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daniel-feist avatar image
daniel-feist asked

VE.Bus DC Voltage suddenly fluctuating even without load.

Had system installed for 9mths running perfectly but all of a sudden VE.Bus voltage is unstable, even under no load. I currently have it "charger-only" because I get constant alarms and shutdowns if inverter operates.

I've read other posts about this which talk about DC ripple and I plan to check all the connections, but what is weird is that there have been no issues for 9mths whatsoever and that this is occuring under no load.

I did a firmware update yesterday, which involved restarting everything and reapplying configuration and interestingly this did resolve the issue for a while. But later the same day, after a 25min DESS discharge at 210A, it reoccured.

Any thoughts or idea?

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Multiplus-II
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2 Answers
daniel-feist avatar image
daniel-feist answered ·

This was bad connection in the end. Not sure exactly if it was crimp, loose bolt of battery switch issue but I replaced battery switch, got electriciation to recrimp this connection and check all nuts with torque wrench and I'm back in action..


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Justin Cook avatar image Justin Cook ♦♦ commented ·

What brand and model battery switch is that? You appear to be running a 48vNom system and there aren't many (if truly any) rotary-style battery switches that are rated to be able to handle 60vDC.

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daniel-feist avatar image daniel-feist Justin Cook ♦♦ commented ·

It's the Victron one. Apparently rated for 60v.

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Justin Cook avatar image Justin Cook ♦♦ daniel-feist commented ·

Ah. Yes, while I know the vendor has assured Victron they're good to 60v, and as such you're covered by warranty on the switch, I will say that I certainly don't recommend them to any of my customers running 48vNom systems. Breakers or mechanical contactors are a much better solution for higher voltage systems like that - something to keep in mind should it happen again, but hopefully it won't be an issue in the future!

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nickdb avatar image
nickdb answered ·

Connections can fail over time due to constant cycling. I have found poor connections many months after they were originally made as the failure eventually cascades into a real problem, but prior to that it all appeared fine.

Start with the basics.

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daniel-feist avatar image daniel-feist commented ·
Will do. Given the low voltage alarm was only showing on L1, does this imply that there is an issue between busbar and L1 Multiplus? Or does the low voltage alarm on L1 represent the shared VE.bus voltage somehow and the issue could be anywhere?
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nickdb avatar image nickdb ♦♦ daniel-feist commented ·
Is your system 3-phase?

If this fluctuation is unique to one phase, then it is a safe assumption that the issue is localised there.

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