Renogy 50A DCDC Mmpt and alternator question

Hi all, I have a Renogy 50A DCDC with 3 x 200w panels running parallel on my RV (Caravan). I live in a hot climate and so solar generation is effective, so assume current generated will be circa 50A from this set up. When I’m towing the caravan for say 7 hrs to the final destination I have power running from my cars alternator into the DCDC to charge my 400ah of lithium batteries. So assuming the DCDC takes a maximum of 50A and the solar panels are trying to push 50Amp and the alternator is pushing 20/30A so say 80A total, so a really dumb question what happens to the 80A -50A = 30A? Eg: should I switch off my solar panels when I’m towing and just leave the car alternator to charge batteries on the journey, or will the Renogy 50A DCDC manage everything and then I don’t have to worry. Again a dumb question, but need help. Thanks

When that 50A DC/DC charger is used as a DC/DC charger only it is 50A. When the DC/DC charger and MPPT solar charge controller are both used at the same time it becomes a 25A DC/DC charger and 25A MPPT CC.
It's brutal, but true.

Haven't met a 200W panel that can hit an Imp of 16.7A. My 200W mono panels are 10A. Best 3 can do is 30A.