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Russ Smith avatar image
Russ Smith asked

Solar Controller PV Input drops when inverter is running

I have a Victron 150/45 MPPT charge controller and a Victron smart shunt that connect into negative and positive bus bars. The bus bars also connect to a 24v 100ah lifepo4 battery bank and a 2000w inverter. Everything worked fine until I expanded my solar array. When there is full sun and the array is charging at 44 amps and no load is running everything is fine. When the inverter is drawing a load then the Solar Controller will constantly cycle where the watts will drop to zero then will go back up and run for a bit and then go down to zero and then back up.

I can fix the issue by dropping the Max Charge Current of the Solar Controller down to 41 amps then it works fine. I checked all the lines with an AMP meter and nothing seems wrong. Does anyone know why the inverter is causing these issues with the solar charge controller?

MPPT SmartSolar
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JohnC avatar image
JohnC answered ·

Hi @Russ Smith

Not much to go on here, so looking for clues. "I expanded my solar array" is one.

Might your new array be tracking to a lower Vmp? This is consistent with a low load allowing Vpv to rise, then when called to deliver that V will drop closer to Vmp. It must remain higher than Vbat plus 1V, and if dropped out, plus 5V to restart.


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Russ Smith avatar image Russ Smith commented ·

I now have enough solar capacity to get near the 45 amp limit of the solar charge controller. When the inverter doesn't have a load running everything is fine. I can charge at 45 amps. However if I'm charging over 42 amps and then I put a load on the inverter the charge controller input wattage will keep dropping to 0w and then recover and do this over and over again. If I limit the controller to 42 amps then everything is fine.

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