New Growatt semi off-grid system questions

[Arg0n]

Hey guys, I'm new to this forum, and to building off-grid systems. I'm currently trying to help my father build a backup system that would run a water pump (and maybe fridge/freezer) off batteries, in case the grid goes down.

I currently have two questions:

1. Would the below setup work? Is there any major safety-concern that anyone can spot? (DC-breaker from PVs?)
2. Is there any way you can have different "Low DC cut-off voltage" depending on if grid is available or not?

E.g. If grid is available, we would like to use solar/batteries until batteries reach 70%, then switch to solar/grid to charge batteries again.
If grid is NOT available, we would like to use the batteries to their full extent.

The reason should be obvious, but: If grid goes down, and the batteries are at, let's say 20%, then they would not be able to power the critical appliances for very long.
Thoughts? (Sorry for some swedish in the image, hopefully it makes sense)

 

[ChrisG]

I’d say there are two thing to consider. First is the grounding difference when on Grid power vs battery. If not done properly when on battery, the ground wire could carry some of the neural load. Second is surge for well pump. I’m going though the same process now. Using an clamp meter with inrush, I can see that my well takes 35amp to start (8400 watts) and 6.7amps to run (1608 watts). I’m now looking for a different solution based on these two considerations. Current thoughts are Outback, Conext, Sol-Ark

 

[Arg0n]

Hmm, maybe this setting is what I'm looking for, regarding (2).
If I set this to max (51.2V), it will still continue using the batteries to Low DC cut-off voltage when utility is not available, right?

 

[Arg0n]

I’d say there are two thing to consider. First is the grounding difference when on Grid power vs battery. If not done properly when on battery, the ground wire could carry some of the neural load. Second is surge for well pump. I’m going though the same process now. Using an clamp meter with inrush, I can see that my well takes 35amp to start (8400 watts) and 6.7amps to run (1608 watts). I’m now looking for a different solution based on these two considerations. Current thoughts are Outback, Conext, Sol-Ark

How should grounding for the batteries be done properly? Any schematic?

The Growatt 5000 should handle surges up to 10000W? The water pump is currently running on a 16A 230V outlet = 3680W. I hope it will be able to handle it. But you're right, it does take a lot of juice to start it, then 1500W to run (when someone is actually taking water).

 

[ChrisG]

There is a thread I am part of with a few people on the grounding topic. I’ve done some tests with others in this forum with far more experience than I have. In my SPF3000, when simulating grid failure and running off of batteries, the ground definitely carries some load. There is a relay you can buy to supplement the Growatt to resolve this via option 24 in the manual. Unsure of your exact model so definitely investigate.

 

[Arg0n]

There is a thread I am part of with a few people on the grounding topic. I’ve done some tests with others in this forum with far more experience than I have. In my SPF3000, when simulating grid failure and running off of batteries, the ground definitely carries some load. There is a relay you can buy to supplement the Growatt to resolve this via option 24 in the manual. Unsure of your exact model so definitely investigate.

So it's almost the same, but the SPF5000ES version. Can't seem to find option 24 in the manual.