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SMA increased self-consumption with backup power configuration

Harakas

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Nov 24, 2021
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Hey!

I have installed an SMA Sunny Island 8 running in battery backup with increased self-consumption mode with a Sunny Home Manager 2.0 that acts as
an energy meter. It's dead winter here at the moment with practically no sun available so I'm using grid power basically. But there are complications related to my limited grid connection: I can only pull 10A from the grid. Hence my questions:
  1. Can you configure the sunny island (SI) to charge batteries from the grid only when there are no other loads connected (to limit grid pull usage to 10A). I can configure it to do timed charging but it would be way more convenient to make it also dependant on available power -- SI has this information from the SHM. I figure that if I reconfigured the network into off-grid mode the SI would basically do this automatically (where grid is connected as a generator).
  2. Can you configure the SI to only provide power when the external power draw is above some threshold. So basically to extend my locally available maximum power. Right now it tries to keep external power draw to 0W. I'd be interested in tapping anything below 1kw from the grid but above that I would like the SI to kick in to help.
Unfortunately SMA documentation and support are extremely poor (or nonexistant really) -- they only talk to professional installers. There are a million configuration options with no documentation and I can't tell if any of them could help me to solve these problems.

Edit: apologies, it seems I've written into a wrong section. Perhaps the mods can move this post to its proper place.
 
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I'm surprised to hear that about their tech support, @Hedges might have some insight
 
I only have experience with SI-5048US/6048US, not the newer 8.0 and other such models.
Most of what I learned about it, I learned from reading the manual and other sources.

The 8.0 probably has different functions related to grid, especially time of use and export, but I'm not sure. So features of using battery when available and grid if needed I don't know about (except treat grid as generator based on SoC as you mention.) I would guess what you want is a reasonable management function for Home Manager, but I'm not familiar with it.

With mine, I can set a maximum current draw from the grid, e.g. 10A. If demand exceeds that, SI would produce the power inverting from battery.
Used with Sunny Boy, it charges batteries however it wants from PV (up to max battery current), charges from grid up to maximum charge from grid parameter, and lets surplus PV production backfeed the grid.

It should manage current through grid connection, except in the case of PV delivering too much. Mine only controls Sunny Boy output by frequency shift, which can only occur disconnected from grid. We are not supposed to exceed 6.7kW per SI. European 220V model would allow about twice that (but for your 10A, only 2200W). Yours probably uses Home Manager and data cable to command Sunny Boy.

I talk to support via email. Typically this has been something like a Sunny Boy that didn't seem to interact as expected (not varying its power output), and they requested serial numbers and upload of log files. That took commands writing to SD card in my case, yours is probably transferred over data cable.
 
Thanks for the reply. I understand that the SI-5048US still uses the old method of having the disconnect inside the sunny islands, so AC2 is connected to grid/generator and AC1 to the house, while the new "on-grid" installation documentation for 4.4/6.0/8.0 now mandates installing it like an inverter on a grid with an external contactor for disconnecting the house from the grid and you do not connect anything to AC1.

I guess that makes sense for beefier systems where you can size the contactor appropriately and there is only one way to do the installation simplifying (dumbing down) the available options as I guess most people would actually want to do it this way -- and SMA can get away with cheaper components inside the SI. Unfortunately it seems many features of the old system have disappeared or regressed with this method. That is quite unfortunate. I guess the main application for users is battery based energy saving instead of backup so it doesn't get that much love from the management.
 
Hi all,
I ran into the same problem. I'm installing the SI 8.0 -13 with LFP and also need the "inline" configuration. The configuration using the transfer box will result in a downtime of ~10seconds when grid failures. I cant have that, and I don't think it's good for the inverter electronics. (it will go into power limit).

I have receive some documentation regarding the "inline" configuration but it's very poor. There's written that the inverter should be in 'off-grid mode' and using the grid as "generator" (with feed-in allowed). Support doesnt know what the capabilities are when using the Island inline with the grid, a Home Manager 2.0 and the sunnyportal. They also stated that the inline configuration may conflict with local grid-regulation (how?). The manual has installation advice for different grid types, I won't switch the nutrual wire for example to prevent a floating the local grid.

I found tha
Did you get more information in the meantime?

Best regards
 

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Hi all,
I ran into the same problem. I'm installing the SI 8.0 -13 with LFP and also need the "inline" configuration. The configuration using the transfer box will result in a downtime of ~10seconds when grid failures. I cant have that, and I don't think it's good for the inverter electronics. (it will go into power limit).

Feeing through Sunny Island, sometimes grid failure results in SI picking up the load very fast (this is the case if I switch off grid connection), but sometimes power can go out for a short while. In either case, Sunny Boy usually goes offline for a while.

When grid power is restored, transfer of SI back to grid should be seamless because SI synchronizes then connects without skipping a beat.

I have receive some documentation regarding the "inline" configuration but it's very poor. There's written that the inverter should be in 'off-grid mode' and using the grid as "generator" (with feed-in allowed). Support doesnt know what the capabilities are when using the Island inline with the grid, a Home Manager 2.0 and the sunnyportal.

They also stated that the inline configuration may conflict with local grid-regulation (how?).

When a GT PV inverter like Sunny Boy is connected to the grid, it is supposed to use active anti-islanding to detect grid failures. In the US, we use settings like "UL1741" to enable that, or "Rule 21", which has active anti-islanding and also does frequency-watts, adjusting power output downward in response to increasing frequency (also good for AC coupling with Sunny Island.)

Sunny Island also does active anti-islanding (when it is told grid is connected) and disconnects, so a Sunny Boy set to "island" mode (no active anti-island, but does frequency-watts) would seem to work. I think the problem could arise if relay in SI gets welded shut, so it can't disconnect from grid. SB would then be on grid and would not get disconnected due to grid failure.

Our written instructions from SMA Germany say to use "UL1741" or "Rule 21" for SB behind SI. But SMA America put out a video where they said to use "island" instead. They did not explain why Rule 21 wasn't good enough, and they didn't put this in writing.

If you used grid as generator, SI would be connected to grid less time, and disconnects when battery is full. That would reduce chances of a grid failure while connected and reduce chances of a glitch on power output, but it could still happen. This configuration would not backfeed power to grid (except very briefly, when a load switches off.)

To completely eliminate glitches, you could set up a separate battery charger. If it was lead-acid battery that would require a shunt so SI is aware of the charge current, maybe not needed with LFP BMS if that provides the information to SI (I'm not sure.)
 
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