question

pmikep avatar image
pmikep asked

Shouldn't the "DC input low pre-alarm" always be higher than "DC input low-shutdown"?

Apparently this 'issue' has been around since 2019, when someone mentioned it in passing. But no one has squawked it since then. (That I can find.)

So perhaps I don't understand the terminology. But shouldn't the DC input low pre-alarm always be higher than the DC input low-shutdown voltage?

As it is now, the pre-alarm defaults to a lower voltage than the low-shutdown voltage. (See photo.)

So then the pre-alarm will never sound because the inverter will have shut off beforehand?

(Multiplus with v500 firmware.)

low-voltage-alarm-too-lowq.jpg

MultiPlus Quattro Inverter Charger
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3 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @pmikep

Most likely someone set these values. There is no check in VC if the pre alarm value is set lower than the shutdown value (you might want to disable it for some reason).

These are the defaults for a MultiPlus 800 24V. We just checked to be sure:

DC input low-shutdown - 18.60V

DC input low restart - 21.80V

DC input low pre-alarm - 21.80V


The 12V defaults are are half of these values.

9.3V and 10.9V for restart and pre-alarm


V500 gives the same defaults (18.6V, 21.8V, 21.8V).

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pmikep avatar image pmikep commented ·

Okay, thanks for checking.


Since I didn't expect to see what I saw, I did not check ahead of time to see if the low voltage pre-alarm was set correctly. BUT - I saw the same thing on MY Multiplus when I reflashed the firmware a few weeks before. And I KNOW that I did not set the value this low.

low-voltage-alarm-too-lowmy-24v-unit.jpg

So, since it's not a Factory Default out of the box, I am now hypothesizing that this has something to do with Exporting and Importing Settings. (I received a warning on both Multiplus's after Importing/Restoring Settings that "Some of the values were not compatible" (Or a message to that effect.))

I'll plan to take video the next time a firmware update is released so that I can document if the settings change.



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JohnC avatar image
JohnC answered ·

Hi @pmikep

Quite so. But I can't explain how those values came to be there. The default values would normally be fairly low anyway, like the shutdown at the bare minimum. Just change them to what you want to use.

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pmikep avatar image pmikep commented ·

The Low voltage alarm is a default value. I took the photo after flashing new firmware and restoring my previous settings.

My Low voltage alarm value was not restored when I restored my previous settings.

Hmmm.. now I'm wondering if the OEM default shutdown voltage is normally very low, but was restored to my higher value when I restored settings?

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Graeme Walker avatar image
Graeme Walker answered ·

I am looking at these values and they are very low for a 12v Lithium battery bank. I set the 'DC input Low shut-down' to 12.5v (~14%) and it defaults the 'DC input low restart' to 13.5v, this is over ~99%. I can't change that value, is there a setting for Lithium batteries. I have it set to Lithium in 'Charger' tab. It would also make sense to have the 'DC input low pre-alarm' set to about 13.0 which is 30%. Maybe I'm not reading this correctly but the values look very much for FLA not anywhere close to Lithium. Thanks.

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