question

matthias-roetzer avatar image
matthias-roetzer asked

PV voltage spike on quick load changes in the system

Hi Forum!

I'm using a MPPT150/45

with around 2,1kWp of PV Panels

connected to a GEL battery at 48V

to the battery are 3 MultiPlusII 5000 connected (3phase)

Sometimes I'm getting strange very short (seconds) PV high voltage peaks to 151V.

I'm managed to catch such an incident. An swichted the MPPT off immediately and measured PV voltage it was about VOC=130V only.

In MPP Mode the PV Operates usally between 80 and 90V

So what can cause these short spikes?

What I found out is that this likely happens when there are quick load changes while the battery is full or nearly full. (working in float or absoption mode). It doesn't occur when battery is in bulk charging mode.

Therefore I presume that this has something to do with input inductance of te MPPT PV Input. The inductance will maintain the current while the MPPT is tryinig to reduce which will naturally raise the voltage. After that it is rapidly declining to effective VOC voltage. (~130V in the example above).

So what should I do? Care? not care? Settings Modifications? Maybe add a capacitor to the input? capacitor is raising short input current spikes to the MPPT which is probably no good idea.

Please suggest! Thank you!



MPPT Controllers
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matthias-roetzer avatar image matthias-roetzer commented ·

Hi all,

the high voltage alarms vanished, mabye because of a firmware update? don't know.

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Alexandra avatar image
Alexandra answered ·

@Matthias Roetzer It is an overshoot of power, the MPPT is working hard then the load drops off and there may be nowhere for it to go. It is common, it happens in the time it takes for the MPPT to react and retrack after the change in conditions. I have seen what you are describing on several systems with no issues so far. In any case the voltage you have measured is close to the MPPTs capabilities. If there are no errors appearing anywhere, such as over voltage warnings, then there does no seem to be a cause for concern.

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matthias-roetzer avatar image matthias-roetzer commented ·

That's exactly what I thought. It's not a bug it's a feature per design. Many thanks for the info!

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texdoe answered ·

what, if it causes an error 21? I have that error on my 100/50 and cant find anything wrong in the system. Is the 100/50 more sensitive than other charge controller? The dealer cant/wont help me with this problem

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Justin Cook avatar image Justin Cook ♦♦ commented ·

@TexDoe I'll note here, for the record, that we have not only replaced your controller once already -with the unit that you sent back to us showing clear arcing at the terminals, which is an excellent indication of the cause of the original Error 21- but have also spent well over an hour on the phone with you discussing all the potential problems elsewhere in your installation, so please don't say that we aren't trying to assist you with your problem.

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