Charging the B300 through the AC200Max

I recently hooked up my AC200Max to my B300 for charging the B300.
The issue is the B300 has been sitting at 98% charge for the last 90min while I can see im getting about 500watts of solar power coming in.
At the start it was charging fairly quickly from my starting point of 55%, but now it seems to have slowed right down.
My concern is this normal.

Im going to partially answer my own question.
Just about 25 min after posting this question, my battery reached full 100% power.
So my question is why do the last few % points take soo much longer than all the previous charging?
Hopefully someone can explain this to me.

Since the battery in any of these units is actually a “battery pack” made from many individual cells wired in some type of series parallel configuration to get the designed voltage and current for the unit. When it is charging near the top of its state of charge the Battery Management System or BMS has wires to each one of those cells and it slows down the overall charge rate to balance all of the cells to the same voltage (or at least very close exactly the same voltage). Those individual wires to each cell are measuring the voltage and the BMS is making charging adjustments based on those measurements to accomplish this “balancing”.

Thanks a lot, PauIL71:
That was a very good explanation, I am reassured I have done everything accordingly.