Why is power taken from the grid instead of the battery?

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Roman Komůrka asked Feb 9, '23

Why is power taken from the grid instead of the battery?

Hello,

I am a newbie so the question might be silly but I am very curious and my dealer isn't helpful much :).

I got the FV setup over 2 years ago but I would swear the behavior was different back then and it started just recently (could have it been an update of the firmware which the dealer didn't tell me about?).

I noticed that even though the battery has enough capacity left (e.g. on the screenshot it's at 100% and SoC is set to 60%) and the house requires more power, it's taken from the grid instead of the battery as can be seen on the screenshot.

This isn't desired behavior in my use case due to different energy tariffs during the day. I would much rather take all energy from the battery instead of the grid to save more money.

Is this normal behavior? Or is there a way to change some settings so that the power is taken primarily from PV and the battery and only if that's not good enough then it's taken from the grid?

Very much appreciate any input here, it's driving me crazy :).

Thank you and have a great day.

Roman

BMS ess discharging

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Bonhardt László commented · Feb 09, 2023 at 01:55 PM

probably you have an inverter power limit setup so you wont overload, so it takes the rest from grid. ( just my guess )

you are doing almost 2500W (pv + battery) which is a good limit for a 3000VA multiplus, though i have no idea what size of inverter you got.

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Roman Komůrka Bonhardt László commented · Feb 10, 2023 at 12:26 PM

Hello @Bonhardt László,

thank you for your reply.

I have MultiPlus-II 48/5000/70-50 and there is no inverter limit set:

Even when I set it manually to 5kW the grid seems to be preferred over battery which doesn't make sense to me. Even right now with lower load the same thing happens:

SoC is set to 50% so there is plenty of power that can be taken from the battery but the grid is preffered instead.

Is there any more info about the setup that might be useful?

Any guess why the grid seems to be preffered?

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Bonhardt László Roman Komůrka commented · Feb 10, 2023 at 03:30 PM

one more thing you could check is the BMS of the battery, if its connected to the Cerbo with CAN bus, than could limit the discharge current from battery

in that case you should be able to see CCL and DCL parameters.

example like this:

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Roman Komůrka Bonhardt László commented · Feb 24, 2023 at 12:21 PM

Hello @Bonhardt László, sorry for the delay, I had a baby born so I put this issue aside for a moment.

Yes, I can see the CCL/DCL parameters and checked them before - that's actually the reason why it was suspicious to me because the limits sit at 100A. I tried some "stress tests" but didn't manage to get more than 50A from the battery.

I raised this with the dealer and they say the battery is at fault but I had the same issue with a replacement they already gave me. Coincidently, they upgraded the firmware of everything. Do you think this could be the issue? That somehow in my setup the new firmware doesn't work properly for whatever reason? Because the issue started around the time the firmware got upgraded but I don't have exact measurements because it was during December with no sunlight.

Thank you for your help.

R.

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