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dl1bax asked

Multiplus II charging voltage at feed-in and service life at full load

Hello everybody.


My name is Ralf, I come from Edewecht and operate the following system as ESS:


1 x Multiplus II 48/3000/35

1 x Cerbo GX

1 x EM 23 (RS-485)

2 x MPPT 150/45 smart

1 x Lynx Distributor

4 x Pylontech US2000C

12 x 385 Wp modules, 6 modules each in 3s2p on one MPPT 150/45

1 x Hoymiles WR HM1500 with 4 x 410Wp directly on the house grid


The system has been approved by the electrician and registered with the grid operator / BNetz since

09/2022.


Now to my questions:


After charging the batteries, I would like to feed the surplus into the grid.

I have limited the charging voltage in the DVCC to 51.6 volts. With the 0.4 volts that the MPPT goes higher, this results in reliable charging up to 52 volts.

Now, when feeding into the grid, the battery oscillates between 51.6 and 52 volts all day, so it is constantly being charged and discharged. Discharge from the battery into the mains until 51.6 volts are reached again and then it is charged to 52 volts again.


The Multiplus then operates all day at its limit of 2400 watts with which it feeds into the grid. The HM1500 covers the base load and only feeds it directly into the grid.


Question 1:

Is the behaviour described above with constant charging and discharging normal and intended?


Question 2:

Can the Multiplus cope with the load in the long term and feed 2400 watts into the grid continuously? The fan is constantly running at high speed.

I am particularly interested in the experiences of users who have been using the Multiplus like this for a longer period of time.


Many thanks

Ralf


Multiplus-II
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1 Answer
manta avatar image
manta answered ·

Question 2 : Since the 3000VA multiplus is according to the datasheet capable of delivering 2400W@25c continuously is see no issues, but keep the temp under control. I have seen older Victron products stressed for years, on some commercial ships and they worked without issues for literally a decade.

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nickdb avatar image nickdb ♦♦ commented ·

It all depends on ambient and internal temps. In our experience anywhere near 20-25C and the 3K MP2 derates fairly quickly. Intending to run an inverter at its max cont rating for extended periods is a bad design choice. It is better to size one up so you have headroom.

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manta avatar image manta nickdb ♦♦ commented ·

If you have the choice to use a 5000VA multiplus, that would be better overall for sure.


I think the only difference with the 3000VA and 5000VA Multiplus II is the size of the transformer, but i don't know for sure. (who knows?)


But at the same time, when you already have a 3000VA Multiplus II hanging i would not buy a new one.

I think the multiplus 3000VA continuous rating, is named continuous for a reason when you maintain constant temp @<25C. Victron will sure have some margin in there. Antoher thing is, Torroidal transformers don't like changes in temperature in general, so a constant load at a contstant temp would be better for the transformer in theory.

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