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zain avatar image
zain asked

Multiplus-II False Overload alarms

Hello. i have noticed alot of warning and alarms in my system. the system is a 3 phase system, 3 multiplus-II units of 5kVA each with a 400Ah battery. It has its own BMS with active cell balancing. It also has two MPPTs attached for solar. (This is in India so there is no Grid code).

The loads connected in all the phases are almost of 2 - 3kW each phase. whenever the overload warning comes, there is less power taken by the load at that time, and when there is an overload, there is no sign of actual overload in the system.

i have checked the entire csv file downloaded from the VRM portal. and also updated the firmware of the VE.system and CerboGX. this was done as a last resort since nothing else was found to be wrong. after updating, the warnings and alarm did come again and the system shut down.

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This was after updating. The overload is always on the 2nd phase. the highest the 2nd phase output power ever went was 3045W which is not an overload value.

I have checked all parameters. But if i have missed something, can anyone please tell me?


Multiplus-II
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mvas avatar image mvas commented ·

Do you have an inductive load? Like a motor, a compressor or an air conditioner. What is the peak amps? What about max amps drawn from the battery bank for that inverter?

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zain avatar image zain mvas commented ·

There are some fans, lights and one 2 ton AC. Peak amps is 20.3 A at 17:53 for phase 2 loads. Max amps drawn from the battery at that time was 133.4 A.

Forgot to mention that the battery is a 48V battery!

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zain avatar image zain commented ·

Now, currently we changed the AC phase to phase 3 (before the AC was connected to phase 2). no alarms yet. a warning came but there was a load of 3123W. there was no warning when the load was almost 3900W.

whats the logic behind this?


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JohnC avatar image JohnC ♦ zain commented ·
@Zain

The problem you have here is the granularity of the VRM figures. At best they're 1 minute snaps, when your overload may be only mS long, and not logged anywhere.

My own system regularly logs overloads, but I've never seen one make it to VRM. I know what it's cause is though (a water pump starting), so don't worry over it.

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zain avatar image zain JohnC ♦ commented ·
okay thanks!!
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georged avatar image georged JohnC ♦ commented ·

I have the same story, I know who is "guilty", the water pump starts. Indeed, the granularity "hides" the peaks, I thought that if there was a way to catch the value that produces the overload, this would have appeared in the warning message. I think it is a hardware limitation, if it is not so it would be very useful to insert the "guilty" value in the warning or alert message or at least in a debug/trace file dedicated to warnings and alarms with details the values involved in the decision.

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Alexandra avatar image Alexandra ♦ georged commented ·
@GeorgeD

The only way is to change the logging. Alot can happen in 60 seconds. The fact is there is an overload a short one maybe. But still. And you snow how you use your system.

I have seen even dedicated power logging equipment missing peaks.

The truth is though, if it is with in the peak rating of the inverter at the temperature it is being used then you are ok.

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zain avatar image zain commented ·
An update: So overload alarm came for L1 and L3. There was a spike in L3's load so it was obvious that alarm would be sent (4878W). But load on L1 was 3.7kW, a warning usually comes here, not an alarm.

The loads attached to each phase are all under 4kW. I have the exact list right now:

10 fans of 75W each

20 LED lights of 12W each

1 2-ton AC (This runs 24/7)

1 1-ton AC

1 1kW water pump (This is connected to all three phases)

The rest are divided. Yet the power went above 4.5kW.

Except load distribution, is there anything else i am overlooking?


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Alexandra avatar image Alexandra ♦ zain commented ·

@Zain

Except load distribution, is there anything else i am overlooking?

Power factor. A load at 4000w with a power factor of 0.6 is actually an overload.

Also confirm your have one central battery bank not a battery to each phase?

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Alexandra avatar image
Alexandra answered ·

@Zain

It is most likely a heat issue. Derating because of temperature.

Usually L2 being in the middle is the warmest.

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zain avatar image zain commented ·
The ambient temperature is always in the range of 22-25 degree Celsius and the battery temperature has at most gone to 27 degree Celsius for a minute. That cannot be enough for it to start derating is it? and that happened on 22/07, no overloads on this day cause the inverter was on bypass.


(Thanks for the fast response!!)


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Alexandra avatar image Alexandra ♦ zain commented ·

Ambient is not the issue. Inverter internal temps are the issue.

If your ambient is at the temperature where its rated power is (25°C) then internally it is much warmer inside.

If it is not sustained overload then it is not much to stress about.

That one warning was on grid/generator connect. That happens as it power assists as it connects, so possibly LOM detection.

Your overloads can also be related to grid voltage. There can be derating from that as well. The last overload (that looks ugly because not cleared as the system is off) is on grid connect.

Try change LOM and your input current limit (revise downwards)

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zain avatar image zain Alexandra ♦ commented ·
ya it is not sustained overload.


The overloads happen when the system is inverting. Yes i noticed that the warnings are when grid is connected. But overload alarms causing system shutdown is when grid is down. We have also not ticked the power assist option(?) while configuring so how?

Can you clarify whats grid connect?


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Alexandra avatar image Alexandra ♦ zain commented ·
You can only power assist when connected or making a connection to grid or generator.

When the overloads are happening, see what power is being pulled from the batteries.

You may have a power factor issue. Which makes the loads seem small in terms of ac watts.

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