Keeping the Solar Panels alive with Powershare

[zeke]

TLDR; scroll down to see a 15kW dual inverter solar panel array stay online during a power outage thanks to Powershare

The story:

March 2024, I took delivery of my truck. It was obviously a very early build with vin in the 4xxx so I knew I was gonna have to work out the early adopter kinks. Like some others, I immediately tried getting and installing the Powershare system but it was a headache all around. I got a grotesque quote from the only installer Tesla trained for these installs and decided to look elsewhere. I eventually convinced a Tesla certified electrician to take the Powershare class and install the system for me, granted I was able to procure the 3V Gateway. A cool $3000 later, the system was up and running!

At the time, solar panels were not allowed on the supply side of the Gateway box so even after pleading with my electrician to at least set up the wiring, he left it where it was, upstream of the Gateway. That meant no solar panels during outages since I don't have fixed batteries in my home.

Fast forward to early last year when solar became supported by the Powershare system. My original electrician ghosted me so I worked with another one that was also willing to learn to do these installs. He comes over, moves the 15kW of solar into the Gateway (mind you, no one could tell us if all 15kW were allowed or if it was too much). We go test it and have no luck.

What we found out later that day was that around that same time of the install, I hit the dreaded PCS2 inverter failure.

No problem. Tesla said 2 weeks to get me in and fix the problem. Naturally that wasn't the case. Day of, after having taken a day off of work, they tell me the part isn't there yet and that I'm pushed back a month. A few weeks go by, the second PCS2 fails so now I'm charging only on DC chargers. The day comes again and they tell me another month.

I just got back the truck with 2 new PCS2 inverters and what do you know, a huge storm hit here in southern NH that took out the grid for a bit. Sure enough, both my SolarEdge inverters detected the micro-grid that the Gateway + truck create and turned on!

In this image you can see how the grid is disconnected (net usage), how my inverters are putting out about 6.5kW of AC power, how my house (Sub panel) is using 2k, and the rest is being dumped back into the truck.

I couldn't ask for a better system. I mean, I could though, as in one that wasn't proprietary and could be installed by any skilled electrician. But this will do for now.

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[Driving D Truck]

My solar puts out more than 13kw regularly, so it’s connected outside of the powershare gateway because I wasn’t sure what would happen if the truck’s charging plus the home usage were somehow less than that amount.

 

[mongo]

The specified solar limit is 11.5kW of AC production (max 60A breaker). I think that is to align with Cybertruck's maximum charge rate.
Ideally, if there is too much production, Cybertruck will shift voltage or frequency to curtail the solar inverters. It must, to handle when the pack is full. However, this control ability is probably linked to the relative capacity of the two systems. Too much solar and the truck might lose control of the micro-grid.
One could put 10kW on the backed up side and 5kW on the grid side to stay within the limits.

 

[zeke]

The specified solar limit is 11.5kW of AC production (max 60A breaker). I think that is to align with Cybertruck's maximum charge rate.
Ideally, if there is too much production, Cybertruck will shift voltage or frequency to curtail the solar inverters. It must, to handle when the pack is full. However, this control ability is probably linked to the relative capacity of the two systems. Too much solar and the truck might lose control of the micro-grid.
One could put 10kW on the backed up side and 5kW on the grid side to stay within the limits.

Would've been nice for my installer to know this. He even talked to Tesla support and they said they weren't sure but to go with 7kW just in case.

I unfortunately can't split my inverters because their output is combined upstream, and splitting them would require a new emergency disconnect switch which means a full redesign of the system specs.

However, my inverters rarely get above 12kw since one points south and the other east. By the time the 10kw inverter is reaching peak capacity, the 5kw is already on its way down.

My plan will be then to manually turn off the 5kw inverter during outages to keep the system safe, though it'd be nice for their engineers to explain this limitation better. I like your theory about the controls not being able to handle the higher amperage, I just don't understand why that would be the case. I thought it was more about the rated capacity of the busbar than the DC control board. Maybe it's only rated for 100A and they don't want to exceed the combined theoretical maximum in the scenario where:
- the house calls for a full 100A
- the truck provides 48A (11.5kW at 240v)
- the panels produce 48A (11.5kW at 240)

In that case, you're still below the 100A busrating

But if you have solar producing 15kw, or 62A, and the house is calling for 130A, the system will work, but you may overheat that tiny busbar on the supply side.

If that's the case, I get why they put in those limits, but it's such a difficult scenario to hit that it'd be easy to stay below the threshold manually

 

[mongo]

Would've been nice for my installer to know this. He even talked to Tesla support and they said they weren't sure but to go with 7kW just in case.

I unfortunately can't split my inverters because their output is combined upstream, and splitting them would require a new emergency disconnect switch which means a full redesign of the system specs.

However, my inverters rarely get above 12kw since one points south and the other east. By the time the 10kw inverter is reaching peak capacity, the 5kw is already on its way down.

My plan will be then to manually turn off the 5kw inverter during outages to keep the system safe, though it'd be nice for their engineers to explain this limitation better. I like your theory about the controls not being able to handle the higher amperage, I just don't understand why that would be the case. I thought it was more about the rated capacity of the busbar than the DC control board. Maybe it's only rated for 100A and they don't want to exceed the combined theoretical maximum in the scenario where:
- the house calls for a full 100A
- the truck provides 48A (11.5kW at 240v)
- the panels produce 48A (11.5kW at 240)

In that case, you're still below the 100A busrating

But if you have solar producing 15kw, or 62A, and the house is calling for 130A, the system will work, but you may overheat that tiny busbar on the supply side.

If that's the case, I get why they put in those limits, but it's such a difficult scenario to hit that it'd be easy to stay below the threshold manually

I can't image it's a busbar thing since the grid can supply 200A versus Powershare's 48A.

My guess it is so that Powershare can suck up all generation if needed to regulate the waveform. Similarly, it can pickup all load if the solar suddenly drops out. Not that there is any guarantee that the home isn't pulling over 11.5 kW, but that's on the user.

 

[zeke]

I can't image it's a busbar thing since the grid can supply 200A versus Powershare's 48A.

My guess it is so that Powershare can suck up all generation if needed to regulate the waveform. Similarly, it can pickup all load if the solar suddenly drops out. Not that there is any guarantee that the home isn't pulling over 11.5 kW, but that's on the user.

But that busbar is independent from the 200A path from the grid to the main service. I was just looking at the gateway box itself and it's isolated from the load and line sides so it might still be the case.

Otherwise, what happens if the truck is at 100% charge? it can't take ANY charge at that point so it wouldn't matter how little solar you have. It should be doing a frequency shift to make the panels shut down at that point.

 

[mongo]

But that busbar is independent from the 200A path from the grid to the main service. I was just looking at the gateway box itself and it's isolated from the load and line sides so it might still be the case.

Otherwise, what happens if the truck is at 100% charge? it can't take ANY charge at that point so it wouldn't matter how little solar you have. It should be doing a frequency shift to make the panels shut down at that point.

The panelboard is 200A bus rated, with the recommendation to put generation toward the top.

Yeah, Cybertruck needs to shift V or F to curtail production and likely has a bit of buffer and/or tapers charging early to prevent the full solar output while going from 99 to 100%.

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