cvo avatar image
cvo asked

MultiPlus-II turns off when grid goes below 215V

Hey there,

today we had the issue that our MultiPlus-II 12/3000/120-32 turned off when the provided "grid" voltage dropped below about 215V. I'm not sure about the exact voltage, but its somewhere between 215 and 218V. The measurements were taken from by the MultiPlus and also a second external device, but both showed the same voltage (just that the MultiPlus is really slow in its reporting).

The "grid" is in this case a generator, an older model from the 80s or 90s, without inverter technology, so the voltage varies a bit. Specifically, the voltage goes up a bit under load and down when there is not much load (mechanical controls..). The upper limit is about 232V under load, the lower limit I saw today was about 205V with nearly no load, so this voltage range is the usual range that we get from this generator. As charging progressed and the charging power went down, the load on the generator also went down and with it the voltage. When we got to the aforementioned about 215V, the MultiPlus turned off (not completely, but switched to inverting as if there was no grid available at all - just that it still reported the about 215V provided to the Cerbo GX).

The reasons why I'm asking on this forum about something that sounds like a generator related problem are:

  1. camping places often provide similar voltages, as their wiring is usually not great and
  2. according to the datasheet, the charger in the MultiPlus accepts Voltages between 187 and 265V

Further, here in germany the grid's is allowed to go down as low as 180V, so this should not be a problem that turns off the charger.

In VE.Configure in the Grid tab, the lower barriers for voltages are set to 180V for disconnect and 187V for recovery. So that should also not be cause of the problem.

215V is a bit too early for my sense, as this has the risk of draining the battery without me noticing. Although the inverter turns off at a certain battery voltage, this doesn't make the situation any better, as this might lead for example to a not cooling fridge, which could be really bad on hot summer days.

How do I get the MultiPlus to not stop charging as long as the provided voltage is above 180V?

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klim8skeptic avatar image klim8skeptic ♦ commented ·
@cvo @JohnC While you are looking at the "Grid" tab, make sure you have "Accept wide input frequency range" ticked.

Probably untick the "UPS function" option.

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kevgermany avatar image kevgermany ♦♦ klim8skeptic ♦ commented ·
I think it's weak AC input.
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cvo avatar image cvo klim8skeptic ♦ commented ·

"Accept wide input frequency range" is ticked. I'll try unticking the "UPS function" and report if that helped, thanks!

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1 Answer
JohnC avatar image
JohnC answered ·

Hi @cvo

This could be any one of a number of things. Old gensets drifting off-frequency quite common, and often a tweak to revs will fix both V and Hz. Victron have this..

Dynamic Current Limiter almost an essential for gensets. Weak AC might work, but may also hide something like a poor connection in a power cord. This is sometimes an easy thing to rectify, sometimes will drive you crazy. If that happens it will always be the thing you overlook because it 'couldn't be that'.

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cvo avatar image cvo commented ·

Thanks already, as pointed out by @klim8skeptic and written in the article you linked, I will try disabling the UPS function and report afterwards.

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