I have 4x3.5kWh Pylontech batteries, and they perform very well. This is more or less 280Ah @48V.
On a number of occasions, I have seen the SOC remain at 88% as per the Venus remote console, even when charging at 30-40A (28A is about the C10 rate). Charging at 28A should result in SOC moving up by about 10%/hour or 1% every 6 minutes (more or less).
But SOC never goes above 88% that day. I have observed reported battery volt go up from 50.8 to 50.9 to 51.2, but the SOC remains at 88%. It only ever gets "stuck" at this specific 88% SOC. IIRC 51.2 is about 95%.
Since the battery voltage does go up, I assume the batteries are charging (they are accepting the current). Is this perhaps an SOC algorithm/BMS issue?
I have not been able to test if they stay at 88% longer as well when they start to discharge at the end of the day.