Battery Isn't Tied to All Roof Panels

[Jomby]

My goal is to not just charge the battery but be able to power off all 30 panels when grid is down. Currently 15 panels on a cloudy day looks like it would only support charging the battery; no usage.

[Ampster]

Okay, I understand your diagram. Yes during a power outage you can only use half your solar panels. During normal operation the solar connected to the main panel shoul also feed your house loads first before going to the grid. You can test that by turning on more loads.
I think this issue turns on the earlier question by @oregon_phil about the system design goal.

[Jomby]

In diagram below (red arrow) I'm wondering why the 15 panels can't also go to the sma automatic battery backup unit so that if I have substantial draw in daytime with sun up I can power something like my heat pump. Longer term I may add an additional 10 KWH battery for heating during night as my energy during night my usage with no rationing is 1.5 to 2 kwh per hour so I figure cutting out something like the water heater reducing light usage etc. but at least during the day I figure I could either heat up or cool down the house. I don't really have space near my service panel to put generac generator and propane tank. Also at 1.5 kwh my heat pump is more effective than space heaters would be I would think. sketch.JPG

[Ampster]

.....I can see the SMA battery management unit appears to only have one of the solar inverters feeding it while the other goes straight out to main panel. I'll see if I can locate the plan diagram.......

Is your observation based on a diagram that you can share or based on reports that you are seeing when the system is operating? Could it be that you are using less than the system is producing and the excess is being sold? Have you tried to put more load on system and observed if the sell back to grid is reduced?

[chrisski]

Is there a max amperage your BYD bank can charge at?

My 4 12 volt Trojan batteries totaling 458 AH and a little over 5 KW can only be charged with 60 amps. I can put in 13% of total battery power at the 20 hour rate. In theory, I should be able to reach that limit with 800 watts of panels, but because these panels are never in perfect sunlight, it takes me around 1300 watts to reach 60 amps.

Other batteries have different charge rates, and I'm sure for a battery bank twice my size even with a charging chemistry of something that can be charged closer to the full 20 hour rate nine times the panels would come close to exceeding that max charge rate. Don't quote me on this, but lithiums might be charged at up to 100% the 20 hour rate, and AGMs close to 20% the 20 hour rate.

[Jomby]

I think you should get an electrical diagram from your installer. Please have them explain your installation to you. I do not think your installation is built as you described it.

I am guessing the installer installed ONE SMA 7.7 -41 SOLAR inverter for your 10.2kW of solar panels. This inverter converts the solar panel DC to split phase 240VAC.

Your BYD battery is connected to ONE SMA SUNNY BOY STORAGE 6.0 US BATTERY inverter. This inverter converts the battery DC to split phase 240VAC.

The two inverters are electrically connected on the AC side hence Sunny boy storage 6.0 AC coupled architecture. Look up the data sheet on the SMA america website. I believe your set up is configured for "energy management" not "backup system" because you didn't mention a transfer switch.

I could be wrong with my assumptions, but I bet I am close because SMA doesn't make a hybrid inverter.

It sounds like the battery inverter is connected to the sub panel as a critical loads panel, but until you look at the schematic you won't know for sure. I think you have the correct number of inverters.

What was your goal for the entire system? Energy management or backup per SMA brochure?

I should have explained further. There are two inverters 15 panels to each inverter and a separare battery inverter; 3 inverters total. Also I'll look further in the morning but I can see the SMA battery management unit appears to only have one of the solar inverters feeding it while the other goes straight out to main panel. I'll see if I can locate the plan diagram. Is there a limit on how much can go to the sma battery management unit? It looks like 50 is allowed based on sticker and the amps from each inverter appears to be just under 25 amp.

[oregon_phil]

There are 30 panels and 2 inverters; 15 panels to each inverter. Panels are 340 watt.10 kwh BYD battery storage.

I think you should get an electrical diagram from your installer. Please have them explain your installation to you. I do not think your installation is built as you described it.

I am guessing the installer installed ONE SMA 7.7 -41 SOLAR inverter for your 10.2kW of solar panels. This inverter converts the solar panel DC to split phase 240VAC.

Your BYD battery is connected to ONE SMA SUNNY BOY STORAGE 6.0 US BATTERY inverter. This inverter converts the battery DC to split phase 240VAC.

The two inverters are electrically connected on the AC side hence Sunny boy storage 6.0 AC coupled architecture. Look up the data sheet on the SMA america website. I believe your set up is configured for "energy management" not "backup system" because you didn't mention a transfer switch.

I could be wrong with my assumptions, but I bet I am close because SMA doesn't make a hybrid inverter.

It sounds like the battery inverter is connected to the sub panel as a critical loads panel, but until you look at the schematic you won't know for sure. I think you have the correct number of inverters.

What was your goal for the entire system? Energy management or backup per SMA brochure?

[Jomby]

There are 30 panels and 2 inverters; 15 panels to each inverter. Panels are 340 watt.10 kwh BYD battery storage. I'm new to all of this so I aplogize. Let me know if there is other info you would need to provide insight. Thanks for your time. Sub panel is 125 amp. Main panel is 200 amp. One of the two inverters runs to the battery and that same inverter goes to the sub panel is my understanding. The other inverter goes
to grid.

I'm just thinking if both inverters went to battery and battery was fully charged it would then feedback through sub panel to the grid?

[SunEagle]

The panel wattage can be a factor as to how many panels are connected to the battery system. You can't always connect all of them because it might be too much for the Ah rating of the battery system.

As Ampster asks, please provide us with some info on your system.

[Ampster]

Tell us more about the specifics of your inverters and the other parts of your system? Two thirds of my solar panels are not connected to my batteries. That is because they are connected to Grid Tie inverters but the GT inverters are AC coupled to the battery inverter so I can charge batteries from all my solar. In my case is was cost effective to do it that way. It is a system that is best analyzed by looking at all the parts instead of just one piece.

[Jomby]

I had solar installed and a BYD battery backup with sunny boy storage installed but learned that only half my solar panels are wired to the battery, the other half aren't. I would think you would want all panels wired to charge the battery so that when power goes down there is sufficient solar production to not only charge the battery but also to power the critical load during the day. Is this not possible? I have 2 inverters, half the solar panels go to each inverter and battery is only hooked to one of these inverters is my understanding. Effectively when power goes down half of my system is doing nothing? Seems silly not to have all panels running to battery to ensure critical load is powered by solar during day and by battery at night?