Multiplus low voltage alarm and shutdown despite good SOC and voltage

Hi, I have a Multiplus 24/3000/70-16. For a couple of years, no problems, but just recently I have had the low voltage alarm sound and the inverter shuts off, this has happened the last 3 times I have used it. This time I did some further investigation and it seems strange behaviour. I might blame the fridge on my boat, but if you can see the log I attach, the fridge seems to have finished its on/off cycle and then the Multiplus shuts off. I left it off all night, but when I looked again in the morning, the voltage levels were fine (and had been soon after the incident), there is no outside source that could have charged the batteries.

I did recently update all the firmware for my Victron equipment, but that may be a coincidence.

Any thoughts on why this shut off despite no problems with my batteries charge? Thanks

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Alexandra ♦ commented · May 06 at 05:25 PM

That is quite a voltage dive under load. I think the batteries cannot make the inrush current.

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si7 Alexandra ♦ commented · May 06 at 08:45 PM

Thank you and I appreciate the help. I'm not much of an expert though so I don't know what "inrush current" means

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snoobler si7 commented · May 07 at 05:23 AM

When an electric motor starts, there is a momentary surge of current typically 5X the run current.

Worth noting that SoC is a calculated value. As your batteries age/degrade, they will lose capacity, but the Shunt can't know this. It must be reprogrammed for a lower capacity.

Also, what kind of batteries? Your displayed voltage is lower than what I would expect for almost any common chemistry.

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si7 snoobler commented · May 07 at 08:52 AM

Thank you, I've got it now. The batteries are Victron 110ah deep cycle AGM.

The point about a device or motor switching on could be the cause, but looking at the graph, I think the fridge was already on and had been for some time before this sudden dive down in voltage. After this, the voltage was steady ( I had turned the multiplus off but some 12v/24v devices were still running) and then at dawn, the solar started to kick in very slightly. This is what it looked like when I switched the Multiplus back on and then had no further problems with all equipment and devices running normally.