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saintb6969 avatar image
saintb6969 asked

Shutdown on gridloss - Low Battery & High DC Ripple

No matter what I check, if I lose the grid for even a second the entire system shouts down and takes forever to reboot and I get a HighDC Ripple error(seems to be corrected after I fixed the settings the update changed) and Overload L1 and Overload L2 even if the load is well below the max of the Multisplus’s.

I am running 2 Multiplus 12/3000/120v in split phase with 900amp hour batteries with a discharge capacity of 400 amp for 3-5s 12v batteries, I have checked and rechecked every connection line length.

Update,

Found that a firmware update changed a bunch of my settings in my inverters, so once I corrected that it seems that the High DC Ripple error might be gone, however the system is still shutting down and I believe the inverters that are in split phase are not doing a pass through on each line which is causing the load draw is causing my inverters to over draw my batteries and causing my BMS to shut down. Why would they not be doing a pass through? My single inverter did the pass through and I would never see overload issues unless the grid was completely down and the inverter had to draw from the battery.

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1 Answer
nickdb avatar image
nickdb answered ·

What's going on? Your batteries are most likely under spec.

Please provide more detail on your inverters and the exact model and spec of the batteries, configuration etc.

All the symptoms you describe relate to an underperforming set of batteries, something Victron can do nothing about.

Where systems are sized correctly these issues just don't appear.

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saintb6969 avatar image saintb6969 commented ·

I do not buy that one bit about the batteries, I have 3 300AMP Hour batteries with a max continuous discharge of 200amp and 2 Multiplus II 12/3000/120. The system worked perfect until I added the additional Multiplus and went to split phase, and yes all my wires are symmetrical, so again the blaming it on the batteries does not work for me. The system should never overload when the load is less than a 1K amps and each inverter is rated for at least 2400w continuous.

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nickdb avatar image nickdb ♦♦ saintb6969 commented ·

Those two inverters can pull well over 500A from those 12V batteries.

It has nothing to do with load (though that plays a part). Low frequency inverters will lean on the battery for all demand, if the grid does not shut down cleanly, and tends to brownout, that pull from the battery will happily drop the BMS.

Believing manufacturer specs (you haven't provided model or details for it) may also disappoint.

An overload warning/alarm should also not be interpreted literally, it can have different causes.

Many of these types of cases have been troubleshooted and resolved, it is always the battery.

You state this started when you added another multi? That further confirms it. Same with the ripple (unless you have bad wiring/connections).

If you want to dispute the advice that is your prerogative, then rather log a formal ticket at professional.victronenergy.com/support and see if that channel comes to a different conclusion.

We have helped enough people with the same symptoms before.


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martin-delp avatar image martin-delp nickdb ♦♦ commented ·

@nickdb , in your view what would an appropriate DCL be for batteries to handle, for example, 2x MPII 5kva 48V inverters running parallel? I appreciate that capacity is usually not the issue here but the current that the batteries can handle under brown-out conditions. I would imagine 100A DCL would not be sufficient, but would a battery with 200A DCL be sufficient? You mention 500A, but this will probably require a substantial investment in order to avoid these types of shutdown/restarts under brownout conditions.

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nickdb avatar image nickdb ♦♦ martin-delp commented ·
Remember the OP is using 12V and that doesn’t scale well.

I like the 2:1 battery to inverter rule of thumb.

On most batteries the DCL is generally quite proportionate to capacity. So 20kwh on a 10kVA system, but it isn’t always the case.

All BMSs aren’t equal which can complicate things but in an ideal world on a 5kVA I wouldn’t go below 200A, double that for 10kVA.

In SA with its iffy grid, more is more, but as you’ve aware this comes with a price attached.

A workaround is to automate (or manually) drop the grid connection prior to a planned outage.

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saintb6969 avatar image saintb6969 nickdb ♦♦ commented ·

Ok,

Sorry I mis posted the answer about my batteries and sorry I was not trying to be argumentive about the batteries. Here is a better look at my batteries, I have 3x300amp hour batteries with a discharge capacity of 400amp for 3-5s and a battery cutoff of 750amp after 150ms. I went back into my system and found that after an update it changed all my settings, so I corrected them and thought problem solved until it did it again today. Then thinking about what nickdb said I started looking through the VRM history during the time of the power loss and sure enough the wattage draw at that moment resulted in a 423amp draw on my battery and I assume it caused the BMS to shut down resulting in me losing 12v and 120v power until the BMS came back online and allowed the 12v to come back on. With that said the problem I am having a hard time in understanding is everytime this has happened I have been connect to shore power, so shouldn’t the inverters that are in split phase still be doing a pass through and never be putting a draw on my batterie? Unless the 120v system were pulling more than the 50a setting in the inverters, but still it should only be pulling what is needed above that one each line (L1 or L2). Everything running on my system is the equipment installed by the manufacturer for a 50amp RV and it never exceeded the amperage at the shore connection so why is the inverters not just doing the pass through when hooked to shore power?

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seb71 avatar image seb71 saintb6969 commented ·

The system should never overload when the load is less than a 1K amps

1000A from 12V battery means 12000kW.

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