FoxESS Community - Owners & Installers Forum

Hello,

I'm trying to achieve a specific outcome with my battery setup (KH9.9 Inverter with EQ4800-L9 Battery Stack).

At the moment, if there's no PV production (at night for example) and my battery discharges to its mininum SoC, the grid will supply power to cover house loads, but will also start charging the battery.

While I do want the house load to be covered by the grid power, I'd prefer the battery didn't draw from the grid to charge and would wait until the following day to charge using daytime solar.

Currently my Minimum SoC is set to 10%.

I've also found a 'MaxSoCFromGrid' setting in the inverter. Presumably this setting dictates what % the battery is allowed to charge to when drawing on grid power.

My thinking is, if I change this 'MaxSoCFromGrid' setting (currently 100%) to 0%, this would functionally prevent the battery from drawing power from the grid to charge when it drops to its minimum SoC. Alternatively I could set it to 10% to ensure it keeps the battery at its minimum SoC, but doesn't charge any further.

Is this how the 'MaxSoCFromGrid' setting works and would this be the correct way to achieve my desired outcome?

Thanks very much.

The MaxSoCfromGrid is a very recent addition to the inverter, only latest firmware versions have it and it’s still not accessible via the website or app so any changes would have to be made at the inverter settings.

The original MaxSoC setting is still there and the idea (as far as we can tell as Fox haven’t confirmed yet) is that MaxSoC will be your System MaxSoC i.e. the inverter will not charge the battery any higher that that from any source, whilst your MaxSoCfromGrid will be the maximum the grid can charge to. You would have to change both as MaxSoCfromGrid cannot be below MaxSoC and the problem there is that your battery wouldn’t charge from solar unless you change back again before the sun comes up.

Just going back to your original requirement, what should happen is when the inverter reaches minSoC it should cut power and the house will be powered from grid but as the inverter is kept running from battery it will still draw a small amount from the batteries and that will cause an occasional maintenance charge to the battery to keep it at or just above minsoc - I wonder is that the behaviour you are seeing ? (sadly there’s no way round this but whilst it charges at 1.5kw it should cycle on for a few minutes and then be off for maybe 60 mins so should only consume a few hundred watts/hour)

Hi Dave,

Thanks for your reply.

What you say about the settings makes sense, I did play around with them a bit and I notice there are some restrictions on how they can be used. So far however, I have noticed that MaxSOC doesn't SEEM to be directly tied to MaxSOCFromGrid. I've been able to lower the MaxSOCFromGrid (on the inverter) without also having to lower MaxSOC. Currently I've been able to successfully lower MaxSOCFromGrid to match the MinSOC value of 10% without needing to alter MaxSOC (which is still at 100%). Although whether that's functioning the way it seems like, I am not completely sure of yet.

Regarding the battery charging behaviour, what you describe could be what is happening, I will have to record and observe a little more to confirm exactly how the battery is behaving when drawing from the grid.

If its just small maintenance charge to keep it at MinSOC, that's manageable I guess. I just want to make sure the battery isn't trying to charge itself all the way back up to MaxSOC from the grid anytime it hits its minimum and stops discharging, that would get fairly pricey fairly quickly for me, and would negate a solid chunk of my PV generation to boot.

I'll keep an eye on things and see what shakes out.

Thanks very much for your help.