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solarfluxindex asked

Limit inverter power applies to total DC power

Hello community,

I am runnig a MultiPlus II 24/3000/70 with Cerbero GX and SmartSolar 100/50 in ESS mode together with a Pylontec UP2400. Installed solar power is 1,5 kW peak power.

To protect the battery I've limited the inverter power to 1450 watts.
According to the documentation, this limit shall only apply to the power, drawn from the battery.

However, when loads like the dishwasher with >2kW are running, I've newer observed more than approx 1500 watts feeding from the multi into the loads even if > 1kW were provided by solar.

Did I misunderstand the documentation or configured something wrong?

--

SFI

MultiPlus Quattro Inverter Charger
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seb71 avatar image seb71 commented ·
Can you post a screenshot from VRM showing that situation?
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solarfluxindex answered ·

I can try, capturing one.
But what you will see is a sum of approx 1,5 kW feeding from Multi into the loads and the missing difference comming from the grid.

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seb71 avatar image seb71 commented ·

Sounds like it's normal.

But a screenshot would be clearer.

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solarfluxindex answered ·

Sorry, I wasn't able to capture a screenshot so far. But as far as I understand the documentation if my battery is fully charged and solar could provide max power, the Multi should provide approx 3 kW into the house if needed:

Quote:

Power coming from the MPPTs is not taken into account. Using this feature in a system with MPPTs can cause the output power from the MPPT to be reduced.

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seb71 avatar image seb71 commented ·

You don't state the issue clearly.


So you say that you limited the inverter power to 1450W and when powering some AC load larger than 1450W the power difference is taken from the grid. This is normal.


In this last post you try to say that you would like that the power difference should be provided by the MPPT and not from grid?

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derrick thomas avatar image derrick thomas commented ·
Limiting inverter output power does exactly that, limits the amount of power being INVERTED. Energy from MPPT has to be inverted in order to provide power to AC loads. What this excerpt from the manual is implying is that in a situation where that batteries are full and the MPPT is capable of providing more than the limit setting (in your case I think you wrote you have the limit set to 1450) and the AC loads exceed the limit, the MPPT is held throttled to 1450 and the remaining load will come from grid. If the batteries are not full then any MPPT energy available over the 1450 inverter limit will go to the batteries. The inverter limit you set does not apply to the batteries only, it is applied to the energy being inverted. Hope that helps clear it up. Unless I have completely misunderstood the question, which is totally possible.
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solarfluxindex answered ·

Below is the screenshot, showing the situation. Finally I was able to capture one.
Derrick, thanks for your explanation. But why should the inverter limit have anything to to if the solar power will be fed into the loads or the battery? You explanation might me correct but doesn't make sense to me, at least not in conjunction with the manual.

So far, I've limited the inverter power to make sure, that I don't draw more power from the battery than it can deliver. Is that even necessary or would the Multi -> Cerbero -> BMS "magic" limit the drawn battery power to the allowed limit?

victron.png




victron.png (192.7 KiB)
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nickdb avatar image nickdb ♦♦ commented ·
Because DC PV must be inverted to power AC loads, whereas DC to DC is unrestricted,

If you clamp the inverter output, you will throttle all generation.

The wording is a bit dated and needs to be amended.

This is the drawback of using an inverter limit, has always been so.

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