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A Sheik
A Sheik

Adding Sunsynk Hybrid + Fogstar battery to existing (separate) solar installation

I'm making this post in the hope it will help others to get their Sunsynk inverter to work with a separate solar panel array, i.e. with another inverter.


Our 4kW panel array was fitted twelve years ago to a SunnyBoy in the loft. Last month we added a 16kWh Fogstar battery with a SunSynk Ecco 8kW hybrid inverter. Unfortunately, the install was on a Saturday, and the installer couldn't get the system working before he had to leave (at 7pm to be fair!).

[Note is was only the inverter settings he was struggling with, all of the cabling, CT clamp etc was sorted out, we just couldn't get the battery to either stop charging from the grid, or if we changed something to stop that then the batteries weren't being used by the house etc. Sunsynk's system was down at the time as well, so we couldn't get set up on the app etc, and in the end we called it a day]

So after reading various Google posts, I changed the settings myself, and when the installer came back to check he signed it off as being correct.


We're not on an economy-rate tariff yet, so our batteries only ever charge from our solar panels, with the house load obviously taking priority. I am not an expert with any of this at all, so bear that in mind if you make any changes based on this post. And if anyone can see anything incorrect, please post to tell me and others.

Overview Screens

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First screen - unlike a full install with solar panels directly connected to the Sunsynk, my set up doesn't know anything about my separate solar array.
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System Flow Chart - again, lots of this screen is sadly redundant for my setup.

Battery Setup

We have the Fogstar Energy 16.1kWh 48V Solar Battery.

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These settings are all specific to your own battery.

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The important setting here is "Grid Charge" - if you don't enable this, later screens won't do as you expect and you won't be able to charge from the grid at all. My understanding is that "Grid Charge" means "Allow my batteries to charge from the grid" - it doesn't mean do it constantly.

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Again, specific to your battery specifications. These values seem to directly affect what you can enter into the scheduler below though (see next screen)

System Mode


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For people on clever economy tariffs, this is where you'd set up your cheap grid charge times. As we are on a flat rate tariff, ours is set up really simply. I seem to remember that I had to tick "use timer" for my system to do what I expected. SOC/V is the minimum charge you are happy for the Sunsynk to keep using batteries for your house load. Note I can't set this lower unless I reduce the "Low Batt" value on the previous screen.
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"Zero Export" combined with "Priority Load" seemed to be the key to getting all solar energy into my house first, and only using excess for the batteries. Grid Trickle feed seems standard at 20W, any lower and it could cause problems with your main meter.

Aux Load

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The Aux Load screen seems to cause the most confusion when I google for info. I think because it can cover a really wide range of use cases. I had to select "For micro inverter input" in order for the system to charge and use battery power as expected. To add to the confusion, clicking some of the other checkboxes undoes the "Micro inverter" setting, but you only realise when you go back into the screen!

Misc

I didn't change any of these settings myself, but I include them for completeness.

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Sunsynk App

It's also worth pointing out that we're missing a lot of stats from the Sunsynk app, eg: regarding money saved etc, I'm guessing because our panels are separate. If anybody knows differently and I'm missing something, please let me know. It would be great to know how many kWh the batteries have supplied over time for example. But at the moment under Equipment->Battery, I just see "no data" :-(.



Stats!

We obviously only have one month of data, but this is from our Ovo electricity account, showing the reduction in usage compared to last year.

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I hope this is helpful to someone, and please do comment if anything looks off!

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