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Topic starter
May 25, 2025 5:29 pm
Hello. I want to add batteries to an existing system that is made up of 3 independent older inverters totaling about 10kW, all ground-mounted, and one 19.2kW rooftop Enphase system. Here are my goals:
- Achieve as close to 100% self-sufficiency as possible with grid available as a rarely used backup.
- Make full use of my existing solar to power loads and charge batteries.
- Be able to physically disconnect the grid whenever I want, probably by manually overriding an ATS.
- Support all loads on battery (whole home backup)
- I don't care about selling back to the grid since my NEM2 contract (California) expired.
From what I can tell, I want the power specs of a FlexBOSS21 with the AC-coupling feature of a GridBOSS. I already have disconnect switching in place, so those GridBOSS features are redundant.
Here's my tentative plan:
- Install a GridBOSS and EG4 inverters, possibly 2 or 3 FlexBOSS21s
- AC couple the Enphase system to the GridBOSS.
- Retire the old inverters and bring the PV strings to the new inverters
- Add batteries to the new inverters.
Here are some questions:
- Does the tentative plan sound reasonable? Is there a better way?
- Will the GridBOSS be able to run the Enphase system and keep it running when grid power is off?
- If yes to 2, can the AC coupled Enphase system charge batteries while simultaneously supplying power to loads?
- If the grid is down for multiple days, will everything be fully functional? (EG4 inverters, GridBOSS, AC coupled PV, DC PV from EG4 inverters, and batteries)
- Can the GridBOSS function with nothing connected to its grid terminals?
I know this post is pretty long, so thanks if you made it this far!
May 25, 2025 6:30 pm
Good Afternoon.
Just a quick question from the curious, as I too am beginning to plan my "next phase". Why did you choose the GridBOSS over the 12000xp? It would seem to me that you solve a lot of your problems (while moving a long way towards meeting most of your goals) using a 12000xp AND save a lot of money that you could use elsewhere.
To keeping the sunny side up! 🍺
L8r
Topic starter
May 25, 2025 9:20 pm
@dfwtinker it's a good question. I would certainly be ok with saving/repurposing funds. 🤑
If I'm reading correctly, the 12000XP can manage 62.5A on the smart port for AC coupling while the GridBOSS is rated up to 80A on port 2 and 125A on port 1. My 19.2kW Enphase system is theoretically 80A. I think that rules out 12000xp for me, but would love to hear otherwise if I'm mistaken.
Topic starter
May 25, 2025 9:40 pm
I think I could also use 18kPV and do away with the GridBOSS, but the cost difference isn't much. Might as well go with newer inverters and higher capacity.
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