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Supplemental 6K "Off-Grid" System (Growatt SPF600T + 4 EG4 LiFePOWER4 in Rack)

Michaells

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May 16, 2022
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I recently installed a 5K array on my roof and a 6K hybrid/off-grid inverter with autotransformer/split-phase output (Growatt SPF600T DVM-MPV) and 4 EG4 48v, 5.12kWhr batteries in a rack to provide uninterrupted power to the critical loads in my house and my business computers (vs installing a whole-home genny like all my neighbors have as the frequency of outages in my area has approached the ridiculous).

I have a 10-year-old 3K net-metered PV system which did not cover 100% of our yearly usage and decided to augment this solar production and create a backup while avoiding having to renegotiate my net-metering deal. As an early adopter my agreement with the utility is way more favorable than it would become if I added to or changed the existing "grid-tied" system.

Like many here, I moved the critical loads in the house to a new sub panel to be powered by the off-grid system and built in a transfer switch so that if the new system went down I could throw a switch and put everything back onto the net-metered system until a repair could be affected. I also decided to keep my portable genny and 6-circuit transfer switch as a backup to the backup in case the utility went down for many days and the sun did not shine. Here is my system diagram.

Screen Shot 2022-07-02 at 3.57.07 PM.png

Many have rightfully cpmplained that the Growatt documentation is inadequate, but this community provides a great resource to fill in the gaps and I found this video full of very helpful info to get the WiFi dongle that works with this inverter up and running:


(A bit of internet searching revealed another bit of crucial, otherwise undocumented info that you will need if asked for the dongle's network login credentials prior to getting it onto your network: username admin and password 12345678.)

I was told by a sales person at Signature Solar that the dongle is not particularly useful, but I disagree. Once it is up and running (via the Growatt server) the associated app and web portal will give you information on the real-time status of the system, allowing you to optimize set points regarding charging and bypass to align with your usage, battery capacity, and solar exposure. Here are screenshots of my system early in the AM, on a hazy day, with the SOC below the setpoint to switch back to solar/battery power and with the battery charging from the PV array, and then a bit later once the SOC setpoint to switch to solar power for loads has been reached.

IMG_FE5F7CC01F5A-1.jpg IMG_5FA32D663116-1.jpg

I find it useful to know when the grid is being tapped to charge the battery (for me, usually for 0-2 hours overnight, depending on the amount of sun received and AC used the day before) and when I am on bypass (usually in the early AM, if at all, when the battery SOC is below the setpoint). This info will also help me decide when to schedule discretionary power use, like the charging of an EV--Better do to so while the sun is hitting the panels (before 2pm for me)--and the optimal capacity of my battery array.

I already see that I might benefit from 2 more batteries in my rack, but a lot depends on how the year plays out. Since I am basically banking most of the power generation from the net-metered system, if after the winter I have a net-zero usage of kWh's from the utility AND am charging my EV I will be happy. Could be that 2 more batteries will help make that difference, but we'll see. I could also change the set point for when my batteries ask for a recharge from the grid, but I want to maintain a level of charge likely to get me through a cloudy day when the utility is down.

You will have to interpret the app a bit, as when it is in bypass the image shows 0W "imported" from the grid and no Load Consumption though in reality there is a load and it is being supported by the grid bypass. Basically, the dongle and app only track load to and from the PV/battery, and not what passes through in bypass mode. So, to complete the monitoring picture, and because I am a data geek, I have two Emporia monitors running as well.


One is tracking the circuits providing the "grid assist" and the overall kWh usage/production from the existing net-metered system and the other is tracking the usage from each of the two legs of the new off-grid system. I am exporting the data from each to create a spreadsheet that gives me a bottom-line calculation as to my overall usage/production per day (or per second, when I want to see what's happening in any moment and to help figure out how my usage is affecting the system).

IMG_B2EEE9614B87-1.jpg Screen Shot 2022-07-04 at 9.41.44 AM.png

Some pics of the installation:

IMG_1913.jpg IMG_1914.jpg

The system is working great, but my one issue is that the Growatt Shine app/portal is showing faults when there appear to be none, but that will be the subject of another posting which I will try and link to here after I have posted it. In short, my results thus far are exactly what I'd hoped for. I did use the Emporia monitor to track the usage on the circuits I wanted to move to the new system before purchase and installation, and that helped me plan things out.

Much thanks to @Will Prowse and the rest of the community for the assistance along the way. May the sun keep on shining!
 
Nice report, thanks! You’re doing almost the same thing as me except I don’t have the solar put up yet. The Growatt is completely installed and has been in operation almost a year with zero issues. I have ten 335 watt solar panels and all the hardware to put in a ground mount. Made it as far as getting the solar combiner connected and mounted outside when some health issues brought my summer plans to a screeching halt. I’m using DIY batteries so will not have the advantage you have of the Growatt communicating with the battery banks. My transfer switch is installed on the grid input of the Growatt so I can use the generator to charge the batteries and run the house in the event of a long term grid down situation with insufficient solar. I also put in a “service bypass” using two interlocked breakers in the sub panel to put everything back on the grid and isolate the Growatt in the event of a failure. My only gap in coverage is the ability to power the house directly from the generator and haven’t decided if the addition of another transfer switch is worth it since that scenario is unlikely.

My grid tie system is 9.1 kw using SolarEdge equipment and with the exception of two failed optimizers which were replaced under warranty, has been bullet proof for almost 7 years. Pennsylvania has very good net metering laws and I was consistently running a banked surplus until I started working from home and set up a home office. Getting those ten panels connected to the Growatt will put me back in the green again with the added security of being able to live off grid indefinitely with careful power rationing.
 
Yes, our situations are very similar. I was also running in the green with the utility before I started working from home. Lucky us that we have decent net metering rules in effect. Although New York is adjusting ours to the detriment of the solar generators like us.
 
Thanks for the detailed install post. I am setting up the 12k in a cargo trailer with an 11.8kw array on a pole barn. There are a lot of blanks in the documentation, but I think it will come together nicely.
 
Update: we bought an EV and I've added yet another transfer switch so I can charge from my off-grid system when the sun is shining and from my grid-tied at other times. I bought a charger that allows me to squeeze the current down to a few settings: 10, 16, 20, 24, and 32 amps as I can only safely power 10 or 16 amps @240v through my off-grid (considering the other things running on that system).

Screen Shot 2022-09-10 at 7.13.16 AM.png
 
Great job!
Growatt has newer firmware that took care of my faults (fanlock, 109/110, import fromgrid/data spikes) and some people have to calibrate the battery voltage (to eleminate error 61).
It blows my mind that anyone would say the WiFi dongle/ShinePhone app has little value.
Obviously he doesn't have an electric car.
I even found that when I used the app (ShinePhone) to report errors, that they responded and provided firmware to resolve it. I attached screenshots of where to go.Screenshot_20221114-081520_ShinePhone~2.jpgScreenshot_20221114-081216_ShinePhone~2.jpg
 
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