Multiplus voltage differences

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dirk-s asked Jun 5, '22

Multiplus voltage differences

Hello,

I'm reading in this community for a while now and get many help/hints to setup my storage system. But now I have a questions and didn't find this kind of topic in this community before.

I have just changed my installation from a Multiplus II 3000 GX to a Multiplus II 5000 GX. It is an grid connected ESS System with 5* Pylontech US3000C. Everything works well so far.

But there is one issue that bothers me a bit. The Multiplus have a voltage difference of 0,30 V between the Multiplus itself and monitored in VRM Portal "VE.Bus DC Voltage And Current" and the real voltage. The BMS from Pylontec and all the other voltages monitored and shown by the GX device shows 0,3 higher voltages. I also messured everything with a multimeter and the higher voltages are correct. If I messure also directly with my multimeter on the DC terminal of the Multiplus directly (without calble and inverter/charger are off) the voltage ist 0,3 Volt higher than monitored by the Multiplus.

As the Multiplus uses this messured voltage to steer everything, the real voltage is everytime higher. For example I need to set charge voltage limit to 50,0 Volt to get 50,3 Volt in reality. Also if I don't limit the charge voltage, the real charge limit will be not 52,4, but 52,7.

It may be that these deviations are normal and are the usual variations of measurements. In this case it is ok. But as I still have the possibility to return the Multiplus and to get a new one, I want to be sure. My former Multiplus II 3000 had a deviation of 0,1V.

What are you experiences and values? Are your messured DC voltage by Multiplus the same like messured from BMS/Multimeter/reality or do you have also these kind of deviations?

Many thanks in advance.

Bye Dirk

Multiplus-II voltage

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Answer 1 · 2022-06-07T10:34:58Z

dirk-s answered · Jun 07, 2022 at 10:34 AM

Hi all,

Does nobody from this Community use a Multiplus II 5000 GX who can check this on his/her installation?

Would be very helpfully for me to know.

Thank a lot.

Dirk

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Answer 2 · 2022-06-07T13:27:06Z

JohnC answered · Jun 07, 2022 at 01:27 PM

Hi @Dirk_S

I've an earlier Multi 48/5000 and see a V difference of up to 0.2V. It varies for some reason, maybe a Temperature thing? I 'fixed' it by using DVCC to pass on to it a better V from a Smartshunt.

With your Pylons I don't think you can do that, but the Pylons should be controlling everything anyway if set up correctly. What the Multi reads itself shouldn't really matter. But I've little experience with the Pylons, so check this out for yourself. With managed batts (at least the Victron-supported ones), if they say they're happy, then all should be good.

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Answer 3 · 2022-08-10T20:08:34Z

anieuwstadt answered · Aug 10, 2022 at 08:08 PM

Picked up a similar problem. The chart below shows differences between the VE.Bus (MultiPlus) and the BMS (Freedomwon). Conditions: no load, no charging, no solar. The variance is sufficient to put the system into Absorb charge when the BMS battery SoC is being reported as 49%. In the large (6 month) chart, the difference between the voltages is increasing over time. In April at the start of the flat line section, the MP II firmware was updated. Going to confirm the bus voltages using a meter to confirm which is more correct, the BMS or the VE.Bus

1660160936566.png (70.7 KiB)

1660161270221.png (13.4 KiB)

1660161854823.png (110.0 KiB)

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Answer 4 · 2022-09-21T04:57:24Z

cedricr21 answered · Sep 21, 2022 at 04:57 AM

Bonjour, j'ai un problème identique. Mon multiplus II indiqué 51,8v alors que la tension de batterie est de 50v. J'ai mesuré la tension réelle au borne du multiplus elle est de 50v mais le multiplusII indiqué au cerbo 51.8v. Quelqu'un sait-il comment résoudre ce problème ou si je dois l'envoyer en réparation ?

Merci

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Answer 5 · 2023-03-01T15:48:47Z

Jörg Becker answered · Mar 01 at 03:48 PM

Same problem here now.

MP II measures 56,8V when the real voltage over the terminals is only 55.6V. The BMS measures 55.6V, the MPPTs show 55.6V but the Multiplus shows more than 1V more.

Anything I can do about it?

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Answer 6 · 2023-03-08T14:58:58Z

anieuwstadt answered · Mar 08 at 02:58 PM

In my case, there was an inverter hardware issue, and an update to the Venus OS resolved the problem.

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