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Power walls only operate when receiving solar energy, will not discharge at night

Jagwease

Member
Dec 12, 2014
60
44
New Braunfels, TX
TL;DNR: Powerwall +s won’t work unless it is getting solar energy – no output at night. Non-Tesla installer awaiting parts to link older solar array production and consumption monitoring to TEG

Background:

I live outside Tesla Energy Service area so I have to pay the Vig for a 3d party installer. The installer is VERY familiar with Powerwalls and install lots of them.

I have a 20KW Sun Power system with 3 Sunny Boy String inverters.

After the Texas fun in February, I decided to use some of my gains from the market and add another 10KW and Powerwalls. The Vig kept me to 2 PW in my allowed budget.

At install they put the 10KW system into the Gateway and wired the gateway below the 20KW system. The 20KW system is not wired into the gateway. They plan to connect the production and consumption monitoring for the 20KW system into the gateway, but Tesla “didn’t send the right connectors” and they are awaiting those parts to finish the monitoring. Unfortunately, parts move at Elon Standard Time so they can arrive anytime between 2 days and when the sun’s coronasphere engulfs the planet.

After all was installed on 1July, I wanted to do a grid cut off test, but two critical 60 amp breakers weren’t able to be installed because things did not get transferred from the design notes to the wire diagram, so the test would have been somewhat pointless as the A/C would not be on.

Over the 4th of July weekend I noticed that power was bring supplied at night and my 20KW system was sending power to the grid during the day and the PW were working to power the house. I found this odd and not very economical. Also, there was no energy from the grid coming or going. On my 10KW system monitoring with Sun Power, power used is always power produced

For the remainder of the year I am on a fixed rate ~0.11 a KWh bought and a ~0.05KWh sold (after production exceeds demand for the month). Next year it goes time based with $5 a KW (not KWh) during Super Peak (for solar users). The buying and selling energy issues aren't critical now, but could be in a year.

I have contacted the installer with many questions and reminded them that they repeatedly told me I would be able to use my legacy solar monitoring and consumption system despite them saying I would be using the Tesla primarily. They are contacting Tesla for their input on Powerwall oddities.

I have contacted Tesla and they said it was wired wrong (no kidding) because she could not see any grid activity. She did not know if that would cause the system to shut down at night. She sent the problem further up the tech chain to see if there was a gateway or PW issue as well. Four days, no further response from Tesla.

I do understand that the PW can only take so much energy in, but does it make sense that I am selling energy while using power walls? I don’t think so. I am guessing I am not the only one who has more production than the power walls can take and it isn’t wired to “waste” the created energy.

Is the lack of the proper monitoring connections from the legacy 20KW the root cause of some/all of the problems regarding PW use? I think the Gateway sees the 20KW system as “the grid” and I don’t know if the proper parts to the monitoring will fix that. It may, but the level of people at the installers I have reached so far don’t know (to be fair, I have a newbie supervisor overseeing the project).

I am confident it will be resolved as the company does stand behind their work and I get that my system is a unicorn with a pre-existing string inverter system with added micro inverter system added, so I cut them a lot of slack.
 

arnolddeleon

Supporting Member
Supporting Member
Jul 21, 2012
894
951
SF Bay Area
A few questions that would make it a little easier to help:

What mode are you running the Powerwalls (e.g. Self Consumption, Backup Only, or Advanced)? What is your goal with your Powerwalls? Peak shaving? Self consumption? Backup power?

What are you reserves? It's possible that your batteries are "depleted" to your reserve by the time nights comes along. I'm guessing you have sizeable loads given the size of your PV arrays. 2 Powerwalls roughly give you only about 26 kWh.

A wiring diagram would be helpful. I'm guessing based on your description of the wiring that the existing solar would not be available to you if the grid went down. The installers probably are doing that to avoid the case of too much solar production not being absorbed by the Powerwalls (max charge rate of the two Powerwalls you have is only 10 kW). Assuming no other considerations I would have moved all the solar behind the gateway so it is all available to me in an grid down situation. Odds are there will be enough load to absorb the excess solar. In your particular case, with three inverters, it would be possible to shutdown individual inverters if needed. Basically worst case is you turn all off the excess solar off, no worse than not having them available.

Powerwalls supplying power and solar being sold to the grid is a valid state for both balanced and cost savings.

It is pretty critical for the system (gateway/Powerwall) to have Current Transducers (CTs) to all the PV and loads if you want it to work in "all" situations although I can easily imagine a configuration that works reasonably well enough if you don't have everything.

String vs Micro Inverters should be pretty much a non-factor. Integrating an existing PV system is very doable (multiple in my case).
 
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Jagwease

Member
Dec 12, 2014
60
44
New Braunfels, TX
Have tried all modes. When was noticing the issue first it was on self powered mode (because that was one of the two modes available at commissioning), I generally leave it on self powered mode after I found it made no difference whether the PW would work at night.

Reserves set at 16%. Reserves were ranging from 100% to 10% depending on cloud cover when sun went down, Tesla asked me if I had power at night. I do from the grid

Just checked my app again and after 10 days, it now is detecting the grid, but still no go on self powered mode after the sun goes down, The fauilure to see the grid seems a Tesla issue.

I get that the types of inverters are irrelevant until you get to having too much energy to the PW in a grid down case.

Per the installers, everything should be able to monitor everything for use and consumption when whatever missing parts arrive. Right now, my 20KW system is reading the consumption of what remains in the main breaker box and production of the 20 KW system. The10 KW monitoring system is reporting "use" where the TEG is sending power to the grid. Consumption remains equal to production in the Sun Power App. The 10KW system parts for monitoring were unaffected, it was the parts for the 20KW system.

Unfortunately my CO-OPs smart meter data is generally backwards looking after the bill is posted, so I do not have contemporaneous data from them.

I have attached the wiring diagram from the proposal.
 

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Jagwease

Member
Dec 12, 2014
60
44
New Braunfels, TX
So it was a Tesla issue after all. The batteries are now discharging at night. I am receiving data from the grid as well. Now to see if I get more functionality when the other production and consumption is attached.
 

arnolddeleon

Supporting Member
Supporting Member
Jul 21, 2012
894
951
SF Bay Area
If you're seeing the grid usage correctly then it would seem the only thing missing is the solar production from the old 20 kW system.

I'm assuming it is not a surprise to you that your original 20 kW solar will go offline if the grid goes down.

Did Tesla tell you what was wrong? Is your system considered "commissioned/having received permission to operate" by Tesla? If you had access to "Advanced" modes then I would guess so.

If I understand correctly once things are setup correctly you will configure for Advanced cost savings mode and try to cover the super peak period.
 
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Jagwease

Member
Dec 12, 2014
60
44
New Braunfels, TX
If you're seeing the grid usage correctly then it would seem the only thing missing is the solar production from the old 20 kW system.

I'm assuming it is not a surprise to you that your original 20 kW solar will go offline if the grid goes down.

Did Tesla tell you what was wrong? Is your system considered "commissioned/having received permission to operate" by Tesla? If you had access to "Advanced" modes then I would guess so.

If I understand correctly once things are setup correctly you will configure for Advanced cost savings mode and try to cover the super peak period.
Tesla never told me what the issue was.

I did know at least some of the 20KW system would go off line in a power outage situation, Awaiting a conference call with designer on how best to optimize system in non-power out situation, It is apparent we talked past each other during the design meeting and I caught most of the errors before the first part of install. Some were glaring (PV panels in areas that were prohibited by the HOA, over metal roof vents, adding extra subpanels, not adding blowers - which made it to notes, but not to final drawings), others were beyond my humanities degree ability to read a wire diagram.
 

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