starting the car charger and the powerwall allowed the inverter to open up again and dump the power into the car.

 

[jjrandorin]

I have just read the above with interest. I have a 10.5 kW PV system, although it is two arrays facing in different directions so never produces anything like that. Most I have seen is 8.5 kW being produced in two and a half years. I have one powerwall.
On a sunny day, I selected "off grid" when the powerwall was full to see how it would behave in a power outage situation. The powerwall increased the frequency to back off the PV system pretty sharpish. It did not shut the whole system down, it just really restricted inverter output to about the house load. I proved this by then starting the car charger and the powerwall allowed the inverter to open up again and dump the power into the car.

Off grid in the app is not the same thing as a power outage. If you want to simulate this, you need to actually physically throw your main breaker during that sunny full production day. Off grid in the app is not the same, thats the gateway managing it, not a real power outage.

I also have no knowledge whatsoever on how these are setup on power systems outside the US, where in some places its more common for residences to have 3 phase power (vs the US where its not at all normal for a residence to have 3 phase power).

 

[holeydonut]

Off grid in the app is not the same thing as a power outage. If you want to simulate this, you need to actually physically throw your main breaker during that sunny full production day. Off grid in the app is not the same, thats the gateway managing it, not a real power outage.

I also have no knowledge whatsoever on how these are setup on power systems outside the US, where in some places its more common for residences to have 3 phase power (vs the US where its not at all normal for a residence to have 3 phase power).

Agreed, if I actually have a power outage (regardless how much sun is shining or the SoC of my Powerwalls), most of my lights will dim, my internet router/wifi go offline, and all my digital clocks in the Kitchen will reset. Same goes if my neighbor steps outside and opens my big azz 200A utility fused disconnect (it is a very enticing massive lever ... so it's like popping those little circles in the mail packaging).

But if I use the app to go "off grid" then it's a seamless cutoff and there is no service interruption.