question

Would it be possible to have some details as to the type of battery you may be running? As this will be a help in diagnosing the issues you are experiencing.

Thank you for prompt response. The system contains solar panels 400W in total, various manufacturers, all have maximum power at 18~20V. There are 4 x AGM 12V Varta start-stop automotive batteries 95Ah each, 380Ah in total. The system is installed in campervan. It maybe worth noting that this problem is most prominent at intense sun and when the batteries are near full. In overcloud days the system appears to be mostly stable. I have also installed Victron battery monitor BMV-712 and 1.6kW pure sine inverter.

Thank you for the information, beyond the obvious making sure that the wiring to the battery is of sufficient size and all the connections are clean and tight what I have done is set up a 100/30 of my own with two 330 watt panels connected to a 200ah lithium battery that I had available and I will monitor the output voltage and see if I can replicate what you are experiencing. I have used 16mm cable from the mppt to the battery and 6mm solar cable on the input to the mppt I will share my results with you after a day of running in full sun.

SVID_20210525_114252_1.mp4

This is the result from our testing today this is with a lithium battery though not an AGM battery but the voltage as you will see is pretty solid and we are pulling the maximum power that the mppt can supply. In your video what is apparent is that when the voltage climbs to that high level the amps go to zero indicating that there is no load on the mppt which leads me to suspect that there may be an intermittent connection somewhere, what is in circuit between the mppt and the battery? Is it possible to see a picture of the setup?

Good evening together.

This is interesting.

I asked the same question in another emnty:

https://community.victronenergy.com/questions/89493/extreme-fluctuation-in-power-output-during-driving.html

I noticed it while driving but the deeper i remember, i also had this problem once the vehicle was stationary.

Thanks for feedback.

Thanks for sharing the results. When the controller is in bulk mode the voltage in my system is also stable. The problem starts in absorption or float mode when the battery is near its full charge so the average current drawn from the controller is relatively small - 1~2 Amps ( I think you call it the tail current) - that is when the controller become unstable. The lithium batteries I think have different V-I characteristics. It looks this experience is also shared by other Users (thanks for sharing the video). My connections between the controller and batteries are less than 50cm in total and the wire is 6mm2 thick.

Hello together,

are there any feedback or workaround about this topic ?

Thanks in advance.

BR JUlian

Hello, is there an update on this issue?