Running a 3 panel, 600W array in series, producing 64-66 max open voltage, and around 56V nominal, into a 100/50 SC. Sometimes I’ll get 64+ voltage readings, 200W or so, 4 amps (it’s late November); other times it will drop to 20 or 40 Volts.
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Voltage Drop on Controller in Panel Series
I would wonder if your connections or panels are ok?
Best way to know is see what your panel voc is, multiply by 3. That should be your voc with nothing attached in the sun. If you arent getting that then your connections/panels are not good.
But it is not abnormal for panel voltage to drop under load and drop in not good sun conditions.
It can also swing up and down when the mppt is tracking the best power point.
The other cause for low charging is the battery cant take more than that.
