Hi
We have 3x 450/200 Mppts, The solar charging is very erratic even when it is sunny. Please see picture attached. We have 6x 540W solar panels connected to to each tracker, 72 panels using all 12 trackers. Can you please advise what is causing this and let me know if you need any additional information. 
Thank you in advance.
Usually the cause is cloudy weather or shadows from objects while the sun is moving from East to West. Here are two examples of days with and without clouds and shadows from trees.
You have pronounced dips around the same time in all 3 examples, which can be caused by shadows from objects, the rest seems to be cloudy weather.
Bit of a long shot but I had some odd behaviour with my mppt chargers awhile back where they'd act similarly.
However mine was occurring when batteries were almost full and sun was high.
It seemed to be due to the battery voltage peaking due to high sun and because smart shunt voltage was showing slightly different to MPPT. The mppt would then turn off rather than go into absorption phase and i was getting similar graphs to above.
For me the solution was enabling SVS Shared voltage sense in DVCC within venus os. Not sure if this will help but worked for me.
