The output of my solar charger fluctuates from the moment the output power exceeds +/- 1000W. This is clearly visible on today’s and yesterday’s graph coming from Home Assistant. Also a detailed screenshot from VRM shows this. Today and yesterday was sunny without clouds.
I have the same problem on one of our installations. There we have two mppt 250/100 chargers. I don’t think both got damaged at the same time.. I think the bms communication is not stable. Hence the charger starts and stops constantly. I will go on site and try changing the cables and maybe even Cerbo gx. In the mean time did you find the problem and solution ?
I have now disconnected the CAN cable, since CAN with my (unknown) BMS caused problems of which this might be one symptom. I lose any ability to sense the LiFePO4 state of charge, until I grok the BMS’ serial protocol to parse that value out. But actually the batteries seem to charge better without CAN, they used to hit 100% then stop accepting charge until they fell down to ~90%, with a persistent high cell voltage error. Since the change I have not seen the high cell voltage and at the end of solar generation for the day they are at 99%. I will go through the BMS logs to see if I am still getting these swings.
An update. I haven’t found a solution yet, but I have a screenshot of the overall picture. The problem described in the first post occurs between +/- 950W and 1300W. This is clearly visible in the graph below. The problem persists, even when I disconnect the VE direct cable from the solar charger, meaning it operates independently. The only thing I still need to test to see if the problem lies with the solar charger is bypassing the battery BMS. I’ll come back to that later.
