question

orion60 avatar image
orion60 asked

Why does MultiPlus stop inverting on an Overvoltage condition?

I am using the "Two-signal BMS support" assistant with my Multiplus (24/300/70) connected to a BMS. Aux 1 is connected to a cell over voltage signal and Aux 1 is connected to a cell under voltage signal. The "Battery state inputs" window is configured as follows:

The battery if full when Auxiliary input 1 is open and the battery is empty when Auxiliary input 2 is open.

The Action window is configured as follows:

Disable charger and do not adapt SOC when battery full and switch to charger only when battery empty.

So far so good. The problem is this:

When the Multiplus is inverting and Auxiliary input 1 opens (which happens on an OVERvoltage condition), the Multiplus shuts down completely! I would expect it to disable the charger and continue inverting, since the battery is obviously full and has plenty of power. Do I have a setup problem, or is there a good reason why the Multiplus stops inverting? It seems like a bug to me.

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4 Answers
netrange avatar image
netrange answered ·

What are the "Over - and Undervoltage" Conditions ... From BMS and the MultiConfiguration ...

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orion60 avatar image orion60 commented ·
The exact values really don't matter. They are just which cell voltages I decide to consider under/over. My point is that the indication from the BMS is that the voltage is too high (Aux 1 = off). That should tell the Multi "Hey, don't charge the batteries because they are plenty full." Therefore, the multi should stop charging. And it does. In fact, it completely shuts off, which means if it was inverting (which uses battery power and would therefore eventually reduce the cell voltage), it stops inverting as well. That seems wrong to me.
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solarchain avatar image
solarchain answered ·

netrange is correct more information is required. The values of the Multi and the values of the BMS are important and dictate which device (either the multi or the BMS) is "in-charge". In other words which device fires first to protect the batteries. From there .. other characteristics of the devices come into play. Consider a BMS which might be firing an HVD event differently (i.e where any one cell exceeds a preset value) vs. the total high voltage level of the battery (how the Multiplus measures it). Each device can measure independently using different methods and timing. Debugging likely requires deeper analysis.

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orion60 avatar image orion60 commented ·

Thanks for responding. Well, for one, the Multiplus does not have a "DC Input High" setting (it only has a low voltage shut-down setting, and of course the voltage is well above that in my case). The Aux1 signal coming from the BMS is in fact triggered by a high cell voltage (and of course that can be simulated for testing purposes by simply opening and closing a switch connected between AUX1+ and AUX1-). If you feel that the situation I describe (inverter function shuts down when a high voltage signal is activated) makes sense under certain Multiplus settings, please describe those settings. It doesn't make sense to me under ANY circumstance.

I feel that if the Multiplus is happily inverting along, with all voltages it measures within its defined parameters/settings, then when it gets a high voltage signal on AUX1, it should not shut down, but only stop charging (assuming the charging function is enabled). Inverter shut-down should only happen (in my opinion) when AUX2 (as I have it defined within the assistant) is opened. In other words, a "low voltage detected" signal should tell the Multiplus to stop inverting, and a "high voltage detected" signal should tell the Multiplus to stop charging (or go into float mode, one of the options in the assistant).

I'm happy to be proven wrong, but I still feel like this is a bug in the assistant. We should at least be given the option to configure the assistant in the manner I describe.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Do you use any grid code?
Some grid codes (Germany for example) use the AUX1 for a signal by default.

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orion60 avatar image orion60 commented ·

Hi Matthias - thanks for responding. No, not using any sort of grid code. It is set to "None". My application is a camper van.

The Action window of the assistant says "Disable charger and do not adapt SOC when battery full". And that makes total sense to me. However, instead of disabling just the charger, the Multiplus is shut down completely whenever the Aux1 signals are opened.

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orion60 avatar image
orion60 answered ·

I see that Victron staff sometimes chime in here. Since the issue I am having seems like a bug (or at a minimum the assistant should be modified to allow inverting to continue after an overvoltage condition), does anyone have a suggestion for getting someone from Victron to view my post? Or is it just hit and miss? Thanks!

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