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pripp asked

Multiplus in parallel leads to unbalanced currents

The setup is 3x Multiplus II 48/5000/70-50 in parallel mode single phase.
One Multiplus is from 2020. The other two are new from 2022.
AC cable lengths are equal and not oversized.
DC cable impedances are equal as possible between the units.

Unfortunately, the Muptiplus from 2020 draws a much higher current from the battery than the two new ones. The two new Multiplus currents are almost equal.





Test Inverting Test Charging
Nr. Serial number AC length [m] AC [mm²] DC [mm²] Firmware AC Limit [A] DC [A] DC [A]
1 HQ2219MY2DF 6 6 70 497 10 37 16
2 HQ2218AXMNP 6 6 70 497 10 38 18
3 HQ2037MH5DX 6 6 70 497 10 47 39



It seems that the "problem" is the old Multiplus from 2020. I think there were design changes on the PCB. PCB dimensions have changed. And the new ones show an unpopulated terminal block. (see pictures)

I bought the old and new MP at different shops.
I am not sure who can give support.

Can someone from Victron check (Serial numbers) if the Multiplus can work together?


img-20230101-194103.jpg

img-20230101-194059.jpg


vic-setup.jpg

multiplus in parallel
img-20230101-194059.jpg (2.8 MiB)
img-20230101-194103.jpg (3.1 MiB)
vic-setup.jpg (1.4 MiB)
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klim8skeptic avatar image klim8skeptic ♦ commented ·

Battery connection to the busbar is not optimal.

Might be worth checking if the multi that draws the the most current is unit that the lugs the batt cables are connected to.

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nickdb avatar image nickdb ♦♦ klim8skeptic ♦ commented ·

I have had the exact same issues with 5k MP2's trying to parallel models with the old power pack and the new one. Asymmetry was terrible, there was also huge issues with negative setpoints. It is a known issue and the supplier can RMA the older unit - it affects serial numbers pre first quarter of 2021.

Obviously first it needs to be confirmed that all wiring is of equal length etc.

As a side note, always make a new model master.

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pripp avatar image pripp klim8skeptic ♦ commented ·

DC wiring, I took equal impedances into account. The Multi with the shortest GND connection has the longest positive connection and vice versa.


AC Cabling is equal due to some meanders.


New Unit is the Master.


ESS zero feed-in is not working correctly but currently, there is no Energymeter connected. Adding an ETH24 may help.


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4 Answers
nickdb avatar image
nickdb answered ·

There was a power pack change and that will cause imbalances between the old and new models.


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yaute avatar image
yaute answered ·

2 months ago we've faced the same situation 2 MP II with hardware 2623 in mono, then we had to add one more. Because the one we had in stock have an 2626 hardware, I asked VE about the compatibility bettween 2623 and 2626. I did not get a clear answer so I decided to move all the MP to 2626 and it works fine. It does not help you so much, but by experience this hazardous to mix hardware.
VE, a compatibility matrix will be apprecited.

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pripp avatar image
pripp answered ·

The old unit was returned to the dealer and I am waiting for the replacement.
Thanks to @Matthias Lange - DE for help.

Currently, the two new units operate as desired in parallel mode.

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nickdb avatar image nickdb ♦♦ commented ·
Glad to hear you’re making progress.
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pripp avatar image
pripp answered ·

Victron replaced the old unit with a new one. Now the DC current deviation is < 5% between the Multis.

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